Author name code: stebbins ADS astronomy entries on 2022-09-14 author:"Stebbins, Robin T." ------------------------------------------------------------------------ Title: Getting Ready for LISA: The Data, Support and Preparation Needed to Maximize US Participation in Space-Based Gravitational Wave Science Authors: Holley-Bockelmann, Kelly; :; Bellovary, Jillian; Bender, Peter; Berti, Emanuele; Brown, Warren; Caldwell, Robert; Cornish, Neil; Darling, Jeremy; Digman, Matthew; Eracleous, Mike; Gultekin, Kayhan; Haiman, Zoltan; Holley-Bockelmann, Kelly; Key, Joey; Larson, Shane; Liu, Xin; McWilliams, Sean; Natarajan, Priyamvada; Shoemaker, David; Shoemaker, Deirdre; Smith, Krista Lynne; Soares-Santos, Marcelle; Robin; Stebbins Bibcode: 2020arXiv201202650H Altcode: The NASA LISA Study Team was tasked to study how NASA might support US scientists to participate and maximize the science return from the Laser Interferometer Space Antenna (LISA) mission. LISA is gravitational wave observatory led by ESA with NASA as a junior partner, and is scheduled to launch in 2034. Among our findings: LISA science productivity is greatly enhanced by a full-featured US science center and an open access data model. As other major missions have demonstrated, a science center acts as both a locus and an amplifier of research innovation, data analysis, user support, user training and user interaction. In its most basic function, a US Science Center could facilitate entry into LISA science by hosting a Data Processing Center and a portal for the US community to access LISA data products. However, an enhanced LISA Science Center could: support one of the parallel independent processing pipelines required for data product validation; stimulate the high level of research on data analysis that LISA demands; support users unfamiliar with a novel observatory; facilitate astrophysics and fundamental research; provide an interface into the subtleties of the instrument to validate extraordinary discoveries; train new users; and expand the research community through guest investigator, postdoc and student programs. Establishing a US LISA Science Center well before launch can have a beneficial impact on the participation of the broader astronomical community by providing training, hosting topical workshops, disseminating mock catalogs, software pipelines, and documentation. Past experience indicates that successful science centers are established several years before launch; this early adoption model may be especially relevant for a pioneering mission like LISA. Title: Space based gravitational wave astronomy beyond LISA Authors: Mueller, Guido; Baker, John; Barke, Simon; Bender, Peter L.; Berti, Emanuele; Caldwell, Robert; Conklin, John W.; Cornish, Neil; Ferrara, Elizabeth C.; Holley-Bockelmann, Kelly; Kamai, Brittany; Larson, Shane L.; Livas, Jeff; McWilliams, Sean T.; Mueller, Guido; Natarajan, Priyamvada; Rioux, Norman; Sankar, Shannon S.; Schnittman, Jeremy; Shoemaker, Deirdre; Slutsky, Jacob; Stebbins, Robin; Thorpe, Ira; Ziemer, John Bibcode: 2019BAAS...51g.243M Altcode: 2019astro2020U.243M; 2019arXiv190711305B This white paper surveys the science, technology and mission concepts for a gravitational wave mission beyond LISA. The proposed small scale activity is a technology development program that would support a range of concepts and a mission concept study to choose a specific mission concept for Astro2030. Title: Building a Field: The Future of Astronomy with Gravitational Waves Authors: Holley-Bockelmann, Kelly; Ziemer, John; Thorpe, Ira; Livas, Jeff; Conklin, John W.; Caldwell, Robert; Berti, Emanuele; McWilliams, Sean T.; Stebbins, Robin; Shoemaker, David; Ferrara, Elizabeth C.; Larson, Shane L.; Shoemaker, Deirdre; Key, Joey Shapiro; Eracleous, Michael; Schnittman, Jeremy; Baghi, Quentin; Kamai, Brittany; Mueller, Guido; Bellovary, Jillian; Rioux, Norman; Baker, John; Cutler, Curt; Natarajan, Priyamvada; Kelly, Bernard J.; Brandt, T. J.; Gabella, William; Jani, Karan Bibcode: 2019BAAS...51g.228H Altcode: 2019arXiv191207642H; 2019astro2020U.228H Harnessing the sheer discovery potential of GW Astronomy will require bold, deliberate, and sustained efforts to train and develop the requisite workforce. This basic infrastructure is needed as an enabling foundation for research. We outline a set of recommendations to help build a thriving, diverse, and inclusive new field. Title: The Laser Interferometer Space Antenna: Unveiling the Millihertz Gravitational Wave Sky Authors: Thorpe, James Ira; Ziemer, John; Thorpe, Ira; Livas, Jeff; Conklin, John W.; Caldwell, Robert; Berti, Emanuele; McWilliams, Sean T.; Stebbins, Robin; Shoemaker, David; Ferrara, Elizabeth C.; Larson, Shane L.; Shoemaker, Deirdre; Key, Joey Shapiro; Vallisneri, Michele; Eracleous, Michael; Schnittman, Jeremy; Kamai, Brittany; Camp, Jordan; Mueller, Guido; Bellovary, Jillian; Rioux, Norman; Baker, John; Bender, Peter L.; Cutler, Curt; Cornish, Neil; Hogan, Craig; Manthripragada, Sridhar; Ware, Brent; Natarajan, Priyamvada; Numata, Kenji; Sankar, Shannon R.; Kelly, Bernard J.; McKenzie, Kirk; Slutsky, Jacob; Spero, Robert; Hewitson, Martin; Francis, Samuel; DeRosa, Ryan; Yu, Anthony; Hornschemeier, Ann; Wass, Peter Bibcode: 2019BAAS...51g..77T Altcode: 2019arXiv190706482B; 2019astro2020U..77T This whitepaper summarizes the status of the ESA-led Laser Interferometer Space Antenna (LISA) mission and advocates for an increased US role within the ‘medium’ mission category. The LISA science case, mission concept, technical readiness, and organizational partnerships are summarized and broad scenarios for US participation are described. Title: NASA's Preparations for ESA's L3 Gravitational Wave Mission Authors: Stebbins, Robin Bibcode: 2016APS..APRJ12003S Altcode: The European Space Agency (ESA) selected gravitational-wave astrophysics as the science theme for its third large mission opportunity, known as `L3,' under its Cosmic Vision Programme. NASA is seeking a role as an international partner in L3. NASA is: (1) participating in ESA's early mission activities, (2) developing potential US technology contributions, (3) participating in ESA's LISA Pathfinder mission, (4) and conducting a study of how NASA might participate. This talk will survey the status of these activities. Title: Mission and Instrument Design Trades for a Space-based Gravitational Wave Observatory to Maximize Science Return Authors: Livas, Jeffrey; Baker, John; Stebbins, Robin; Thorpe, James; Larson, Shane; Sesana, Alberto Bibcode: 2016APS..APRJ12005L Altcode: A space-based gravitational wave observatory is required to access the rich array of astrophysical sources expected at frequencies between 0.0001 and 0.1 Hz. The European Space Agency (ESA) chose the Gravitational Universe as the science theme of its L3 launch opportunity. A call for mission proposals will be released soon after the completion of the LISA Pathfinder (LPF) mission. LPF is scheduled to start science operations in March 2016, and finish by the end of the year, so an optimized mission concept is needed now. There are a number of possible design choices for both the instrument and the mission. One of the goals for a good mission design is to maximize the science return while minimizing risk and keeping costs low. This presentation will review some of the main design choices for a LISA-like laser interferometry mission and the impact of these choices on cost, risk, and science return. Title: NASA's Preparations for ESA's L3 Gravitational Wave Mission Authors: Stebbins, Robin T. Bibcode: 2016AAS...22740502S Altcode: In November 2013, the European Space Agency (ESA) selected the science theme, the "Gravitational Universe," for its third large mission opportunity, known as 'L3,' under its Cosmic Vision Programme. The planned launch date is 2034. NASA is seeking a role as an international partner in L3. NASA is supporting: (1) US participation in early mission studies, (2) US technology development, (3) pre-decadal preparations, (4) ESA's LISA Pathfinder mission and (5) the ST7 Disturbance Reduction System project. This talk summarizes NASA's preparations for a future gravitational-wave mission. Title: Progress Toward a Space-Based Gravitational Wave Observatory Authors: Livas, Jeffrey C.; Stebbins, Robin T. Bibcode: 2016IAUFM..29B.357L Altcode: The discovery of binary pulsar PSR 1913+16 by Hulse & Taylor in 1974 established the existence of gravitational waves, for which the 1983 Nobel Prize was awarded. However, the measurement of astrophysical parameters from gravitational waves will open an entirely new spectrum for discovery and understanding of the Universe, not simply a new window in the electromagnetic spectrum like gamma ray telescopes in the 1970s. Two types of ground-based detectors, Advanced LIGO/Virgo and Pulsar Timing Arrays, are expected to directly detect gravitational waves in their respective frequency bands before the end of the decade. However, many of the most exciting sources are in the band from 0.1-100 mHz, accessible only from space due to seismic and gravity gradient noise on Earth. The European Space Agency (ESA) has chosen the 'Gravitational Universe' as the science theme for its L3 Cosmic Visions opportunity, planned for launch in 2034. NASA is planning to participate as a junior partner. Here we summarize progress toward realizing a gravitational wave observatory in space. Title: Status of a Space-Based Gravitational-Wave Observatory at NASA Authors: Stebbins, Robin Bibcode: 2015IAUGA..2257752S Altcode: For over two decades, NASA has studied a flight project to build a gravitational-wave observatory, and partnered with the European Space Agency (ESA) to formulate and study such a mission. The spectacular science and the well-defined and well-studied Laser Interferometer Space Antenna (LISA) mission concept got high recommendations in the U.S. astrophysics decadal surveys of 2000 and 2010.In 2013, ESA selected the science theme, the “Gravitational Universe,” for the third large mission opportunity, known as L3, under its Cosmic Vision Programme. The planned launch date is 2034. ESA is considering a 20% participation by an international partner, and NASA's Astrophysics Division has begun negotiating a NASA role. The US research community has studied the design consequences of a NASA contribution, evaluated the science benefits and identified the technology requirements for hardware that could be delivered by NASA.This talk will describe the current state of: mission concept studies, US participation in an ESA-led study, technology development, other relevant activities and preparation for the 2020 decadal survey. Title: The Gravitational Universe - ESA's L3 mission Authors: Mueller, Guido; Ando, Masaki; Binetruy, Pierre; Bouyer, Philippe; Cacciapuoti, Luigi; Cruise, Mike; Favata, Fabio; Gehler, Martin; Genzel, Reinhard; Jennrich, Oliver; Kasevich, Mark; Klipstein, Bill; Perryman, Michael; Safa, Frederic; Schutz, Bernard; Stebbins, Robin; Vitale, Stefano Bibcode: 2015APS..APR.U7001M Altcode: Following the advice of ESA's Senior Survey Committee (SSC) the Science Programme Committee (SPC) decided in November 2013 to select the science theme ``The Gravitational Universe'' for their L3 mission. The Director of Science and Robotic Exploration (D/SRE) has established a Gravitational Observatory Advisory Team (GOAT) to advise on the scientific and technological approaches for a gravitational wave observatory with a planned launch date in 2034. Our team is comprised of scientists from Europe and the US as well as scientists and engineers from ESA and observers from NASA and JAXA. We meet about every ten weeks, evaluate the technical readiness of all necessary technologies, study the science impact of different mission designs, and will advise ESA on the required future technology development. We will report on our progress and plans forward to a future space-based gravitational-wave observatory.

For JAXA. Title: Architectures for a Space-based Gravitational-Wave Observatory Authors: Stebbins, Robin Bibcode: 2015APS..APR.U7004S Altcode: The European Space Agency (ESA) selected the science theme, the ``Gravitational Universe,'' for the third large mission opportunity, known as L3, under its Cosmic Vision Programme. The planned launch date is 2034. ESA is considering a 20% participation by an international partner, and NASA's Astrophysics Division has begun negotiating a NASA role. We have studied the design consequences of a NASA contribution, evaluated the science benefits and identified the technology requirements for hardware that could be delivered by NASA. The European community proposed a strawman mission concept, called eLISA, having two measurement arms, derived from the well studied LISA (Laser Interferometer Space Antenna) concept. The US community is promoting a mission concept known as SGO Mid (Space-based Gravitational-wave Observatory Mid-sized), a three arm LISA-like concept. If NASA were to partner with ESA, the eLISA concept could be transformed to SGO Mid by the addition of a third arm, thereby augmenting science, reducing risk and reducing non-recurring engineering costs. The characteristics of the mission concepts and the relative science performance of eLISA, SGO Mid and LISA are described. Title: Future Gravitational-Wave Missions Authors: Stebbins, Robin T.; NASA Gravitational-Wave Study Team Bibcode: 2015AAS...22533844S Altcode: In November 2013, the European Space Agency (ESA) selected the science theme, the 'Gravitational Universe,' for its third large mission opportunity, known as L3, under its Cosmic Vision Programme. The planned launch date is 2034. ESA is considering a 20% participation by an international partner, and NASA's Astrophysics Division has indicated an interest in participating. We have studied the design consequences of a NASA contribution, evaluated the science benefits and identified the technology requirements for hardware that could be delivered by NASA.The European community proposed a strawman mission concept, called eLISA, having two measurement arms, derived from the well studied LISA (Laser Interferometer Space Antenna) concept. The US community is promoting a mission concept known as SGO Mid (Space-based Gravitational-wave Observatory Mid-sized), a three arm LISA-like concept. If NASA were to partner with ESA, the eLISA concept could be transformed to SGO Mid by the addition of a third arm, augmenting science, reducing risk and reducing non-recurring engineering costs. The characteristics of the mission concepts and the relative science performance of eLISA, SGO Mid and LISA are described. Note that all results are based on models, methods and assumptions used in NASA studies. Title: Gravitational-wave Missions at NASA Authors: Stebbins, Robin; McNamara, Paul; Jennrich, Oliver Bibcode: 2014cosp...40E3193S Altcode: In November 2013, ESA selected the science theme, the “Gravitational Universe,” for its third large mission opportunity, known as L3, under its Cosmic Visions Programme. The planned launch date is 2034. ESA is considering a 20% participation by an international partner, and NASA's Astrophysics Division has indicated an interest in participating. We have studied the design consequences of a NASA contribution, evaluated the science benefits and identified the technology requirements for hardware that could be delivered by NASA. The European community proposed a strawman mission concept, called eLISA, having two measurement arms, derived from the well studied LISA (Laser Interferometer Space Antenna) concept. The US community is promoting a mission concept known as SGO Mid (Space-based Gravitational-wave Observatory Mid-sized), a three arm LISA-like concept. If NASA were to partner with ESA, the eLISA concept could be transformed to SGO Mid by the addition of a third arm, augmenting science, reducing risk and reducing non-recurring engineering costs. The characteristics of the mission concepts and the relative science performance of eLISA, SGO Mid and LISA are described. Title: eLISA: Astrophysics and cosmology in the millihertz regime Authors: Amaro-Seoane, Pau; Aoudia, Sofiane; Babak, Stanislav; Binétruy, Pierre; Berti, Emanuele; Bohé, Alejandro; Caprini, Chiara; Colpi, Monica; Cornish, Neil J.; Danzmann, Karsten; Dufaux, Jean-François; Gair, Jonathan; Hinder, Ian; Jennrich, Oliver; Jetzer, Philippe; Klein, Antoine; Lang, Ryan N.; Lobo, Alberto; Littenberg, Tyson; McWilliams, Sean T.; Nelemans, Gijs; Petiteau, Antoine; Porter, Edward K.; Schutz, Bernard F.; Sesana, Alberto; Stebbins, Robin; Sumner, Tim; Vallisneri, Michele; Vitale, Stefano; Volonteri, Marta; Ward, Henry; Wardell, Barry Bibcode: 2013GWN.....6....4A Altcode: 2012arXiv1201.3621A This document introduces the exciting and fundamentally new science and astronomy that the European New Gravitational Wave Observatory (NGO) mission (derived from the previous LISA proposal) will deliver. The mission (which we will refer to by its informal name ``eLISA'') will survey for the first time the low-frequency gravitational wave band (about 0:1 mHz to 1 Hz), with sufficient sensitivity to detect interesting individual astrophysical sources out to z = 15. The measurements described here will address the basic scientific goals that have been captured in ESA's ``New Gravitational Wave Observatory Science Requirements Document''; they are presented here so that the wider scientific community can have access to them. The eLISA mission will discover and study a variety of cosmic events and systems with high sensitivity: coalescences of massive black holes binaries, brought together by galaxy mergers; mergers of earlier, less-massive black holes during the epoch of hierarchical galaxy and black-hole growth; stellar-mass black holes and compact stars in orbits just skimming the horizons of massive black holes in galactic nuclei of the present era; extremely compact white dwarf binaries in our Galaxy, a rich source of information about binary evolution and about future Type Ia supernovae; and possibly most interesting of all, the uncertain and unpredicted sources, for example relics of inflation and of the symmetry-breaking epoch directly after the Big Bang. eLISA's measurements will allow detailed studies of these signals with high signal-to-noise ratio, addressing most of the key scientific questions raised by ESA's Cosmic Vision programme in the areas of astrophysics and cosmology. They will also provide stringent tests of general relativity in the strong-field dynamical regime, which cannot be probed in any other way. This document not only describes the science but also gives an overview on the mission design and orbits. LISA's heritage in the eLISA design will be clear to those familiar with the previous proposal, as will its incorporation of key elements of hardware from the LISA Pathfinder mission, scheduled for launch by ESA in 2014. But eLISA is fundamentally a new mission, one that will pioneer the completely new science of low-frequency gravitational wave astronomy. Title: The Gravitational Universe Authors: eLISA Consortium; Amaro Seoane, P.; Aoudia, S.; Audley, H.; Auger, G.; Babak, S.; Baker, J.; Barausse, E.; Barke, S.; Bassan, M.; Beckmann, V.; Benacquista, M.; Bender, P. L.; Berti, E.; Binétruy, P.; Bogenstahl, J.; Bonvin, C.; Bortoluzzi, D.; Brause, N. C.; Brossard, J.; Buchman, S.; Bykov, I.; Camp, J.; Caprini, C.; Cavalleri, A.; Cerdonio, M.; Ciani, G.; Colpi, M.; Congedo, G.; Conklin, J.; Cornish, N.; Danzmann, K.; de Vine, G.; DeBra, D.; Dewi Freitag, M.; Di Fiore, L.; Diaz Aguilo, M.; Diepholz, I.; Dolesi, R.; Dotti, M.; Fernández Barranco, G.; Ferraioli, L.; Ferroni, V.; Finetti, N.; Fitzsimons, E.; Gair, J.; Galeazzi, F.; Garcia, A.; Gerberding, O.; Gesa, L.; Giardini, D.; Gibert, F.; Grimani, C.; Groot, P.; Guzman Cervantes, F.; Haiman, Z.; Halloin, H.; Heinzel, G.; Hewitson, M.; Hogan, C.; Holz, D.; Hornstrup, A.; Hoyland, D.; Hoyle, C. D.; Hueller, M.; Hughes, S.; Jetzer, P.; Kalogera, V.; Karnesis, N.; Kilic, M.; Killow, C.; Klipstein, W.; Kochkina, E.; Korsakova, N.; Krolak, A.; Larson, S.; Lieser, M.; Littenberg, T.; Livas, J.; Lloro, I.; Mance, D.; Madau, P.; Maghami, P.; Mahrdt, C.; Marsh, T.; Mateos, I.; Mayer, L.; McClelland, D.; McKenzie, K.; McWilliams, S.; Merkowitz, S.; Miller, C.; Mitryk, S.; Moerschell, J.; Mohanty, S.; Monsky, A.; Mueller, G.; Müller, V.; Nelemans, G.; Nicolodi, D.; Nissanke, S.; Nofrarias, M.; Numata, K.; Ohme, F.; Otto, M.; Perreur-Lloyd, M.; Petiteau, A.; Phinney, E. S.; Plagnol, E.; Pollack, S.; Porter, E.; Prat, P.; Preston, A.; Prince, T.; Reiche, J.; Richstone, D.; Robertson, D.; Rossi, E. M.; Rosswog, S.; Rubbo, L.; Ruiter, A.; Sanjuan, J.; Sathyaprakash, B. S.; Schlamminger, S.; Schutz, B.; Schütze, D.; Sesana, A.; Shaddock, D.; Shah, S.; Sheard, B.; Sopuerta, C. F.; Spector, A.; Spero, R.; Stanga, R.; Stebbins, R.; Stede, G.; Steier, F.; Sumner, T.; Sun, K. -X.; Sutton, A.; Tanaka, T.; Tanner, D.; Thorpe, I.; Tröbs, M.; Tinto, M.; Tu, H. -B.; Vallisneri, M.; Vetrugno, D.; Vitale, S.; Volonteri, M.; Wand, V.; Wang, Y.; Wanner, G.; Ward, H.; Ware, B.; Wass, P.; Weber, W. J.; Yu, Y.; Yunes, N.; Zweifel, P. Bibcode: 2013arXiv1305.5720E Altcode: 2013arXiv1305.5720C; 2013arXiv1305.5720D The last century has seen enormous progress in our understanding of the Universe. We know the life cycles of stars, the structure of galaxies, the remnants of the big bang, and have a general understanding of how the Universe evolved. We have come remarkably far using electromagnetic radiation as our tool for observing the Universe. However, gravity is the engine behind many of the processes in the Universe, and much of its action is dark. Opening a gravitational window on the Universe will let us go further than any alternative. Gravity has its own messenger: Gravitational waves, ripples in the fabric of spacetime. They travel essentially undisturbed and let us peer deep into the formation of the first seed black holes, exploring redshifts as large as z ~ 20, prior to the epoch of cosmic re-ionisation. Exquisite and unprecedented measurements of black hole masses and spins will make it possible to trace the history of black holes across all stages of galaxy evolution, and at the same time constrain any deviation from the Kerr metric of General Relativity. eLISA will be the first ever mission to study the entire Universe with gravitational waves. eLISA is an all-sky monitor and will offer a wide view of a dynamic cosmos using gravitational waves as new and unique messengers to unveil The Gravitational Universe. It provides the closest ever view of the early processes at TeV energies, has guaranteed sources in the form of verification binaries in the Milky Way, and can probe the entire Universe, from its smallest scales around singularities and black holes, all the way to cosmological dimensions. Title: A Possible U.S. Contribution to eLISA, a Gravitational-Wave Mission Concept for ESA’s L2 Opportunity Authors: Stebbins, Robin T. Bibcode: 2013HEAD...1312104S Altcode: Scientists from the member states of the European Space Agency (ESA) that proposed the New Gravitational Wave Observatory (NGO) have organized the eLISA Consortium to propose for ESA's next large mission opportunity, called L2. The Evolved Laser Interferometer Space Antenna (eLISA) concept is derived from the well studied LISA concept for a space-based, gravitational-wave mission. eLISA will use the technology being developed in the LISA Pathfinder mission in a two-arm version that achieves much of the LISA science endorsed by the Decadal Survey. If invited, NASA could join the project as a junior partner with a ~15% share. This could enable a third arm and substantially augment the science return. While the details of the eLISA concept to be proposed have not yet been finalized, the SGO Mid concept, recently studied in the U.S., constitutes a possible augmented concept for an ESA/NASA partnership. The eLISA concept and the SGO Mid concept are described and compared. Title: Status of eLISA Authors: Stebbins, Robin T.; Jennrich, O.; Consortium, eLISA Bibcode: 2013AAS...22115305S Altcode: Scientists from the member states of the European Space Agency (ESA) that proposed the New Gravitational Wave Observatory (NGO) are organizing the eLISA Consortium to propose for the next large mission opportunity. The Evolved Laser Interferometer Space Antenna (eLISA) concept is derived from the well studied LISA concept for a space-based, gravitational-wave mission. eLISA will use the technology being developed in the LISA Pathfinder mission in a two-arm version that achieves much of the science of LISA. eLISA will: (1) survey very many compact stellar-mass binaries and study the structure of the Milky Way; (2) discover black holes formed at early epochs that grew over cosmic time to generate the supermassive black holes present in most galactic nuclei today; (3) trace the interaction of galaxy growth and massive black hole growth over the entire history of galaxy formation; (4) explore the populations of stellar-mass compact objects in galactic nuclei and their dynamics; (5) observe highly relativistic coalescences of black hole binaries, and provide exceptionally strong tests of the predictions of General Relativity; and (6) probe new physics and cosmology with gravitational waves, and search for unforeseen sources of gravitational waves. The key parameters of the design concept and a quantitative assessment of the science performance are given. NASA and the U.S. research community may be able to participate, and possibly extend the capabilities of the mission. Title: NASA's Gravitational-Wave Mission Concept Study Authors: Stebbins, Robin; Jennrich, Oliver; McNamara, Paul Bibcode: 2012cosp...39.1890S Altcode: 2012cosp.meet.1890S With the conclusion of the NASA/ESA partnership on the Laser interferometer Space Antenna (LISA) Project, NASA initiated a study to explore mission concepts that will accomplish some or all of the LISA science objectives at lower cost. The Gravitational-Wave Mission Concept Study consisted of a public Request for Information (RFI), a Core Team of NASA engineers and scientists, a Community Science Team, a Science Task Force, and an open workshop. The RFI yielded were 12 mission concepts, 3 instrument concepts and 2 technologies. The responses ranged from concepts that eliminated the drag-free test mass of LISA to concepts that replace the test mass with an atom interferometer. The Core Team reviewed the noise budgets and sensitivity curves, the payload and spacecraft designs and requirements, orbits and trajectories and technical readiness and risk. The Science Task Force assessed the science performance by calculating the horizons, the detection rates and the accuracy of astrophysical parameter estimation for massive black hole mergers, stellar-mass compact objects inspiraling into central engines, and close compact binary systems. Three mission concepts have been studied by Team-X, JPL's concurrent design facility, to define a conceptual design, evaluate key performance parameters, assess risk and estimate cost and schedule. The Study results are summarized. Title: Low-frequency gravitational-wave science with eLISA/NGO Authors: Amaro-Seoane, Pau; Aoudia, Sofiane; Babak, Stanislav; Binétruy, Pierre; Berti, Emanuele; Bohé, Alejandro; Caprini, Chiara; Colpi, Monica; Cornish, Neil J.; Danzmann, Karsten; Dufaux, Jean-François; Gair, Jonathan; Jennrich, Oliver; Jetzer, Philippe; Klein, Antoine; Lang, Ryan N.; Lobo, Alberto; Littenberg, Tyson; McWilliams, Sean T.; Nelemans, Gijs; Petiteau, Antoine; Porter, Edward K.; Schutz, Bernard F.; Sesana, Alberto; Stebbins, Robin; Sumner, Tim; Vallisneri, Michele; Vitale, Stefano; Volonteri, Marta; Ward, Henry Bibcode: 2012CQGra..29l4016A Altcode: 2012arXiv1202.0839A We review the expected science performance of the New Gravitational-Wave Observatory (NGO, a.k.a. eLISA), a mission under study by the European Space Agency for launch in the early 2020s. eLISA will survey the low-frequency gravitational-wave sky (from 0.1 mHz to 1 Hz), detecting and characterizing a broad variety of systems and events throughout the Universe, including the coalescences of massive black holes brought together by galaxy mergers; the inspirals of stellar-mass black holes and compact stars into central galactic black holes; several millions of ultra-compact binaries, both detached and mass transferring, in the Galaxy; and possibly unforeseen sources such as the relic gravitational-wave radiation from the early Universe. eLISA’s high signal-to-noise measurements will provide new insight into the structure and history of the Universe, and they will test general relativity in its strong-field dynamical regime. Title: Plans For A Next Generation Space-based Gravitational-wave Observatory (NGO) Authors: Livas, Jeffrey C.; Stebbins, R. T.; Jennrich, O.; NGO Mission Development Team Bibcode: 2012AAS...21914626L Altcode: The European Space Agency (ESA) is currently in the process of selecting a mission for the Cosmic Visions Program. A space-based gravitational wave observatory in the low-frequency band (0.0001 - 1 Hz) of the gravitational wave spectrum is one of the leading contenders. This low frequency band has a rich spectrum of astrophysical sources, and the LISA concept has been the key mission to cover this science for over twenty years. Tight budgets have recently forced ESA to consider a reformulation of the LISA mission concept that will allow the Cosmic Visions Program to proceed on schedule either with the US as a minority participant, or independently of the US altogether. We report on the status of these reformulation efforts. Title: Concepts For A Space-based Gravitational-wave Observatory (SGO) Authors: Stebbins, Robin T.; Gravitational Wave Concept Definition Team Bibcode: 2012AAS...21914624S Altcode: The low-frequency band (0.0001 - 1 Hz) of the gravitational wave spectrum has the most interesting astrophysical sources. It is only accessible from space. The Laser Interferometer Space Antenna (LISA) concept has been the leading contender for a space-based detector in this band. Despite a strong recommendation from Astro2010, constrained budgets motivate the search for a less expensive concept, even at the loss of some science. We have explored the range of lower-cost mission concepts derived from two decades of studying the LISA concept. We describe LISA-like concepts that span the range of affordable and scientifically worthwhile missions, and summarize the analyses behind them. Title: New Concepts for Space-Based Gravitational Wave Missions Authors: Stebbins, Robin T.; Baker, J. G.; Cooley, D.; Gallagher, R. J.; Hughes, S. P.; Livas, J. C.; Simpson, J. E.; Thorpe, J. I.; Welter, G. L. Bibcode: 2011HEAD...12.0902S Altcode: The most interesting astrophysical sources in the gravitational wave spectrum lie in the low-frequency band (0.0001 - 1 Hz), which is only accessible from space. For two decades, the LISA concept has been the leading contender for a detector in this band. Despite a strong recommendation from Astro2010, there is strong motivation to find a less expensive concept, even at the loss of some science. We are searching for a lower cost mission concept by examining alternate orbits, less-capable measurement concepts, radically different implementations of the measurement concept and other cost-saving ideas. We report the results of our searches to date, and summarize the analyses behind them. Title: Characterization of photoreceivers for LISA Authors: Guzmán Cervantes, F.; Livas, J.; Silverberg, R.; Buchanan, E.; Stebbins, R. Bibcode: 2011CQGra..28i4010G Altcode: 2012arXiv1203.2862G LISA will use quadrant photoreceivers as front-end devices for the phasemeter measuring the motion of drag-free test masses in both angular orientation and separation. We have set up a laboratory testbed for the characterization of photoreceivers. Some of the limiting noise sources have been identified and their contribution has been either measured or derived from the measured data. We have built a photoreceiver with a 0.5 mm diameter quadrant photodiode with an equivalent input current noise of better than 1.8 pA Hz-1/2 below 20 MHz and a 3 dB bandwidth of 34 MHz. Title: Preliminary Investigations of an Optical Assembly Tracking Mechansim for LISA Authors: Ira Thorpe, James; Stebbins, Robin Bibcode: 2010cosp...38.3793I Altcode: 2010cosp.meet.3793I After injection into their specific orbits, the position of the LISA spacecraft are not actively controlled. Rather the spacecraft are allowed to passively follow their trajectories and the roughly equilateral triangular constellation is preserved. Slight variations in the orbits cause the constellation to experience both periodic and secular variations, one consequence of which is a variation in the interior angles of the constellation on the order of one degree. This variation is larger than the field of view of the LISA telescope, requiring a mechanism for each spacecraft to maintain pointing to its two companions. This Optical Assembly Tracking Mechanism (OATM) will be used to accommodate these variations while maintaining pointing at the ten nanoradian level to the far spacecraft. Here we report on a possible design for the OATM as well as initial results from a test campaign of a piezo-inchworm actuator used to drive the mechanism. Title: LISA Technology Development, Risk Reduction and Mission Formulation at NASA Authors: Stebbins, Robin; Ziemer, John; Livas, Jeffrey; Ira Thorpe, James; Merkowitz, Stephen Bibcode: 2010cosp...38.3757S Altcode: 2010cosp.meet.3757S The Laser Interferometer Space Antenna (LISA) is a joint ESA-NASA project to design, build and operate a space-based gravitational wave detector based on a laser interferometer. LISA relies on several technologies that are either new to spaceflight or must perform at levels not previously demonstrated in a spaceflight environment. The ESA-led LISA Pathfinder mission is the main effort to demonstrate LISA technology. NASA also supports complementary ground-based technology development and risk reduction activities. This presentation will report the status of NASA work on micronewton thrusters, the telescope, the optical pointing subsystem and mission formulation. More details on some of these topics will be given in posters. Other talks and posters will describe NASA-supported work on the laser subsystem, the phasemeter, and aspects of the interferometry. Two flight-qualified clusters of four colloid micronewton thrusters, each capable of thrust levels between 5 and 30 µN with a resolution ¡0.1 µN and a thrust noise ¡0.1 µN/sqrtHz (0.001 to 4 Hz), have been integrated onto the LISA Pathfinder spacecraft. The complementary ground-based development focuses on lifetime demonstration. Laboratory verification of failure models and accelerated life tests are just getting started. LISA needs a 40 cm diameter, afocal telescope for beam expansion/reduction that maintains an optical pathlength stability of 1 pm/sqrtHz in an extremely stable thermal environment. A mechanical prototype of a silicon carbide primary-secondary structure has been fabricated for stability testing. Two optical assemblies must point at different distant spacecraft with nanoradian accuracy over 1° annual variation in the angle between the distant spacecraft. A candidate piezo-inchworm actuator is being tested in a suitable testbed. In addition to technology development, NASA has carried out several studies in support of the mission formulation. The results of systems engineering work on flight software, avionics and reliability will be summarized. Title: Instrumentation and Technology for the Laser Interferometer Space Antenna (LISA) Authors: Prince, Thomas Allen; Jennrich, O.; Klipstein, W.; Livas, J.; McNamara, P.; Merkowitz, S.; Sallusti, M.; Stebbins, R. Bibcode: 2010AAS...21548210P Altcode: 2010BAAS...42..575P This poster discusses the present status of the technology and instrumentation for the joint ESA/NASA gravitational wave detector, LISA, focusing on&nbspa description of the main payload items, such as: (1) the interferometric measurement system, comprising the optical system, which includes the optical bench and the telescope, the laser system, and the phase measurement system; and, (2) the disturbance reduction system, including the gravitational reference sensor, the charge control system, and the micro-propulsion&nbspsystem. Title: Preliminary LISA telescope spacer design Authors: Livas, Jeffrey; Stebbins, Robin; Arsenovic, Petar; Castellucci, Kevin; Generie, Joseph; Howard, Joseph; Mueller, Guido; Preston, Alix; Sanjuan, Josep; Williams, Luke Bibcode: 2010cosp...38.3783L Altcode: 2010cosp.meet.3783L The LISA mission observes gravitational waves by measuring the separations between freely floating proof masses located 5 million kilometers apart with an accuracy of 10 picometers. The separations are measured interferometrically. The telescope is an afocal Cassegrain style design with a magnification of 80x. The entrance pupil has a 40 cm diameter and will either be centered on-axis or de-centered off-axis to avoid obscurations. Its two main purposes are to transform the small diameter beam used on the optical bench to a diffraction limited collimated beam to efficiently transfer the metrology laser between spacecraft, and to receive the incoming light from the far spacecraft. It transmits and receives simultaneously. The basic optical design and requirements are well understood for a conventional telescope design for imaging applications, but the LISA design is complicated by the additional requirement that the total optical path through the telescope must remain stable at the picometer level over the measurement band during the mission to meet the measurement accuracy. This poster describes the requirements for the telescope and the preliminary work that has been done to understand the materials and mechanical issues associated with the design of a passive metering structure to support the telescope and to maintain the spacing between the primary and secondary mirrors in the LISA on-orbit environment. This includes the requirements flowdown from the science goals, thermal modeling of the spacecraft and telescope to determine the expected temperature distribution, layout options for the telescope including an on-and off-axis design, and plans for fabrication and testing. Title: The LISA Pathfinder Mission Authors: Stebbins, Robin T.; LISA Pathfinder Science Working Team Bibcode: 2010AAS...21548214S Altcode: 2010BAAS...42..575S LISA Pathfinder (formerly known as SMART-2) is a European Space Agency (ESA) mission designed to pave the way for the joint ESA/NASA Laser Interferometer Space Antenna (LISA) mission by testing in flight the critical technologies required for space-borne gravitational wave detection: it will put two test masses in a near-perfect gravitational free-fall and control and measure their motion with unprecedented accuracy.

LISA Pathfinder is currently in the integration and test phase of the development, and is due to be launched on a dedicated launch vehicle in late 2011, with first results on the performance of the system being available approximately 6 months later.

This poster will describe the mission in detail, give the current status of the spacecraft development, and highlight the future milestones in the integration and test campaign. Title: LISA telescope spacer design investigations Authors: Sanjuan, Josep; Mueller, Guido; Livas, Jeffrey; Preston, Alix; Arsenovic, Petar; Castellucci, Kevin; Generie, Joseph; Howard, Joseph; Stebbins, Robin Bibcode: 2010cosp...38.3791S Altcode: 2010cosp.meet.3791S The Laser Interferometer Space Antenna (LISA) is a space-based gravitational wave observa-tory with the goal of observing Gravitational Waves (GWs) from astronomical sources in a frequency range from 30 µHz to 0.1 Hz. The detection of GWs at such low frequency requires measurements of distances at the pico-meter level between bodies separated by 5 million kilo-meters. The LISA mission consists of three identical spacecraft (SC) separated by 5 × 106 km forming an equilateral triangle. Each SC contains two optical assemblies and two vacuum en-closures housing one proof mass (PM) in geodesic (free fall) motion each. The two assemblies on one SC are each pointing towards an identical assembly on each of the other two SC to form a non-equal arm interferometer. The measurement of the GW strain is done by measuring the change in the length of the optical path between the PMs of one arm relative to the other arms caused by the pass of a GW. An important element of the Interferometric Measurement System (IMS) is the telescope which, on one hand, gathers the light coming from the far SC (∼100 pW) and, on the other hand, expands and collimates the small outgoing beam ( 1 W) and sends it to the far SC. Due to the very demanding sensitivity requirements care must be taken in the design and validation of the telescope not to degrade the IMS performance. For instance, the diameter of the telescope sets the the shot noise of the IMS and depends critically on the diameter of the primary and the divergence angle of the outgoing beam. As the telescope is rather fast telescope, the divergence angle is a critical function of the overall separation between the primary and secondary. Any long term changes of the distance of more than a a few micro-meter would be detrimental to the LISA mission. Similarly challenging are the requirements on the in-band path-length noise for the telescope which has to be kept below 1 pm Hz-1/2 in the LISA band. Different configurations (on-axis/off axis) and materials such as Silicon Carbide (SiC) and Carbon Fiber Reinforced Plastic (CFRP) are considered to be used in the telescope spacer structure. We will describe our experimental efforts to understand and quantify the behavior of different materials and also discuss a first investigation of a specific on-axis SiC telescope spacer for LISA. This work is supported by NASA contract 00069955. Title: Rightsizing LISA Authors: Stebbins, R. T. Bibcode: 2009CQGra..26i4014S Altcode: 2009arXiv0904.1029S The Laser Interferometer Space Antenna (LISA) science requirements and conceptual design have been fairly stable for over a decade. In the interest of reducing costs, the LISA Project at NASA has looked for simplifications of the architecture, at downsizing of subsystems and at descopes of the entire mission. This is a natural activity of the formulation phase and one that is particularly timely in the current NASA budgetary context. There is, and will continue to be, enormous pressure for cost reduction from both ESA and NASA, reviewers and the broader research community. Here, the rationale for the baseline architecture is reviewed, and recent efforts to find simplifications and other reductions that might lead to savings are reported. A few possible simplifications have been found in the LISA baseline architecture. In the interest of exploring cost sensitivity, one moderate and one aggressive descope have been evaluated; the cost savings are modest and the loss of science is not. Title: LISA Pathfinder Authors: Stebbins, Robin T.; McNamara, P. W. Bibcode: 2009AAS...21344906S Altcode: 2009BAAS...41Q.341S LISA Pathfinder, formerly known as SMART-2, is the second of the European Space Agency's Small Missions for Advanced Research and Technology. The mission will pave the way for the joint ESA/NASA Laser Interferometer Space Antenna (LISA), by testing the core assumption of gravitational wave detection - and to a larger extent, General Relativity - that free particles follow geodesics.

In order to meet the goals of the mission, and to prepare the way for LISA, several new technologies must be demonstrated in a space environment. These include: inertial sensors, high-precision laser metrology, drag-free control and micro-Newton proportional thrusters.

LISA Pathfinder will carry two payloads: the LISA Technology Package (LTP), provided by European Member States and ESA, and the Disturbance Reduction System (DRS) provided by NASA. The DRS has passed its pre-ship acceptance review and has been delivered to ESA, while the LTP has passed its Critical Design Review, with flight hardware currently being manufactured and tested.

The spacecraft development is also proceeding well; the flight structures of both the science module and propulsion module are undergoing environmental testing, while subsystem flight hardware is being delivered to the spacecraft testbeds.

LISA Pathfinder will be launched on a dedicated launch vehicle in late 2010. After 15 apogee raising manoeuvres, the sciencecraft will enter its final orbit around the first Sun-Earth Lagrange point. First science results are expected approximately three months after launch.

Here we will give an overview of the mission including the technologies being demonstrated. We will also report on the status of the flight hardware testing, and on the status of the ground system. Title: Recent progress at NASA in LISA formulation and technology development Authors: Stebbins, R. T. Bibcode: 2008CQGra..25k4050S Altcode: Over the last year, the NASA half of the joint LISA project has focused its efforts on responding to a major review, and advancing the formulation and technology development of the mission. The NAS/NRC Beyond Einstein program assessment review will be described, including the outcome. The basis of the LISA science requirements has changed from detection determined by integrated signal-to-noise ratio to observation determined by uncertainty in the estimation of astrophysical source parameters. The NASA team has further defined the spacecraft bus design, participated in many design trade studies and advanced the requirements flow down and the associated current best estimates of performance. Recent progress in technology development is also summarized. Title: Astrophysics At z 10 With Gravitational Waves Authors: Stebbins, Robin T. Bibcode: 2008HEAD...10.0602S Altcode: What astrophysics can be done at redshifts beyond 5 using gravitational waves? Historically, gravitational wave antennas have been characterized by their detection capability. This is measured in terms of signal-noise ratio, and implies a rate of false positives and false negatives. But to do useful astrophysics, one would like to measure - or more properly, estimate - astrophysical parameters of the gravitational wave sources. In the interest of strengthening the connection between science objectives and a specific instrument performance, the LISA community has reformulated the LISA science requirements around the anticipated uncertainty in astrophysical parameter estimation. The rationale for this characterization of LISA and a summary of the astrophysics that LISA can do will be given. Title: LISA Technology Development at GSFC Authors: Thorpe, James Ira; Livas, Jeffrey; Stebbins, Robin Bibcode: 2008cosp...37.3184T Altcode: 2008cosp.meet.3184T The prime focus of LISA technology development efforts at NASA/GSFC has been in LISA interferometry, specifically in the area of laser frequency noise mitigation. Laser frequency noise is addressed through a combination of stabilization and common-mode rejection. Current plans call for two stages of stabilization, pre-stabilization to a local frequency reference and further stabilization using the constellation as a frequency reference. In order for these techniques to be used simultaneously, the pre-stabilization step must provide an adjustable frequency offset. Here we report on a modification to the standard modulation/demodulation technique used to stabilize to optical cavities that generates a frequency-tunable reference from a fixedlength cavity. This technique requires no modifications to the cavity itself and only minor modifications to the components. The measured noise performance and dynamic range of the laboratory prototype meet the LISA requirements. Title: Science requirements for LISA Authors: Stebbins, Robin Bibcode: 2008cosp...37.3029S Altcode: 2008cosp.meet.3029S Historically, gravitational wave antennas have been characterized by their detection capability. This is measured in terms of signal-to-noise ratio, and implies a rate of false positives and false negatives. But to do useful astrophysics, one would like to measure - or more properly, estimate - astrophysical parameters of the gravitational wave sources. In the interest of strengthening the connection between science objectives and a specific instrument performance, the LISA community has reformulated the LISA science requirements around the anticipated uncertainty in astrophysical parameter estimation. The rationale for this characterization of LISA and a summary of the astrophysics and fundamental physics that LISA can do will be given. LISA will be able to make precision measurements of sources out to z∼10. Title: The LISA Pathfinder Mission Authors: Stebbins, Robin T.; LISA Pathfinder Science Team Bibcode: 2007AAS...21114009S Altcode: 2007BAAS...39..990S LISA Pathfinder is an ESA mission designed to pave the way for the joint ESA/NASA Laser Interferometer Space Antenna (LISA) mission by testing in flight the critical technologies required for space-borne gravitational wave detection. It will put two test masses in a near-perfect gravitational free-fall and measure their motion with unprecedented accuracy.

LISA Pathfinder will carry two technology payloads, the European provided LISA Technology Package (LTP), and the NASA provided Disturbance Reduction System (DRS), also known as the ST-7 mission of the New Millennium Program. The LTP comprises two inertial sensors, high precision laser metrology, drag-free control and an ultra-precise micro-Newton propulsion system. The DRS consists of a drag-free control system and a micro-Newton propulsion system. The DRS will use the LTP inertial sensors, each of which has a proof mass, reference housing with electrodes for capacitive sensing and actuation and discharging systems.

LISA Pathfinder is due to be launched in the first half of 2010, with first results on the performance of the system being available approx 6 months later.

This poster summarizes the mission concept and reports the progress in the last year, and the current status as the mission nears final integration. Many spacecraft subsystems have been delivered. Detailed planning for the orbital test sequences and development of the data reduction software has advanced significantly. Ground support equipment and test procedures for the spacecraft and payloads is also well along. Details of the LISA technology to be flight tested will be given. Title: The LISA Pathfinder Mission Authors: Stebbins, Robin T.; LISA Pathfinder Science Team Bibcode: 2006AAS...209.7403S Altcode: 2006BAAS...38..990S LISA Pathfinder (formerly known as SMART-2) is an ESA mission designed to pave the way for the joint ESA/NASA Laser Interferometer Space Antenna (LISA) mission by testing in flight the critical technologies required for space-borne gravitational wave detection: it will put two test masses in a near-perfect gravitational free-fall and control and measure their motion with unprecedented accuracy.

LISA Pathfinder will carry two technology payloads, the European provided LISA Technology Package (LTP), and the NASA provided Disturbance Reduction System (DRS). The LTP comprises two inertial sensors, high precision laser metrology, drag-free control and an ultra-precise micro-Newton propulsion system. The DRS consists of a drag-free control system and a micro-Newton propulsion system. The DRS will use the LTP inertial sensors.

LISA Pathfinder is due to be launched in late 2009, with first results on the performance of the system being available approx 6 months later.

This poster gives an introduction to, and status of, the mission, followed by more details on the technologies to be tested in a space environment. It will also highlight the ways in which the LISA Pathfinder mission will be used for the preparation of LISA, e.g. ground segment development, on-orbit commissioning of the hardware, etc. as well as technology development. Title: LISA Mission Architecture Authors: Jedrich, Nicholas M.; Stebbins, R. T.; Livas, J. C.; Merkowitz, S. M.; Mink, R. G. Bibcode: 2006AAS...209.7402J Altcode: 2006BAAS...38..990J The Laser Interferometer Space Antenna (LISA) mission is unique from a mission design perspective in that three spacecraft and their associated operations form one distributed science instrument, unlike more conventional missions where an instrument(s) is a component of an individual spacecraft. The interferometer measurements between spacecraft that form the basis for the science measurements, i.e. strain, relies on all three of the spacecraft interacting as designed. The performance of one spacecraft in the LISA constellation is directly coupled to the performance of the two remaining spacecraft in order for the instrument to collect meaningful science data. This dependency on all three spacecraft to function as the instrument is the primary driver for unique design requirements that span all spacecraft subsystems and the overall mission design. A detailed discussion will be presented that describes the spacecraft and current mission architecture needed to meet the LISA science requirements. Title: System Validation and Verification Testing for the Laser Interferometry Space Antenna (LISA) Authors: Livas, Jeffrey C.; Jedrich, N.; Merkowitz, S. M.; Stebbins, R. T. Bibcode: 2006AAS...209.7404L Altcode: 2006BAAS...38..990L The Laser Interferometry Space Antenna (LISA) mission is a set of 3 spacecraft that fly in a heliocentric orbit in an equilateral triangle formation to detect gravitational waves. Each side of the triangle is 5 million km long, and the formation detects passing waves by closely monitoring the distance between spacecraft.

The ideal for system-level testing of instruments and spacecraft is to “test as you fly”. Given that the inter-spacecraft distance is approximately 13 times the distance between the earth and the moon, Ground testing for the LISA instrument will not be able to meet this ideal in a number of areas, so a combination of testing, simulation, and analysis will be needed instead. This paper will outline some of the areas where direct testing on the ground will not be possible, and discuss some of ideas, concepts and methods to meet that challenge.

The focus of the discussion will be on the optical and system-level aspects of the testing, as many of the issues associated with the proof masses and drag-free spacecraft are covered by the LISA Pathfinder mission. Title: LISA Mission Tutorial Authors: Stebbins, Robin Bibcode: 2006AIPC..873....3S Altcode: The Laser Interferometer Space Antenna (LISA) relies on concepts and instrumentation techniques to observe gravitational waves that are not widely known in astrophysics or engineering for spaceflight. This tutorial explains the basic scientific concepts, the mission concept, the top-level architecture of the flight system and the character of the resulting data for interested astrophysicists and engineers. Title: Demonstration of the zero-crossing phasemeter with a LISA test-bed interferometer Authors: Pollack, S. E.; Stebbins, R. T. Bibcode: 2006CQGra..23.4189P Altcode: 2006gr.qc.....5154P The laser interferometer space antenna (LISA) is being designed to detect and study in detail gravitational waves from sources throughout the Universe such as massive black hole binaries. The conceptual formulation of the LISA space-borne gravitational wave detector is now well developed. The interferometric measurements between the sciencecraft remain one of the most important technological and scientific design areas for the mission. Our work has concentrated on developing the interferometric technologies to create a LISA-like optical signal and to measure the phase of that signal using commercially available instruments. One of the most important goals of this research is to demonstrate the LISA phase timing and phase reconstruction for a LISA-like fringe signal, in the case of a high fringe rate and a low signal level. We present current results of a test-bed interferometer designed to produce an optical LISA-like fringe signal previously discussed in Jennrich O, Stebbins R T, Bender P L and Pollack S (2001 Class. Quantum Grav. 18 4159 64) and Pollack S E, Jennrich O, Stebbins R T and Bender P (2003 Class. Quantum Grav. 20 S291 00). Title: A demonstration of LISA laser communication Authors: Pollack, S. E.; Stebbins, R. T. Bibcode: 2006CQGra..23.4201P Altcode: 2006gr.qc.....5155P Over the past few years, questions have been raised concerning the use of laser communications links between sciencecraft to transmit phase information crucial to the reduction of laser frequency noise in the LISA science measurement. The concern is that applying medium frequency phase modulations to the laser carrier could compromise the phase stability of the LISA fringe signal. We have modified the table-top interferometer presented in Pollack and Stebbins (2006 Demonstration of the zero-crossing phasemeter with a LISA test-bed interferometer Class. Quantum Grav.) by applying phase modulations to the laser beams in order to evaluate the effects of such modulations on the LISA science fringe signal. We have demonstrated that the phase resolution of the science signal is not degraded by the presence of medium frequency phase modulations. Title: Low-frequency active vibration isolation for advanced LIGO Authors: Hua, Wensheng; Adhikari, R.; DeBra, Daniel B.; Giaime, Joseph A.; Hammond, Giles D.; Hardham, C.; Hennessy, Mike; How, Jonathan P.; Lantz, Brian T.; Macinnis, M.; Mittleman, R.; Richman, S.; Robertson, Norna A.; Rollins, J.; Shoemaker, David H.; Stebbins, Robin T. Bibcode: 2004SPIE.5500..194H Altcode: LIGO is dedicated to the detection of gravitational waves. To achieve the design sensitivity of the proposed Advanced LIGO detectors, the seismic isolation system is required to isolate the interferometer mirrors from ground motion above 0.1 Hz. The dominant source of motion above 0.1 Hz is the microseismic peaks near 0.15 Hz. The system needs to isolate the payload from this motion by at least a factor of five in all three translational degrees of freedom. Tilt-horizontal coupling is the most challenging problem for seismic isolation below 1 Hz. Tilt-horizontal coupling results from the principle of equivalence: inertial horizontal sensors cannot distinguish horizontal acceleration from tilt motion. Tilt-horizontal coupling rises dramatically at low frequencies, which makes low frequency isolation difficult. Several techniques are used to address the tilt-horizontal coupling problem. The isolation platform is designed to separate horizontal motions from tilt motions. Feedback control to displacement sensors is used to command the platform in all degrees of freedom. These sensors are "corrected" by ground seismometers, using an optimal FIR filtering technique to separate tilt noise from horizontal acceleration. With these techniques, we obtained isolation factors of 10 to 20 simultaneously in all three degrees of freedom at 0.15 Hz. Title: The Laser Interferometer Space Antenna: An Overview Authors: Stebbins, Robin Bibcode: 2004APS..APR.L9001S Altcode: The Laser Interferometer Space Antenna (LISA) is a joint ESA-NASA mission that will explore the Universe for gravitational wave sources between 0.1 mHz and 1 Hz. Anticipated sources of gravitational waves include: the inspiral of supermassive black holes resulting from galactic mergers; the inspiral of intermediate mass black holes; the inspiral of compact objects into supermassive black holes; thousands of close, compact binaries in our own Galaxy; and, possibly, density fluctuations in the early universe if their (much more uncertain) amplitude permits. LISA consists of three spacecraft orbiting the Sun in a triangular formation. Gravitational waves are detected by interferometrically monitoring the 5 million kilometer separations between free-falling reference masses within the spacecraft. LISA employs technology from Â"drag-freeÂ" control systems, spaceborne accelerometers, microthrusters, interferometric distance-ranging and precision measurements to measure strains of 10-23 over very long baselines. Title: Current error estimates for LISA spurious accelerations Authors: Stebbins, R. T.; Bender, P. L.; Hanson, J.; Hoyle, C. D.; Schumaker, B. L.; Vitale, S. Bibcode: 2004CQGra..21S.653S Altcode: The performance of the LISA gravitational wave detector depends critically on limiting spurious accelerations of the fiducial masses. Consequently, the requirements on allowable acceleration levels must be carefully allocated based on estimates of the achievable limits on spurious accelerations from all disturbances. Changes in the allocation of requirements are being considered, and are proposed here. The total spurious acceleration error requirement would remain unchanged, but a few new error sources would be added, and the allocations for some specific error sources would be changed. In support of the recommended revisions in the requirements budget, estimates of plausible acceleration levels for 17 of the main error sources are discussed. In most cases, the formula for calculating the size of the effect is known, but there may be questions about the values of various parameters to use in the estimates. Different possible parameter values have been discussed, and a representative set is presented. Improvements in our knowledge of the various experimental parameters will come from planned experimental and modelling studies, supported by further theoretical work. Title: LISA data reduction Authors: Stebbins, R. T.; Bender, P. L.; Folkner, W. M. Bibcode: 2003AdSpR..32.1259S Altcode: The passage of gravitational waves changes the arm lengths between corners of the LISA spacecraft formation. These changes are detected interferometrically and recorded as phase measurements. The time series are reduced to reveal several signal types. First, the strong periodic signals from all types of galactic binaries and any strong chirped signals are identified by template fitting, and removed. Then weak, periodic signals and poorly characterized signals (e.g., generic bursts) are searched for. Next, weak signals with complex waveforms, such as from compact objects orbiting massive black holes, are sought with templates. Genetic algorithms, template structure or hierarchical searches are used to efficiently search the very large parameter space. Finally, backgrounds from galactic binaries, extragalactic binaries and the Big Bang will/may be separable by their signatures. Title: Status of LISA phase measurement work in the US Authors: Pollack, S. E.; Jennrich, O.; Stebbins, R. T.; Bender, P. Bibcode: 2003CQGra..20S.193P Altcode: Currently there are two implementations for LISA phase measurement being investigated in the United States. In this paper, we present the current status of one of these implementations, the so-called zero-crossing approach or stopwatch method. This method uses a technique of counting and timing to make phase measurements. Herein we present a description of the status of an experiment which produces an optical LISA-like fringe which we use to test our phase meter. Title: Information about Intermediate Mass Black Hole Growth from Gravitational Waves Authors: Bender, P. L.; Stebbins, R. T. Bibcode: 2002AAS...201.5707B Altcode: 2002BAAS...34R1207B It is likely that coalescences of roughly 10 M/sun and probably 100 M/sun black holes (BHs) with intermediate mass black holes (IMBHs) occurred during the growth of the IMBHs in galactic nuclei and/or globular clusters. Thus it is interesting to review the types of associated gravitational wave (GW) signals that may be observable by the Laser Interferometer Space Antenna (LISA), a planned joint ESA/NASA mission, or by a later follow-on mission. For example, simulations by Abel, Bryan and Norman indicate high masses for the first stars, and a substantial fraction may form roughly 100 M/sun BHs. Madau and Rees have suggested that, if this occurs, perhaps a few tens of them can get to the nucleus in a Hubble time for Milky Way type galaxies. If some arrive while IMBHs are growing there and don't plunge in rapidly, they could give detectable GW signals. LISA could observe such signals for 100 M/sun BHs coalescing with non-rotating 10,000 M/sun or larger IMBHs even at z = 5, in agreement with the conclusions of Madau and Rees. In the future, if a high-frequency LISA follow-on mission is chosen, it might have 1 m diam. telescopes (instead of 0.3 m diam.), 10 W lasers, and 500,000 km arm lengths. With our present estimate of the GW background due to extragalactic white dwarf binaries, such a mission could observe 10 M/sun BHs coalescing with nonrotating IMBHs at z = 5 for IMBH masses between about 1,500 and 20,000 M/sun. Similar events could be observed out to z = 10 for Kerr IMBHs. Title: Seismic isolation for Advanced LIGO Authors: Abbott, R.; Adhikari, R.; Allen, G.; Cowley, S.; Daw, E.; DeBra, D.; Giaime, J.; Hammond, G.; Hammond, M.; Hardham, C.; How, J.; Hua, W.; Johnson, W.; Lantz, B.; Mason, K.; Mittleman, R.; Nichol, J.; Richman, S.; Rollins, J.; Shoemaker, D.; Stapfer, G.; Stebbins, R. Bibcode: 2002CQGra..19.1591A Altcode: The baseline design concept for a seismic isolation component of the proposed 'Advanced LIGO' detector upgrade has been developed with proof-of-principle experiments and computer models. It consists of a two-stage in-vacuum active isolation platform that is supported by an external hydraulic actuation stage. Construction is underway for prototype testing of a full-scale preliminary design. Title: Demonstration of the LISA phase measurement principle Authors: Jennrich, O.; Stebbins, R. T.; Bender, P. L.; Pollack, S. Bibcode: 2001CQGra..18.4159J Altcode: We present an experiment designed to test a type of phase measurement system that could be used for LISA. The set-up consists of two parts: one is an optical signal generator to provide an optical signal similar to that expected for the interferometry in LISA. The other is a phase-meter which uses a technique of counting and timing to measure the phase of the signal as a function of time. Title: Interferometric Techniques for Gravitational Wave Detection in Space Authors: Stebbins, Robin T; Bender, Peter L. Bibcode: 2000STIN...0009820S Altcode: The Laser Interferometer Space Antenna (LISA) mission will detect gravitational waves from galactic and extragalactic sources, most importantly those involving supermassive black holes. The primary goal of this project is to investigate stability and robustness issues associated with LISA interferometry. We specifically propose to study systematic errors arising from: optical misalignments, optical surface errors, thermal effects and pointing tolerances. This report covers the first fiscal year of the grant, from January 1st to December 31st 1999. We have employed an optical modeling tool to evaluate the effect of misplaced and misaligned optical components. Preliminary results seem to indicate that positional tolerances of one micron and angular tolerances of 0.6 millirad produce no significant effect on the achievable contrast of the interference pattern. This report also outlines research plans for the second fiscal year of the grant, from January 1st to December 31st 2000. Since the work under NAG5-6880 has gone more rapidly than projected, our test bed interferometer is operational, and can be used for measurements of effects that cause beam motion. Hence, we will design, build and characterize a sensor for measuring beam motion, and then install it. We are also planning a differential wavefront sensor based on a quadrant photodiode as a first generation sensor. Title: Active seismic isolation for enhanced LIGO detectors Authors: Giaime, Joseph; Lantz, Brian; Debra, Daniel; How, Jonathan; Hardham, Corwin; Richman, Sam; Stebbins, Robin Bibcode: 2000AIPC..523..300G Altcode: 2000grwa.conf..300G The levels of seismic isolation needed for LIGO II will require a dramatic technological shift from the systems used in the initial LIGO detector. To take advantage of the improved thermal noise of a 30 kg test mass made of high-Q material and suspended with fused silica fibers, one must attenuate the ground motion by more than 10 orders of magnitude at 10 Hz. Aggressive active isolation of ground motion to reduce the root-mean-squared ground displacement and the displacement noise in the gravitational wave band, coupled with multiple pendulum suspensions, can make this possible. We will describe the mechanical design for such a system, and discuss the issues of active control that confront this endeavor. . Title: Separation of LISA Galactic and Extragalactic Signals Authors: Bender, Peter L.; Hils, Dieter; Stebbins, Robin T. Bibcode: 2000APS..APRH20013B Altcode: Data obtained by the Laser Interferometer Space Antenna (LISA) is expected to include gravitational wave signals from several types of sources involving massive black holes at cosmological distances. In addition, there will be a very large number of signals from short period galactic binaries. For 1 year of observations, the average number of galactic binaries per frequency bin will be large enough at frequencies below 1 mHz so that most of their signals cannot be resolved. At higher frequencies, above roughly 3 mHz, most individual galactic signals can be solved for and removed from the data record. Studies have been started to investigate, for frequencies from roughly 1 to 10 mHz, how much information about the extragalactic black hole sources will be lost because of having to solve for the galactic sources. An axisymmetric but fairly realistic model is being used for the distribution of binaries in the galaxy. It probably will be desirable to subtract out some sources whose reality and signal parameters are only moderately certain, but whose frequency characteristics differ from the massive black hole signals of interest. Title: What Information May Gravitational Waves Carry About Early Galaxies? Authors: Bender, Peter L.; Hils, Dieter; Stebbins, Robin T. Bibcode: 1999ASPC..182..539B Altcode: 1999gady.conf..539B No abstract at ADS Title: Progress on Low-Frequency Active Vibration Isolation Authors: Richman, S. J.; Giaime, J. A.; Stebbins, R. T.; Bender, P. L.; Faller, J. E. Bibcode: 1999magr.meet.1066R Altcode: No abstract at ADS Title: LISA operations and sensitivity Authors: Stebbins, R. T.; LISA Team Bibcode: 1998AIPC..456...17S Altcode: 1998lain.conf...17S The three LISA spacecraft must monitor changes in their relative separation to about 10 pm. The various operating modes during the mission lifetime will be summarized, and the science mode will be described in detail. The science operations involve the optical system, the attitude and position control system, the on-board processing for signal extraction, telemetry and ground operations. The instrumental origins of the anticipated LISA sensitivity curve will also be described. Title: Experimental demonstration of some aspects of LISA interferometry Authors: Giaime, J. A.; Stebbins, R. T.; Bender, P. L.; Faller, J. E.; Hall, J. L. Bibcode: 1998AIPC..456..169G Altcode: 1998lain.conf..169G Plans are described to experimentally demonstrate at JILA a possible phase measurement technique for use in LISA interferometry. This demonstration will include use of a compact system for fringe generation and photodetection with realistic beam powers in a Mach-Zehnder interferometer, and development of a stable digital fringe phase measurement system. Title: Possible use of a narrow-field star tracker on the New Millennium SSI mission Authors: Bender, Peter L.; Stebbins, Robin T.; Folkner, William M. Bibcode: 1998SPIE.3350..626B Altcode: A separated spacecraft interferometer (SSI) demonstration mission with three spacecraft has been proposed for flight under the NASA New Millennium Technology Development Program. Both the rotation rate of the interferometer about the normal to the plane containing the three spacecraft and the orientation in the plane must be determined accurately in order to permit the detection of white light fringes from sources that have visual magnitudes as high as possible. It presently is planned to use signals from tracking the science object plus other auxiliary information to determine the interferometer rotation rate d(theta) /dt and the angular position (theta) . We have investigated a possible supplementary approach that makes use of a combined beacon tracker and narrow-field star tracker on one of the two collector spacecraft. A very small beacon mounted on the other collector spacecraft can be viewed with respect to a reference star nearly 180 degrees away to determine d(theta) /dt and (theta) for the interferometer. Beacon/star tracker observations over roughly an hour appear sufficient to determine the sweep rate for starlight fringes in the interferometer to adequate accuracy and to detect the fringes. Title: Gravitational Wave Frequency Range for the LISA Mission Authors: Folkner, W. M.; Bender, P. L.; Stebbins, R. T. Bibcode: 1998AAS...192.1708F Altcode: 1998BAAS...30..843F Studies of the Laser Interferometer Space Antenna mission are being pursued actively both in Europe and in the US. The present mission design calls for three spacecraft to be launched on a single Delta II launch vehicle and placed in an equilateral triangle configuration about 20 degrees behind the Earth in orbit around the Sun. Laser heterodyne measurements made over the 5 million km sides of the triangle permit the detection and detailed study of gravitational wave signals. The frequency range discussed for LISA usually has been limited to 0.0001 to 1 Hz because of reliance on passive thermal isolation to keep noise due to temperature fluctuations in the most sensitive part of the payload small. However, the possibility of actively controlling the temperature of the thermal shield around the payload is now being investigated. The expected improvement in the LISA sensitivity below 0.0001 Hz will be discussed. This would extend the useful sensitivity to include possible sources with larger masses, such as the coalescence of massive black holes after galaxy mergers. Title: On the Origin of Solar Oscillations Authors: Goode, Philip R.; Strous, Louis H.; Rimmele, Thomas R.; Stebbins, Robin T. Bibcode: 1998ApJ...495L..27G Altcode: 1998astro.ph..1008G We have made high-resolution observations of the Sun in which we identify individual sunquakes and see power from these seismic events being pumped into the resonant modes of vibration of the Sun. A typical event lasts about 5 minutes. We report the physical properties of the events and relate them to theories of the excitation of solar oscillations. We also discuss the local seismic potential of these events. Title: LISA Mission Concept Study, Laser Interferometer Space Antenna for the Detection and Observation of Gravitational Waves Authors: Folkner, W. M.; Bender, P. L.; Stebbins, R. T. Bibcode: 1998STIN...0055623F Altcode: This document presents the results of a design feasibility study for LISA (Laser Interferometer Space Antenna). The goal of LISA is to detect and study low-frequency astrophysical gravitational radiation from strongly relativistic regions. Astrophysical sources potentially visible to LISA include extra-galactic massive black hole binaries at cosmological distances, binary systems composed of a compact star and a massive black hole, galactic neutron star-black hole binaries, and background radiation from the Big Bang. The LISA mission will comprise three spacecraft located five million kilometers apart forming an equilateral triangle in an Earth-trailing orbit. Fluctuations in separation between shielded test masses located within each spacecraft will be determined by optical interferometry which determines the phase shift of laser light transmitted between the test masses. Title: Getting astrophysical information from LISA data Authors: Stebbins, R. T.; Bender, P. L.; Folkner, W. M. Bibcode: 1997CQGra..14.1499S Altcode: No abstract at ADS Title: LISA data acquisition Authors: Stebbins, R. T.; Bender, P. L.; Folkner, W. M.; LISA Science Team Bibcode: 1996CQGra..13A.285S Altcode: The method for measuring changes in the lengths of the three arms for the LISA gravitational-wave detector is described. Accurate phase measurements are required on signals with Doppler shifts of about 1 MHz for the two main arms of the interferometer, and up to 15 MHz for the third arm. This is accomplished by shifting the signal frequencies down to near 100 kHz, filtering and then timing zero crossings of the signals. The basic methods for correcting for the laser phase noise and for phase noise in the ultra-stable oscillators used to derive various radio frequencies are described briefly. The corrections are made on the spacecraft, before the data are telemetred to the ground. Title: Sensitivity of the LISA Gravitational Wave Mission Authors: Ward, H.; Bender, P.; Faller, J. E.; Stebbins, R. T. Bibcode: 1996APS..MAY..E901W Altcode: The sensitivity achievable by the Laser Interferometer Space Antenna (LISA) will be discussed (see also abstracts by Stebbins et al and by Bender and Hils). Below about 1 mHz, the sensitivity will be limited mainly by spurious accelerations of the proof mass in each spacecraft and by a random superposition of signals from many short period galactic binaries. At higher frequencies, the main limitations will come from shot noise in determining the difference in length of the interferometer arms and from fluctuations in the pointing of the laser beams. Hundreds to thousands of galactic binaries resolved in frequency and direction will be detectable throughout the galaxy. A few known sources will be included. One possible type of source is black hole-massive black hole (BH-MBH) binaries, with periapsis speeds of about half the speed of light, very rapidly precessing elliptical orbits, and possible fast orbit plane precession around Kerr MBHs. The observation of such signals or of those from MBH-MBH binaries would permit extremely strong tests of the dynamical predictions of general relativity. Title: The LISA Gravitational Wave Mission Authors: Stebbins, R. T.; Bender, P. L.; Faller, J. E.; Folkner, W. M.; Ward, H. Bibcode: 1996APS..MAY.J1506S Altcode: The Laser Interferometer Space Antenna (LISA) is a mission designed for detailed studies of gravitational waves with frequencies of roughly 0.1 mHz to 1 Hz. Gravitational waves will be detected by interferometrically monitoring the relative distances between proof masses in different spacecraft, separated by 5× 10^6 km. LISA will detect strains as low as 10-23 with a 1 yr observation time and a S/N ratio of 5. The sensitivity will be sufficient to detect many gravitational wave sources which cannot be readily observed by any other means. The 3-arm interferometer consists of 6 spacecraft orbiting the Sun, with two at each vertex of an equilateral triangle. Proof mass disturbances are kept small by a drag-free system and the benign environment of solar orbit. LISA was selected in 1994 as a Cornerstone mission in the proposed ESA Horizon 2000 Plus program. Technology development studies for LISA are being started by ESA. Investigations of possible US contributions to LISA currently are in progress under a NASA program for studies of new mission concepts in astrophysics. Title: The Sun's Acoustic Spectrum and Normal Mode Parameters Authors: Stebbins, R. T.; Hill, F.; Stark, P. B.; GONG Data Reduction Team; GONG Analysis Team Bibcode: 1996AAS...188.5306S Altcode: 1996BAAS...28..904S GONG seeks to measure the frequencies, amplitudes and line widths of the Sun's acoustic normal modes. The Project estimates these parameters for more than 250,000 acoustic modes of the Sun from every 36 day-long set of data. Data from the network are archived, calibrated, reduced to several science products and made available for distribution to researchers at the pace of observations. GONG also produces magnetograms and temporally filtered solar images for convective velocity and magnetic field studies. The frequency resolution of a single data set is 0.321 mu Hz. For m- averaged frequencies the median formal error is 0.044 mu Hz, and the associated median fractional frequency error is 1.6 x 10(-5) . Results from concatenated data sets are now becoming available. For a three-year data set, the fractional error is expected to be 3 x 10(-6) , providing the highest quality helioseismic frequency measurements to date. Examples of power spectra and mode parameters will be shown. To demonstrate the reliability of the initial GONG frequencies, m-averaged frequency measurements will be compared with other helioseismic data sets. The mean systematic variations among the data sets are 0.03 to 0.08 mu Hz. The differences arise from a combination of systematic errors, random errors, and possible changes in solar structure and dynamics. Error sources will be discussed. Title: The Solar Acoustic Spectrum and Eigenmode Parameters Authors: Hill, F.; Stark, P. B.; Stebbins, R. T.; Anderson, E. R.; Antia, H. M.; Brown, T. M.; Duvall, T. L., Jr.; Haber, D. A.; Harvey, J. W.; Hathaway, D. H.; Howe, R.; Hubbard, R. P.; Jones, H. P.; Kennedy, J. R.; Korzennik, S. G.; Kosovichev, A. G.; Leibacher, J. W.; Libbrecht, K. G.; Pintar, J. A.; Rhodes, E. J., Jr.; Schou, J.; Thompson, M. J.; Tomczyk, S.; Toner, C. G.; Toussaint, R.; Williams, W. E. Bibcode: 1996Sci...272.1292H Altcode: The Global Oscillation Network Group (GONG) project estimates the frequencies, amplitudes, and linewidths of more than 250,000 acoustic resonances of the sun from data sets lasting 36 days. The frequency resolution of a single data set is 0.321 microhertz. For frequencies averaged over the azimuthal order m, the median formal error is 0.044 microhertz, and the associated median fractional error is 1.6 x 10-5. For a 3-year data set, the fractional error is expected to be 3 x 10-6. The GONG m-averaged frequency measurements differ from other helioseismic data sets by 0.03 to 0.08 microhertz. The differences arise from a combination of systematic errors, random errors, and possible changes in solar structure. Title: Multiresolution-element imaging of extrasolar Earthlike planets Authors: Bender, Peter L.; Stebbins, Robin T. Bibcode: 1996JGR...101.9309B Altcode: It has been suggested recently that imaging of extrasolar Earthlike planets should be considered as a possible future goal of the NASA space program. As an aid to discussing what would be required in order to undertake imaging, a partial design is described for a separated spacecraft interferometer which could achieve images in the visible with 10 resolution elements across the planet. Between 15 and 25 large collector telescopes or clusters of telescopes spread out over roughly a 200-km baseline in solar orbit at 1 AU from the Sun or possibly in high Earth orbit are required. A very preliminary approach to the use of multispectral remote sensing techniques is discussed also. Finally, the generalization of this approach to larger numbers of resolution elements across the planet is considered. Clearly, imaging is possible only if the truly staggering problem of avoiding the 1010 times stronger scattered light from the nearby star can be overcome. However, even if this can be done, the amount and precision of the required hardware for even poor-quality images appears to present an obstacle to such a program which would be extremely difficult to overcome. Title: Active/Passive Vibration Isolation at 1 HZ and Above Part II: Main Stages Authors: Richman, S. J.; Newell, D. B.; Stebbins, R. T.; Bender, P. L.; Faller, J. E. Bibcode: 1996magr.meet.1426R Altcode: No abstract at ADS Title: Thermal Stability Analysis for a Heliocentric Gravitational Radiation Detection Mission Authors: Folkner, W. M.; McElroy, P.; Miyake, R.; Bender, P. L.; Stebbins, R. T.; Supper, W. Bibcode: 1996magr.meet.1655F Altcode: No abstract at ADS Title: Active/Passive Vibration Isolation at 1Hz and Above Part I: Single Stage, Six Degrees of Freedom Authors: Newell, D. B.; Richman, S. J.; Stebbins, R. T.; Nelson, P. G.; Mason, J. E.; Bender, P. L.; Faller, J. E. Bibcode: 1996magr.meet.1421N Altcode: No abstract at ADS Title: The LISA Gravitational Wave Mission Authors: Stebbins, R. T.; Bender, P. L.; Faller, J. E.; Hils, D.; Folkner, W. M. Bibcode: 1995AAS...187.7105S Altcode: 1995BAAS...27R1384S The Laser Interferometer Space Antenna (LISA) is a mission designed for detailed studies of gravitational waves with frequencies of roughly 0.0001 to 1 Hz. It is a Cornerstone mission in the proposed ESA Horizon 2000 Plus program. Investigations of possible US contributions to LISA currently are in progress under the NASA program for studies of new mission concepts in astrophysics. LISA is a formation of 6 spacecraft in the shape of an equilateral triangle 5 million km on a side, with 2 spacecraft at each vertex. The formation is in orbit around the Sun, following about 20(deg) behind the Earth. Orbital parameters are chosen so that the distances between the spacecraft stay nearly constant for years. Each spacecraft is made drag-free by keeping it centered on a carefully shielded test mass at its center. Laser distance measurements are made between the test masses using roughly 0.5 W per beam and about 40 cm diameter telescopes. Laser phase noise can be determined by observing the apparent changes in the 5 million km arm lengths, since the real variations in the arm lengths at the frequencies of interest are very small. The desired gravitational wave signals are obtained from the corrected differences in the arm lengths. For 1 yr of observations and a S/N of 5, the LISA sensitivity reaches its maximum of 10(-23) at frequencies of 0.001 to 0.03 Hz. This sensitivity is sufficient to detect sources such as a 5 to 10M_sun black hole orbiting around and coalescing with a roughly 10(6M_sun) black hole at z=1. Scenarios in which such events would be observed appear to be quite plausible if 0.01% or more of the stars in the cusps around supermassive black holes in galactic nuclei are black holes. Coalescences of two supermassive black holes after galactic or pregalactic mergers also may be observed. For short period galactic binaries, hundreds to thousands of individual sources will be resolved and their distribution in the galaxy determined. Title: Dark Lanes in Granulation and the Excitation of Solar Oscillations Authors: Rimmele, T. R.; Goode, P. R.; Strous, L. H.; Stebbins, R. T. Bibcode: 1995ESASP.376b.329R Altcode: 1995help.confP.329R; 1995soho....2..329R No abstract at ADS Title: 15-m laser-stabilized imaging interferometer Authors: Stebbins, Robin T.; Bender, Peter L.; Chen, Che Jen; Page, Norman A.; Meier, D.; Dupree, A. K. Bibcode: 1995SPIE.2477...31S Altcode: The LAser-Stabilized Imaging Interferometer (LASII) concept is being developed as an astronomical telescope for the next generation of optical resolution beyond Hubble Space Telescope (HST). The essential ingredients are: a rigid and stable structure to minimize mechanical and thermal distortion, active control of the optical geometry by a laser metrology system, a self-deploying structure fitting into a single launch vehicle, and ultraviolet operation. We have modified earlier design concepts to fit the scale of an intermediate sized NASA mission. Our present design calls for 24 0.5 m apertures in a Mills Cross configuration, supported on four trusses. A fifth truss perpendicular to the primary surface would support the secondary mirror and the laser metrology control points. Either separate interferometers or two guide telescopes would track guide stars. This instrument would have about 6 times the resolution of HST in the visible and the same collecting area. The resolution would reach 2.5 mas at 150 nm. The primary trusses would fold along the secondary truss for launch, and automatically deploy on orbit. Possible orbits are sun-synchronous at 900 km altitude, high earth orbit or solar orbit. Infrared capability could be included, if desired. Title: Dark Lanes in Granulation and the Excitation of Solar Oscillations Authors: Rimmele, Thomas R.; Goode, Philip R.; Harold, Elliotte; Stebbins, Robin T. Bibcode: 1995ApJ...444L.119R Altcode: We made simultaneous, high-resolution observations of the Sun's granulation and solar acoustic events in the photosphere. We find that the acoustic events, which are a local by-product of the excitation of solar oscillations (Goode, Gough, & Kosovichev 1992), occur preferentially in the dark, intergranular lanes. At the site of a typical acoustic event the local granulation becomes darker over several minutes leading up to the event with a further, abrupt darkening immediately preceding the peak of the event. Further, the stronger the acoustic event the darker the granulation. Thus, the excitation of solar oscillations seems more closely associated with the rapid cooling occurring in the upper convection layer, rather than the overshooting of turbulent convection itself. We find no substantial role for so-called 'exploding' granules in the excitation of solar oscillations. Title: Photospheric Wave Behavior Authors: Stebbins, R. T.; Rimmele, T. R.; Goode, P. R. Bibcode: 1995ASPC...76..354S Altcode: 1995gong.conf..354S No abstract at ADS Title: The Global Oscillation Network Group Site Survey - Part One Authors: Hill, Frank; Fischer, George; Grier, Jennifer; Leibacher, John W.; Jones, Harrison B.; Jones, Patricia P.; Kupke, Renate; Stebbins, Robin T. Bibcode: 1994SoPh..152..321H Altcode: The Global Oscillation Network Group (GONG) Project is planning to place a set of instruments around the world to observe solar oscillations as continuously as possible for at last three years. The Project has now chosen the sites that will comprise the network. This paper describes the methods of data collection and analysis that were used to make this decision. Title: The Global Oscillation Network Group Site Survey - Part Two Authors: Hill, Frank; Fischer, George; Forgach, Suzanne; Grier, Jennifer; Leibacher, John W.; Jones, Harrison P.; Jones, Patricia B.; Kupke, Renate; Stebbins, Robin T.; Clay, Donald W.; Ingram, Robert E. L.; Libbrecht, Kenneth G.; Zirin, Harold; Ulrichi, Roger K.; Websteri, Lawrence; Hieda, Lester S.; Labonte, Barry J.; Lu, Wayne M. T.; Sousa, Edwin M.; Garcia, Charles J.; Yasukawa, Eric A.; Kennewell, John A.; Cole, David G.; Zhen, Huang; Su-Min, Xiao; Bhatnagar, Arvind; Ambastha, Aashok; Al-Khashlan, Abdulrahman Sa'ad; Abdul-Samad, Muhammad-Saleh; Benkhaldoun, Zouhair; Kadiri, Samir; Sánchez, Francisco; Pallé, Pere L.; Duhalde, Oscar; Solis, Hernan; Saá, Oscar; González, Ricardo Bibcode: 1994SoPh..152..351H Altcode: The Global Oscillation Network Group (GONG) Project will place a network of instruments around the world to observe solar oscillations as continuously as possible for three years. The Project has now chosen the six network sites based on analysis of survey data from fifteen sites around the world. The chosen sites are: Big Bear Solar Observatory, California; Mauna Loa Solar Observatory, Hawaii; Learmonth Solar Observatory, Australia; Udaipur Solar Observatory, India; Observatorio del Teide, Tenerife; and Cerro Tololo Interamerican Observatory, Chile. Title: Observation of Impulsive Acoustic Events and the Excitation of Solar Oscillations Authors: Restaino, Sergio R.; Stebbins, Robin T.; Goode, Philip R. Bibcode: 1993ApJ...408L..57R Altcode: The 5 minute solar oscillation has been exploited in numerous seismic studies in which internal properties of the sun have been inferred. It is generally regarded that these modes are excited by turbulent convection in the sun's outermost layers. We observe the oscillatory wakes caused by impulsive events, related to those described in 1909 by Lamb. These correspond to the events modeled by Goode et al. (1992) which they associate with excitation of the global 5-min oscillations. Title: Observation of impulsive acoustic events and the excitation of solar oscillations Authors: Restaino, Sergio R.; Stebbins, Robin T.; Goode, Philip R. Bibcode: 1992njit.rept.....R Altcode: The five-minute solar oscillation has been exploited in numerous seismic studies in which internal properties of the Sun have been inferred. It is generally regarded that these modes are excited by turbulent convection in the Sun's outermost layers. The oscillatory wakes caused by impulsive events were observed, matching those described by Lamb (1909). These correspond to the events modeled by Goode, et al., which they associate with excitation of the global five-minute oscillations. Title: Movies of Velocity and Acoustic Flux in the Solar Photosphere Authors: Stebbins, R. T.; Restaino, S. R.; Goode, P. R. Bibcode: 1992AAS...180.0605S Altcode: 1992BAAS...24..737S CCD images of FeI 5434 Angstroms line profiles have previously been collected and analyzed for the average characteristics of wave propagation in the photosphere. The previous analysis determined the velocity at nine depths in the spectral line and 100 horizontal spatial points spanning 70 arc sec. Time series of these velocity frames, lasting 37 minutes, have been Fourier transformed and filtered to pass the five minute modes of the Sun. Through the Hilbert transform and the analytic signal, the instantaneous velocity amplitude and phase were computed at every point in the three dimensional space of altitude, horizontal slit position and time. These data have been further processed to create color-contour maps of vertical acoustic propagation at each time sample. Velocity amplitude, velocity phase, kinetic energy density and acoustic flux are all mapped. Time series of these maps have been assembled into a movie which shows the evolution of vertical acoustic propagation. This movie is a complete visualization of sound waves in the photosphere, based on observation. The amplitude and kinetic energy density behaves as one might expect in the presence of the solar p-modes. However, the phase and acoustic flux have characteristic spatial and temporal scales which are very different from the amplitude. For example, upward and downward flux may occur in the same amplitude structure at different times, or at the same time. These results are consistent with the localized model of p-mode excitation advanced by Goode, Gough and Kosovichev. Title: Gravitational radiation observations on the moon Authors: Stebbins, R. T.; Armstrong, J. W.; Bender, P. L.; Drever, R. W. P.; Hellings, R. W.; Saulson, P. R. Bibcode: 1990AIPC..207..637S Altcode: 1990am...proc..637S A Laser-Interferometer Gravitational-Wave Observatory (LIGO) is planned for operation in the United States, with two antennas separated by several thousand kilometers. Each antenna would incorporate laser interferometers with 4 km arm lengths, operating in vacuum. The frequency range covered initially would be from a few tens of Hz to a few kHz, with possible extension to lower frequencies later. Similar systems are likely to be constructed in Europe, and there is a possibility of at least one system in Asia or Australia. It will be possible to determine the direction to a gravitational wave source by measuring the difference in the arrival times at the various antennas for burst signals or the phase difference for short duration nearly periodic signals. The addition of an antenna on the Moon, operating in support of the Earth-based antennas, would improve the angular resolution for burst signals by about a factor 50 in the plane containing the source, the Moon, and the Earth. This would be of major importance in studies of gravitational wave sources. There is also a possibility of somewhat lower noise at frequencies near 1 Hz for a lunar gravitational wave antenna, because of lower gravity gradient noise and microseismic noise on the Moon. However, for frequencies near 0.1 Hz and below, a 107 km laser gravitational wave antenna in solar orbit would be much more sensitive. Title: A lunar gravitational wave antenna using a laser interferometer Authors: Stebbins, R. T.; Bender, P. L. Bibcode: 1990AIPC..202..188S Altcode: 1990palb.work..188S A moon-based laser interferometer for detecting gravitational radiation could detect signals in the band 10-1 to 104 Hz. A preliminary evaluation of the noise budget for an optimistic antenna design is reported here and compared to that for other planned gravitational wave interferometers. Over most of the frequency range, the sensitivity is controlled by the thermal noise in the test mass suspensions. From roughly 3 to a few hundred Hertz, it is about the same as the sensitivity expected in terrestrial antennas of the same construction, which will have been operating for at least a decade. Below 0.3 Hz, a proposed space-based interferometer, designed for operation down to 10-5 Hz, would have better sensitivity. As pointed out by others, the most important role of a lunar antenna would be the improved angular resolution made possible by the long baseline to terrestrial antennas. Title: An Algorithm for Removing Pattern Noise in Reticons Authors: Stebbins, R. T.; Restaino, S. R. Bibcode: 1990BAAS...22R.887S Altcode: No abstract at ADS Title: Optical interferometer in space. Authors: Bender, Peter L.; Faller, J. E.; Hall, J. L.; Hils, D.; Stebbins, R. T.; Vincent, Mark A. Bibcode: 1989NASCP3046...80B Altcode: 1989rges.rept...80B The present design concepts for a Laser Gravitational-Wave Observatory in Space are described. Laser heterodyne distance measurements are made between test masses located in three spacecraft separated by roughly 106km. The science objectives are: to measure discrete sinusoidal gravitational wave signals from individual sources with periods of 1 second to 1 day; to measure the stochastic background due to unresolved binaries; and to search for gravitational wave pulses with periods longer than 1 second from possible exotic sources such as gravitational collapse of very massive objects. Title: Disturbance Reduction Techniques for a Laser Gravitational Wave Observatory in Space Authors: Bender, P. L.; Faller, J. E.; Hils, D.; Stebbins, R. T. Bibcode: 1989grg..conf..566B Altcode: No abstract at ADS Title: a 1-TO-10-HZ Prototype Isolation System for Gravitational Wave Interferometers and Thermal Noise Measurements Authors: Stebbins, R. T.; Bender, P. L.; Faller, J. E.; Newell, D. B.; Speake, C. C. Bibcode: 1989grg..conf..585S Altcode: No abstract at ADS Title: Wave Behavior in the Solar Photosphere - a Comparison of Theory and Observation Authors: Marmolino, Ciro; Stebbins, Robin T. Bibcode: 1989SoPh..124...23M Altcode: We report detailed comparisons between theoretical and empirical eigenfunctions of velocity and intensity for the 5-min modes in the photosphere. The comparison process is accomplished by obtaining synthetic profiles of the FeI λ5434 Å line in the presence of waveforms given by dynamical calculations and then applying a common procedure of reduction both to the observed and to the synthetic data. For the velocity waveforms, our results show a general agreement between theory and observations together with some systematic differences; in particular the theory systematically underestimates the observations in the low photosphere. These systematic differences are stressed by the intensity results since both the computed amplitudes and phases appear to be wrong in the deeper layers. Title: An antenna for laser gravitational-wave observations in space Authors: Faller, J. E.; Bender, P. L.; Hall, J. L.; Hils, D.; Stebbins, R. T.; Vincent, M. A. Bibcode: 1989AdSpR...9i.107F Altcode: 1989AdSpR...9..107F Progress during the past two years on a proposed Laser Gravitational-Wave Observatory in Space (LAGOS) is discussed. Calculated performance for a 106 km sized antenna over the frequency range of 10-5 to 1 Hz is given. The sensitivity from 10-3 to 10-1 Hz is expected to be 1 × 10-21/Hz0.5. Noise sources such as accelerations of the drag-free test masses by random molecular impacts and by fluctuations in the net thermal radiation pressure will limit the sensitivity at lower frequencies. The scientific objectives are the observation of CW gravitational waves from large numbers of binary systems and the detection of pulses which may have been emitted during the period of galaxy formation. Title: The 5-minute oscillation in the solar photosphere - Theoretical behaviour versus observations Authors: Marmolino, C.; Stebbins, R. T. Bibcode: 1989MmSAI..60...71M Altcode: Calculations are used to explore how theoretical waveforms for the five-minute solar oscillation reproduce the observed behavior of the solar Fe I 5434 A line. Comparison of theoretical and empirical velocity eigenfunctions shows some systematic differences in a framework of general agreement. The theory systematically underestimates the observations in both amplitude and phase shift in the low photosphere; the differences between the various theoretical treatments is much smaller than the difference between theory and observation. The intensity agreement is poor, with the theoretical treatments again differing much less with each other than with observation. These results are evidence for systematic problems with the assumptions involved in the calculation of the waveforms pertaining to the deeper layers of the photosphere. Title: Preliminary Optical Design for a Laser Gravitational Wave Antenna in Space Authors: Bender, P. L.; Faller, J. E.; Hall, J. L.; Hills, D.; Stebbins, R. Bibcode: 1988soae.conf...12B Altcode: No abstract at ADS Title: Waves in the Solar Photosphere Authors: Stebbins, Robin; Goode, Philip R. Bibcode: 1987SoPh..110..237S Altcode: Time-sequences of line profile data have been subjected to a unique analysis which produces an amplitude and phase of the velocity and intensity at several line depths for each time sample and spatial point on the Sun. The data have been filtered to pass only the frequencies and spatial wavenumbers of the 5-min band. Yet, a secondary oscillation emerges, the phase of which propagates downward. Empirical eigenfunctions for velocity and intensity are given, and the kinetic energy flux is computed. Title: Proposed studies of a 30-meter imaging interferometer concept Authors: Stebbins, R. T.; Bender, P. L.; Faller, J. E. Bibcode: 1987ESASP.273...85S Altcode: 1987ois..work...85S An imaging interferometer in space based on the use of 15 m sections of graphite-epoxy truss structure to form the basic mechanical support system is suggested. One simple design is a Y-shaped array of 3 coplanar arms, each 15 m long and 1.5 m in diameter, together with a perpendicualr mast of similar length. Roughly 15 observing telescopes of 0.5 m diameter would be used, with laser interferometers controlling the optical pathlengths. The total mass of the imaging interferometer is 3000 kg. With this design, the entire interferometer can be carried to orbit with a single STS launch and then deployed. The interferometer could be operated either in a fully illuminated Sun-synchronous orbit at 1400 km altitude or loosely attached to the Space Station. Title: A Simple Irradiance Monitor for Testing Solar Global Oscillation Network Sites Authors: Fischer, G.; Hill, F.; Jones, W.; Leibacher, J.; McCurnin, W.; Stebbins, R.; Wagner, J. Bibcode: 1986SoPh..103...33F Altcode: We describe a simple irradiance monitor intended for use in assessing the suitability of candidate sites for a worldwide network of small solar telescopes. The network will observe the Sun as continuously as possible in order to provide high quality solar oscillation data with low diurnal sidelobe contamination and high temporal frequency resolution. Title: Observation of Solar Brightness Oscillations at the South Pole Authors: Stebbins, R. T.; Ronan, R.; Arrambide, M. Bibcode: 1985AnJUS..20..219S Altcode: No abstract at ADS Title: A preliminary report on brightness oscillation observations made at South Pole during the 1982-83 Austral Summer Authors: Stebbins, R. Bibcode: 1984MmSAI..55..229S Altcode: No abstract at ADS Title: Observations of Solar Oscillations at the South Pole Authors: Stebbins, R. T.; Mann, R. Bibcode: 1984AnJUS..18..268S Altcode: No abstract at ADS Title: The measurement of long-period oscillations at Sacramento Peak Observatory and South Pole Authors: Stebbins, R.; Wilson, C. Bibcode: 1983SoPh...82...43S Altcode: 1983IAUCo..66...43S A program to measure long-period brightness oscillations at the solar limb has been pursued at Sacramento Peak Observatory for several years. Past improvements in observing technique and data analysis are reviewed. The encouraging results aid in the verification of the reality and the origin of oscillatory signals. However, the main stumbling block to this and other observational programs is the length of observing sequences imposed by the day/night cycle. The South Pole has received considerable attention as a site where extended observations might be possible. Currently, the Sacramento Peak program is developing a South Pole telescope designed for the observing technique and data analysis proven in Sunspot. A review of pertinent South Pole site parameters is given here for other workers who may be considering South Pole observations. Observing sequences longer than 150 hr are possible, though rare. Data sets of this duration are very attractive for solar oscillation studies. Title: Observation of five-minute-period gravity waves in the solar photosphere Authors: Stebbins, R. T.; Goode, Philip R.; Hill, Henry A. Bibcode: 1983SoPh...82..163S Altcode: 1983IAUCo..66..163S Vertically propagating traveling waves have been observed in the solar photosphere. These waves have a period of 278 ± 41 seconds and a vertical phase velocity of about 2 km s-1. It is noted that these waves also have approximately the same period as the well-studied five-minute-period acoustic mode, which is evanescent in the photosphere. The only consistent interpretation of the traveling waves implies that they are gravity waves. About half the time the gravity waves are outgoing, while the remainder of the time they are ingoing. Title: Observations of Solar Oscillations at the South Pole Authors: Stebbins, R. T.; Mann, R. Bibcode: 1983AnJUS..18..268S Altcode: No abstract at ADS Title: Observation of nonacoustic, 5 minute period, vertical traveling waves in the photosphere of the sun Authors: Hill, H. A.; Goode, P. R.; Stebbins, R. T. Bibcode: 1982ApJ...256L..17H Altcode: Nonacoustic, radially propagating traveling waves have been observed in the solar photosphere. These traveling waves have a period of 278 + or - 41 s. The vertical wavelength (approximately 500 km) and phase velocity (approximately 2 km/s) of the waves are among their properties deduced from the data. It is also observed that the waves have outgoing phase part of the time and ingoing phase the remainder of the time. The traveling waves are interpreted to be gravity waves. Their role in the heating of the chromosphere is discussed. Title: Observation of Photospheric Gravity Waves Authors: Stebbins, R. T.; Goode, P. R.; Hill, H. A. Bibcode: 1981BAAS...13..858S Altcode: No abstract at ADS Title: Vacuum Solar Telescope Alignment System Authors: Dunn, R.; Spence, G.; Stebbins, R.; Hill, H. Bibcode: 1981siwn.conf..613D Altcode: No abstract at ADS Title: A Antarctic Telescope Authors: Stebbins, R. Bibcode: 1981siwn.conf..390S Altcode: No abstract at ADS Title: Extended Observations of Solar Oscillations Authors: Stebbins, R. T.; Mann, R. Bibcode: 1981AnJUS..16..223S Altcode: No abstract at ADS Title: Observational tests of pulsation theory in the solar envelope Authors: Stebbins, R. T.; Hill, H. A.; Zanoni, R.; Davis, R. E. Bibcode: 1980LNP...125..381S Altcode: 1980nnsp.work..381S An improved observing technique has been used to look for long period oscillations in the brightness of the extreme solar limb. This technique provides a means for analyzing power spectra to secure a signature characteristic of the signal's origin. Results show significant improvement in the discrimination between solar oscillations, other signals, and noise. Long period intensity oscillations can be seen at the extreme solar limb. Title: Observations of long period oscillations in the solar limb darkening function Authors: Stebbins, R. T. Bibcode: 1980LNP...125..191S Altcode: 1980nnsp.work..191S The FFTD (finite Fourier transform definition) method was extended by simultaneous application of multiple edge definitions in a study of long period solar oscillations. Results are presented as evidence of the reality of long period brightness oscillations in the solar limb darkening function. Title: Analysis of Pulsation Theory Tests in the Solar Envelope Authors: Stebbins, R. T. Bibcode: 1979BAAS...11..398S Altcode: No abstract at ADS Title: Empirical tests of solar pulsation theory. Authors: Stebbins, R. T. Bibcode: 1978BAAS...10..730S Altcode: No abstract at ADS Title: Long-period oscillations of the apparent solar diameter: observations. Authors: Brown, T. M.; Stebbins, R. T.; Hill, H. A. Bibcode: 1978ApJ...223..324B Altcode: New observations of the time-varying component of the apparent solar diameter are reported. Power spectra derived from these observations reveal narrow-band oscillations at frequencies consistent with the normal mode frequencies of a standard solar model. The amplitudes of these oscillations are discussed and related to the observations of other investigators. A detailed analysis of the experiment and its associated sources of error is presented and used to show that there is a very small likelihood that the power spectrum peaks are due to nonsolar causes. Title: Observations of Long Period Solar Oscillations. Authors: Stebbins, R. Bibcode: 1977BAAS....9R.568S Altcode: No abstract at ADS Title: Observed Oscillations of the Apparent Solar Diameter Authors: Brown, T. M.; Stebbins, R. T.; Hill, H. A. Bibcode: 1976ssp..conf....1B Altcode: No abstract at ADS Title: Recent solar oblateness observations: data, interpretation, and significance for earlier work. Authors: Hill, H. A.; Stebbins, R. T. Bibcode: 1975NYASA.262..472H Altcode: The paper compiles the evidence necessary for the interpretation of an observed solar oblateness. Emphasis is on time-varying excess brightness, intrinsic visual oblateness, and normal oscillation modes of the sun. Solar edge definition is discussed, with particular attention paid to the finite Fourier transform definition. The possible role of solar oblateness in gravitation theory is considered. Title: The finite Fourier transform definition of an edge on the solar disk. Authors: Hill, H. A.; Stebbins, R. T.; Oleson, J. R. Bibcode: 1975ApJ...200..484H Altcode: A technique for locating the edge of the sun is proposed. The technique uses a finite Fourier transform of the observed limb-darkening function to achieve reduced sensitivity to atmospheric and instrumental effects and heightened sensitivity to the shape of the intrinsic limb-darkening function. A theory is developed that predicts these sensitivities. In order to facilitate wider application, general relations are calculated. A testing program which complements the theory is also reported. The location of the edge is shown to be influenced only by solar phenomena down to the milli-arcsecond range. Title: The intrinsic visual oblateness of the sun. Authors: Hill, H. A.; Stebbins, R. T. Bibcode: 1975ApJ...200..471H Altcode: Solar oblateness observations are reported which yield a value of 18.4 plus or minus 12.5 milli-arcsec for the difference between equatorial and polar diameters. These observations were conducted when the time-varying excess equatorial brightness was markedly reduced, greatly simplifying the interpretation of the apparent solar oblateness. The experimental scheme for defining the 'edge' of the sun and monitoring the shape of the extreme limb-darkening function is summarized along with a description of the instrumentation. Sources of systematic error are exhaustively surveyed to extract the intrinsic visual oblateness of the sun. The result further strengthens the conclusion of Hill et al. (1974) that the grave consequence of the Dicke-Goldenberg (1967) work for Einstein's general theory of relativity is removed. This result excludes an oblateness as large as that required by the rapidly rotating interior models used to explain the low neutrino flux. Title: INVITED PAPER - Recent Progress in Solar Oblateness Studies Authors: Hill, H. A.; Stebbins, R. T.; Brown, T. M. Bibcode: 1975BAAS....7R.478H Altcode: No abstract at ADS Title: Solar Oblateness, Excess Brightness, and Relativity. Authors: Hill, H. A.; Clayton, P. D.; Patz, D. L.; Healy, A. W.; Stebbins, R. T.; Oleson, J. R.; Zanoni, C. A. Bibcode: 1975PhRvL..34Q.296H Altcode: No abstract at ADS Title: An observational investigation of the solar oblateness Authors: Stebbins, Robin Tucker Tuck Bibcode: 1975PhDT.......304S Altcode: No abstract at ADS Title: Errata: "Solar oblateness, excess brightness, and relativity" [Phys. Rev. Lett., Vol. 33, p. 1497 - 1500 (1974)]. Authors: Hill, H. A.; Clayton, P. D.; Patz, D. L.; Healy, A. W.; Stebbins, R. T.; Oleson, J. R.; Zanoni, C. A. Bibcode: 1975PhRvL..34..296H Altcode: No abstract at ADS Title: An Observational Investigation of the Solar Oblateness. Authors: Stebbins, R. T. Bibcode: 1975PhDT.........8S Altcode: In recent years, the sun's figure has come under close scrutiny because it may reflect certain properties of the solar interior, and because an aspherical solar mass would alter the interpretation of a basic test of gravitation theories. A flurry of activity in this area has been triggered by the 1967 report of an equatorial diameter significantly larger than the polar diameter. A measurement of the solar oblateness using different experimental techniques which finds no comparable oblateness is reported. Further, the evidence indicates an explanation for the disagreement between previous results. A number of other interesting facets of the sun are also revealed. Title: Solar Oblateness, Excess Brightness, and Relativity Authors: Hill, H. A.; Clayton, P. D.; Patz, D. L.; Healy, A. W.; Stebbins, R. T.; Oleson, J. R.; Zanoni, C. A. Bibcode: 1974PhRvL..33.1497H Altcode: New observations show a small difference between the sun's polar and equatorial limb darkening functions. This excess equatorial brightness varies in time and can be of sufficient magnitude to account for the solar oblateness inferred by Dicke and Goldenberg from their measurements. This removes the serious consequence of their work for Einstein's general theory of relativity. The problems of a solar-edge definition and the derivation of a solar mass quadrupole moment are discussed. Title: Upper Limit on the Gravitational Flux Reaching the Earth from the Crab Pulsar Authors: Levine, Judah; Stebbins, Robin Bibcode: 1972PhRvD...6.1465L Altcode: A 30-m laser interferometer has been used in a search for gravitational radiation from the Crab pulsar. The minimum detectable signal would be produced by an incident gravitational flux of 109 ergs/sec cm2 and we find no effect at this level.