DUTCH OPEN TELESCOPE Report for NOVA ISC meeting nr. 12 October 30, 2002 R.J. Rutten, F.C.M. Bettonvil, P. Suetterlin Overall status -------------- The "DOT science exploitation period" during 2002-2004 is funded by UU, NWO, NOVA and EC, following the recommendations of the DOT Evaluation Committee (summer 2001), to - complete and exploit multi-wavelength solar speckle imaging for atmospheric tomography; - automate and safeguard DOT control to permit common-user operation. All work since March addressed these goals. Detail is given below. At present two of the six wavelength channels are working; two more will follow soon. The two "difficult" ones (tunable Lyot filters for Balmer-alpha and Ba II 4554) are planned for next year. The DOT participated in two multi-telescope observing campaigns since March. Our principal next priority is to speed up the speckle processing, presently limiting DOT exploitation to a few campaigns per year, through parallel/distributed processing. When frequent observing becomes practical we aim to initiate student-serviced peer-reviewed time allocation. The goal is to participate often in international multi-telescope campaigns by mid-2004. Project management ------------------ The DOT team presently consists of R.J. Rutten, R. H. Hammerschlag, P. Suetterlin, F.C.M. Bettonvil and D. van Tricht, with technical support from SIU programmer E.B.J. van der Zalm (part-time) and from the UU Faculty workshop IGF (including technician P.W. Hoogendoorn full-time). R.J. Rutten (solar physicist, project scientist) accepted a professor appointment at the Institute of Theoretical Astrophysics of Oslo University. This part-time (4-5 visits of a week per year) appointment strengthens DOT science by tapping another source of undergraduate and graduate students and also strengthens the triangular ties between Utrecht, Oslo and Stockholm. Oslo shares in the cost of the New Swedish Solar Telescope (recently completed, 96~cm aperture, first Nature paper in press) from whose building the DOT is operated in close collaboration. Two ex-Utrecht students start soon as postdocs at Oslo. P. Suetterlin (solar physicist, speckle expert, principle DOT observer, responsible for all DOT speckle reconstructions so far) was hired as NWO postdoc (May 1 2002 - April 30 2004) after his EC-TMR ESMN network postdocship ended. F.C.M. Bettonvil (optics and mechanical engineering, IGF contact point) has his contract with NWO via ASTRON renewed (October 1 2002 - September 30 2005). Technician D. van Tricht is hired on external funding (SOZOU) for one year starting October 1 2002. He continues work on DOT automation and safeguarding that he started as graduation project in engineering school. UU student A.G. de Wijn graduates October 28 both in astronomy on DOT research and in computational physics on parallelizing the DOT speckle code. He will start as DOT AIO on November 1. The EC-RTN ESMN network contract ((UU coordinator) was signed on October 17. The UU postdoc has been selected: K. Tziotziou will commence early next year for 2.5 years. He specialised as EC-TMR ESMN postdoc at Meudon in precisely the Balmer-alpha data inversions that are needed to interprete future DOT observations. The UU search for a professor in solar physics is gearing up. Search committee members and prospective candidates have been identified tentatively; official installation of the search committee by the Dean of the Faculty Natuur- en Sterrenkunde comes next. It is most likely that the eventual solar physics professor will be willing to accept DOT PI-ship for NOVA phase 2. Progress since ISC 11 --------------------- The major technical advance was the successful installation of a sophisticated focus control system. During the speckle reconstruction of last autumn's dual-channel sequences it became clear that temperature drifts affect the DOT focus more than can be diagnosed and corrected from real-time image inspection. The original DOT video acquisition system (camera, analog fiber link, frame grabber, image analysis software) was turned into a focus monitor using phase-diverse image contrast as diagnostic. It permits accurate focus adjustment. The camera and optics were mounted along the telescope top besides the incoming beam, at the other side from the multi-channel optics system. Automatic closed-loop focusing is foreseen but is not a high priority. The bad-weather canopy opening and closing control has successfully been automated. This is an important step in DOT safeguarding. The multi-channel beam and the focusing beam cross the incoming beam, from the telescope axis to the respective mounting platforms besides the telescope top. Extensive experiments showed that the initially employed guide-pipes, designed to inhibit straylight and dust contamination, affected the image quality noticeably. Their removal improved the diffraction pattern considerably. The DOT platform received a wooden floor consisting of removable panels, instead of the rather risky and deteriorating canvas cover used so far. The floor is needed for bad-weather protection and is partially or fully removed during the observing, depending on the conditions. The Ca II H channel and the red channel (continuum near H-alpha) are in fabrication at IGF, with completion estimated by the end of this year (see "critical issues" below). The upgrade of the speckle-burst acquisition and fiber link software, also being done by IGF, should also be completed by the end of the year. The optics elements required for the Ba II 4554 channel are all in house. The speckle reconstruction code was optimised. A parallel version resulted from A. de Wijn's graduation work who ported it from IDL to C and implemented parallelization including performance tests on small Beowulf clusters and the derivation of a performance model. This work will help in defining the optimum speckle processing architecture. Major meetings -------------- Observing campaigns: - Apr 20 - May 4: JOP 154 = Joint SOHO-GBO campaign to study chromospheric and photospheric network (both DOT and NSST); - Jun 21 - Jul 5: Joint observation with THEMIS/TRACE within PICS programme (http://www.fisica.uniroma2.it/solare/news/picsrome.html). Travel to the DOT: - Apr 13 - May 4: Bettonvil, Suetterlin, Hammerschlag Installation focuser, tests, observations; - May 4 - May 18: Hammerschlag, Hoogendoorn Platform floor; - May 31 - Jun 14: Hammerschlag, Hoogendoorn, Bettonvil, Langedijk (IGF) van Schie (Delft) Platform floor, canopy control automation; - Jun 21 - Jul 05: Suetterlin, Bettonvil, Hammerschlag Observations, aperture tests and modification; - Jun 28 - Jul 12: Hoogendoorn, van Schie, Bettonvil, Hammerschlag, Noordervliet (Delft) Platform floor, canopy safeguarding; - Sep 7 - Sep 21: Hammerschlag, Hoogendoorn Platform floor, maintenance. Milestones ---------- Presentations: - talk by Suetterlin at Potsdam Thinkshop (May); - talks by Rutten at UvA (May) and conferences in Uppsala (June), Prague (Sep) and Budapest (Sep); - talks by Bettonvil and by Hammerschlag at SPIE Hawaii (August); - posters at conferences at Lunteren (May), Santorini (June), Uppsala (June) and Prague (Sep). Publications: writeups of the above conference talks, available on the DOT website. Relations with collaborators ---------------------------- ASTRON: - measurements of optical components for the multi-wavelength system; - optical prism polishing; - discussions with J. Bregman on applying Mask Programmable Gate Array technology for DOT speckle processing. NSST (New Swedish Solar Telescope): the successor to the SVST (Swedish Vacuum Solar Telescope) in the building from which the DOT is operated started observing at its full 96 cm aperture with a low-order (19 actuators) adaptive optics system, becoming the first solar telescope to reach 0.1 arcsec resolution. At Oslo Rutten started supervising students analysing NSST data. Frequent DOT-NSST co-observing becomes highly desirable when the DOT safeguarding and processing permit so. Various experiments using the NSST optical bench with DOT hardware are foreseen (Ba II 4554 polarimetry, NSST speckle registration). Critical areas -------------- The present speed of realization of the multi-wavelength hardware and data-acquisition software is limited by IGF manpower. It is not impossible that the IGF work packages planned for 2002 will indeed be completed by the end of 2002, but only if the IGF efforts continue at their present pace. The Utrecht Faculty of Physics and Astronomy is starting "Planning and Control Cycle" procedures in which the Faculty directorate aims to resume full control over faculty-wide UU budget distribution (everything over personnel and "pen and paper" daily exploitation costs) including IGF time allocation. It is unclear what this new policy will imply for DOT progress. As noted before, the smallness of the DOT team remains a critical constraint, surely to be addressed in UU solar physics professor negotiations. As noted before and above, the speckle processing bottleneck (which increases with every extra wavelength-channel addition) has become the main limitation to "open the DOT to the world". Budget ------ The present three-year budget is allotted for: - completion and installation of the multi-channel optics; - safeguarding the DOT operation to enable trained-person observing; - DOT science exploitation, but does not cover speedup of the image reconstruction processing. We aim to submit fast-processing proposals this winter after defining the appropriate architecture, a non-trivial choice. Plans for the coming half year ----------------------------- - december: Joint Observation Program with VTT/POLIS (Tenerife); - winter: first light and first science observing in red continuum and Ca II H; - winter: definition and submission of a high-throughput speckle processor system; - spring: start of a joint project with the Kiepenheuer Institut and Ondrejov to study prominences and filaments (3-year duration; proposal submitted). Items for specific consideration by the ISC ------------------------------------------- The DOT effort remains vulnerable in team smallness and corresponding progress speed. The worst consequence is that the DOT science niche is not fully exploited. For Utrecht science needs alone the present 2-4 campaigns per year suffice quite well (one good multi-wavelength image sequence can fill a complete PhD thesis; only two image sequences from the former SVST produced 80% of the SVST papers) - but since DOT co-observing is highly desirable to almost any solar observing campaign, the actual worldwide niche for DOT data is much larger and not filled. At this moment there is no obvious ISC action that would remedy this situation, but the ISC is asked again to take note. The upcoming Utrecht professor negotiations are likely to have pivotal importance. Possibly: ISC support in defending the share of IGF time allocated to the DOT may be desirable in the coming months.