How to operate Potsdam: K. G. Strassmeier, T. Granzer, M. Weber, M. I. Andersen, H. Korhonen, E. Popow, M. Woche, C. Fuhrmann, D. Fügner, U. Laux, et al. Bremerhaven: A. Herber, A. Gröschke, S. Debatin Padua: P. Rafanelli, S. Ciroi, F. Di Mille, F. Angrilli Catania: G. Cutispoto, I. Busà , A.F. Lanza, S. Messina, I. Pagano, A.C. Lanzafame Barcelona: I. Ribas, J. Colome, J. Isern St Andrews: K. Horne, A. Collier Cameron Sydney: M. Ashley Perugia: G. Tosti, A. Mancini et al.
How to operate A typical ill-posed problem: need regularization ! (i.e. logistics …)
Basic requirements from science specifications • Uninterrupted tracking of the same stellar field during the entire polar night. • A large field of view (65 square degrees at 3”/px) • Flat-field calibration to better than 10-4 per exposure. • A minimum of two separated bandpasses simultaneously. • Achieve a time resolution of 10 seconds • Aim for a three-year operation minimum.
The must-do list • be able to continuously rotate the telescope • pointing accuracy and tracking not critical • minimize air mass and its variation • minimize differential refraction across FOV • minimize moon impact and other streylight • minimize AV and thus reddening • optimize sampling on chip (psf width vs. star count) → optimal field selection
Optical design: FOV 11.5º Field flattener 82cm 60cm 18cm CCD, 3“/px
Proposed ICE-T field -60º -70º 8.1º × 8.1º
full 360/24hr for 3 months 15 Simplest possible operation: • parallactic mount • close to the cel. pole • no image rotation • no motion in DEC • needs (periodic) RA-axis • realignment • requires slip-ring support • „open“ dome
hours Duration of night at Dome C Coordinates: 123°23', -75°06'
3. Moonlight. Closest dist=40º 1. Airmass 1.01-1.29/24hours 1.29 2. Differential refraction Edge-to-edge 10-15″ ≈ 3.3-5 px/24hours 1.19 1.01
The cornerstone list • continuously track for 3 months (error acumulation?) • keep tracking even if dome must be closed • enable manual operation • enable for automatic sky flat fields during dawn • automatic acquisition and reacquisition during night • enable for add. optical & mechanical realignment • (c/o talk by M. I. Andersen) • automatic pointing model and implementation • (c/o talk by T. Granzer) → design selection
Main problem: data handling Simplest possible solution: Local storage with 3x safety If no storage space, entire telescope is useless.
What speed is needed for data saving? 450 MB/16.4sec = 27 MB/s 2x loss-less compression: 14 MB/s HP Storageworks Ultrium 960 SCSI, 80 MB/s for 400-GB SDLTs But 512-GB SDLT tapes needed If tape writing fails, one looses data after approx. 48 hours
Data storage and pre-processing; data back-up facility Pre-processing leads to level-2 data. Store only level-2 data? Possible approach: 1. Combine always 30 CCD frames 2. Keep only „Master flat“ Rules out certain additional sciences! Solution would be to store level-2 data as backup or transfer it via a satellite link.
WorkShop Antarctic Research: a European Network in Astrophysics Telescope and Instrument Robotization at Dome C 26.-29.3.2007 Puerto Santiago, Tenerife www.aip.de/arena_robot SOC: A. Allan (U. Exeter), M. Ashley (UNSW, Sydney), M. Candidi (IFSI/CNR, Rome), J.-B. Daban (LUAN, Nice), E. Fossat (LUAN, Nice), A. Herber (AWI, Bremerhaven), R. Lenzen (MPIA, Heidelberg), E. Martin (IAC, LaLaguna), I. Ribas (IEEC, Barcelona), P. Salinari (INAF, Firenze), K. G. Strassmeier (AIP, Potsdam, chair), J.-P. Swings (IfAG, Liege), G. Tosti (U. Perugia)