How to operate Potsdam: K. G. Strassmeier, T. Granzer, M. Weber, M. I. Andersen, H. Korhonen, E....
-
Upload
donna-carter -
Category
Documents
-
view
215 -
download
2
Transcript of How to operate Potsdam: K. G. Strassmeier, T. Granzer, M. Weber, M. I. Andersen, H. Korhonen, E....
How to operatePotsdam: 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. DebatinPadua: 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. IsernSt Andrews: K. Horne, A. Collier CameronSydney: M. AshleyPerugia: G. Tosti, A. Mancini et al.
How to operate
A typical ill-posed problem: need regularization !
(i.e. logistics …)
Basic requirements from science specifications
1. Uninterrupted tracking of the same stellar field during the entire polar night.
2. A large field of view (65 square degrees at 3”/px)
3. Flat-field calibration to better than 10-4 per exposure.
4. A minimum of two separated bandpasses simultaneously.
5. Achieve a time resolution of 10 seconds
6. 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
60cm 82cm
18cmCCD, 3“/px
Field flattener
Proposed ICE-T field
8.1º × 8.1º -70º
-60º
full 360/24hr for 3 months
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
15
Duration of night at Dome C
Coordinates: 123°23', -75°06'
hours
February 25
March 25
April 25
May 25
June 25
July 25
August 25
September 25
September 25
1.19
1.29
1.01
1. Airmass 1.01-1.29/24hours
2. Differential refractionEdge-to-edge 10-15″ ≈ 3.3-5 px/24hours
3. Moonlight. Closest dist=40º
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
Simplest possible solution:Local storage with 3x safety
If no storage space, entire telescope is useless.
Main problem: data handling
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 ortransfer it via a satellite link.
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)
Antarctic Research: a European Network in Astrophysics