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