Stability of IR-arrays for robotized observations at dome C 27.3.2007, Tenerife Page Nr. 1
IR wide field imaging MPIA IR projects and studies OMEGA2000: NIR WFI Calar Alto NACO: NIR AO-supported Imager and Spectr. (VLT) LUCIFER: NIR AO-supported Imager and Spectr. (LBT) T-OWL study: TIR and MIR at a 100m telescope Science case Atmospheric constrains Technical realization Problems MIDIR study: TIR and MIR at a 30m/42m/60m telescope Dito, especially for new E-ELT design PRIME/Dune (ESA Corner Stone) All sky 0.5µm 1.8µm survey 4x0.5 square deg 0.15/0.3 arcsec/pixel ARENA: TIR and MIR wide field 0.18arcsec/pixel at J,H,K, 8 arrays Hawaii II 0.18 arcsec/pixel at L,M 8 arrays InSb 0.36 arcsec/pixel at N,M 8 arrays Si:As 27.3.2007, Tenerife Page Nr. 2
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Infrared Arrays Company Type Pixel pitch Pixel number Wavelength range Temperature Teledyne Hawaii I 18 1024x1024 0.9 2.6 77K Teledyne Hawaii I RG 18 2048x2048 0.9 2.6 77K Teledyne Hawaii II RG 18 2048x2048 0.9 2.6 77K Raytheon (SBRC) VIRGO 20 2048x2048 0.9 2.6 77K Teledyne Hawaii II RG 18 2038x2048 0.9 5.0 40K Raytheon (SBRC) Raytheon (SBRC) Raytheon (SBRC) Aladdin III InSb 27 1024x1024 0.9 5.4 ORION InSb 25 2048 x 2048 0.9 5.4 Si:As 50 320 x 240 2 28 DRS (Boeing) Si:As BIB 50 256 x 256 2 28 DRS (Boeing) Si:As BIB 75 126 x 126 2-28 JPL Si:As 18 1024x1024 5-25 Raytheon (SBRC) Si:As 30 (tentative) 1024x1024 5-28 23K 23K 3K 3K 3K 3K 3K 27.3.2007, Tenerife Page Nr. 5
MIR survey competitors Mission Wise: cryogenic 40cm-telescope 3.5, 4.7, 12, 23 µm bands simultaneously 4x 1kx1k: 2 HgCdTe, 2 Si:As pixel size:2.7arcsec confirmation Oct 2006 50% budget reduction 1m->40cm Spitzer JWST 27.3.2007, Tenerife Page Nr. 6
NIR Quantum efficiency of Hawaii-2 array #1005 in H-band Dark current of Hawaii-2 array #1005 27.3.2007, Tenerife Page Nr. 7
NIR/TIR Mosaic of 2x2 2Kx2K λc =5 µm HgCdTe arrays 27.3.2007, Tenerife Page Nr. 8
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Readout noise as function of number of Fowler sample pairs. 27.3.2007, Tenerife Page Nr. 12
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Gemini (NIRI science array) Array Pixel format Spectral Response Dark Current Dark Background Read Noise (low background mode) Read Noise (medium background mode) Aladdin InSb (Hughes SBRC) 1024x1024 27-micron pixels 1 to 5.5 microns 0.25 e - /s/pix 0.5 e - /s/pix 10 e - /pix 35 e - /pix Read Noise (high background mode) Gain 70 e - /pix 12.3 e - /ADU Well depth (near-ir) 200,000 e - Well depth (thermal-ir) 280,000 e - Quantum efficiency about 90% Flat field uniformity* +/-18% Flat field repeatability* +/-0.3% Residual image retention Centered Sub-array dimensions 0.5-1% of a bright (saturated) source in the next frame 768x768, 512x512, 256x256 pixels 27.3.2007, Tenerife Page Nr. 14
MIR 10.0 K 9/22/2004 1.00 MIRI Assy 7581011.1 Wafer 9601/A05 & Assy 7581009.1 Wafer 9581/A05; Diodes D28 at -1.0 V Bias Relative Response / Photon 0.10 9601 @ - 1.0 volt hanger queen @-1.0 volt 9581 @ -1.0 volt 0.01 0.0 5.0 10.0 15.0 20.0 25.0 30.0 Wavelength (µm) Relative quantum efficiency of MIRI detectors. 27.3.2007, Tenerife Page Nr. 15
basic specifications of the Aquarius 1Kx1K Si:As array. Units specs Parameter Pixel pitch µm 30 Number of video outputs 32 Maximum frame rate Hz 150 Storage capacity spectroscopy e - 1E6 Storage capacity imaging e - 1.5E7 27.3.2007, Tenerife Page Nr. 16
8 or 32 outputs (selectable) Column shift register Row shift register Column shift register Readout topology of Aquarius array. 27.3.2007, Tenerife Page Nr. 17
320x240 CRC 774 Si:As array used for ground based instruments such as Michelle, Timmi2, TRECS, VLTI-MIDI, COMICS... 27.3.2007, Tenerife Page Nr. 18
How to produce Flat-fields at Dome C NIR: best choice: twilight flats sophisticated dome flats or instrumental flats calibrated by sky-flats, use variable DITs TIR/MIR: best choice: reconstruction from dithered science obs. Dark current frames required! 27.3.2007, Tenerife Page Nr. 19
Flat field Stability Detector temperature should be stable within +/- 0.005 K. Relatively easy to meet by temperature controller (NACO, CRIRES, ISAAC...) Stabilization of voltages typically within mv. Technically no problem if independent on external temperature variations (Temperature stabilization of electronics racks). d(ln Gain)/dT= (2-3)x10-4 /K NIR flat field should be taken every 24h. MIR flat field is deduced from dithered images. 27.3.2007, Tenerife Page Nr. 20
Special constrains at Dome-C Continuous use over years Cold ambient No maintenance in situ, no human intervention Icing problem Solutions: CCC instead of LN 2 and LHe, respectively Entrance window ventilation Pulse tube cooler at higher frequencies to avoid orientation dependence instead of Stirling type or Gifford-McMahon TB specified for low ambient temperatures 27.3.2007, Tenerife Page Nr. 21
Long time Stability Aging of IR arrays: 1. storage aging (near ambient temperature at non-operation state) 2. thermo-cycling aging ( significant only after hundreds of cycles ) 3. operational aging (not considering radiation damage for space application) Based on experience at Omega2000, CRIRES, NACO etc. (Gert Finger, H.-U. Käufl), operational aging of arrays is not observed over > 5years, neither QE nor hot/dead pixels. Detector aging mainly due to thermal cycling (not a problem here) Main problems arise from long time contamination of the detector due to bad vacuum conditions, power interruption, dust within the cryostat (black painting abrasion, Zeolith, etc.). In consequence, special care should be taken in the design of the cryostat to avoid such long time problems. 27.3.2007, Tenerife Page Nr. 22