IR wide field imaging MPIA IR projects and studies

Rainer LenzenMax-Planck-Institut für Astronomie, Heidelberg

27.3.2007, Tenerife Page Nr. 1

Stability of IR-arrays for robotized observations at dome C




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



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)

Aladdin III InSb 27 1024x1024 0.9 – 5.4 23K

Raytheon (SBRC)

ORION InSb 25 2048 x 2048 0.9 – 5.4 23K

Raytheon (SBRC)

Si:As 50 320 x 240 2 – 28 3K

DRS (Boeing) Si:As BIB 50 256 x 256 2 – 28 3K

DRS (Boeing) Si:As BIB 75 126 x 126 2 - 28 3K

JPL Si:As 18 1024x1024 5-25 3K

Raytheon (SBRC)

Si:As 30 (tentative) 1024x1024 5-28 3K



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 200650% budget reduction1m->40cm

Spitzer

JWST



Quantum efficiency of Hawaii-2 array #1005 in H-band

Dark current of Hawaii-2 array #1005

NIR



Mosaic of 2x2 2Kx2K λc =5 µm HgCdTe arrays

NIR/TIR



Readout noise as function of number of Fowler sample pairs.



Array Aladdin InSb (Hughes SBRC)

Pixel format 1024x1024 27-micron pixels

Spectral Response 1 to 5.5 microns

Dark Current 0.25 e-/s/pix

Dark Background 0.5 e-/s/pix

Read Noise (low background mode) 10 e-/pix

Read Noise (medium background mode) 35 e-/pix

Read Noise (high background mode) 70 e-/pix

Gain 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 retention0.5-1% of a bright (saturated) source in the next

frame

Centered Sub-array dimensions 768x768, 512x512, 256x256 pixels

Gemini (NIRI science array)



MIRI Assy 7581011.1 Wafer 9601/A05 & Assy 7581009.1 Wafer 9581/A05; Diodes D28 at -1.0 V Bias

0.01

0.10

1.00

0.0 5.0 10.0 15.0 20.0 25.0 30.0

Wavelength (µm)

Re

lati

ve

Re

sp

on

se

/ P

ho

ton

9601 @ - 1.0 volt

hanger queen @-1.0 volt

9581 @ -1.0 volt

10.0 K 9/22/2004

Relative quantum efficiency of MIRI detectors.

MIR



basic specifications of the Aquarius 1Kx1K Si:As array.

ParameterUnits specs

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



Column shift register


Ro

w sh

ift register

8 or 32 outputs (selectable)



Ro

w sh

ift register

8 or 32 outputs (selectable)

Readout topology of Aquarius array.



320x240 CRC 774 Si:As array used for ground based instruments such as Michelle, Timmi2, TRECS, VLTI-MIDI, COMICS ...



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!



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.



Special constrains at Dome-C

• Continuous use over years • Cold ambient • No maintenance in situ, no human intervention • Icing problem

• Solutions: CCC instead of LN2 and LHe, respectively

• Entrance window ventilation

Pulse tube cooler at higher frequencies to avoid orientation dependence instead of Stirling type or Gifford-McMahonTB specified for low ambient temperatures



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.

IR wide field imaging MPIA IR projects and studies

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