HST WFC3 IR channel: 1k x 1k HgCdTe detector, QE 80% 18 micron pixels (0.13”/pix), ~2’x2’ FOV Detector sensitivity engineered to cut off above 1.7 micron,
Post on 19-Dec-2015
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HST WFC3 IR channel:
1k x 1k HgCdTe detector, QE 80%
18 micron pixels (0.13”/pix), ~2’x2’ FOV
Detector sensitivity engineered to cut off above 1.7 micron, so can operate at -128 C (6-stage thermoelectric cooler) without thermal noise from telescope and detector.
J (1.1 micron) and H (1.6 microns) bands.
Dominant background: zodiacal light: 0.6-1.3 e/s/pix
Sensitivity: J=27 (ABmag, S/N=5) in 45 min (point src.), 1.4 hr (1” diam src.) H=26.4 53 min 1.5 hr
Sensitivity: J=26 (ABmag, S/N=5) in 10 min (point src.), 18min (1” diam. src.) H=25.4 12 min 19min
4k pixels , 7.4cm
HAWK-I on VLT:
0.1/”pixel, 7.5’ FOV
1 hr exposure:
J=24.9, H=23.9 (S/N=5)
i.e. 100 hrs exposure needed to reach WFC3 1-orbit depth!
No place like space for NIR!
Why not make a “mini” (HST+WFC3-IR)/10?
2.4m 24cm = 9.5 in
For 24 cm aperture
@ 1.6 micron, diffraction limit: ~1.3”.
f/10 mirror, 18-micron pixels 1.5”/ pixel.
Need ~100 hrs to get to HST-WFC3 depth (same as VLT)
BUT
FOV can be much bigger! With 4k x 4k detector (like HAWK-I)
FOV=1.66x1.66=2.8 degree^2 = 2500 X WFC3 !
A unique instrument for deep and wide NIR surveying.
Science:
Surveys for transients in NIR – High z and obscured regions
Survey Mode Examples:
1. All sky (1.3hr exposures): in 2 years,
to J=23.4, H=22.5
Ideal complement to LSST
2. 500 deg^2 transient search (180 fields,1.3hr exposures), every 10 days to J=23.4, H=22.5.
1 year: 10,000 SNe Ia, 10,000 CC-SNe
3. 30 deg^2 (10 fields, 30-hr exposure), every 13 days
to J=26, H=25.4
1 year: 10,000 SNe Ia, 10,000 CC-SNe, z>1, z>2
Type-Ia SN delay time distribution
Two approved HST MC Treasury programs
(1400 orbits)
predictions by K. Sharon
predictions by K. Sharon
Payload logistics:
Telescope Weight: Off-shelf Celestron 10” telescope ~40kg -- can shave off with custom lightweight mirror
Camera: few kg?To keep it simple/light/cheap: minimum optics,minimum moving parts, fixed filters on chips:
J
J
J
J
J
J
J
J
H H
H H
H
H
H
H
Thermoelectric cooler:Weight ~0
Power consumption: ~250 W
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