LIM :

Near IR from a mini-satellite

Dani Maoz

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