WHIRCAM has been superceded by INGRID, and is no longer available as a common-user instrument. The notes below supplement the main instrument manual . See also the WHIRCAM software page .
CHIP: SBRC InSb array 256*256 30-micron pixels SCALE: .24"/pix -> 61" .08"/pix (MARTINI) -> 20" .05"/pix (MARTINI) -> 13" READOUT: 0.12 sec (256*256) 0.036 sec (128*128) 0.012 sec (64*64) 4 readouts, each reads every 4th column READNOISE: 40 e- (ND STARE), 55 e- (STARE) SATURATION: 10000 (ND STARE), 38000 (STARE) (p.16) (saturation, but non-linear 1% 3000 counts ND STARE 10% 17000 counts ND STARE) (defined by well capacity pixels, not A/D dyn range) DARK: 1e-/sec, but thermal leaks -> 10 e-/sec GAIN: 6e-/ADU BAD COLS: (54,256) -> (55,81) (hot pixels plot p.6 of manual) RESET LEVEL ("BIAS"): 22000 counts even cols, 30000 odd cols, hence striped appearance (made different so that they saturate at similar levels) FLATFIELD: varies on tiemscale ~ hours J H Ks L Wavelength (microns) 1.28 1.67 2.20 3.42 Bandpass (microns) .3 .3 .3 .06 Extinction (1 airmass) .10 .11 .07 Throughput (empirical) .16 .17 .17 (atm + tel + instr) (MARTINI halves it) Throughput (theoretical) .22 .22 .22 QE .8 .8 .8 Photons/sec mag = 0 (=6 * counts/sec) 9.2e9 4.9e9 3.0e9 (deduced from 15% throughput quoted in the manual, value for H was confirmed 9/97) Sky mag/arcsec**2 15.6 13.9 11.4 Compared with UKIRT: same same 1 mag brighter Due to: --- sky lines --- --- sky + tel --- Sky photons/sec ~ 120 500 2800 Longest integration (sec) with ND-STARE ~ 500 120 20 < 1 (sky saturation) mag -> S:N = 5 with 100 sec in .8" seeing 19.6 18.2 17.1 (p.24) Saturation mag 0.12 sec if seeing = 0.5" 8.6 8.4 7.8 Min exp time for sky noise to be > readout noise 3 1 0.5