Acquisition Camera Detector

The Acquisition Camera in both telescopes employs a 1024 x 1024 EEV CCD (CCD47). The pixel size is 13 microns (~0.12"). The CCD can be operated over a range of temperatures controlled through an interface to a thermoelectric cooler. The device full well is just over 70,000 counts/pixel. The CCD employs a 16 bit encoder which saturates at 65,536 counts, i.e. somewhat before the CCD full well. The minimum exposure time is 0.006 s. The full frame readout time  is about 1.7 seconds.

At a temperature of -30 ^oC the bias level is ~550 ADU and the dark current is ~ 13 electrons/pixel/second.  The gain setting is 1.0 (left amplifier) and 1.03 (right amplifier) electrons/ADU. The read noise on the telescope is ~5 electrons rms (in the HIA lab it was 4.4 and 4.6 electrons rms for the left and right channel, respectively).  Laboratory measurements at HIA also indicated good charge transfer efficiency (CTE), with 1-CTE = 5.22E-6 (parallel) and 3.18E-6 (serial). Departure from linearity will be determined from data taken during commissioning (in the HIA lab, the maximum departure from linearity was ~7%).
 
 

At a temperature of -30 ^oC the bias level is ~260 counts and the dark current is ~9.5 counts/pixel/second. It maybe necessary to run the detector at a warmer temperature to avoid condensation on the vacuum window. This will result in a higher dark current. The gain setting is 0.74 (left amplifier) and 0.71 (right amplifier) electrons/ADU. The read noise on the telescope is ~6 electrons rms. (In the HIA lab it was 4.4 and 4.6 electrons rms for the left and right channel, respectively.)  The maximum difference from linearity measured in the HIA lab was 6.9%. Laboratory measurements at HIA also indicated good chargmeasurements at HIA also indicated good charge transfer efficiency (CTE), with 1-CTE = 4.77E-7 (parallel) and 2.32E-5 (serial). Because the CCD always operates with both amplifiers, the expected signal loss in the serial register corresponds to a 1% edge-to-center photometric drop off for point sources.
 

Last update February 14, 2002; Cláudia Winge
In original form June 3, 2000; Ted von Hippel