From: C. Jacob Wolfson Date: Wed Jul 23, 10:37am To: t_test@sag.space.lockheed.com Cc: Subject: CCD Linearity & Gain CCD GAIN & LINEARITY Before we shipped the instrument back to GSFC we did a few ltc runs (9 and 10 July). The exposure levels used were 2, 20, 180 msec and 1.448, 2.896, and 9.740 seconds. We did B amplifier and dark room - maximum average intensity 2401 DN A amp & dark room - saturated at 9.74 sec; intensity @ 2.896 sec = 2679 DN B amp & some light - max was 3781 DN at full 9.74 seconds These values are the average over an extraction (nearly 1/4th of the CCD) where the extraction does not include a vignetted edges or the grid. Doing a simple linear fit to the data (Intensity vs Exposure) and using IDL's poly_fit routine the predicted values are all less than 1% from the actual values. If one assumes the noise on the maximum achieved images is all shot noise and calculates camera gain the results are 54 and 53 e/DN for the two B amplifier runs and 15 e/DN for the A amplifier run. These values would increase by a little (<1 electron) if read noise were removed from the calculation. Dexter's E-mail of 17 October gave values of 46.0 and 12.5 e/DN. His measurements were for the CCD (and preamp) at -65 C and the ones we made were at room (coolish) temperature. It is all pretty consistent. It will be interesting to see a) what we get when the CCD is cold during observatory TVac. b) what the linearity and offset are on a pixel by pixel basis.