LRS's CCD
Quantum Efficiency
The CCD quantum efficiency (QE) was measured in the wavelength interval 2000 10500 Å in incremental steps of 500 Å. The CCD was illuminated using monochromatic light obtained through a Xenon lamp, a series of filters and a monochromator. The signal integrated on the CCD is then compared to the response of a calibrated photodiode.
Dark Current
The dark current is measured taking a short dark exposure and a long dark exposure. The signal level in the two exposures is then compared. The frame is divided in 10×10 pixel sub-frames and the dark current is computed for each of them. The average value of the dark current turns out to be 6 electrons/pixel/hour.
Charge Transfer Efficiency
The charge transfer efficiency (CTE) is measured using the X-ray stimulation method. In particular, the parallel CTE is obtained exposing the CCD to the Fe55 source for a given amount of time. After integration, the columns are stacked together and the signal is plotted versus the number of pixel transfers. The CTE is then given by CTE= 1- (Charge loss)/1620 e-/N
1 - ( s(0) - s(4095) ) / ( s(0) * 4096)
The LORAL CTE turned out to be 0.999982.
CCD Image
The image area of the CCD is 2048 X 2048 pixels, the length of the output register is 2048
pixels. The dimension of the image produced by the acquisition system is 2048×2100 pixels
(without binning). This means that the overscan zone depends by the readout mode and by the
binning utilised.
The User Interface allows different acquisition modes and different binning on chip.
In Table 1 the overscan zone for the different kind of acquisition are showed.
Readout Mode | Binning | Image Size | X prescan | X image | X Overscan | Y overscan |
Left | 1 X 1 | 2048 X 2100 | NO | 0 - 2047 | NO | 2048 - 2099 |
Right | 1 X 1 | 2048 X 2100 | NO | 0 - 2047 | NO | 2048 - 2099 |
Two outs | 1 X 1 | 2048 X 2100 | NO | 0 - 2047 | NO | 2048 - 2099 |
Left | 1 X 2 | 2048 X 1050 | NO | 0 - 2047 | NO | 1024 - 1049 |
Right | 1 X 2 | 2048 X 1050 | NO | 0 - 2047 | NO | 1024 - 1049 |
Two outs | 1 X 2 | 2048 X 1050 | NO | 0 - 2047 | NO | 1024 - 1049 |
Left | 2 X 2 | 1024 X 1050 | NO | 0 - 1023 | NO | 1024 - 1050 |
Right | 2 X 2 | 1024 X 1050 | NO | 0 - 1023 | NO | 1024 - 1050 |
Two outs | 2 X 2 | 1024 X 1050 | NO | 0 - 1023 | NO | 1024 - 1050 |
For any comments please contact Rosario Cosentino.