Cosmic Origins Spectrograph Instrument Handbook for Cycle 17

12.3 FUV ACCUM Data

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12.3.1 Raw FUV ACCUM Data

The raw data is an array of dimensions 16384 × 1024 pixels. Each pixel is 16 bits deep and so can handle up to 65,535 counts. Note that the actual image size sent from the instrument is only 128 pixels high to minimize data quantities, but the full image size is maintained in the ground processing to allow for future movements of the spectrum on the detector. The unused pixels are filled with zeroes. There are separate sub-arrays for the stim pulses. Because it is done on-board in the flight software, the raw data are already corrected for the doppler motion of the spacecraft.

12.3.2 Corrected FUV ACCUM Data

The corrected image is also 16384 × 1024 pixels and is corrected for doppler motion of the spacecraft (done on-board in the flight software), flat-field response, and detector dead time. The value in each pixel is effective counts sec^-1, which is the total counts in a pixel multiplied by that pixel's factor and divided by the exposure duration. The images are corrected for geometric distortion, but not for background or thermal drift.

12.3.3 FUV ACCUM Error Array

The error array is another 16384 × 1024 image that has per-pixel errors computed from Poisson statistics using the gross counts and correcting for flat-field effects and the dead time.

12.3.4 FUV ACCUM Science Spectrum

This includes the same quantities described for FUV TIME-TAG data; see Section 12.1.5.