This is accomplished by the CDS routine VDS_DEBIAS:
vds_debias, qlds
Unlike the GIS detectors, the VDS is not a
photon counting device, so describing the data as ``counts'' is inappropriate.
Normally NIS studies are designed to include four VDS background windows
in the corners of the CCD.
Average CCD readout biases can then be removed by VDS_DEBIAS from each of the
four CCD sections.
The error associated with this step is small
(1 in ADC units, ~ 0.5 photon-events/pixel)
when compared to the scattered light.
Raw data from the VDS detector are in `ADC' (Analog to Digital Conversion) units.
After applying VDS_DEBIAS, the units of the data are `DEBIASED-ADC'.
