LRIS-R Clock Delay Calibration Procedure | ||||||||||||||||
| BackgroundThe new LRIS red-side detector electronics exhibit a change in noise characteristics when the temperature of the controller changes. In order to minimize fixed pattern noise, it is necessary to periodically check the temperature of the detector electronics and to reset the clock delay parameter (keyword LSERCLKD). The appropriate value of this keyword depends not only on temperature (keyword UTBTEMP), but also on the CCD readout speed (keyword CCDSPEED) and CCD binning mode (keyword BINNING). This document describes the procedure for determining the optimal clock delay value for a given set of these parameters, plus the procedure for updating the LSERCLKD keyword when conditions change.Clock Delay ParametersThe LRIS keyword library includes 4 keywords which control the value of LSERCLKD in various operating modes, as shown below:
Setting USERnAs part of the afternoon setup procedure, the observer or support astronomer must reset the values of the USERn keywords appropriately for the current UTBTEMP value. This is accomplished by executing the following command frmo the lriseng account on lrisserver:set_clock_delayThis script will read the current value of UTBTEMP and will look up the optimal values of USERn for that temperature. Calibrating LSERCLKDThe framework above relies on the existence of a table listing the optimal clock delay for the various observing modes and CCD controller temperature. Following this procedure to derive new values for the current temperature:
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Last modified: 08/06/2009 21:23 Send questions or comments to:LRIS Support |