Project Support


Contexts:Network socket, serial console, stage2 only
Function:Remove charge from a CCD to prepare it for integration
Required Parameters:none.
Optional Parameters:
iter=[1] Number of iterations or cleaning cycles to perform
width=[set from detsize] Override detector pixel column (serial) count
height=[set from detsize] Override detector pixel row (parallel) count
binning=[1] Number of parallel shifts to do before each serial register clean
scupdump=[0] Before cleaning, number of reverse ("upward") parallel shifts to perform
idle=[0] If non-zero, begin background cleaning cycles after idle msec
idlegap=[0] Number of additional msec to wait between background cleaning cycles
quiet=[false] Set to true to suppress progress messages
dev=[current] Select dev 0 1 or all

Normal Usage

clean iter=5


clean 5

Will perform clocking similar to 5 full readouts (only without sampling.) On an OTA device, each clean cycle will be 8 times faster than a full readout because all 64 cells are selected at once. On a normal CCD, the clean cycle will take the same amount of time as a readout, unless additional options are used.

Detsize Interaction, Binning

The most recent detsize configuration will affect how many parallel and serial shifts happen in each clean cycle. It is possible to override this with width= and height=. Binning is recommended (otherwise the clean cycle takes just as long as a readout, unless a faster clocking pattern is set before the clean.)

Background Cleans

The following clean parameters are currently used on GPC1:

clean binning=32 scupdump=9000 idle=1 idlegap=3000 quiet=t

The effect is that one cleaning cycle is performed immediately, first involving 9000 parallel clock cycles with the parallel phases running in reverse (scupdump). Experiment on your own devices to see whether moving charge away from the serial register directly into scupper causes any unwanted side effects before using this option. In our case, it removes any remaining excess charge just as effectively as moving it the other way, but prevents the serial register from flooding.

Next, this command performs a binned by 32 (in the parallel direction) clocking pattern similar to a readout, but (for OTAs) with all cells selected, and no ADC operation. This takes a few hundred milliseconds. After that, it repeats this last step (binned 32 clean) every 3 seconds.

Any command sent to the controller cancels this background cleaning loop.

You may want to use a command such as leds off before opening the shutter to accomplish two things: stop the controller from cleaning, and make the controller LEDs dark before integration begins.

Avoid using a slow cleaning pattern with the idle feature because the controllers response to a new command request could be delayed by up to the time it takes for one cleaning cycle to complete, when you send a command during the time that it starts executing one of these clean cycles (every 3 seconds or so, in this example.)

Serial Dump Gate

Devices with a serial dump gate are cleaned the same as devices without. In other words, the dump gate is never clocked because the STARGRASP does not support this feature yet.