Detector controller

When NOTCam came to the NOT in 2001 it was foreseen that a new controller would arrive soon. NOTCam has given useful data but its potential has been limited by the old controller and the design of the data acquisition software. Compared to similar instruments NOTCam has very large overheads for short exposures, introduced mainly by the long readout time but also by the way data is handled. This limits the use of typical observing modes in the near-IR (averaging of multiple short exposures) and fast photometry. In addition, the darks are not well understood, and the measured dark current is very high and also variable. There is a dead column in the centre of the array which is due to the design of the old controller. The DC-gradient (or ``bias tilt'') across each quadrant is not a smooth gradient, but has several jumps that are not always subtracting out well, producing stripes or bands in the images. It is also not possible to abort an ongoing integration.

We have had no access to the lower level commands in order to experiment with readout and exposure modes recommended by detector experts to minimise for instance the well known ``reset anomaly'' problem for this type of arrays. All the above problems are expected to be solved with the new controller. The user requirements for the new controller and data acquisition system for NOTCam have been defined and detailed in a draft document.