Control and data acquisition

The SCUBA data acquisition and signal processing electronics is transputer-based. The transputer system is linked to a VAX/VMS system. Signals from the bolometers are digitized by nine 12-bit A/D converters, each connected to an Inmos T800 transputer via a link adaptor and high speed serial link. The nine transputers carry out signal processing functions such as demodulation of the chop and calibrator signals and spike removal. These transputers connect to an image processing transputer, which resamples the data onto a square grid, removing sky rotation in the process. Images are sent via EtherNet to a workstation for real-time display.

Control of the telescope during observing is managed via the Observation Management Program (OMP) software. Observation programs are divided into Minimum Schedulable Blocks (MSBs), typically about an hour in duration, in which the parameters of the science observations as well as any calibrations are described. These are then submitted in advance to the OMP database, which can then be queried at the summit to find the highest priority project in a given weatherband. (See here for a deeper discussion of policy etc.) The query software then interacts with the telescope control software to carry out the observations as prescribed in the MSB, although the oprator and observer retain full control of the telescope at all times, and can repeat or avoid individual observations as necessary.