General Design

The detector mosaic and its mount are shown in Fig. 1. Each pixel is sampled with a 16 bit ADC, producing a 32 megabyte scientific image size. For guiding, one small sub array of pixels (typically 8x8) containing a guide star is chosen for each of the four arrays of the science image. These pixels are blanked out in the science image and sent to the guide host.

Figure 1. WIRCam detector arrays mounted on the GL Scientific module (photo by

There are two separate host computers, one for guiding, which is mounted in the telescope cage, and another for science data, located in the control room. The science detector host runs Linux. It hosts 2 SDSU-3 PCI cards, with a split fiber connection. One is a two-way connection for scientific data transfer and the other only connects to the guide computer. Each SDSU-3 controller handles 2 arrays. The detector host runs CFHT Detcom to receive images and archive them with one chip per extension in MEF (Multi-Extension FITS) format. Focus and microdither sequences are saved as MEF cubes.

The guide host runs Linux based on kernel 2.4.20, built with RTAI realtime support. Two SDSU-3 cards are installed in the guide host, both in receive-only mode. The guide host also has a PowerDAQ A/D converter which supplies analog output, analog input, and digital control output and digital error status input from the ISU (Image Stabilization Unit). The SDSU-3 driver and the PowerDAQ A/D converter driver are installed as RTAI real time drivers. Figure 2 shows the connections of the two hosts to the detector arrays.

Figure 1. WIRCam detector arrays mounted on the GL Scientific module (photo by

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