Developing new data acquisition devices for COMICS

We developed a new data acquisition device for COMICS, a mid infrared instrument of the Subaru telescope. The new device was installed in place of our previous data acquisition device with a lower data transfer speed. The new device is 32 bit PCI bus and PC Linux based and provides bus-master DMA transfer function. It consists of a clock pattern generator, frame memories, and an image co-adder. In order to achieve high operational efficiency for mid infrared instruments, the data handling speed is essential as well as the speed of A/D converter. The data transfer to the hard disk drive on the PC is made during acquiring the data at the rate higher than the data generation rate. As a result, we succeeded to reduce the dead time due to the data transfer procedure from 60 sec to less than 1 sec for 200 frames (64M bytes). Furthermore by replacing the host computer by a higher performance PC, the observation efficiency of COMICS was improved from 44% to 74% in the imaging mode. This PCI based data acquisition device can also be applied to the other instruments that have fast data rates.