Since its lengthy planning and budgeting process, the start of the construction of NASA - Goddard's adaptive optics system is being met with enthusiasm and more than a little apprehension. To some extent, this apprehension reflects a lack of familiarity with the new technology on the part of the general public and the media. However, a careful engineering analysis shows that any number of problems can be eliminated if certain high-priority issues are addressed early. This article examines one such issue, the limitations of the existing power system, and suggests how the system could be improved.
The first generation of bolometric imager systems included integral-field spectrometers with a detector array and a physical field of view of typically 5x5-24x22 arcmin. It was found that the scanning mirror covered only part of the field of view and that the detector array was much smaller than the field of view (VoF). It was also found that the response of the detectors changed with position within the FoV. According to the signal-to-noise ratio (SNR) criterion, the DC SNR of the measurements at the edges of the FoV was almost 2 times lower than at the center. To improve the SNR, the sliding2 detector array was added, which stretched the detector FoV to the full size of the physical field of view. The detector array has 1024 detectors, digitized at 12 bit and stored later on a frame-to-frame basis in 128x128 chunks (see Fig. 1). Delineating the area of the detector array from the lunar surface and synchronizing both the scanning mirror and the detector array are critical tasks. The latter procedure was originally executed as a 'constant velocity' method, in which the detector array was scanned at constant velocity, and the Roche formulas were used to calculate the surface of the moon. A later observation of different detectors drifting with respect to each other made them realize that the proper way was to slow the field rotation rate rather than the detector scan rate. In fact, the detector array has a much larger diameter than the aperture of the telescope and is rotated at a speed only 1.4 times higher than the angular rate of the reflection of the telescope. d2c66b5586