Automatic satellite tracking system for the NASA Satellite Photometric Observatory
The development of an Automatic TV Tracking System for NASA's mobile 61 cm aperture Satellite Photometric Observatory is described. The analysis techniques used to match the FOV and resolutions to changing seeing conditions are covered in details. Theoretical reasons for such matching of general interest are discussed. It is shown that the energy density in a satellite image is 11 times greater during good seeing conditions than during typical seeing conditions. The Z7987 image tube is shown to be able to detect 16th magnitude objects under ideal seeing conditions using only 8 percent of the light collected by the main telescope. Experimental results show that the SPO equipped with a Z7987 camera can track a satellite at any orbital velocity with less than 0.14 mr accuracy using the DBA Series 606 TV Tracker. The manual system used prior to the installation of the Automatic TV Tracking System could maintain track at 1.1 mr accuracy for comparison.
Television System Optimization For Astronomy And Special Applications
The predominance of television systems which operate at standard broadcast rates tend to mask several system optimization techniques which can improve performance of nonstandard systems. Astronomical systems, in particular, benefit by use of nonstandard frame rates, line numbers, and a proper balance between exposure time and sensor gain. Resolution and signal-to-noise from a given sensor can be maximized by proper selection of the number of TV lines and the frame time. In addition, the signal-to-video noise for a given TV resolution has a peak value for the video bandwidth picked from sensor and system parameters.
HRTEM study of orthorhombic zirconia in MgO-PSZ
High-resolution transmission electron microscopy (HRTEM) was used to study the phase of orthorhombic ZrO2 formed in magnesia partially stabilized zirconia (MgO-PSZ) during HRTEM specimen preparation. Based on the three reported crystal structures of orthorhombic ZrO2, with the space groups Pbcm, Pbc21 and Pbca, here it is shown that orthorhombic ZrO2 formed in MgO-PSZ has the Pbcm structure.