LOCKHEED MISSILES AND SPACE CO INC PALO ALTO CA PALO ALTO RESEARCH LAB
The design, fabrication, calibration, and flight of a double-focused refractive optical system employing a solid cryogen for operation at 22K on a balloon-supported platform are described. The inherent out-of-field energy rejection and the diffraction limited characteristics of a refractive system have been combined with a four-element HgGe detector array for an optimized radiometric measuring system for the 8-to 13-micrometers wavelength range. Additional features include an eight-position spectral filter wheel, a two- position neutral density filter, a four-decade logarithmic amplifier, and a frost-prevention system. The system was developed to measure the atmospheric emittance as a function of elevation angle near the earths horizon while at a nominal floating altitude of 90,000 ft. The results of laboratory evaluation of the individual optical, detector and electronic components, as well as the system performance for responsivity, optical resolution, optical resolution, out-of-field energy rejection and field-of-view, are presented. Simulated flight tests in an evacuated chamber were performed to verify the cryogenic and electro-optical design. Finally, the results of a successful balloon flight in June 1971 are summarized in the Appendixes. A follow-on contract, No. F19628-72- C-0033, is in progress to fabricate an attachable calibration source, modify some of the electronic and mechanism components, and perform a complete calibration, and to support two additional balloon flights in 1972.