Jul 4 1968
From The Space Library
July 4-8: NASA launched 417-lb Explorer XXXVIII, Radio Astronomy Explorer (RAE-A), from WTR by three-stage Thrust-Augmented Delta booster in first of two missions to measure frequency, intensity, and source direction of radio signals from solar, galactic, and extragalactic sources. Spacecraft entered elliptical transfer orbit, where it was spin-stabilized with 3,656.1-mi (5,884-km) apogee, 397.7-mi (640-km )perigee, 157-min period, and 59A° inclination. Apogee motor was fired July 7, placing Explorer XXXVIII into planned near-circular orbit with 3,654.3-mi (5,881-km) apogee, 3,641.2-mi (5,860-km) perigee, 224.4-min period, and 59.2° inclination. On July 8, yo-yo despin mechanism reduced spin rate from 93 rpm to 2.8 rpm. As primary objective, spacecraft would measure intensity and direction of radio signals from cosmic sources in 0.5- to 10-mhz range, not normally observable from earth. Secondary objectives were to place spacecraft into circular orbit of about 3,728-mi (6,000-km) altitude and to obtain useful data during first 30 days in orbit, for detailed study of dynamic spectra and decay rates of sporadic radio bursts. Spacecraft was expected to provide first low-frequency radio map of Milky Way and additional data on low-frequency signals from Jupiter and sun. Explorer XXXVIII was equipped with unique antenna system consisting of two antennas made of four 1/2-in-dia booms which could be deployed up to 750 ft each, to form X-shaped array. Configuration was to be gravity-gradient stabilized [see July 22]. Spacecraft was also equipped with damper boom, dipole antenna, and TV cameras to monitor spacecraft performance and determine source of radio signals monitored with upper array. Radio Astronomy Explorer project was managed by GSFC under OSSA direction. GSFC constructed, designed, and tested spacecraft and provided scientific instrumentation. (NASA Proj Off; NASA Release 68-109K; Schmeck, NYT, 6/29/68; 8; AP, W Star, 7/5/68; AP, NYT, 7/5/68, 26; W Post, 7/8/68, A6; 7/9/68, A7)
Explorer XXVIII, Interplanetary Monitoring Platform launched by NASA May 29, 1965, to investigate earth's magnetosphere and study earth-sun relationships, reentered atmosphere as had been predicted at GSFC August 1967. Mrs. Barbara Lowrey of GSFC Laboratory for Theoretical Studies had found in analysis of satellite's orbit that-during perigee pass on July 4 (actually early next day in Indian Ocean reentry area)-joint effect of sun and moon would alter orbit and cause Explorer XXVIII to make high-angle reentry and burn up in earth's at- mosphere. Computer tests had verified analysis. (GSFC SSR, 7/15/68; NASA Release 68-117; Marshall Star, 3/6/68)
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