Jun 3 1975
From The Space Library
Explorer 49-Radio Astronomy Explorer B, launched 10 June 1973 into lunar orbit to measure galactic and solar radio noise at frequencies below ionospheric cutoffs and beyond terrestrial background interference by using the moon for occultation, focusing, or aperture blocking for increased resolution and discrimination-had completed nearly 2 yr of successful operation and was adjudged successful.
Explorer 49's lunar orbit, away from the noisy environment of earth, had increased the effectiveness of the instrumentation. The spacecraft had been able to detect very weak solar-noise bursts up to 13 mhz and as low as 25 khz. Its predecessor, Explorer 38-Radio Astronomy Explorer A, launched 4 July 1968--had been able to observe relatively intense solar-noise bursts only in the 200 khz to 9 mhz range because of its orbit within the earth's magnetosphere. Explorer 49 also was able to observe and follow solar bursts out of the ecliptic plane.
Data from Explorer 49 had verified two major magnetospheric noise regions, one on the morning side of the earth and the other on the evening side. In addition, spacecraft data showed that intense noise occurred in the 8 to 12 pin time zone with less intense noise in midmorning. The intense late-evening noise was generated within 10 000 to 12 000 km of the earth's surface, and the dayside emission seemed to come from an. altitude of less than 4000 km. (NASA MOR, 3 June 75)
3-6 June: A Kennedy Space Center team tested a parachute system designed to lower an instrumented probe through the dense atmosphere of Venus to its surface. The tests-made for Ames Research Center in preparation for a Pioneer mission to Venus in 1978-were conducted in KSC's Vehicle Assembly Building, an ideal wind-free testing facility. Full-scale 3.7-m parachutes with simulated pressure vessels weighing 204 kg were dropped 13 times from heights of up to 137 to the floor of the VAB with impact cushioned by a honeycomb cardboard impact arrester. The performance of the parachute system was monitored photographically during the drop to determine the aerodynamic trim characteristics of the parachute.
The 197$, Pioneer -Venus mission would include the launch of two separate spacecraft toward Venus. The first would orbit the planet collecting data for about 250 days; the second would carry one large probe, which would use the parachute to descend to the surface, and three small probes decelerated by aerodynamic drag only. The parachute on the largest probe would be used to separate an instrument bearing pressure vessel and stabilize it for a series of critical scientific measurements as it passed through the Venusian cloud layer. None of the probes was designed to communicate with earth after impact. (KSC Release 98-75; Lockyer, Public Affairs Office, interview, 6 Oct 75)
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