Jun 12 1975
From The Space Library
NASA launched Nimbus 6 on a thrust-augmented Thor-Delta booster from the Western Test Range at 1:12 am PDT after a 6-min delay to clear a ship from the jettison trajectory of the Delta's solid rockets. The spacecraft entered sun-synchronous polar orbit with a 1103-km apogee, 1094-km perigee, 107-min period, and 99.96° inclination. Separation of the spacecraft from the launch vehicle was normal, at 59 min into the flight. The solar panels were deployed and the attitude-control system quickly acquired earth. A wheel control provided three-axis stabilization. Checkout of the power system, telemetry, command links, and tape recorder was completed on the first day of operation.
At 7 hr after launch, a cryogenic vent valve associated with the limb-radiance inversion radiometer was pyrotechnically actuated as planned. This caused unexpected high torques and excessive control gas usage. Nimbus 6 was put into a safe wideband gravity-gradient mode to conserve gas, and an investigation was begun to find the cause of the problem and determine possible remedies. By 24 June the 9 experiments and all spacecraft systems had been checked out and all instrumentation, except for 2 tape recorders, was working normally.
The primary objective of the Nimbus 6 mission was to contribute to the Global Atmospheric Research Program (GARP) by refining and extending the capability of vertically sounding the temperature and moisture of the atmosphere, with particular regard to altitude resolution and interference effects of clouds. GARP, a cooperative worldwide weather program, was established to improve understanding of meteorological atmospheric processes in the tropics and to improve observation and computing systems for weather prediction and analysis: Nimbus 6 would also monitor environmental conditions such as sea ice and rainfall and would measure the earth's radiation budget with a precision never before attained.
Secondary objective of the mission was to demonstrate the ability to track and relay data from a low-altitude polar-orbiting spacecraft using a geosynchronous satellite as a communications relay. Ats 6, the Applications Technology Satellite launched on 30 May 1974, would be the relay comsat.
A data-collection, processing, and relay-to-earth system was also on board to collect data from approximately 300 balloon-borne platforms, designed to float at an altitude of 20 km, and a large number of earth- and sea-based data platforms. Nimbus 6, unlike previous spacecraft, could receive and process up to eight incoming signals at a time.
The satellite carried nine new instruments to extend measurements of atmospheric parameters to significantly higher altitudes than had previously been possible: the tracking and data-relay (T&DR) experiment; a high-resolution temperature sounder (AIRS) and a scanning microwave spectrometer (SCAMS) to take temperature soundings in the atmosphere outside the tropics; a tropical wind-energy conversion and reference level experiment (TWERLE) to provide data on tropical areas; a limb-radiance inversion radiometer (LRIR) and a pressure modulated radiometer (PMR) to provide high-altitude temperature soundings; an earth radiation budget (ERB) experiment to establish the earth's atmospheric radiation balance; an electrically scanning microwave radiometer (ESMR) to map the liquid-water content of the clouds, ocean rainfall,, and distribution and variation of sea-ice cover; and a temperature/humidity infrared radiometer (THIR) to provide data on cloud cover, ground temperatures, and water-vapor distribution.
Nimbus 6 was next to last in a planned series of seven experimental meteorological satellites. Nimbus 1 (launched 28 Aug. 1964) and Nimbus 2 (launched 15 May 1966) achieved all their objectives. Launch of the third Nimbus, on 19 May 1968, failed when the launch vehicle malfunctioned; an identical spacecraft launched 14 April 1969 successfully functioned as Nimbus 3. [[Nimbus 4]] and 5 (launched 8 April 1970 and 10 Dec. 1972) had both completed all mission objectives and were still operating.
General Electric Co. was the prime contractor responsible for Nimbus 6 integration and test, stabilization control, control-subsystem integration, and spacecraft structures and antennas, Seven U.S. and two British companies, in addition to the Jet Propulsion Laboratory, provided the nine instruments. Goddard Space Flight Center managed the Nimbus program under the direction of the NASA Office of Applications and was also responsible for the Thor-Delta launch vehicle. (NASA MORs 21 May 74, 12 June 75, 24 June 75; NASA Release 75-145)
An Apollo-Soyuz Test Project flight readiness review at Kennedy Space Center was attended by Dr. George M. Low, NASA Deputy Administrator; ASTP Program Director Chester M. Lee; and top management from NASA Headquarters and Marshall, Johnson, and Kennedy Space Centers.
During the meeting Lee said that "ASTP is on schedule and ‘go’ for launch on July 15." Top management had reviewed and closed out all aspects of flight preparations. ASTP Technical Director Glynn S. Lunney reported that no hardware problems remained that might interfere with an, on-time launch.
MSFC Saturn Program Manager Ellery B. May reported that the 8yr-old Saturn IB launch vehicle had been carefully checked out and all components were being monitored by periodic inspections; during one of these inspections corrosion cracks had been discovered in the fins, requiring them to be replaced [see 19 Feb.-19 March]. May reported that the vehicle was ready to fly.
William H. Rock, manager of the Sciences and Applications Project Office at JSC, said that modifications, including a larger, more effective lightning rod on the launch tower, had been made to the launch pad to minimize the hazards from lightning strikes. Jesse R. Gulick, KSC meteorologist, said that thunderstorm probability for launch day was 23% and that the probability of a tropical storm or hurricane winds was less than 3%. Based on previous years' data, chances were good that, even if bad weather postponed the primary launch date, the Apollo spacecraft could be launched within 4 days. (MSFC Release 75-119; KSC Release 104-75; Marshall Star, 18 June 75, 1; Ezell et al., The Partnership: A History of the Apollo-Soyuz Test Project, 310-12)
Viking Lander 1 would undergo a critical milestone in its development, terminal sterilization, beginning 13 June, Robert S. Kramer, NASA Director of Planetary Programs, said at a Viking news conference in Washington, D.C. The Lander would remain in the oven for 2.5 days and then be removed and checked out. Past missions had failed because "maybe we knew how to sterilize a spacecraft but we didn't know how to make one work after it was sterilized," Kramer said. However, "we think we know a lot more now than we did 15 years ago. We believe we have developed the techniques to be fully reliable, but when we complete that test along about next Tuesday morning, then we are going to find out for sure." A. Thomas Young, Viking Mission Operations Manager at Langley Research Center, said that plans called for launch of Viking 1 on 11 Aug. and launch of Viking 2 on 21 Aug. Mission planners had deliberately arranged for the first Viking to arrive at Mars on 18 June 1976, after 10 mos of travel, and Viking 2 to arrive on 7 Aug. 1976, about 1 yr after it was launched. Both spacecraft would spend about 17 days in orbit examining landing sites "to assure ourselves that they continue to be safe." The sites, which had not been examined since 1971, must be checked again because Mars was a dynamic planet.
Lander 1 was scheduled to begin its descent 4 July and start black-and-white photography immediately upon landing. Color photography would begin 18 hr later. The first soil sample would be collected on the eighth day. Analysis of the sample would take 12 days to complete, and 20 days would be required to complete one cycle of all surface science. Young noted that, to avoid confusion during the mission, Martian days would be called "sols" because they were a half-hour longer than earth days.
During surface operations, the Orbiter passing overhead once a day would remain synchronized with the Lander; on the pass, the Orbiter, acting as a communications satellite, would relay information from the Lander to earth. When the Lander completed its work, the Orbiter would perform observations of its own, studying Martian surface features, including the proposed Lander B landing site, from orbit. (Transcript)
A theory that the moon was actually a piece of the earth broken away early in the planet's formation 4.5 billion yrs ago was presented in a paper by Dr. John A. O'Keefe, a Goddard Space Flight Center scientist, and Professor Harold C. Urey, Nobel Prize winner from the Univ. of California. The paper, presented by Dr. O'Keefe at a meeting of the Royal Society in London, stated that although the moon had little, if any, metallic core, data from Apollo lunar-landing missions and earlier unmanned lunar flights had provided chemical evidence that lunar rocks were once a part of a mass that had included a considerable portion of molten iron.
The higher proportion of molten metal in the earth supported the theory that, before the split, the iron in the earth had sunk to the center, drawing with it the gold, platinum, and other rare metals found in molten rock originally mixed with the iron. According to the theory, the moon was pushed to its present distance from the earth by interaction with the tides of the body of the earth.
Other theories about the formation of the moon included the possibility that the moon had been captured by the earth's gravitational field when it passed near the earth, or that it had been formed simultaneously with the earth. Neither of those theories explained the moon's lack of a substantial metallic core. (NASA Release 75-171)
S. Neil Hosenball, NASA's Deputy General Counsel, had been appointed General Counsel, effective immediately, replacing R. Tenney Johnson, who had been named General Counsel of the Energy Research and Development Administration in February.
Hosenball, who had been Deputy General Counsel since 1967, had been Assistant General Counsel for Procurement from 1966 to 1967 and previously had served for 4 yr as Chief Counsel at Lewis Research Center. (NASA Release 75-173)
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