Aug 24 1978
From The Space Library
NASA reported it had launched Isee 3 from ETR on a Delta rocket at 11:12am EDT Aug. 12, 1978. Eleven days into the mission, the spacecraft had traveled approximately 900 000km in a transfer trajectory out from earth to a halo orbit about the sun-earth libration point. All scientific instruments had been activated and were operational; all spacecraft appendages had been deployed except the + / - Z-axis antennas, which had partially deployed.
The international sun-earth explorers (ISEE) project, a NASA/ESA joint contribution to the International Magnetospheric Study (IMS), consisted of two missions using three spacecraft to study solar-terrestrial relationships, NASA providing ISEE-A and -C and ESA providing ISEE-B. NASA had launched ISEE-A and -B (Isee 1 and 2) on Oct. 22, 1977, on a single Delta vehicle into the same highly elliptical earth orbit, where they were both operating. Isee 3, just launched toward a heliocentric orbit near the sun-earth libration point, had carried a scientific payload of 16 detector systems and associated electronics provided by 12 principal U.S. and European investigators to measure the solar wind and its fluctuations in detail.
Whereas ISEE-A, -B, and -C were capable of contributing individually to scientific knowledge, the greatest return would result from acquiring data from all three spacecraft: ISEE-C in its heliocentric orbit would measure the sun's input function unperturbed by the earth's influence, while ISEE-A and -B were measuring the effect of this input on the region surrounding the earth. At the time the ISEE-C entered its halo orbit in November 1978, it would become the world's first libration-point satellite. (MOR S-862-78-03 [postlaunch] Aug 24/78, [prelaunch] July 31/78; Marshall Star, Aug 30/78, 2; Spaceport News, Aug 18/78, 1; ESA release Aug 10/78; Nature, Aug 17/78, 630; D/SD, Aug 17/78, 630; Aug 14/78, 199)
NASA had decided to launch its Venus-orbiting imaging radar (VOIR) late in 1984 rather than mid-1983 to reduce schedule risk, Aerospace Daily reported. Officials said the change, not meant to enhance VOIR's prospects as a new-start candidate for FY80, would reduce the program's first-yr and peak-yr funding needs. A 1984 launch funded in FY80 would permit Phase-B definition studies of the mission's primary instrument -a synthetic-aperture radar (SAR)-to precede those of the spacecraft by about 6mo and to produce data for use in the spacecraft work. Work on both the SAR and the spacecraft development would begin simultaneously in the second quarter of 1981. Although the Dec. 1984 launch opportunity was less favorable than that of May-June 1983, officials considered it acceptable and weight margins, based on completed Phase-A studies, adequate. (A/D, Aug 24/78, 241)
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