Nov 28 1978
From The Space Library
The most extensive study ever made of Venus would begin in December when Pioneer Venus 1 and 2 arrived at the planet, NASA announced. Pioneer Venus 1 would swing into orbit around the planet Dec. 4, taking pictures and making measurements for one Venusian yr (225 earth days) or more. On Dec. 9 the four probes and transporter bus constituting Pioneer Venus 2 would plunge into the Venusian clouds at widely separated points to make detailed measurements of the dense atmosphere from top to bottom. These flights, the first devoted to studying the atmosphere and weather of another planet on a global scale, would use the largest number of vehicles so far for such a study, and would make measurements at the greatest number of locations. They also would seek information on characteristics of Venus's upper atmosphere and ionosphere, as well as the lower atmosphere, and would study the interactions of these regions with the solar wind.
At periapsis (orbital low point) the Pioneer orbiter would come as close as 150km (90m) to the planet's surface, dipping into the thin Venus upper atmosphere, sampling its composition, and making radar measurements of surface elevations and roughness. It would also take daily ultraviolet and infrared pictures of the thick clouds and atmosphere. The orbiter's primary mission was designed to cover the time it took Venus to make one revolution on its axis; the slow rotation of the planet under the periapsis of the orbit would permit closeup radar mapping of the entire circumference.
The four probes of Pioneer Venus 2 would enter the atmosphere at points 10 000km (6000mi) apart over the planet's earth-facing hemisphere: the large probe would enter Venus's atmosphere near the equator on the day side; the day probe would enter Venus's southern hemisphere on the planet's day side; the night probe, the night southern hemisphere on the night side; and the north probe, the north polar vortex on the night side. The transporter bus would enter in the southern hemisphere on the day side.
Critical operations on arrival near the planet would be to inject Pioneer Venus 1 into orbit while it was out of radio contact behind Venus, and the entry and descent through the atmosphere of the four probes and bus. On Dec. 2, controllers at ARC would orient the orbiter for orbit insertion, and the next day would load command-memory sequences. On Dec. 9, the probes would be in position to make their hr long descent through Venus's atmosphere. Major operations problem would be retrieving probe data; during the critical 1hr 38min of probe and bus operations at Venus, all the Pioneer spacecrafts would be transmitting simultaneously. Radio frequencies of the probe signals would shift rapidly because of huge entry decelerations-from 42 000km/hr (26 000mph) to about 65km/hr (40mph)-and signal distortions caused by Venus's dense atmosphere. One consequence would be that, after the 10- to 15-sec communications blackout during entry, signals would reappear again at new frequencies. To ensure recovery of the data, NASA had installed special equipment in DSN stations at Goldstone, Calif., and Canberra, Australia. To avoid loss of data, both DSN stations would use newly developed receivers and recorders with a frequency band wide enough to ensure receipt of the four shifting signals. The real-time system would use automatic tuners, but would lose some data.
Scientists believed that the coordinated Pioneer Venus atmospheric data, combined with similar data from Mars, Jupiter, and other planets, would aid understanding of atmospheres in general. Studies of the interactions of temperatures, pressures, composition, clouds, and atmospheric dynamics different from those of earth should define mechanisms on another planet that would improve scientists' understanding of earth's complex weather processes. (NASA Release 78-181) ESA's meteorological satellite, Meteosat 1, had been in orbit for a yr carrying out its image-taking, dissemination, and data-collection missions, ESA announced. Ground facilities at the European Space Operations Center (ESOC) in Darmstadt, Germany, for receiving, processing, archiving, and disseminating meteorological data from the satellite were ready to fulfill all requirements for the first GARP experiment, scheduled to begin Dec. 1. Meteosat 1, which transmitted every half hr visible and infrared images of the earth, had been retransmitting to primary and secondary data-user stations some 300 formats per day in various digital and analog forms. It also acted as a relay for image data from the U.S. satellite Goes 1 over the Atlantic, transmitted through the Centre de Meteorologie Spatiale at Lannion at the rate of about 20 formats per day. Meteosat 1 had also participated in Nov. in the first transmission tests of image data from the U.S. Goes 3 satellite over the Indian Ocean, so that users had received data from three geostationary satellites covering approximately two-thirds of the globe.
Data-collection platform experiments had demonstrated the high quality of the links between Meteosat Land the mobile platforms; about 15 DCPs were operational, and about 10 were in the process of being admitted and would come into service in early 1979.
Another mission of Meteosat 1 was to supply immediately usable meteorological products (wind speed, cloud height, sea-surface temperature, etc.). Meteosat image quality should maintain the serviceability of these products; results already achieved were at least comparable to those obtained by other geostationary satellites participating in the GARP. Use of the water-vapor channel, an original feature on Meteosat 1, was considered by the meteorological community as a major advance in refinement of interpretation techniques. (ESA Release Nov 28/78)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
