Venus Strategy for Exploration (1970) / Chapter Skim
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6 SCIENTIFIC CAPABILITIES OF THE PLANETARY EXPLORER
6 SCIENTIFIC CAPABILITIES OF THE PLANETARY EXPLORER
Pages 66-72
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From page 66... ...
The studies of entry probes and orbiters were extensive, and we concluded that weight and cost figures were firm; balloon capability was based on extrapolation from thorough studies and was thought to be relatively secure but not in the same category as the probe and orbiter data; lander studies were only sufficient to demonstrate that a capability existed. We reviewed these studies and considered that the Planetary Explorer was almost ideally suited to answering the science questions posed, and one of our most important conclusions is that the Planetary Explorer should be the prime vehicle for exploration of Venus in the next decade.
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From page 67... ...
Limited to a 350 circle from subearth point Impact velocity 17 m/sec Spin rate Variable Lifetime Survival after impact not currently planned SMALL PROBES Descent time 95 min Science weight 4 lb Science power 3W Telemetry rate 1 bps Landing sites Limited to annular region from '\)
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From page 68... ...
Shadow duration ~30 min (12-h orbit period) Orbit inclination 20-90° Velocity at periapsis 8-10 km/sec TABLE 4 Planetary Explorer Orbiter -- 1976-l977 Mission (Launch Date: December 1976; Travel Time: 169 Days)
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From page 69... ...
69 TABLE 5 Atmospheric Balloon Mission Number of separate packages 2 Number of balloons per package 3 Float levels (typical) 50, 500, 1200 mbar Float altitude 70, 57, 51 km Initial target sites lOoN, 400N latitude 20° on dark side of terminator Lifetime 30 interrogations Duration of interrogation 5 min Tracking accuracy :t200 km Float Level 50mb ar 500 mbar 1200 mbar Science weight 4.3 lb 4.8 lb 4.8 lb Science power 22 IN 23 IN 23 IN Telemetry rate Tracking only 20 bps 20 bps plus plus tracking tracking TABLE 6 Planetary Explorer Landera Impact site Subearth point Lifetime 2 h minimum Lander weight 245 1b Total power 127 H average 220 1\1peak Science weight 55 Ib Telemetry rate rv2000 bps aValues given depend on payload and number of landers derived from the primary vehicle.
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From page 70... ...
For a typical mission designed to send instrumented probes through the atmosphere to the surface of Venus, the spacecraft consists of a bus that will operate down to 130 km altitude, a main probe to carry ~70 lb of instruments to the surface, and three smaller probes, each carrying 4 lb of instruments, which are separated from the bus and provide measurements from three widely separated regions of Venus. Some of the important characteristics of the spacecraft are given in Table 2.
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From page 71... ...
The primary concern appears to be the power supply, usually a battery, but all equipment must be provided with extensive thermal shielding. A significant increase in payload or lifetime could be obtained if spacecraft and experiment components could be developed to withstand temperatures of ~)
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From page 72... ...
Although elaborate equipment for the Planetary Explorer could greatly increase its cost, it is clear that the Plane tary Explorer is fundamentally cheaper, because, as compared to Mariner, it has about half the capacity, a booster costing about 40 percent as much, and a simpler stabilization system. Even on the basis of a fixed cost per pound, a costs factor of 2 lower can be anticipated.
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