May 30 1978
From The Space Library
May 30-June 1: NASA launched Pioneer Venus 1 -from Cape Canaveral at 9:13am EDT May 20 atop an Atlas Centaur rocket. It would launch a Venus lander toward the planet 3mo later, about Aug. 7. Pioneer Venus 1, an orbiter, should reach its destination by Dec. 7, 1978; Pioneer Venus 2, a multiprobe spacecraft, would arrive 5days later after splitting into a bus and 4 atmospheric-entry probes 13 million km (8 million miles) and 20days out from the planet. Most engineering systems and the interplanetary experiments had signaled normal operation. "Performance so far has been extremely good," said Marshall Johnson, Venus-orbiter flight director at ARC. "Of course, we have 300 million miles and 6mo to go," he added. At 9am PDT June 1 the spacecraft was 4 800 000km (2 890 000mi) from earth and had traveled toward Venus at 16 580kph (10 296mph). Controllers would make the first midcourse correction June 8, changing velocity to 12.6kph (7.8mph) to aim the Pioneer at the exact point for Venus orbit insertion.
Pioneer Venus 1, a spin-stabilized spacecraft with its spin axis perpendicular to the ecliptic plane, consisted of a cylindrical thrust tube serving to transmit acceleration loads into the spacecraft; a 97.5in-diameter circular equipment shelf for mounting electronic units and scientific instruments; a 100in-diameter cylindrical substrate 48in long for mounting the solar-cell array; and a despun mast assembly supporting three antennas, including a high-gain antenna. A single-piece fitting that would remain on the Centaur at spacecraft separation would be the mechanical/ structural interface with the launch vehicle. Payload was 12 scientific instruments with a total weight of 1001b, using average power of 58watts and peak power of 85watts. The instruments could handle 75 redundant discrete commands and 6 redundant quantitative commands, as well as 17 serial-digital, 24 bilevel, and 31 analog telemetry channels. Three of the instruments would use pyrotechnic firing pulses for various functions. The magnetometer had been put at the tip of a 15.7ft beam to isolate it from spacecraft magnetic fields. The Pioneer Venus Haunch vehicle was an Atlas SLV-3D Centaur D-14 131ft tall, weighing about 328 6401b at liftoff. The nosecover protecting the spacecraft, a conical/ cylindrical fiberglass fairing about 29ft high attached to a 56in-high aluminum split barrel, had been designed for jettison early in the Centaur burn.
NASA had launched Pioneer Venus 1 into an ascent trajectory varying from 3° to 18° south of due east during the first 15days; the Imo flight to Venus would take the spacecraft more than halfway around the sun (through about 200°), covering about 480 million km (300 million mi). The orbiter would take 3mo longer for the trip than the multiprobe, and would have a slower speed upon arrival at Venus, requiring less power from the orbit-insertion motor. For the first 82 days after launch, Pioneer Venus 1 would fly outside the earth's orbit. In Aug. it would return inside earth's orbit and, during the last 4mo of the journey, would cross 42 million km (26 million mi) on a long curving trajectory between the orbits of the earth and Venus. The orbiter's flight path would resemble that of the Venus multiprobe, to be launched a few days after the orbiter crossed back inside earth's orbit.
NASA had designed the flights to answer questions such as: Why had two planets with about the same mass, formed of similar materials and situated at comparable distances from the sun, evolved different atmospheres? Why had the surface of Venus baked in searing heat, while earth had climate friendly to life? Answers would aid in understanding the evolution of Venus and earth atmospheres and the forces affecting earth's weather. The Pioneer Venus flights, first devoted to studying another planet's atmosphere and weather on a global scale, would use the largest number of vehicles devoted to such studies and would make measurements at the greatest number of locations. The flights would record characteristics of Venus's upper atmosphere and ionosphere, as well as of the lower atmosphere, and interactions of these regions with the solar wind (the continuous stream of ions and electrons flowing outward from the sun) and with the solar magnetic and electric fields. Circling the planet for at least 80mo, the Pioneer Venus orbiter would make the longest observations of Venus to date and would be the first U.S. spacecraft to orbit the planet. A NASA-contractor team under KSC's expendable vehicles directorate had been responsible for preparing and launching Pioneer Venus I. Hughes Aircraft Co. had built the spacecraft and radar mapper. (Ames Release 78-21; MOR S-825-78-01 [prelaunch] May 15/78; [prelaunch summary] May 11/78; NASA Release 78-68; NASA press brief May 9/78; Marshall Star, May 17/78, 1; May 24/78, 1; Lewis News, May 26/78, 1; JSC Roundup. May 26/78, 1; DFRC X-Press, May 19/78, 2; C Trib, May 21/78, 1-3 W Post, May 21/78, A6; NYT, May 22/78, A10; W Star, May 21/78, A-2)
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