Dec 10 1974
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(New page: 10 December-16 January 1975: NASA launched West German-built Helios 1 solar probe at 2:11 am EST from Eastern Test Range on a Titan Centaur vehicle, putting it on a path that would tak...)
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10 December-16 January 1975: NASA launched West German-built Helios 1 solar probe at 2:11 am EST from Eastern Test Range on a Titan Centaur vehicle, putting it on a path that would take it closer to the sun than any spacecraft had yet traveled. The spacecraft first entered a parking orbit and then an elliptical orbit of the sun with a 0.985-AU aphelion, 0.3095-AU perihelion, 190.15-day period, and 0.02° inclination to the ecliptic. All vehicle systems performed normally during launch.
The Titan-Centaur carried a Delta solid-fueled rocket-motor kick stage as a 4th stage and required seven interdependent ignition systems.
Following separation from the 1st stage, the Centaur, with 2300 kg of propellants remaining, began maneuvers to provide data for the 1977 Mariner Jupiter-Saturn mission, future synchronous orbit missions, and continued development of the launch vehicle. Maneuvers included a one-hour coast and restart, three-hour coast with thermal maneuvers, boost-pump operation experiment with igniter on, and zero-g boost-pump dead-head operation.
Helios 1 was to investigate the fundamental solar processes and solar-terrestrial relations by studying the solar wind, magnetic and electric fields, cosmic rays, and cosmic dust from launch to the first perihelion, 0.31 AU from the sun. The 370-kg spool-shaped spacecraft carried 10 instruments-7 West German and 3 U.S.-to measure the solar wind, magnetic field, and related shock waves; study radio waves and oscillations in the electron plasma; measure the spatial gradient of solar and galactic cosmic rays; observe composition and dynamics of inter-planetary dust; and monitor x-ray activity of the solar disc.
By 16 Jan. orientation and spin-rate maneuvers had been conducted and the high-gain antenna despun and pointed toward the earth. Control of the spacecraft had been passed to Germany. Instruments had been turned on and were operating normally with two exceptions: One of two antennas in the U.S. plasma-wave experiment had jammed during extension and unrolled inside the drive enclosure, producing an electrical ground and degrading all low-frequency data. Rewinding the antenna had not eliminated the ground. In addition, operation of the high-gain antenna for the West German plasma experiment produced a space charge near the spacecraft, preventing detection of electrons with energies less than 100 ev. The medium-gain antenna would be used during selected periods.
To prepare for its demanding mission, Helios 1, designed to withstand the highest temperatures ever demanded of a spacecraft, had been successfully subjected to six days at 644 K (700°F), the highest heat load expected at 0.3 AU, during spring 1974 tests at Jet Propulsion Laboratory. The spacecraft had also withstood radiation 11 times the solar intensity at the outer edge of the earth's atmosphere. Independent payload components, louver systems, optical surface reflectors and mirrors, and several layers of insulation dissipated spacecraft heat. In addition the spacecraft spun at one revolution per second to distribute evenly the heat coming from the sun. Temperatures within the experiment area were kept between 263 and 303 K (14° and 86°F).
A second Helios spacecraft would be launched in 12 to 18 mos and information from the two spacecraft would be received simultaneously from widely differing locations, for comparison with each other and with data from Pioneer- and IMP-class spacecraft.
Helios, the third cooperative U.S. and West German project, was agreed on during 1966 talks. Following technical discussions and mission definition, a Memorandum of Understanding was signed 10 June 1969. NASA provided three scientific instruments, spacecraft technical support, launch vehicle and operations, and initial tracking and data acquisition and flight operations. The German Federal Ministry for Re-search and Technology (BMFT) designed, built, and tested the space-craft and provided seven scientific instruments, data acquisition and analysis, and spacecraft control. Goddard Space Flight Center was responsible for NASA project management; Lewis Research Center had responsibility for the launch vehicle. (NASA MORS, 6 Dec 74, 16 Jan 75; NASA PAO, interview, 10 Dec 74; NASA Releases 74-314, 75-68; UPI, NYT, 9 Dec 74, 45)
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