Dec 10 1985
From The Space Library
ESA announced it signed three contracts with Arianespace, two for future launches-ECS-4 scheduled for the second quarter of 1986 and Hipparcos scheduled for June 1988-and one for technical assistance for satellite launches on the first flight of Ariane 4.
ECS-4 would replace ECS-3, lost as a result of the launch failure September 12 of Ariane V15. ECS-4 was in production at that time, and ESA accelerated its completion. Arianespace was providing the earliest possible launch slot in accordance with the relaunch conditions in the ECS-3 launch contract.
Hipparcos would provide measurements of the positions, annual proper motions, and parallaxes of some 100,000 stars. From its position in geostationary orbit, the satellite systematically and repeatedly throughout its two and-a-half-year lifetime would scan the whole sky, providing measurements that would serve as a reference system of unprecedented precision, important in studies of earth's motion, the solar system, and our galaxy, and forming a basis for future ground and space astrometry.
Under the third contract, the first flight of Ariane 4, part of ESA's Ariane 4 development program, would be carried out under ESA's responsibility. The launch, scheduled to take place during the third quarter of 1986, was designed to demonstrate the operational capability of Europe's most powerful launcher. ESA was supplying part of the payload, Meteosat P2, a refurbished spacecraft from the preoperational series, designed to bridge a possible gap between Meteosat 2 and the first of the operational meteorological spacecraft, MOP-1, scheduled for launch in late 1987. Additional payload elements would be Amsat Phase III-C, the second unit of the third generation of the amateur radio “Oscar” series, and a telecommunications satellite yet to be selected. (ESA release Dec 10/85)
Marshall Space Flight Center announced that NASA's first experiments to construct large structures in space were a success [see Space Transportation System/Mission, Nov. 30 and Dec. 2]. EASE (Experimental Assembly of Structures in Extravehicular Activity) and ACCESS (Assembly Concept for Construction of Erectable Space Structures) carried out by astronauts Jerry Ross and Sherwood Spring “went exactly as we had planned, and all experiment and Space Transportation System objectives were met,” said Ed Valentine, mission manager for the EASE/ACCESS payload flown on Space Shuttle mission 61-B. Those objectives included gathering data to compare assembly rates and techniques in space to those used during simulations on the ground and in neutral buoyancy water tests, evaluating potential space station assembly and maintenance concepts and techniques, and identifying ways to improve erectable structures to ensure productivity, reliability, and safety.
“Preliminary data obtained from live downlink TV looks very good,” Valentine explained. “But we won't be able to make a complete analyses until we see the rest of the data,' which was in the form of videotape and film shot while Ross and Spring performed the construction tasks.
Once the data were analyzed and reported, Valentine said, it would give large space structure designers baseline data on the two construction approaches studied. “They can then determine which approach would be appropriate for a particular task,” he explained.
On December 11 Valentine said he would meet for a debriefing with the Space Shuttle crew and principal investigators. Then in about three weeks the principal investigators would receive the videotape and film shot during the experiments, and Valentine would publish a final report in about three months. (NASA Release 85-66)
NASA announced that scientists from the U.S., France, the United Kingdom, and West Germany released their findings from the rendezvous on September 11 of the International Cometary Explorer (ICE) spacecraft with Comet Giacobini-Zinner. Although some ICE data confirmed the traditional portrait of a comet, other information was unexpected.
Perhaps most surprising was detection of electrical wave (plasma) disturbances and high-speed molecular species coming from the comet more than a day before rendezvous. The spacecraft's Plasma Wave Experiment, developed by TRW's Dr. Frederick Scarf, detected the electrical waves while ICE was 1,429,200 miles from the comet. Scientists had theorized that first detection might occur just a few hours before the spacecraft crossed the comet's tail.
A few hours after initial detection, but still one day before intercept, two of ICE's instruments discovered electrically-charged particles (ions) as far as 1,130,000 miles from the comet. The Energetic Proton Experiment, directed by Dr. Robert Hynds, Imperial College, London, and the Low-Energy Cosmic Ray Experiment, directed by Dr. Dieter Hovestadt of the Max Planck Institute for Extraterrestrial Physics, Garching, West Germany, detected these ions. According to Hynds, it was believed solar ultraviolet light ionized gas molecules escaping from the comet's nucleus, then the solar wind picked up and accelerated the ions back toward the comet.
In another finding, Dr. Samuel Bame of the Los Alamos National Laboratory reported that, in contrast to the hot electrons on the outskirts of the comet, its tail consisted of a dense narrow structure of cool plasma. The Radio Wave Experiment of France's Meudon Observatory made this same finding.
The ICE's Ion Composition Experiment, directed by Dr. Keith Ogilvie of Goddard Space Flight Center, made the first direct measurements of molecules in a comet. The experiment found mainly water vapor ions, confirming the “dirty snowball.” model of comets.
A major prediction confirmed by the ICE data was that the magnetic structure of the comet's plasma tail consisted of two parallel lobes, each threaded by a magnetic field of opposite polarity. ICE's Magnetometer Experiment of Dr. Edward Smith of the Jet Propulsion Laboratory mapped this structure, which was predicted in 1957 by Nobel physicist Dr. Hannel Alfven.
Putting conflicting scientific conjectures to rest, the ICE mission revealed that no clear-cut bow shock-a surface moving ahead of the comet like that through which a jet aircraft passes as it breaks the sound barrier-accompanied the comet. Instead, researchers found around the head of the comet what they called “a transition region” in which the solar wind was heated compressed, and slowed.
Neither the ICE spacecraft nor its instrument payload suffered any detectable damage as a result of the impact with the comet's dust. (NASA Release 85-166)
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