Magellan radio loss remains mysterious.Magellan radio loss remains mysterious Venus-orbiting Magellan--its wayward radio link now restored for the second time -- has forced NASA NASA: see National Aeronautics and Space Administration. NASA in full National Aeronautics and Space Administration Independent U.S. to devise new measures to restore communications should the spacecraft go silent again. Mission engineers at the Jet Propulsion Laboratory “JPL” redirects here. For other uses, see JPL (disambiguation). Jet Propulsion Laboratory (JPL) is a NASA research center located in the cities of Pasadena and La Cañada Flintridge, near Los Angeles, California, USA. in Pasadena, Calif., have written emergency commands to send to Magellan if the signal problem recurs. They plan to send the new instructions slowly, at 40 bits a second, to the craft's low-gain antenna The low-gain antenna (LGA) is an antenna with a broad radiowave beam width. This very wide beam allows for a more reliable signal that is best used in mountainous regions, where the signal will propagate reasonably well regardless of terrain. , which has a wider field of view than the other antennas. Officials adm it they don't know Don't know (DK, DKed) "Don't know the trade." A Street expression used whenever one party lacks knowledge of a trade or receives conflicting instructions from the other party. and may never determine precisely what silenced Magellan on either occasion (SN: 8/25/90, p.1117) Magellan lost contact with Earth for nearly 15 hours on Aug. 16 and for 17 hours on Aug. 21. both signal interruptions apparently occurred when the crafts unaccountably un·ac·count·a·ble adj. 1. Impossible to account for; inexplicable: unaccountable absences. 2. entered a "safe mode." Magellans's attitude-control-system computer is programmed with several such modes to help protect the craft against malfunctions that arise without warning. Officials hope the new commands will rapidly correct any future communications losses. "I want a safing action that the spacecraft takes to establish quick communications to Earth," says project manager Anthony Spear. "My heart can't stand this 17 hours' loss of signal." Magellan science manager Thomas W. Thompson Thomas Weston Thompson (March 15, 1766 - October 1, 1821) was a United States Representative and Senator from New Hampshire. Born in Boston, he attended Dummer Academy in Byfield, Massachusetts and graduated from Harvard University in 1786. says engineers succeeded on Aug. 24 in getting the craft to send 1,200 bits of information per second, not just the 40 bits per second to which it dropped during its recovery from the first signal loss. The data speed-up was only a test, however, because transmissions sometimes prove less reliable at the faster rate, Thompson says. Project officials have formed a special team of about 12 experts from inside and outside NASA to study the communications failures. Spear says the group is analyzing several possible causes, including an electric spark Electric spark A transient form of gaseous conduction. This type of discharge is difficult to define, and no universally accepted definition exists. It can perhaps best be thought of as the transition between two more or less stable forms of gaseous conduction. ; a cosmic ray striking and altering a computer chip; and computer memory failures during the jettisoning of the rocket motor that put Magellan into its Venus orbit. With the communications mystery still unsolved. Thompson says Magellan will not begin its full radar-mapping of Venus before late September. The long-term mapping had been scheduled to start on Sept. 1. |
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