Akatsuki Venus Climate Orbiter |
Akatsuki Venus Climate Orbiter |
Mar 13 2010, 11:29 AM
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#501
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Senior Member Group: Members Posts: 1729 Joined: 3-August 06 From: 43° 35' 53" N 1° 26' 35" E Member No.: 1004 |
I thought it was time to start a separate thread on this mission, launching soon
some good medium-resolution images of the spacecraft are available on JAXA digital archives http://jda.jaxa.jp/jda/p3_e.php?time=N&...mp;mission=4066 |
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Oct 16 2011, 10:00 AM
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#502
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Senior Member Group: Members Posts: 1729 Joined: 3-August 06 From: 43° 35' 53" N 1° 26' 35" E Member No.: 1004 |
pandaneko,
I don't have the original references at hand now, but here are some sentences from the forthcoming "Robotic Exploration of the Solar System - part 3" book: QUOTE In Nozomi’s case, a latching valve in the pressurization system of the oxidizer suffered a malfunction that caused the engine to burn a non-optimal mixture of more fuel and less oxidizer than required. As a result, Nozomi was left with a velocity shortfall of 100 m/s. If ISAS had been in communication with the spacecraft, it could have ordered an immediate follow-on burn to compensate, but contact was not established until 12 hours later, and by that time the engine could not recover the trajectory and still fly a nominal mission. QUOTE At the end of April 2002, Nozomi ceased to issue telemetry, apparently after a power supply malfunction. The cause was never determined, but could have had something to do with the massive solar flare that completely saturated solar proton monitors. Engineers soon found that they could not perform attitude maneuvers or course corrections. It was inferred that the loss of the power supply must have also switched off the hydrazine tank heaters, causing the fuel to freeze. QUOTE After 2 months, however, it proved possible to restore the beacon. Japanese controllers then employed a clever trick in which they reprogrammed the on/off status of the beacon as a means of producing the telemetry required to gain some understanding of the health of the spacecraft. QUOTE engineers had still to determine how to regain use of the power supply, as this would be essential for orbit insertion and for scientific operations. With Nozomi finally heading for its target, disaster struck again with contact being lost on 8 July 2003 and never re-established. The reason for this failure was never determined.
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