Voyager Status, What is it? |
Voyager Status, What is it? |
Dec 6 2006, 05:48 AM
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#1
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Member Group: Members Posts: 428 Joined: 21-August 06 From: Northern Virginia Member No.: 1062 |
Anyone know the latest Voyager status? I've hear rumors, but I'm wondering if anyone has anything more concrete (I won't share the rumors, as I really don't know much about it, so...)
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Dec 14 2023, 11:07 PM
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#2
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Senior Member Group: Members Posts: 1592 Joined: 14-October 05 From: Vermont Member No.: 530 |
Speaking of SEU. Found in IEEE Spectrum June 1987...
QUOTE A faraway bit fix Just six days before Voyager 2's closest approach to Uranus, in 1985, compressed photographic images transmitted from the spacecraft's cameras began to include large blocks of black-and-white lines. Engineers at the Jet Propulsion Laboratory, Pasadena, Calif., ran an old data stream received from the craft through the programs used to decompress the images back on earth. The engineers concluded that the problem lay not in the ground computers, but in the craft's flight-data subsystem (FDS), which controls on-board instruments and formats data for transmission back to earth. To test the theory, they directed the FDS to transmit the contents of its 8-kilobyte CMOS memories. By comparing that copy of the image-compression program with the original on earth, engineers Dick Rice and Ed Blizzard determined that a single bit of one 16-bit instruction word had changed from a 0 to a 1. Rice and Blizzard prepared a patch that would circumvent the faulty location in the memory. The patch overwrote the instruction before the failed memory cell with a jump command to unused memory. It then executed a copy of the overwritten instruction and the instruction from the defective location, and jumped back to the address following the failed cell. The patch was transmitted to Voyager, along with a command to reset the incorrect bit. The patch corrected the failure, and in the least possible time, since transmitting a message to Voyager and receiving a response took 41 hours. The reset command failed, and Rice and Blizzard therefore concluded that the bit failure was permanent. With the patch installed, the program sent error-free images. But engineers acknowledged that the actual cause of the failure would likely never be known. The craft will not return to earth "within our lifetime," said a Voyager team member. So, precedented. Of 32kbit on both, there's been at least one bit failure. |
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Lo-Fi Version | Time is now: 24th September 2024 - 02:04 AM |
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