Voyager Status, What is it? |
Voyager Status, What is it? |
Dec 6 2006, 05:48 AM
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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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Guest_Analyst_* |
Jan 5 2007, 05:11 PM
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#2
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Guests |
Since the main receiver failed on Voyager 2 shortly after launch back in 1977, and they had to rely on the backup receiver which is apparently tone deaf, for lack of a better technical phrase, how is that rather critical piece of equipment holding up? And how are they keeping it so finely in tune after all this time? The only working receiver (there are two) is unable to change its receiving frequency, so it can only listen in a very, very narrow frequency spectrum. It can't stay in lock if the incomming frequency shifts. There are at least two problems resulting: - The receiving frequency can't be changed by the spacecraft to stay in lock, but it can change because of temperture variations. A one degree temperature change means a frequency shift of x Hz. So you have to look very carefully at the receiver temperature when the signal arrives (Ten hours or so after being sent). If there is an attitude change (MAGROL etc.) of the spacecraft, the temperature and therefore the frequency can't be predicted good enough. Then they declare a command moratorium and no commands are sent for some days. - But even if you know the receiving frequency you have to take into acount the doppler effect: Voyager is moving away from the sun, but the earth moves arround the sun and so the distance between earth and spacecraft sometimes rises, sometimes falls. Earth itself rotates, this complicates things too. And the atmosphere changes the signal too. So you must predict the receiver frequency and then sent a command at a frequency, that adjusted for the doppler effect and atmospheric changes matches this predicted frequency within a few Hz. Because of the uncertainty commands are sent more than once at different frequencies nearby (brackated) so that at least some get through. They do since 1978! If this last receiver fails, the Voyager 2 command loss routine will configure the spacecraft for longterm science return even without further commanding from earth. Of course you lose the capability to react to science events and failures of other subsystem components, but you get (limited) science as long as nothing happens the spacecraft can't handle by itself (by switching to redundant subsystems etc.). Analyst |
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