Extricating Spirit, Digging out from Troy |
Extricating Spirit, Digging out from Troy |
Nov 7 2009, 04:13 PM
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#1
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Member Group: Members Posts: 239 Joined: 18-December 07 From: New York Member No.: 3982 |
5 downsampled navcam frames from sol 2078 are down. Someone might want to make an animation.
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Apr 13 2010, 05:24 PM
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#2
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Senior Member Group: Members Posts: 1591 Joined: 14-October 05 From: Vermont Member No.: 530 |
Well, since it is the doppler shift they're interested in, the distance of the Spirit from the center of Mars affects its radial velocity, so that movement upslope...
...is going to be a probably immeasurable difference. Actually, compared to the frequency variability implicit in the temperature of the oscillator on the rover... yeah, it would be very lost in the wash. |
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Apr 13 2010, 05:55 PM
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#3
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Member Group: Members Posts: 267 Joined: 5-February 06 Member No.: 675 |
I don't know the techniques being used on the ranging experiment but two points seem (at least theoretically) relevant.
1) The signal's wavelength need not be an absolute lower limit for position. If they're measuring phase shift of the received signal, they can probably get down to a fraction of a wavelength. (Precise GPS surveys do that all the time although in the Earth-Mars case the signal strength is much lower and it may be much more difficult to do.) 2) The stability of the local oscillator on the rover is not relevant to a doppler signal, where the frequency is set by the stability of the signal transmitted from the Earth ground station, received by the rover and retransmitted (perhaps with some alteration) back to Earth. Steve M (talking outside his area of expertise). |
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