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Cees Bassa Sep 9
An update on the Dwingeloo observations of the landing attempt. If we assume that the Madrid ground station compensated for the Doppler of the pre-burn orbit, these are the approximate line-of-sight velocities during the descent.
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Cees Bassa Sep 9
Replying to @ProjectJupyter
Many thanks to Fabian Schmidt () for figuring out what happens to the signal when the uplink ground station compensates for the Doppler effect. For those interested, this is the derivation. The updated notebook is at .
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Cees Bassa Sep 9
Replying to @dsn_status
Note the two assumptions that we make! First, we assume that the Madrid ground station kept on Doppler compensating using the pre-burn (~30x110 km) orbit of . It is not clear if this is what actually happened...
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Cees Bassa Sep 9
Replying to @radiotelescoop
The second assumption is less of a problem. Because of the Madrid uplink, the observed frequencies depend on the velocity between the spacecraft and Madrid as well as the spacecraft and . Since those velocities will be similar, we assume they are the same.
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Cees Bassa
We find that the line-of-sight velocity of at loss of signal was only 54 m/s different than that of the Moon. Due to projection effects, the real velocity of with respect to the lunar surface could have been higher.
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Cees Bassa Sep 9
Replying to @radiotelescoop
Thanks to this analysis it may now be possible to simulate the descent trajectory of and allow a direct comparison of predictions against the Dwingeloo frequency measurements. That's something for the future.
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Cees Bassa Sep 9
Replying to @nascom1 @ea4gpz and 2 others
Finally, any input from satellite tracking experts such as would be appreciated!
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CHANDRAMOULI Sep 9
Replying to @cgbassa
For a layman, does it mean with some certainity that Vikram crash landed without disintegrating as is being told?
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