During Perseverance's powered descent, cameras aboard the descent stage recorded Perseverance's deployment using its Sky Crane. After rover touchdown, the descent stage flew away until it ran out of fuel and crashed far from the rover.

How were these images (and, one hopes, eventually the complete videos) sent from the descent stage to Earth?

The descent stage's flyaway was until fuel exhaustion, rather than towards a planned landing zone. Its crash landing was uncontrolled: no fuel means no maneuvering. So after its crash, it probably couldn't aim an antenna at any data receiver: any moving parts might have become entirely inoperative, and it was probably not sitting upright.

It's also unlikely that the descent stage transmitted all of that data to the rover during flyaway. I'm not sure how long the flyaway lasted, but the descent stage wouldn't have carried a heavy excess of fuel. The color images were at least 3 megapixels, and if video was recorded from backshell separation to rover touchdown, that's about 20 seconds. Guessing more: at 10 frames per second and 5 megabytes per second with a modern video codec, that's 100 MB, hardly a trivial amount.

Or was the data sent in real time from descent stage to rover for storage, during powered descent?

Edit: Recorded video included a camera on the rover viewing the Sky Crane, and one on the Sky Crane viewing the rover. The view from the Sky Crane vanished about one second before touchdown ("tango delta" announcement), while the other view continued. That indeed suggests real time data transfer to the rover, interrupted when the two physically separated, thus through a cable, not wireless.

  • $\begingroup$ Do you have a source that says that the sky crane continued taking images/video after it disconnected from the rover? $\endgroup$ – Phiteros Feb 20 at 19:41
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    $\begingroup$ While the skycrane was lowering the rover, it was attached to it by a data cable; you can actually see it in the image you linked. It's the curly wire. $\endgroup$ – Phiteros Feb 20 at 19:48
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    $\begingroup$ @Phiteros I don't know or claim that recording continued after rover touchdown. $\endgroup$ – Camille Goudeseune Feb 20 at 20:12
  • $\begingroup$ Okay, it sounded a bit like you had heard/read that that was the case. It would definitely be cool if it took images if it flew away. $\endgroup$ – Phiteros Feb 20 at 20:18
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    $\begingroup$ Well, according to this site, the descent stage did have a UHF antenna which it used to communicate with Earth during the descent. So it is possible that the descent stage sent videos and images either to the rover (through the data cable) or the MRO or Maven even after the data cable was cut. $\endgroup$ – Phiteros Feb 20 at 21:35

According to the press conference:

... that gold umbilical, that's what's transferring all the information between the rover and the descent stage, including this video; this picture is coming down from the camera up on the descent stage down to the rover through that cord ...

Later, the video ends just after the harness goes slack as the rover touches the ground, which is the point at which that cable would be cut.


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