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Comment by somedude895 | Hacker News Reader

This is incredible quality. What's the file size of the video and what path did the data take?

It got sent back via orbiters ranging from the ESA's Trace Gas orbiter, the Mars Reconnaissance Orbiter or Mars Odyssey. Through those they can get up to 2 megabits per second [0] back to earth but that depends a lot on the orbiter it's talking to at a given time. The TGO is doing a lot and is one of the early high speed relays for the data from Perseverance. [1] There's also direct links to and from Earth but they're significantly slower.

[0] https://mars.nasa.gov/mars2020/spacecraft/rover/communicatio...

[1] https://scitechdaily.com/nasas-mars-2020-perseverance-rover-...

The more impressive part is that the sky crane shot pictures, video and data and had to download everything to the rover before it was cut loose. As soon as the rover wheels touched ground, the tether was cut and the lander flew away.

That's relatively simple just wire them directly into the rover to start with so the data is always in the right place.

I'd like to know how they cut/released the tether, and if there's any fallback in case 1st release attempt fails. The entire mission is fucked if the tether release failed, or if the sky crane tries to fly away while still tethered.

They use explosive bolts that attach the tether to the deck of the rover. They're almost 100% fool proof. Here's a Wikipedia entry, they're called pyrotechnic fasteners and NASA uses a lot of them.

https://en.wikipedia.org/wiki/Pyrotechnic_fastener

But the image of the cables show what looks to actually be a literal cut cable. Not just a connector being disconnected but a clean slice.

From today's Reddit AMA with the NASA team, they use pyrotechnics to set off a guillotine like device to cut the cables. Possibly something like https://psemc.com/products/pyrotechnic-cable-cutter/

Source: https://www.reddit.com/r/IAmA/comments/lpzbzo/were_scientist...

I don't know how they achieved it specifically, but there is a moment in the broadcast[0] they did where they show the umbilical on the rover and mention that it was cut. I'm curious as well how they did it!

[0] https://youtu.be/gYQwuYZbA6o?t=1898

I believe the data is uplinked through orbiters than relayed back from there.

The briefing said they had downloaded ~20 GB of data over the last few days. I'm sure much of that was _not_ EDL data.

30 GB of data and 23000 images. Crazy. https://youtu.be/gYQwuYZbA6o?t=562

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