Anyone has insights on how data in such volumes can be transferred from Mars to Earth in the absence of a direct link? Do the intermediate nodes have gigabytes of available storage to emit data to the next available node once it becomes visible ?
Reddit had AMA with engineers from this mission, IIRC last week. They provided good info on different aspects including how they were able to get video over low bandwith connection, including various mission site link for more info. You might want to check out AMA for your question.
EDIT: Apparently the rover has an antenna that can directly communicate with Earth at 10 bits per second! That's obviously not useful for pictures or anything, but it's an amazing capability for emergency comms.
From my layman's understanding, it's relayed via the orbiters.
There are a few orbiters around Mars. NASA appears to have an arrangement with the ESA to upload data from the rovers to the ESA's orbiters, depending on whose orbiters are within line of sight at any given time. Then the orbiter sends the information back to Earth, which are received by NASA's Deep Space Network
During the time when line of sight between Earth and Mars is blocked by Sol, there isn't any communication.
It never ceases to impress me that we have the ability to do this sort of stuff. A couple thousand years ago, the height of technology was shooting something from a few hundred metres away with a bow and arrow, now we are landing machines on another planet and transmitting data back and forth through the solar system. Incredible.
Vint Cerf has been working with NASA for over a decade on a design for interplanetary internet. I work at Google and he shared a story about how the earlier rovers had radios that were overheating at higher bandwidth transmissions. A smart engineer noted that they had an X band radio on the rover and still had one in an orbiter around Mars. The rover could transmit at 128mbps over xband to the orbitter, which in turn had large antennas to transmit back to earth at 128mbps. I assume Perseverance supports more bandwidth but it may be limited by whatever equipment we have in orbit around Mars.
They added dedicated storage in the rover itself to store phots and videos. So for example they can compress the video files before transmitting. I've hear they use ffmpeg for this purpose. There are 4 orbiting satellites that can relay any data sent to it.
Perseverance sends the data to various orbiters (satellites already in orbit around Mars) during overflights (time windows when the orbiter is in range of the rover) and those orbiters then send (relay) the data to Earth via the Deep Space Network (satellite dishes on Earth).
This is a video presenting ten milestone images that revealed what we've learned about Mars after decades of exploration prior to the landing of Perseverance [1]. It's nice to see the evolution of image resolutions of the Red Planet.
Great. Sometimes it feels like there's little progress made in space exploration. But such a compilation is a good reminder that - yes, maybe it's a bit too slow for the impatient, but progress is being made, and it shows.
Stupid question maybe but like is there a reason the picture quality seems worse than a decent dslr photo? I'm so curious what that photo would look like, taken with an everyday camera, without the bizarre 'scientific' look of these shots.
Generally, these cameras are many years out of date. They don't load up the rovers with the latest gear from today, but with the latest gear from when the design review process was closed. I don't know when that was for Perseverance, but it would not surprise me if that was a decade ago. The cameras are also not specifically designed for image capture, but for scientific study. In that they take images at a wider range of wavelengths than what humans can see. It's a subtle difference, but an important one. Additionally, the cameras' chips are not what we have commercially. They are designed to withstand the vacuum, the solar radiation on the long transit, and for use on the Martian surface for many years. You can't swap them out, ever. As such, they are much more 'rugged', which may effect image quality as well.
Yep, that’s the same reason why it runs on a PowerPC750 chip. They cost $200k+ for under 200Mhz on a 150-250 nm process, but can withstand up to 1,000,000 rads of radiation and function within extreme temperature ranges for decades. They have been proven to work in the harshest environments on prior missions, and the risk of an unproven processor is giant; a CPU failure could jeopardize the mission just as much as a crash landing. Design constrains are so very different when you shoot something 140M miles away!
It takes 15min but this plus the comment section on CMOS (can’t link directly) is excellent. The other comment about being made a decade ago is also relevant and accurate. They will certainly be better next time with evolutions in camera tech thanks to smartphones.
My question is why was the “sound of Mars” release only 18 seconds long?
Why not record hours of what it sounds like to be on another planet? Even the sound recordings from decades ago on (I think Titan) was only a short creepy clip.
I understand it’s mostly going to be wind and interspliced with the robots sounds but I still don’t get how we don’t have hours of Mars already.
My guess would be bandwidth. Every bit of bandwidth is precious, so they probably dont have the spare budget to send long audio files without obvious scientific value...
One of the most beautiful and haunting things I've ever heard was a tape cassette that had EM signals recorded by Voyager transposed into human-audible sound domain somehow. It was like whale song of space.
It would surprise me if they used lossy compression. However I once read about a space probe using a custom image compression and transmission format which does not require 100% data integrity for proper decoding. So if the transmission is cut off after 60% NASA will still be able to view whatever they received. I assume such methods are still applied.
In some interviews with the mast cam engineers, they say they can capture higher resolution images later on. Maybe they were reducing the image size to get then transmitted quicker.
If anyone is curious about the technology powering the Perseverance rover, there's this great video on YouTube explaining the incredible engineering behind it:
If they didn't include at least one Instagram ready camera, the team majorly misstepped on the "secure funding by inspiring a generation" part of NASA's mission.
> SuperCam fires a laser at mineral targets that are beyond the reach of the rover’s robotic arm, and then analyzes the vaporized rock to reveal its elemental composition. Like the ChemCam on rover Curiosity, SuperCam fires laser pulses at pinpoint areas smaller than 1 millimeter from more than 20 feet (about 7 meters) away.
I want to see that little helicopter fly! I scoured the site and as yet can't find any images of it, when I thought they were going to take mutual selfies -- heli of the rover and vice versa.
a glowing green sandwich covered in red sand. But seriously, this stuff is powering those voyager probes 40 years later. Which makes me ask: why do we have to send there technologies 10 billion miles away to make them work? Why can't my fridge be powered this way?
The MMRTG is a cylinder 25" in diameter and 26" high, it's going to seriously impact space in your 'fridge. Plus it weighs nearly 100 lbs.
It outputs around 100W of power, which might be enough for a small refrigerator, but it also emits around 2000W of thermal energy, so your kitchen's going to get a little warm (probably a good thing in the winter, not so much in summer).
Though probably the biggest drawback is the cost -- the MMRTG costs around $100M to manufacture. The US Department of Energy makes the plutonium for it.
The Russians tried powering a bunch of remote stuff with plutonium batteries during the Soviet era. It did not end well, and cleaning those up has been an ordeal. Pu-238 was also used in pacemakers. The basic problem is just that plutonium is toxic as hell.
What's powering Voyager is a plutonium pile. Pretty sure you don't want that in your fridge. 10 billion miles from me? Sure, knock yourself out. 10 feet from me? No way.
Back in the 60's, people thought everything would be nuclear-powered; atomic cars, planes, trains, houses, etc. But like with building-sized computers, we've chosen a different path through the tech tree.
There were terrestrial exceptions though, like "the Beta-M is a radioisotope thermoelectric generator (RTG) that was used in Soviet-era lighthouses and beacons." https://en.wikipedia.org/wiki/Beta-M
But people happened across them and got radiation poisoning, so imagine that happening a lot more often if they were powering all manner of home appliance. Also a lot more dirty bombs.
Smoke detectors rely on a circuit powered by atomic fission ionizing the air. It isn't their power source (they still need batteries), but it is a safe way to get continuous electricity.
There's probably a way to get a little more power out of it without being too dangerous. But then we'd have ordinary citizens buying things over-the-counter that could be abused in bulk. And I don't see any hassle being worth an extra free outlet or not replacing batteries.
You know I was about to say something about how your fridge draws so much more power than these probes, but actually I just googled it and they're pretty close. Today I learned.
(I don't know how much power the probes actually use, but anyway the wattage of the RTG itself is pretty close to the steady state power consumption of a fridge.)
Aside from the high cost of a consumer grade plutonium RTG, and the size constraint issues with putting one in the base of a fridge, or the health risks with having a reactor in your house under your food, one reason might be to prevent people exploding them.
Because if you can power a fridge this way, you can power an automobile this way. They won't let this happen.
The current power structures in the world (petrodollar, etc) and world economy as a whole (massive employment within oil industry and throughout supply chains catering to oil industry) are too intertwined with the oil industry to allow any other technologies to swiftly disrupt that.
Readit News
Edit: added following links
This Q&A about storage https://www.reddit.com/r/IAmA/comments/lpzbzo/were_scientist...
These Q&A about data rate https://www.reddit.com/r/IAmA/comments/lpzbzo/were_scientist...
https://www.reddit.com/r/IAmA/comments/lpzbzo/were_scientist...
This Q&A about RTG (operational life) https://www.reddit.com/r/IAmA/comments/lpzbzo/were_scientist...
https://old.reddit.com/r/IAmA/comments/lpzbzo/were_scientist...
EDIT: Apparently the rover has an antenna that can directly communicate with Earth at 10 bits per second! That's obviously not useful for pictures or anything, but it's an amazing capability for emergency comms.
There are a few orbiters around Mars. NASA appears to have an arrangement with the ESA to upload data from the rovers to the ESA's orbiters, depending on whose orbiters are within line of sight at any given time. Then the orbiter sends the information back to Earth, which are received by NASA's Deep Space Network
During the time when line of sight between Earth and Mars is blocked by Sol, there isn't any communication.
May interest you: https://mars.nasa.gov/mars2020/spacecraft/rover/communicatio...
https://www.quantamagazine.org/vint-cerfs-plan-for-building-...
[1]https://www.youtube.com/watch?v=e1eFMzO3iPc
TLDR worth a listen
Why not record hours of what it sounds like to be on another planet? Even the sound recordings from decades ago on (I think Titan) was only a short creepy clip.
I understand it’s mostly going to be wind and interspliced with the robots sounds but I still don’t get how we don’t have hours of Mars already.
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Some of the fuzzy photos remind me of the Sahara Desert when there was a little wind.
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https://www.youtube.com/watch?v=yqqaW8DCc-I
These are ENGINEERING cameras for taking incredibly precise measurements. Not for populating an Instagram page.
Holy shit, that rocks.
Many thanks.
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Answer: Plutonium
It powers a Multi-Mission Radioisotope Thermoelectric Generator.
The plutonium decays at a few % per year, so that means it should be able to bring Elon a sandwich when he lands.
https://mars.nasa.gov/mars2020/spacecraft/rover/electrical-p...
The MMRTG is a cylinder 25" in diameter and 26" high, it's going to seriously impact space in your 'fridge. Plus it weighs nearly 100 lbs.
It outputs around 100W of power, which might be enough for a small refrigerator, but it also emits around 2000W of thermal energy, so your kitchen's going to get a little warm (probably a good thing in the winter, not so much in summer).
Though probably the biggest drawback is the cost -- the MMRTG costs around $100M to manufacture. The US Department of Energy makes the plutonium for it.
There were terrestrial exceptions though, like "the Beta-M is a radioisotope thermoelectric generator (RTG) that was used in Soviet-era lighthouses and beacons." https://en.wikipedia.org/wiki/Beta-M
But people happened across them and got radiation poisoning, so imagine that happening a lot more often if they were powering all manner of home appliance. Also a lot more dirty bombs.
https://www.nrc.gov/reading-rm/doc-collections/fact-sheets/s...
There's probably a way to get a little more power out of it without being too dangerous. But then we'd have ordinary citizens buying things over-the-counter that could be abused in bulk. And I don't see any hassle being worth an extra free outlet or not replacing batteries.
(I don't know how much power the probes actually use, but anyway the wattage of the RTG itself is pretty close to the steady state power consumption of a fridge.)
https://en.wikipedia.org/wiki/Goi%C3%A2nia_accident
The current power structures in the world (petrodollar, etc) and world economy as a whole (massive employment within oil industry and throughout supply chains catering to oil industry) are too intertwined with the oil industry to allow any other technologies to swiftly disrupt that.
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