Hacker News new | past | comments | ask | show | jobs | submit login

I don't know why I'm surprised at the amount of footage and the quality, but I am. This is really setting a new bar for missions like this, similar to what SpaceX has done in recent years. Stuff like this has got to be huge for getting interest and excitement from the general public and especially kids.



I still can't get over the fact this mission has legit good cameras on it.


agree! I remember seeing still pictures from mars from the viking missions taken in the 70's and although they are pretty good this latest video quality and clarity means NASA/JPL has come a long way. Just seeing that alien surface where no person has(yet) walked is absolutely amazing.


It would be great to see some startups work on interplanetary video streaming tech. If you're building an other video streaming service, stop what your doing, and give this a try. I know I know. Very, very hard to solve and all, and this is totally a fanboy speaking, but it would have been awesome if we could have seen this footage in (as close as possible to) real-time when the landing happened.


Nothing about "interplanetary streaming" needs to be invented. The limiting factor is the size and power of the transmitter on Mars (or wherever). The MRO orbiter for instance is the highest bandwidth probe we've sent to Mars and it maxes out at about 4Mbps when Mars is closest to Earth. When Mars is farther it can only do about 500Kbps. That relatively prodigious rate requires the use of 34m receiving antennas on Earth.

So if you wanted to stream video from a GoPro on a Mars orbiter you could do so with current technology, you'd just need to build some big-ass antennas on Earth and then build and launch the Mars orbiters. Besides being technically difficult (because rocket science) it would be really expensive.


Maybe that's what Elon has planned for the back side of the Starlink v2.0 satellites - to create an Earth-sized massively distributed phased array and get a super-high-bandwidth downlink from Mars.


Don't need particularly large antennas at the Mars end. Basically if you double the size of the antenna at the Mars end you can halve the size of the antenna back here on Earth.

So to establish a link comparable to the Earth-MRO link which has 35m dish here on Earth and 3m antenna at Mars, you could have a 11m antenna at both ends. The hard part is lofting that 11m antenna into Earth orbit in the first place (shipping it to Mars from Earth orbit is easy in comparison).

As an example you could cut the 11m antenna into two pieces, each being a half of a circle with 5.5m radius. That would easily fit into the SpaceX Starship cargo hold. Loft that into orbit, assemble it in orbit, then send it on its way to Mars. The only technical challenges there are flying a spaceship which hasn't reached orbit yet, and performing orbital assembly of a spacecraft (which hasn't been done yet).

Then for completeness put two more of those relay satellites at the leading and trailing Lagrange points for Mars so that we have communication with Mars even when it's on the other side of the Sun.


Wow. That's not how any of that works.


Oh, do explain a little more about why that doesn't work; wavelengths, total power, distances, etc.


Let me enumerate the ways.

1. Starlink satellites have Ku and Ka transceivers for uplink and downlink. They simply aren't capable of talking to any Mars probes using X band radios for Earth communications which is all of the current and near future ones.

2. A phased array can use beam forming to "aim" and to use aggregate receivers for resolution but they're seeing limited. Tiny receivers on Starlink satellites (even arrayed) would be no good for Mars probes even if they covered the right bands.

3. Every element involved in the question is in motion relative to every other element. Starlink satellites have orbital periods of about 90 minutes. Each satellite would only have Mars visible for at best half its orbit. With Mars effectively a point source any Starlink satellites arrayed to receive signals from Mars would need to rotate in sync to keep Mars in view. That necessitates pointing all a satellite's other antennas away from each other and Earth since they're all bus mounted. This means they can't simultaneously do Starlink and Mars relay tasks and you'd need a lot of Starlink sats to even begin to effectively receive Mars transmissions.


"You are wrong and should feel bad! I rest my case!"


So, the minimum delay between Mars and Earth is around 11 minutes, usually higher. And the bandwidth is something like 60 MiB/Sol. This is just totally unrealistic with any known tech for the foreseeable future


Current delay is ~11 minutes, but minimum is much lower (~4 minutes, per https://blogs.esa.int/mex/2012/08/05/time-delay-between-mars... ). We were last at that closest point in October, and the various voyages (this one, UAE's Hope, China's Tianwen-1) were timed so the closest pint was during the transit; we're a bit past it now.




Guidelines | FAQ | Lists | API | Security | Legal | Apply to YC | Contact

Search: