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12746412 No.12746412 [Reply] [Original]
Quoted By: >>12746429 >>12746547

I believe NASA is using some kind of new technology for long-range communications (Mars-Earth).

Here is an image that was sent back to us.
1280 x 960

Perseverance has been on Mars 5 days now.

About 5000 images of this type have been sent already, including videos (24fps).

Can someone calculate the network speed needed for sending this amount of data in 5 days?

Official speeds say 500 bits to 32000 bits per second.

I think if we calculate how much data was sent during these 5 days we can find out the true speed of the network that they are using. And then we can figure out if its possible with standard technology or if it violates the speed of light or some other physics.

>> No.12746420
Quoted By: >>12746429

Also keep in mind that the rover is not communicating 100% of the time with Earth, only "a few hours" each day:

The rover can only transmit direct-to-Earth for a few hours a day due to power limitations or conflicts with other planned activities, even though Earth may be in view much longer.


>> No.12746429
Quoted By: >>12746495

No, official says up to 800 bits/s for direct communication, and up to 2 million with relay communications (2Mbit/s).
So 250Kbytes/s in the best case. (bytes, not bits)
Naturally disponibility is limited in both cases, as you correctly say.

>> No.12746435
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>> No.12746495

ok and at that speed can you send all those images and video in 5 days, with a few hours each day with direct link to earth?

>> No.12746547
Quoted By: >>12746557

It's 2 megabits when the satellite is overhead. That's faster than my internet and yet the image loads instantly for me.

>> No.12746557

>2 megabits is faster than my internet
do americans really?

>> No.12746567
Quoted By: >>12746580

fuck it I'll do it myself you guys suck

let's assume maximum rate of 2x10^6 bps
each b&w image uses 8 bits per pixel
lets say each image is 1280x960
that's 1,228,800 pixels
so 9,830,400 bits per image

At that speed it would take:
9830400 [bits] / 2x10^6 [bits per second]
= 4.9 seconds

5000* 4.9 = 24,500 seconds
24,500 seconds = 6.8 hours

damn, I guess it is possible. But what is "the relay" using that is giving it such a high communing rate compared to the rover? (2,000,000 bps vs 800 bps)

>> No.12746580
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Quoted By: >>12746598 >>12746675

>But what is "the relay" using that is giving it such a high communing rate compared to the rover? (2,000,000 bps vs 800 bps)
MRO's antenna is as wide as the rover, might give you an idea.

>> No.12746598
Quoted By: >>12746643

So without the MRO they would never be able to get the data this quickly. And MRO was launched 15 years ago. What if they didnt have this they would be screwed.

Also there's some weird shit going on with MRO. They're using a PowerPC750 computer, but the flash memory is 120 GB, doesn't make sense.

MRO's main computer is a 133 MHz, 10.4 million transistor, 32-bit, RAD750 processor. This processor is a radiation-hardened version of a PowerPC 750 or G3 processor with a specially built motherboard. The RAD750 is a successor to the RAD6000. This processor may seem underpowered in comparison to a modern PC processor, but it is extremely reliable, resilient, and can function in solar flare-ravaged deep space.[58] The operating system software is VxWorks and has extensive fault protection protocols and monitoring.[59]

Data is stored in a 160 Gb (20 GB) flash memory module consisting of over 700 memory chips, each with a 256 Mbit capacity. This memory capacity is not actually that large considering the amount of data to be acquired; for example, a single image from the HiRISE camera can be as large as 28 Gb

>> No.12746643

It shouldn't need to be that large. It is acting as a switch. The memory would essentially be a comm buffer. I don't know if they oversized, but it should be something proportional to the longest continuous send-time datarate, whatever space required for systems management and then safety margins, like redundancy for encoding or failure.

>> No.12746675

They must need a pretty big solar panel to power that thing, especially consider how much further Mars is from the Sun

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