Author Topic: Operation of Mars ISRU - laser communications  (Read 3285 times)

Offline aero

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Operation of Mars ISRU - laser communications
« on: 06/02/2014 04:45 PM »
ISRU on Mars is often discussed as  operating autonomously for periods of years. To what extent could such equipment be tele-operated from Earth?

Would a laser communications system between Earth and Mars be feasible and would such a system provide the bandwidth needed to operate such equipment?

Would it be useful/possible to use the idle communications cycles to transmit other data, photographic or whatever.
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Offline Burninate

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Re: Operation of Mars ISRU - laser communications
« Reply #1 on: 06/02/2014 05:25 PM »
Forget ISRU for a moment?

A high-bandwidth laser communications system to Mars was an important companion to the Mars Science Laboratory.  The Mars Telecommunications Orbiter was supposed to be in place in high orbit with a powerful radiotransmitter to the Martian surface and a laser hookup to Earth, so that the Curiosity rover and anything else we decided to send could return picture after picture, enormous quantities of data.

Instead, it was cancelled by Congress in 2005, and the upcoming Mars Science Laboratory mission has been somewhat crippled ever since.  Since it landed, we've had to deal with relays on Mars Odyssey and Mars Reconnaissance Orbiter.  These are polar-orbitting survey imagers with incentive to fly as low as possible for resolution - that means they're at or below the horizon except for a several-minutes-long conjunction twice a day.  With these four brief fixes per day, Curiosity can send its data up in place of the imagery these satellites are supposed to be producing.  30 megabytes per day early in the program, with hopes to increase that to 250 or so.  MTO would have brought us to 10-30 megabits per second transfer to Earth, and reduced our reliance on Deep Space Network megadishes by routing MRO and MO data as well as Curiosity's data collection through its laser link.

The MAVEN satellite is an atmospheric monitoring science mission rather than a survey imager, and this allows it to fly a higher orbit where it's much better suited to act as a satellite relay for ground missions;  It is still hamstrung by a lack of lasers, but it's on the way to Mars, and should significantly increase the quantity of data returned, particularly as MO & MRO start to break down.

We're getting a small fraction of the value we could be getting out of Curiosity, because we cancelled the laser link.  Maybe now that LADEE has done the work of demonstrating laser comms, everyone will finally admit that This Stuff  Is The Future?
« Last Edit: 06/02/2014 05:29 PM by Burninate »

Offline gosnold

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Re: Operation of Mars ISRU - laser communications
« Reply #2 on: 06/02/2014 06:12 PM »
Bandwidth is less of an issue than lag if you want to remotely operate things on Mars. You can have infinite bandwidth, you will still have to do with a 8min-40min two-way light delay, depending on the orbital positions.
But for returning science (especially images), lasers are very interesting. The last figures I've seen from NASA are that lasers have 10x the bandwidth of RF links all other things (power, mass) being equal.

Offline Jim

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Re: Operation of Mars ISRU - laser communications
« Reply #3 on: 06/02/2014 06:15 PM »

Instead, it was cancelled by Congress in 2005, and the upcoming Mars Science Laboratory mission has been somewhat crippled ever since. 

We're getting a small fraction of the value we could be getting out of Curiosity, because we cancelled the laser link. 

Both statements are, in my view, incorrect.   There has no crippling or reduced value of MSL.

Edit/Lar: PoliteJim3000
« Last Edit: 06/02/2014 09:52 PM by Lar »

Online Blackstar

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Re: Operation of Mars ISRU - laser communications
« Reply #4 on: 06/02/2014 08:14 PM »
Forget ISRU for a moment?

A high-bandwidth laser communications system to Mars was an important companion to the Mars Science Laboratory.  The Mars Telecommunications Orbiter was supposed to be in place in high orbit with a powerful radiotransmitter to the Martian surface and a laser hookup to Earth, so that the Curiosity rover and anything else we decided to send could return picture after picture, enormous quantities of data.

Instead, it was cancelled by Congress in 2005, and the upcoming Mars Science Laboratory mission has been somewhat crippled ever since.  Since it landed, we've had to deal with relays on Mars Odyssey and Mars Reconnaissance Orbiter. 

SNIP

We're getting a small fraction of the value we could be getting out of Curiosity, because we cancelled the laser link.  Maybe now that LADEE has done the work of demonstrating laser comms, everyone will finally admit that This Stuff  Is The Future?

Er, I suspect you are misstating the case a lot. NASA likes to test technology before it launches a mission that depends upon it. I'd have to go look up the Mars Telecommunications Orbiter, but I suspect that it was more tech development than part of the operational architecture. Note that only last year did NASA prove lasercom from the Moon. Mars is harder, so there's a logic to developing it at the Moon then extending it to Mars (which is now NASA's plan). Sometimes things that you disagree with can actually happen for logical reasons. Not everybody in a position of authority is dumber than residents of the internet.

And...

Okay, I just googled on MTO and it turns out that you're wrong when you say that it was Congress that canceled it. Turns out it was the president's budget that canceled it.

I suggest going back and checking some of your other assumptions. That's always a good thing to do, no matter what the subject.

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Re: Operation of Mars ISRU - laser communications
« Reply #5 on: 06/02/2014 08:36 PM »
And continuing to prove my core belief that nothing is as simple as it appears, take a look at this report.

"Recommendation: Ensure that the primary role of the Mars Science and Telecommunications Orbiter
is to address science questions, and not simply to serve as a telecommunications relay. This distinction
is particularly important with respect to the required orbital parameters that are adopted."


Now the report came out after the telecommunications orbiter was canceled in 2005, but often these kinds of reports finally put onto paper what lots of people start saying privately and then publicly. I suspect (without looking, because I'm too lazy) that the Mars Telecommunications Orbiter evolved into the Mars Science and Telecommunications Orbiter because the science community was complaining that it was stupid to spend a lot of money simply to send a technology development spacecraft to Mars without including science. And I suspect that what then happened was that NASA slapped some sciency stuff onto the mission, perhaps as it was getting canceled. And I suspect that what this report reflects was the science community saying to NASA "You can put tech development onto a Mars mission, but it should be secondary and not primary to the mission."

So yeah, it's possible that if MTO had been funded and if the lasercom had worked, that then Curiosity could be sending back more data. Of course, considering that MTO was originally supposed to launch in 2009, NASA would have had to include the lasercom package on Curiosity before it knew if the technology would actually work (remember that Curiosity was also supposed to launch in 2009). That's not a good approach.

So I don't think that things worked out the way you characterized them.

Offline SaxtonHale

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Re: Operation of Mars ISRU - laser communications
« Reply #6 on: 06/02/2014 11:09 PM »
Curiosity isn't crippled in its scientific or engineering operations without the larger data volume, but it feels like Galileo without its high-gain antenna - capable of producing so much more data than we will ever see.

The science team has to settle for MastCam images coming down days later through multiple uplinks (unless they know to prioritize certain images over other data), after the rover is several drives away from a potentially interesting rock, though it will have seen it with the NavCams.

The MERs gave us practice at operating with limited data, but geologists certainly daydream of getting full color panoramas down before the rover has left a location. Not that it is good to get distracted too often from the main far-off objective of the foothills. But many pictures are just not taken.

Offline sheltonjr

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Re: Operation of Mars ISRU - laser communications
« Reply #7 on: 06/03/2014 03:45 AM »
It looks like this thread is taking a detour onto Curiosity Bandwidth and politics.  ;D

I agree with gosnold. The problem is the Lag not the bandwidth. (Where is that faster than light quantum entanglement I was working on???)

For Mars ISRU creating methane, I see two possibilities. One, ISRU system pulls moister from the air and uses electrolysis to create Hydrogen and Oxygen as feed stock for CH4 and LOX. And/Or almost fully autonomous excavators dig 1-2 meters into the soil and transport it to the ISRU unit where the water is extracted.

A command would come from Earth. Dig a 2x2x20 meter trench here.  The robot excavator will take care it from there.  Sound like a cool project. Not a lot of bandwidth required for command like that.  Any more control will be difficult/slow considering the lag. It takes and army of engineer and scientist to move the rovers. 

Offline aero

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Re: Operation of Mars ISRU - laser communications
« Reply #8 on: 06/03/2014 06:09 AM »
It looks like this thread is taking a detour onto Curiosity Bandwidth and politics.  ;D

I agree with gosnold. The problem is the Lag not the bandwidth. (Where is that faster than light quantum entanglement I was working on???)

For Mars ISRU creating methane, I see two possibilities. One, ISRU system pulls moister from the air and uses electrolysis to create Hydrogen and Oxygen as feed stock for CH4 and LOX. And/Or almost fully autonomous excavators dig 1-2 meters into the soil and transport it to the ISRU unit where the water is extracted.

A command would come from Earth. Dig a 2x2x20 meter trench here.  The robot excavator will take care it from there.  Sound like a cool project. Not a lot of bandwidth required for command like that.  Any more control will be difficult/slow considering the lag. It takes and army of engineer and scientist to move the rovers.

Maybe a little like that. If all goes well and Murphy stays home, then a lot like that. But an unsuspected boulder or a seam of clay or something of high interest may be uncovered (How do you say "unearthed" on Mars?), then what? I think you want reasonably high frame rate photos, or even video monitoring the trench from the excavator. The excavator can't be remotely operated because of the distance and time lag but a visual feed of its activity would allow determination of and fixes for problems encountered. Not in real time, but quicker than time measured in days. Ok, so no one is watching the video feed, but it is available if telemetry indicates that a problem has occurred. And that takes bandwidth. And expense. Expense traded against lost time delays.
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Online Asteroza

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Re: Operation of Mars ISRU - laser communications
« Reply #9 on: 06/03/2014 07:52 AM »
A martian synchronous orbit, plus near zero clouds (aside from the occasional dust storm), does make mars orbit teleoperation interesting for martian ground ops via laser. Latency there wouldn't be so bad, and ground teleops from orbit has been proposed in the past (from a Phobos base?)

Came across something odd today that might be of interest.

A recent press release by a new solar powered UAV firm http://www.sunlightphotonics.com/ led to a patent of theirs, US patent https://www.google.com/patents/US8224189 which seems to describe something that I would consider to be a nearly passive externally powered communications link. Employing the same basic concept behind a LCD display panel with a specialized retroflector, external laser light that's getting received/reflected gets blinked on/off like a morse signal lamp. For that company's usage, that means a ground laser is doing the heavy work, while the UAV basically only needs to power the LCD panel to blink correctly, which means the UAV doesn't need a laser of it's own.

For satellite applications, earth particularly, that could enable laser comms without putting a laser on the satellite bus, reducing power and weight consumption, the ideal case being a large flat panel or perhaps a pyramid lined with the mentioned semiconductor based retroreflector mirror panels on the nadir side. For long distances, say earth to mars though, I would imagine optics issues like diffraction limits might make this impractical, but then again, the Apollo retroreflectors seem to work well enough.

Online hop

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Re: Operation of Mars ISRU - laser communications
« Reply #10 on: 06/04/2014 05:50 AM »
A martian synchronous orbit, plus near zero clouds (aside from the occasional dust storm), does make mars orbit teleoperation interesting for martian ground ops via laser. Latency there wouldn't be so bad, and ground teleops from orbit has been proposed in the past (from a Phobos base?)
The Lunokhods was driven in real time from the ground, using very low res, low frame rate video. You could do far better from Mars orbit using current technology, without any particular need for laser com.

Offline Hog

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Re: Operation of Mars ISRU - laser communications
« Reply #11 on: 06/04/2014 06:46 PM »
Bandwidth is less of an issue than lag if you want to remotely operate things on Mars. You can have infinite bandwidth, you will still have to do with a 8min-40min two-way light delay, depending on the orbital positions.
But for returning science (especially images), lasers are very interesting. The last figures I've seen from NASA are that lasers have 10x the bandwidth of RF links all other things (power, mass) being equal.

Average distance between Earth/Mars=1.7Au or approx 14.1 light/minutes
The closest know approach of Earth and Mars was 56 million km (in 2003)  Even at this closest approach to Earth, Mars is still 3.1 light/minutes away, when furthest apart  22.3 light/minutes apart.

Best case 2 way transmissions are 6.2 minutes, average of 30 minutes, and worse case 44.6 minutes, your 8.66 minute(4.33 minutes one way) example is on the side of almost best case example.
Paul

Offline gosnold

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Re: Operation of Mars ISRU - laser communications
« Reply #12 on: 06/04/2014 06:47 PM »
Teleoperation from a low Mars orbit (with relay satellites in low Mars orbit) is an interesting option, it gives a maximum 70ms round-trip time (with an average around half that) and halves the radiation dose (the planet blocks out half the sky).

Offline gosnold

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Re: Operation of Mars ISRU - laser communications
« Reply #13 on: 06/04/2014 06:51 PM »
Bandwidth is less of an issue than lag if you want to remotely operate things on Mars. You can have infinite bandwidth, you will still have to do with a 8min-40min two-way light delay, depending on the orbital positions.
But for returning science (especially images), lasers are very interesting. The last figures I've seen from NASA are that lasers have 10x the bandwidth of RF links all other things (power, mass) being equal.

Average distance between Earth/Mars=1.7Au or approx 14.1 light/minutes
The closest know approach of Earth and Mars was 56 million km (in 2003)  Even at this closest approach to Earth, Mars is still 3.1 light/minutes away, when furthest apart  22.3 light/minutes apart.

Best case 2 way transmissions are 6.2 minutes, average of 30 minutes, and worse case 44.6 minutes, your 8.66 minute(4.33 minutes one way) example is on the side of almost best case example.
I wrote 8min-40min, which is indeed best case-worst case (roughly), not 8min40s.

Offline Misha Vargas

Re: Operation of Mars ISRU - laser communications
« Reply #14 on: 06/04/2014 09:16 PM »
Employing the same basic concept behind a LCD display panel with a specialized retroflector, external laser light that's getting received/reflected gets blinked on/off like a morse signal lamp. For that company's usage, that means a ground laser is doing the heavy work, while the UAV basically only needs to power the LCD panel to blink correctly, which means the UAV doesn't need a laser of it's own.

Interesting. I'm trying to think why this won't work...

What's the fastest you can strobe LCDs?

Offline Hog

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Re: Operation of Mars ISRU - laser communications
« Reply #15 on: 06/05/2014 04:04 PM »
Bandwidth is less of an issue than lag if you want to remotely operate things on Mars. You can have infinite bandwidth, you will still have to do with a 8min-40min two-way light delay, depending on the orbital positions.
But for returning science (especially images), lasers are very interesting. The last figures I've seen from NASA are that lasers have 10x the bandwidth of RF links all other things (power, mass) being equal.

Average distance between Earth/Mars=1.7Au or approx 14.1 light/minutes
The closest know approach of Earth and Mars was 56 million km (in 2003)  Even at this closest approach to Earth, Mars is still 3.1 light/minutes away, when furthest apart  22.3 light/minutes apart.

Best case 2 way transmissions are 6.2 minutes, average of 30 minutes, and worse case 44.6 minutes, your 8.66 minute(4.33 minutes one way) example is on the side of almost best case example.
I wrote 8min-40min, which is indeed best case-worst case (roughly), not 8min40s.
My sincerest apologies, wow, I totally missed that one.  I was wondering where you were getting this 8:40 time was coming from, when in fact it was originating in my own mind.
Thank you.
Paul

Offline Burninate

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Re: Operation of Mars ISRU - laser communications
« Reply #16 on: 06/05/2014 04:25 PM »
Employing the same basic concept behind a LCD display panel with a specialized retroflector, external laser light that's getting received/reflected gets blinked on/off like a morse signal lamp. For that company's usage, that means a ground laser is doing the heavy work, while the UAV basically only needs to power the LCD panel to blink correctly, which means the UAV doesn't need a laser of it's own.

Interesting. I'm trying to think why this won't work...

What's the fastest you can strobe LCDs?
60-240Hz is pretty much the maximum for the range of types used in computer/television displays.  You can strobe LEDs and laser diodes in useful patterned data extraordinarily fast, LADEE hit 622 megabits per second... so a 10^7 factor difference at the outset for the first demonstrated unit.