Author Topic: Mars Micro Orbiter  (Read 1725 times)

Offline vjkane

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Mars Micro Orbiter
« on: 05/13/2018 03:57 PM »
NASA is considering flying Malin's Mars Micro [CubeSat] Orbiter as a secondary payload with the 2020 rover launch.  Like the MARCO cubesates, MMO would be a fully independent spacecraft that would enter and operate in Mars orbit on its own.  It would conduct global weather observations.

A decision on whether or not to fly MMO is expected soon.  NASA's officials have said that the recent design reviews were very positive.

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« Last Edit: 05/13/2018 11:20 PM by gongora »

Online Blackstar

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Re: Mars Micro Orbiter
« Reply #1 on: 05/13/2018 06:17 PM »
This one was discussed at LPSC. It did not make it into phase 2, so I'm surprised to see it reemerge.

I haven't seen any good overall discussion of CubeSats/Smallsats and planetary missions, but they're in a bit of a conundrum: NASA decided that none of the missions being studied would be allowed to interfere with a primary mission. That makes sense, but it had the effect of driving many of the CubeSat missions to look for alternative rides to their targets and/or alternative methods for entering orbit/landing. That resulted in some expensive/risky design choices that negated the supposed value of the small spacecraft.

I'm not sure that there's a way out of that Catch 22. After all, primary missions are meeting major space science goals, and you don't want to impact them, and the impact may be greater than any benefit that the smallsat can provide. But I'm glad that NASA is now considering this spacecraft and I hope that they can pull it off.

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Re: Mars Micro Orbiter
« Reply #2 on: 05/13/2018 06:20 PM »
I vaguely remember somebody at LPSC joking about this mission that it might grow to be so many U that it's now as big as a Discovery mission. So keeping it small has been a challenge. I also remember somebody saying that the biggest risk to the mission is losing a CMG and the biggest risk reduction would be adding a CMG. But my memory could be faulty on that.

Offline vjkane

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Re: Mars Micro Orbiter
« Reply #3 on: 05/14/2018 03:20 AM »
This one was discussed at LPSC. It did not make it into phase 2, so I'm surprised to see it reemerge.

I haven't seen any good overall discussion of CubeSats/Smallsats and planetary missions, but they're in a bit of a conundrum: NASA decided that none of the missions being studied would be allowed to interfere with a primary mission. That makes sense, but it had the effect of driving many of the CubeSat missions to look for alternative rides to their targets and/or alternative methods for entering orbit/landing.
If chosen for flight, MMO would be deployed from the rear of the upper stage as the MARCO cubesats were.

I could be mis-remembering what was said in a meeting, but my memory is that the mission's last review was very positive and a decision on flight would come this spring.

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Re: Mars Micro Orbiter
« Reply #4 on: 05/14/2018 03:20 PM »
I just checked with somebody who knows. They got positive reviews, but they were canceled a few weeks ago.

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Re: Mars Micro Orbiter
« Reply #5 on: 05/15/2018 10:09 PM »
Okay, looking at this slide, it had 3 reaction wheels. I think that what I heard at LPSC was that both the biggest risk to mission success and the most likely thing to fail was a reaction wheel, so adding one reaction wheel (i.e. four instead of three) was the best way to dramatically decrease risk on the mission. The problem was that a fourth reaction wheel would have pushed them over their mass and/or budget limits. They wanted to do it, but couldn't do it because of other constraints.

There were a number of proposed Mars cubesats at LPSC. The problem almost all of them had is that if they hitched a ride to Mars, it put them in the wrong orbit for their mission, so they needed a dedicated launch to Mars, and that of course cost a lot of money relative to the spacecraft cost. You don't want to spend more money on your rocket than you do on the spacecraft.

The engineering trades just don't close for the vast majority of planetary cubesats.
« Last Edit: 05/15/2018 10:10 PM by Blackstar »

Offline ccdengr

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Re: Mars Micro Orbiter
« Reply #6 on: 05/16/2018 04:02 AM »
There were a number of proposed Mars cubesats at LPSC. The problem almost all of them had is that if they hitched a ride to Mars, it put them in the wrong orbit for their mission...
MMO as proposed had enough delta V to get into an acceptable orbit from the M2020 heliocentric orbit.  The SALMON-3 SIMPLEx AO ( https://www.nasa.gov/smallsat-institute/nasa-smallsat-opportunities/small-innovative-missions-for-planetary-exploration ) describes a flight opportunity on Psyche, which is doing a Mars flyby.  Proposals are due this July.

Offline Don2

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Re: Mars Micro Orbiter
« Reply #7 on: 05/18/2018 06:51 AM »
For planetary missions, a big problem is getting the data back to earth. That requires either a lot of power or a big antenna, and that isn't a good fit for the cubesat concept. Also, telescope resolution decreases with the diameter of the mirror.

A way around the first problem is to use a mothership to relay the data. A way around the second problem is to fly closer to the  target. The best use for a cubesat would be an an auxillary spacecraft that works together with a large probe. For measuring fields and particles four point measurements are desirable. That may be the best use for cubesat technology in planetary missions.

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Re: Mars Micro Orbiter
« Reply #8 on: 05/19/2018 02:44 PM »
For planetary missions, a big problem is getting the data back to earth. That requires either a lot of power or a big antenna, and that isn't a good fit for the cubesat concept. Also, telescope resolution decreases with the diameter of the mirror.


During the planetary cubesats "microsymposium" at LPSC in March there were a bunch of them discussed (they may all be on the internet somewhere, I haven't looked). I only attended part of that session, but the data rate problem jumped out for several of them. For instance, there was a Phobos/Deimos cubesat proposal. I was interested, sounded great... and then they got to the issue of its data rate home and it was really bad. I mean really bad. Phobos/Deimos missions are hindered in this respect because the moons are above the orbits of the existing data relay satellites, so they cannot use them but have to beam straight back to Earth.

The proposer did not discuss it, but I wondered if such a very low data rate made it impossible to actually achieve the science goals. Could they possibly collect all kinds of great data and then have no ability to send it back?

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Re: Mars Micro Orbiter
« Reply #9 on: 05/19/2018 02:52 PM »
A way around the first problem is to use a mothership to relay the data. A way around the second problem is to fly closer to the  target. The best use for a cubesat would be an an auxillary spacecraft that works together with a large probe. For measuring fields and particles four point measurements are desirable. That may be the best use for cubesat technology in planetary missions.

So this then leads into a policy issue. Somebody has to make a decision on the rules for planetary cubesat missions. Of course, the rules can be different for each mission, but right now they had to be applied to general studies of cubesats. Off the top of my head the rules could go like this:

---the cubesat has to be stand alone, with no impact on a primary mission (meaning all its own comm, delta-v requirements, etc.)--this is very hard

or:

---the cubesat can have its own mission, and can have minimal impact on the primary mission (for various definitions of "minimal")

or:

---the cubesat is entirely complementary to the primary mission, adding new measurements/observations (the opportunities for this are very limited, however)

If you take as an example the Phobos/Deimos mission I mentioned up-thread, there is a way to use the data relay satellites in lower orbits to relay the data from the cubesat up around Phobos or Deimos. A way to do that is to have the data relay satellite alter its orientation and point its antenna up toward the cubesat to retrieve data, then turn around and orient toward Earth and beam the data home to Earth. That's possible from an engineering standpoint. But there are a couple of problems. First, it interferes with the mission of the data relay satellites (like MRO and MAVEN) because they are not collecting their own science data while doing this relay function. Second, it increases risk to those missions because any time you point a satellite in a different direction you run the risk of losing control of it or breaking it in some way. So because that was now allowed for this cubesat study, the Phobos/Deimos cubesat proposal got stuck with the requirement to beam directly to Earth, at a very low data rate. And that appears to make the mission non-viable.

What the recent set of studies demonstrate is that there is a very small niche for planetary cubesats. They don't hold a lot of promise for planetary missions.
« Last Edit: 05/19/2018 02:53 PM by Blackstar »

Offline ccdengr

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Re: Mars Micro Orbiter
« Reply #10 on: 05/19/2018 02:55 PM »
The proposer did not discuss it, but I wondered if such a very low data rate made it impossible to actually achieve the science goals.
Galileo achieved a lot of its science goals with a 10 bit/sec downlink.  The original mission concept for Mars Observer allocated 150 bits/sec to each instrument.

With Ka-band, Cubesats can get rates of at least 10s of kbits/sec from a couple of AU.  Anyone who's severely data limited from Mars isn't trying hard enough on their telecom design.

Offline Don2

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Re: Mars Micro Orbiter
« Reply #11 on: 05/19/2018 07:56 PM »
I agree that planetary cubesats are a niche technology, and the niche might be quite small. If a cubesat needs a communications relay, then it really should be on the cubesat to get itself into the right position rather than the mothership.

One future mission that will likely attract some cubesat proposals is Europa Clipper. Cubesats are well suited for fields and particles measurments, and Jupiter has the largest and most interesting magnetosphere in the solar system. Also, the evidence for oceans on Callisto and Ganymede comes from the interaction of the Jupiter magnetosphere with the moons, so fields and particles studies can support the ocean investigation mission. Another possibility would be sending a cubesat to do a single close fly-by of Io. All those missions would depend on Europa Clipper as a communications relay.

At Mars cubesats could be used for gravity field measurements if the measurement technique used by GRAIL and GRACE could be downsized to fit in a cubesat.

Offline Comga

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Re: Mars Micro Orbiter
« Reply #12 on: 05/19/2018 09:34 PM »
A Cubesat GRACE/GRAIL mission is possible and has been proposed.

At least one proposed cubesat Mission th Phobos and Deimos indeed discussed using the same technology as The Mars Cube One spacecraft to send down adequate data direct to the DSN to meet their mission goals. Not a lot, but sufficient.

There are probably other ways to get the data to the lower orbit relay craft without repointing them, but they are “owned” by JPL.  While the outfit who seamlessly patched the Cassini/Huygens interplanetary trajectory could figure out some acceptable relay method, it’s not their problem and not directly advantageous to them.
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline vjkane

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Re: Mars Micro Orbiter
« Reply #13 on: 05/20/2018 02:44 PM »
So this then leads into a policy issue. Somebody has to make a decision on the rules for planetary cubesat missions. Of course, the rules can be different for each mission, but right now they had to be applied to general studies of cubesats.

What the recent set of studies demonstrate is that there is a very small niche for planetary cubesats. They don't hold a lot of promise for planetary missions.
NASA has now put out a call for SmallSat/CubeSat missions that could be launched with several upcoming planetary and lunar missions.  I believe that the SIMPLEX call specifies the rules.

https://nspires.nasaprs.com/external/solicitations/summary!init.do?solId={523A5AF4-07C1-1FA4-0734-9C0253A172DF}&path=open

My understanding is that the limitation on data relay from orbiting Small/CubeSats by existing Mars is because of the orientation of the antennas.  A future orbiter (none currently planned) could have down and upward oriented antennas.

My reading of MMO is that it would have been primarily a demonstration mission that could also do useful science.  The data relay problem from a mission whose science is to do a lot of data gathering is significant.

We are in the earliest stages of planetary Small/CubeSats.  I don't judge their value by what they can do now but where the experimentation will lead to in 15 or 20 years.

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