Cube-Sat Payload - Suggestions?

[RealityCheck]

Hello ASIF members; I am looking for suggestions please.

I have an unexpected opportunity to include a small payload on a cube-sat that is due to be launched into low earth orbit next year. This will be Phase 1 of a multi-phase project over several years, and the aim is to demonstrate certain technological capabilities in preparation for a more significant project at Phase 2.

We will be including at least one sensor that will be earth-facing, but we are not fixed on what that will be (the objectives of this phase do not include specific target data, more to do with the on-board technology on the cube-sat). So, I wondered if the ASIF community might have ideas as to what we could do, i.e. what type of sensor & data would be useful from an ASIF perspective, albeit within the limitations of the project.

Our timeline is very tight, so we must make decisions quickly. Criteria to be met:
1. Total payload will be small, c. 100 grammes weight.
2. Sensor must be COTS (commercial off the shelf) - not 'in development'
3. Readings can be intermittent. It is NOT a requirement to take continuous readings
4. Cube-sat will fly for an estimated 1 year only, to conduct its experiments (unfortunately)
5. The equipment must have a low power requirement.

Now, obviously I fully recognise that these limitations mean any data collected will probably be of interest value only. I don't expect scientific-grade output in this phase. Its not an ICE-Sat. But there you go, I thought I'd give you all a chance to pitch ideas in.

If you do have suggestions, any links to relevant technical data sheets would be appreciated.

Thanks.
RealityCheck

[Neven]

How much does an Advanced Microwave Scanning Radiometer weigh? 

[RealityCheck]

More than the sled that Santa would have to use to deliver it to me, if all my (our?) Christmases were to come at once... fat chance of that happening 

[Neven]

Yes, I looked it up. It weighs over 300 kg. The laser altimeter thing on ICESAT-2 weighs half a tonne, or so they just said in the live NASA emission following the launch (they also talked about Cube-Sats BTW). I always thought they were relatively light, because of the word 'sensor', and because everything keeps getting smaller and smaller.

So, 100 grammes of weight... Is it even possible to do anything with that to monitor something cryospheric?

[RealityCheck]

Yeah, I actually don't know yet.  As I said at the outset of this thread, I don't expect much beyond interest value, regarding the actual data we collect. I am open to be surprised though, if anyone has a bright idea...! But at the end of the day, we may be limited to a low-res RGB camera or some such, given our power constraints as well. We're going to be operating a standalone system...

[Neven]

Maybe it'd be interesting to look at one region in the Arctic, like those blowholes on Yamal or some such. How does the Cube-Sat orbit, RC? How often does it fly over a particular location?

[jacksmith4tx]

How long can a string of high strength material (carbon fiber?) be deployed from a cube-sat? If the length is long enough and the tensile strength is high enough it could provide valuable data in developing a space elevator. This might have already been done before but there might be new materials available now.

Physics tells us a space elevator is feasible so we are just waiting for technology to make it happen.

[Sigmetnow]

Maybe it'd be interesting to look at one region in the Arctic, like those blowholes on Yamal or some such. How does the Cube-Sat orbit, RC? How often does it fly over a particular location?

“Low earth orbit” sounds like International Space Station speed — orbiting every 90 minutes or so.

How about a simple camera other than RGB, maybe filtered to a frequency to detect a specific kind of emissions or phenomena?

[SteveMDFP]

 . . .
Our timeline is very tight, so we must make decisions quickly. Criteria to be met:
1. Total payload will be small, c. 100 grammes weight.
2. Sensor must be COTS (commercial off the shelf) - not 'in development'
3. Readings can be intermittent. It is NOT a requirement to take continuous readings
4. Cube-sat will fly for an estimated 1 year only, to conduct its experiments (unfortunately)
5. The equipment must have a low power requirement.
 
RealityCheck

I'd think maybe a smartphone-based solution.  Dual cameras, one to face earth.  One can be kept covered, and used as a radiation detector.  Maybe an OTG connector to both bring solar power in to charge it, and connect a sensor like a magnetometer?  Keep WiFi and blutetooth switched off, of course.  GPS measurements could relay information about slow orbital decay.

[RealityCheck]

Thanks for feedback, folks.

Yes, orbital period 90 minutes, sun-synchronous. I have no more details than that.

Interesting idea of a trailing carbon fiber or similar, but weight would be the issue. I am hoping/aiming for a solution that does not need mechanical adjustment e.g. moving lever arms, motors, etc.

A smartphone: hmm, I wonder...
Much obliged all...

Keep 'em comin'!

[RealityCheck]

Maybe it'd be interesting to look at one region in the Arctic, like those blowholes on Yamal or some such.

How about a simple camera other than RGB, maybe filtered to a frequency to detect a specific kind of emissions or phenomena?

Sig: If we were to use an RGB + filter, could we successfully target e.g. methane emissions in the northern regions? Any reason why Yamal vs other regions, Neven?

[SteveMDFP]

An important question is whether the cubesat will be retrieved, or allowed to burn up on re-entry?  I'd guess burn up, as retrieval would be quite difficult and costly.  The question determines much of design.  If it's to burn up, assessing carbon fiber degradation becomes probably impossible.  If it's to be retrieved, data storage would be easier than transmission.

[RealityCheck]

An important question is whether the cubesat will be retrieved, or allowed to burn up on re-entry?  I'd guess burn up, as retrieval would be quite difficult and costly.  The question determines much of design.  If it's to burn up, assessing carbon fiber degradation becomes probably impossible.  If it's to be retrieved, data storage would be easier than transmission.

Thanks Steve. The CubeSat will be allowed burn up on re-entry - no retrieval is envisaged. Data will be transmitted to the surface during the mission.

[Niall Dollard]

Hi Reality Check.

Wondering if anything could be done to monitor/further research on noctilucent clouds, from a low polar orbit ?

[Neven]

Any reason why Yamal vs other regions, Neven?

I believe that's where most of the holes have occurred so far.

The explosion and the resulting hole near Seyakha village is the latest of a dozen or so substantial known craters to form in Arctic Russia, mainly on Yamal, since 2014.

Source: Siberian Times

[TerryM]

Hi Reality Check.

Wondering if anything could be done to monitor/further research on noctilucent clouds, from a low polar orbit ?

I like the idea!


Possibly an RGB + filter could identify NLclouds and provide raw data that a future mission could use for comparison?
Would a filter covering 1/2 the lens to eliminate and include UV radiation in one picture provide additional useful data?
Would some other 1/2 filter be better?


What's the drop dead date?
How high will you fly?


Terry
 

[RealityCheck]

Hi All

Thanks for all the recent replies. I have been offline the last few days for a funeral.

Wondering if anything could be done to monitor/further research on noctilucent clouds, from a low polar orbit ?

Maybe, yes... certainly an interesting idea. Terry - thanks for expanding on this idea...

 

What's the drop dead date?
How high will you fly?

We will have to make decisions within 2-3 weeks for sure; not much time for us to debate internally, unfortunately.
Details of proposed orbit all to be confirmed - maybe on a design team call this PM.

All feedback is much appreciated, folks.

[Ned W]

This is a ... very bizarre thread.  I've served on review committees and planning committees for proposed satellite missions, and it's freaking me out a bit to see someone asking for feedback like this.  Obviously it's different for a lightweight, low-cost Cubesat mission.  But still...

Thanks for feedback, folks.

Yes, orbital period 90 minutes, sun-synchronous. I have no more details than that.

OK, so if the orbital period is 90 minutes, then the altitude is roughly 300 km.  And if it's sun-synchronous, then the orbital inclination is around 96.7 degrees.  So the satellite's ground track will go to about 83 North.   

If you are wanting to detect methane emissions, you'll need a sensor that can make fine-spectral resolution measurements in the shortwave infrared, around 2.3 micrometers, or else in the thermal infrared around 7.65 micrometers.  This probably won't be a matter of sticking a filter on an RGB detector array.  It's a bit outside my area of expertise, but for the 2.3 micrometer range I think you'd need an indium gallium arsenide (InGaAs) or mercury cadmium telluride (HgCdTe) sensor, probably InGaAs because unlike the other it wouldn't need to be cooled.

Here's a paper about methane sensing using an airborne imaging spectrometer.  You wouldn't be using this kind of spectrometer, but it -- and the references it cites, particularly ref. 13 -- might give you some ideas about how methane is measured using remote sensing in the SWIR:

http://www.pnas.org/content/pnas/113/35/9734.full.pdf

[Sigmetnow]

Curious:  does the Cubesat itself maintain your selected earth-specific orientation?  (Perhaps using cold gas thrusters?)  Just wondering how you can assure it will remain pointed at the location you want.

Image: here are some cubesats being deployed from the ISS.  They are adorable! 
http://www.spaceref.com/news/viewsr.html?pid=42238

[Ned W]

Curious:  does the Cubesat itself maintain your selected earth-specific orientation?  (Perhaps using cold gas thrusters?)  Just wondering how you can assure it will remain pointed at the location you want.

Based on what the original poster said, this will be in a sun-synchronous, near-polar orbit.  Every 90 minutes it makes one orbit around the Earth, passing near the north pole (83 North) down across the equator, near the south pole (83 south), and then around the back (nighttime) side of the planet.  During those 90 minutes, the Earth rotates slightly around its own axis, so the next orbit is offset westward. 

So unlike a geostationary orbit (e.g., GOES) this Cubesat won't remain pointed at a single location.  Its ground track will loop around the Earth a bunch of times, until it eventually starts repeating.  We could use its altitude (~300km) and inclination (~96.7 degrees) to calculate this "revisit period".  It will probably be on the order of days to a couple of weeks.

If you mean "how does it keep its sensors pointing downward towards the Earth, rather than in some random direction out to space", that's historically been a thorny problem, and it depends on the Cubesat. Normal (non-Cubesat) satellites have a three-axis stabilization system (ADC) that keeps the satellite oriented so its sensors are always facing downward. Only a few Cubesats have ADCs, because of the difficult size constraints. 

[TerryM]

So ---
We should be thinking of a cube spinning and tumbling through space ~300km from earth?


Ice crystals will reflect visible light which might indicate noctilucent clouds, if we could determine what direction our sensor was pointed in, and where we were in our orbit.
A time stamp and/or tracking should indicate our orbital position, but determining which side is "up" might be difficult?


Would painting each of the 6 sides with a photo voltaic film, then measuring the deltas provide any meaningful real time data? The highest output side would be aligned towards the sun through most of the orbit, but it's opposite wouldn't necessarily be aligned with the earth.
When our cube is shaded by earth I'd imagine the moon would be the strongest source of light, but what about lunar cycles?


Can GPS system signals help with location and alignment?


2 weeks !
Sorry guys, just stream of consciousness.
Terry

[Ned W]

So ---
We should be thinking of a cube spinning and tumbling through space ~300km from earth?

RealityCheck would have to answer that one.  Some CubeSats have stabilization, others don't.  It's generally essential if the goal is to be looking at the Earth.

https://en.wikipedia.org/wiki/CubeSat#Attitude_control

[Sigmetnow]

...

If you mean "how does it keep its sensors pointing downward towards the Earth, rather than in some random direction out to space", that's historically been a thorny problem, and it depends on the Cubesat. Normal (non-Cubesat) satellites have a three-axis stabilization system (ADC) that keeps the satellite oriented so its sensors are always facing downward. Only a few Cubesats have ADCs, because of the difficult size constraints.

Yes, this.  Satellite orientation tech is unlikely to be an “off the shelf,” lightweight addition, so if it is not a part of the basic cubesat, any most attempts to study phenomena on the earth’s surface or atmosphere seems unlikely to succeed.

It might work better if the satellite transmitted a simple signal, (or received one and retransmitted it), rather than gathering data itself.  Variations in signal strength or light intensity received on earth could be used to study radiation, or atmospheric light blockage (depending on the frequency).

Think less like IceSat and more like... Sputnik? 

[RealityCheck]

Thanks for observations and comments, all.
A few things: yes, we will have 3D stabilisation.
As said at outset, I have an unexpected opportunity to be involved in this launch, and might be able to include an additional element of interest to ASIF folks. Main mission objectives are preset already - I am thinking of this as a possible 'nice to do' in addition.
Perhaps throwing this question out for feedback might seem unusual to some - but this site's tagline does say 'Interesting discussions'. Mission accomplished on that score I think!
Regards,
RC

[Sigmetnow]

Thanks for thinking of us, and allowing the Forum to kick around some ideas.

Please keep us updated.  Best of Luck!

[RealityCheck]

Thanks Sig. Will do.

[RealityCheck]

Hi All
I am locking this thread for now, for the sake of tidiness. Thanks again to responders. I will unlock and update when appropriate.
Regards
RC