A video on YouTube shows how a microcontroller could be used on an Amateur Satellite to conserve power when over certain areas of the world.
The YouTube description says
This video illustrates how a small satellite or cubesat could employ an on-board micro-controller to track its own location in real time in order to change its mode or transmit power based on the region of the earth over which it is passing.
I did not intend to suggest that this is novel in all aspects. Certainly, this work is based on G3RUH's Plan 13 above all else, and the work in the LVB tracker made me feel confident I could produce the Plan13 library.
However, the point of this presentation was the very low power consumption of tracking with today's micro-controlling hardware, making self-tracking a power-budget benefit even for conserving tens of milliwatts! Moreover, I wanted to highlight that it is pretty easy to build up ideas like this when the tracking code and the keplerian-storing code are nicely packaged up in open-source, freely available libraries.
That said, I'm not convinced that your example is analogous, even with the question of power set aside. The point of this video is a system in which the bird knows exactly what part of the world is under the bird (SSP), and changes modes based on that. Thereby it avoids transmitting over, say, the 'empty' parts of the S. Pacific. AO-13 had a scheduling system based (in part) on where the spacecraft was located in its orbital plane (mean anomoly) and sun angle. Were these used to accurately calculate SSP? If so, it is a different method that might not be as suitable for low-budget, space-constrained missions as a $4 micro-controller.
In any case, the approach I outline would not be very sensible for a HEO bird, I don't think. This is because with a LEO, especially the ones in low orbit being launched these days, there are times that the footprint is entirely over unpopulated areas, making it wise to try to find out a low-budget way to turn off the beacon/transponder while in these places. That is not true for P3-style HEOs.
I would be most interested if people had examples of amateur satellites or others that determined their own SSP through on-board tracking.
What happens when the processor takes a radiation hit, and is destroyed, turning the satellite off?
How do you recover the bird?
Instead of trying to make the satellite as complicated as possible,I believe you would be better off making it as simple as possible.
I have been, off and on, a financial supporter of AMSAT (I own a solar cell sitting at the bottom of the Atlantic ocean), IMHO, they need simple, single transponder birds that actually make their intended orbit, Have a link budget that ends up within 3db of the pre-launch prediction, and don't have transponders that can be permanently silenced by "Improper ground station commands"
Rege
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Now my mistakes travel at the speed of light!
You might have misunderstood my role: I'm not actively involved in the design of any satellite at all; I'm just demoing an idea. As I note in the video, this idea does add some complexity as it adds functionality. We present and trade ideas like this on earth (note, not 'on paper', because the demo shows the code operating) so that we can decide if the trade-offs makes sense in space. Satellite designers would be as unwise to blindly adopt any new idea that comes along as they would be to reject them out of hand.
However, as you noted in your previous posting, people have striven for something like this for some time using timers and scheduling. This, of course, is also done in silicon, and therefore also subject to the problems you describe. (AO-27's scheduler seems to crash from time to time.) Moreover, the use of micro-controllers as IHUs aboard satellites is pretty much standard operating procedure, and therefore the process for reprogramming them when something goes wrong is also well-understood. AO-51 gets reprogrammed every three months or so. It is with these concerns in mind that, in the video, I recommend that the chip be on a bus through which it can be reprogrammed.
Your post slightly misrepresents the implementation described in the video. It achieves a 15% savings through a change in modes between 120 mW input power and 30 mW input power. Worst-case failure would entail the micro-controller dying with its pins high, which would result in the low power mode -- not 'turning the satellite off' -- and the designer hard-wiring this functionality into the system, which would be unwise.
AMSAT-NA has an excellent, practical plan for 'return to space' in the next couple of years. Among other things, they have a student team working on programming FPGA chips, which are widely seen as being much more resistant to radiation. There are, moreover, several linear birds on the go outside of AMSAT: Kiwisat, Hamsat2, the coming Chinese bird. The problem is getting anything into a HEO orbit, and short of a $5M gift, no solution is in sight for this.
We appreciate your support.
Satellite power-saving by on-board tracking
Linear Mode
