[amsat-bb] Introducing qrpTracker, a $4 microwatt satellite tracker

Bruce Robertson ve9qrp at gmail.com
Sat Oct 24 18:13:40 PDT 2009

Over the last couple of months I've ported the Plan13 satellite
tracking algorithm to a library for the Arduino platform. To inspire
Arduino hobbyists and fellow amsaters, I've made a website to explain
and explore this material, http://sites.google.com/site/qrptracker/
There you'll find a 4 min. introductory video. Around 1:33, the
Arduino demo starts.

Though I was originally thinking of making a sort of doppler tuning
dongle for my FT-817 -- a sort of LVBTracker for the trail -- along
the way I've become aware that there are many uses of a $4 device that
can track 13 tles all alone, and leave about 14kB for other
programming, all with the possibility of average power use in the tens
or hundreds of microwatts and SMD dimensions of 8mm^2.

For instance, equipped with a low-power tracker like this, an amateur
satellite could track its own location over the earth by means of a
reliable real time clock, and it could change its mode depending on
its calculated location, say turning off its beacon over the poles and
oceans. (Plan13 *in* outer space!)

I've implemented this idea in the demo
Regions of earth, defined with latitude and longitude limits, are
stored as an array, and when  Plan13  finds the satellite is within
one of these regions, it raises one of its pins to a 'high' state,
otherwise, this pin is 'low'. When not calculating position, the
AtMega328 can drop into a low-power sleep, consuming around 20
microWatts, but retaining the state of its signaling pin. The
satellite uses the state of the pin to turn off its beacon, or to
switch from a linear to an FM mode. I plan to illustrate this in a
future screencast.

Of course, the same idea could be implemented in a multitasking IHU of
any platform. qrpTracker is offered as a simple means by which people
can play around with satellite tracking in microcontrollers, and I
welcome collaborators and bug reports at its open-source code
repository at http://code.google.com/p/qrptracker/

Finally, if anyone has use of a chip that spits out AZ/EL and doppler
info, either through serial-line requests or off of the I2C bus, I'd
be happy to send off a chip loaded with the keps you need. Your
application would have to supply the real time clock, and eventually
the loaded keps would get stale, but by that time you'll be hooked and
have the equipment to update the keps yourself :-)

73, Bruce

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