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Current situation with CoCom regulations and GPS receivers for balloons and cubesats
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I wanted to ask this at aviation SE because they are quite rules-and-regulations oriented there, but this question is not (really) about aviation.
I'm trying to understand the current situation for obtaining, and using GPS receivers that continue to work at very high altitude, or high speed, or both. Due to the existence of CoCom reguations I believe all GPS module manufacturers added limits to their products - probably in firmware - so that they would stop working if some combination of two limits had been reached. The limits are (I believe) altitude > 18km and speed > 1000 knots (about 0.5 kilometer per second). I think, although I am not sure, that these were implemented across the board by all manufacturers to avoid any possibility of sanctions or falllout similar to the CNC machines sold and potential use for quiet sub propellors and subsequent sanctions.
One subtlety is the question if the two limits (altitude, speed) are applied in an OR or AND configuration, which matters if your application is balloon borne or even testing cubesat subsystems via balloon.
This paragraph in Wired is intriguing, but it doesn't actually tell what the "more relaxed rules" are!
"Due to more relaxed rules, we now have the possibility to use GPS signals at higher altitudes and speeds. The problem is people normally don’t know how to either construct their own receivers or disable/modify the limits inside ready available modules (until now).
One can find references to changing/updating/hacking the firmware to remove limits here, and here, and as a product here.
My Question is: What exactly are the rules now? Is it "OK" to change firmware or otherwise remove limits on ones own module? Can manufacturers of GPS modules ship them without the limits in certain cases? What are the conditions? Where are the rules written so we can read them?
cubesat<br>gps<br>balloons<br>regulatory
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edited Apr 7, 2016 at 14:15
asked Apr 7, 2016 at 14:09
user12102
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$\begingroup$<br>Just to clarify, are you saying that your application is specifically intended for balloons approaching or exceeding the Karman line and/or balloons used for cubesat testing? Otherwise, I'm having trouble seeing how this fits here rather than Aviation.<br>$\endgroup$
called2voyage
called2voyage
2016-04-07 14:16:54 +00:00
Commented<br>Apr 7, 2016 at 14:16
$\begingroup$<br>Cubesats are my target here @called2voyage . Balloons come into play in two ways. One might be wise to test a model cubesat or subsystem (communications, thermal, imaging, GPS, possibly sun or star finding) using a high altitude balloon flight first. This involves the altitude limit but not the velocity limit, which is the second issue - different GPS modules may use AND or OR on the criteria.<br>$\endgroup$
user12102
user12102
2016-04-07 15:47:07 +00:00
Commented<br>Apr 7, 2016 at 15:47
$\begingroup$<br>Someone on the Raspberry Pi forums says: "Commercial GPS receivers conform to COCOM limit, (altitude<br>$\endgroup$
called2voyage
called2voyage
2016-04-07 15:56:12 +00:00
Commented<br>Apr 7, 2016 at 15:56
$\begingroup$<br>That discussion in the Raspberry Pi forums is actually quite helpful. It mentions the Adafruit Ultimate GPS which states the 515 m/s velocity limit. While the PDFs state 18,000 meter altitude limit, the VIDEO (found here) states 50 kilometers. This is consistent with the "newer" rules (see answer below).<br>$\endgroup$
user12102
user12102
2016-04-08 02:18:03 +00:00
Commented<br>Apr 8, 2016 at 2:18
$\begingroup$<br>There is additional discussion in [community.balloonchallenge.org of GPS units which work at high-altitude, but at low speed. These are high altitude balloon applications. Also in this post in Ars Technica Openforum<br>$\endgroup$
user12102
user12102
2016-04-10 07:37:22 +00:00
Commented<br>Apr 10, 2016 at 7:37
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There is a standard clause included in all GPS receiver manuals regarding COCOM Limits. I cannot find the source of this clause, but since it is worded exactly the same in all the manuals I could find, I assumed it was probably derived directly from the regulation at some point:
COCOM Limits
The U.S. Department of Commerce requires that all exportable GPS<br>products contain performance limitations so that they cannot be used<br>in a manner that could threaten the security of the United States. The<br>following limitations are implemented on...