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Originally Posted by Targan
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When these quotes were posted the programmer in me was thinking, what engineer would allow that. The next paragraph radically changes the context of the quotes as far as this discussion goes.
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The engineers who designed the GPS system included these relativistic effects when they designed and deployed the system. For example, to counteract the General Relativistic effect once on orbit, they slowed down the ticking frequency of the atomic clocks before they were launched so that once they were in their proper orbit stations their clocks would appear to tick at the correct rate as compared to the reference atomic clocks at the GPS ground stations. Further, each GPS receiver has built into it a microcomputer that, in addition to performing the calculation of position using 3D trilateration, will also compute any additional special relativistic timing calculations required
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Also this
https://en.wikipedia.org/wiki/GPS_satellite_blocks
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The Block IIA satellites were slightly improved versions of the Block II series, designed to provide 180 days of operation without contact from the control segment.
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Given how important the GPS system is I could see MILGOV sacrificing quite a bit to make sure they can update them twice a year. Don't know how long they could keep them working but they would sure try.
In my world the GPS system would be some where between useless (If ASATs or EMP were really effective), to only being able to provide accurate time (if say 3 or 4 are alive) , to the least likely option partially functional (with like 8 sats working properly, like during the deployment for "desert shield").
If you say you can only get a link for 4 hours every 4 days that could be a useful plot device. You could even have a few sats giving out erroneous information so if you check during other times you get totally wrong information.