According to amsat-uk.org, the AO 91 satellite should not be accessed during eclipse because it is near EOL.

  • AO-91 (RadFxSat / Fox-1B) Near end of life. If you find it on, do not attempt to access in eclipse! (That is, don't use it at night)

I'm happy to play by the rules, but I'm curious: What about it getting old precludes it from use in the dark?

  • 4
    $\begingroup$ I'm guessing due to its batteries' age specifically? So when it's in sunlight it's still powered fine but at night its backup power no longer has the original capacity? $\endgroup$ Commented Nov 21, 2023 at 22:29

1 Answer 1


In all likelihood the batteries on AO-91 are exhausted. So contact during eclipse could POSSIBLY (at this time probably a very small possibility) cause the batteries to short and not allow any contact even during daylight. Also the telemetry beacon probably has battery information which gives somewhat accurate information about the status of the satellite itself.

Found some telemetry info here from AmSat https://www.amsat.org/tlm/health.php?id=2&port=

It's just a snapshot of the latest telemetry data, but I'm sure over time you can see the condition of the battery(or batteries) and how they've degraded.

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