[Let's try this again ... that should be microseconds (us) not (is)]

As another random datapoint there's a
MetOp document regarding the LRPT satellite
transmissions which says:

Frequency range * * * Group delay
(kHz) * * * * * * * * * * * *variation (us)
[0-40] * * * * * * * * * * * *+/- 2
[40-60] * * * * * * * * * * *+/- 5

-- John