[IGSMAIL-6698] AMC2 USN3 clock offset calibrations in RINEX

[Stowers, David A (3350)]

Author: Dave Stowers

Please be advised, that as of d342 (Dec 7) calibration corrections which had been applied
to AMC2 RINEX data are no longer included. The same omission applies to USN3 RINEX 
data starting d346 (Dec 11). The change occurred when moving from using edited data, to simply
using teqc to process the raw files directly from the receiver, which also has some benefits.

As this correction has been noted as useful in the timing community, we intend to reintroduce
this feature to both AMC2 and USN3 data starting at on d349 UTC0:00 (tomorrow, Dec 14).

If/when we are prepared to reconvert the raw data from both sites from the above-listed dates
through today (Dec 14) with the calibration applied, and resubmit the data set to IGS Global Data 
Centers, another announcement will be provided.

Apologies for the inconvenience, and best regards,

-dave