[IGSSTATION-6030] USN3 data from November 18-19

[Stowers, David A (3350)]

Author: Dave Stowers

Urgent: USN3 antenna type and location (height) has been significantly changed.

At least one daily 30s file from Nov 18 was unintentionally published
which did not include necessary changes in metadata (RINEX header).
Processing will result in a position that is ~5 -feet- higher than nominal.

Suggest not using any subsequent USN3 data until further notice.

IGS Data centers should remove these erroneous files.

Data will be backfilled with appropriate headers as soon as the entire
scope of the change is fully documented.

Apologies for the inconvenience and the error in publishing.

Best regards,

-dave