On 25th April there was a bad TLE bulletin issued by NORAD (the US agency responsible for satellite tracking), which appeared for a while on the space-track and the celestrak web sites. This caused problems at some centres. If you think you might have been affected, please check your tle_noaa18.index file (normally at AAPP/orbelems/tle_db). If there is a line towards the end of the file containing *******, please delete that line, to ensure that future bulletins are used correctly.
Note that EUMETSAT TLEs at http://oiswww.eumetsat.org/metopTLEs/html/index.htm were unaffected. EUMETSAT generate their own TLEs for the NOAA-15, 18 and 19 satellites, based on NOAA’s operational 4-line elements. We recommend that AAPP users use the EUMETSAT TLEs where possible.
Nigel