If you are working with very recent AVHRR data, it may be necessary for you to obtain more up-to-date TLE files. These TLE files are publicly available and most easily acquired through the Internet. For example, try the site: http://celestrak.com. There you will find recent TLE files named something like noaa-12.tle. When you download such a file, rename it properly (noaa-12.2le) and place it in the current working directory. The files obtained from this site may need to be edited. For example, some of the files at this site contain TLE entries for more than one satellite and distinguish between satellites by preceding each TLE entry with the satellite name. To construct a proper TLE file which AVHRRAD can use, you must extract the relevant TLE entries from such a file but omit the satellite name portion. TLE files placed in the current working directory override the ones in the PCI etc directory.
For best results, ensure that the TLE file contains a TLE entry with a date which is close to the scan date of the AVHRR image which is to be radiometrically corrected. The dates of TLE entries in a TLE file are typically separated by 1 or 2 days.