Loads sample times. Called by analysis_pet(), and pet_analysis_done(). Calls FindHeader(), and GetSampleTimes(). This function checks the BLR file for sample time data. If this data is found, it is loaded and the sample_times_existflag is set true. Otherwise, GetSampleTimes() is called to try and retrieve the sample time data from the VAX. If this is successful, the data is loaded, copied into the BLR file, and the sample_times_existflag is set true. If the data is unavailable, the sample_times_existflag is set false.