You should reduce this data of type ``scan'' before anything else. REDUCEBG DATA: examine and edit the data with PLOT. Plot the background rate (four channels at a time) versus time. (Select channels for the first panel, don't forget to hit return after entering your selection, and then the Next options in the data selection widget to plot all channels in groups of four.) Do this for all output beams (i.e. spectrometers). Remove scans taken on a star (instead of on blank sky) by identifying the scan number (or time) and then editing the data in a plot with ScanNo (or Time) along the Y-axis. Look out for the laser light in channel 11 (the default is to delete this channel). Remember that editing is only allowed in single plot windows (i.e. a window containing only a single plot). Save the BGFlagTable.
Use PROCESS BG if you want to replace edited scans with an average value from other valid scans in the same channel. Use EXPAND BG to create new background scans for non-existing ones by correlating the BGTable with the ScanTable. (Check the background form or use UTILITIESLISTBGSCANS to see missing background scans.) The reason for reducing the background data first is that average will not average the point data of a scan for which no background data exists.