An embodiment of a method of automatically generating a background measurement in a spectrometer is described that comprises the steps of: collecting a plurality of candidate scans in the spectrometer; determining for each of the plurality of candidate scans if the candidate scan correlates to an orthonormal basis set that is associated with a recent background description; saving each candidate scan that correlates to the orthonormal basis set as a background scan in a scan cache; and generating a new background measurement from a plurality of the background scans stored in the scan cache if a current background measurement is older than a preselected time interval.