This routine is not a command run from the prompt or schedule, but rather code that eliminates redundancy. When the commands HS or HL are used or executed from within a schedule the HH code is used to configure the instrument to scan HG emission lines. HS (Short wavelength) scans the 296.728 nm line while the HL (Long wavelength scans the 334.148 nm wavelength.
The test can indicate the accuracy of the dispersion and the accuracy of the spherical mirror placement within the instrument by measuring the wavelength of the emission line/s against the ideal wavelength and recording the measured slit width (FHHB - Full height, Half Base of the scanned emission line image). A mirror that is mounted too close or too far from the other optics within the optical frame will increase the FHHB value in angstroms.