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Calibration Lamp

The ultraviolet calibration lamp is a quartz mercury discharge tube and is mounted on the opposite side of the spectrometer from the detector. It is indicated as the ``Reference lamp" in Figure 2-4. From this location, two of the spectral lines produced by the lamp fall on the detector face. A wide slit placed over the lamp provides lines that are about 80 pixels wide, with a weak line located near pixel 1660 and a very weak secondary line near pixel 1490. These UV emissions are used to test the operation of the detector and spectrometer subsystems and provide a means of tracking any degradation of the sensitivity throughout the instrument integration. They do not provide a wavelength calibration, nor do they yield a photometric calibration of the instrument.