The ultraviolet spectrometers that observed the atmosphere of Mars in July and August of 1969 consist of a planetary coronagraph and an Ebert-Fastie monochromator. The spectral range 1100–4300 Å was measured using two photomultiplier tubes, one with a cesium iodide photocathode, the other with a bialkali photocathode. These tubes were operated with fixed high voltage supplies and charge sensitive amplifiers. The instruments were calibrated by comparison with a tungsten lamp, a sodium salicylate screen, and a flowing nitric oxide cell. The instruments were able to satisfactorily reject off-axis light at a distance of 6600 km and measure the emission spectrum of the upper atmosphere 170 km above the surface.
J. B. Pearce, K. A. Gause, E. F. Mackey, K. K. Kelly, W. G. Fastie, and C. A. Barth, "Mariner 6 and 7 Ultraviolet Spectrometers," Appl. Opt. 10, 805-812 (1971)