A rocket-borne spectroheliograph designed to take monochromatic pictures of the sun in the Mg II line at 2802.7 Å is described in detail. The photographic system consists of a Questar telescope, a Šolc type birefringent filter, and an automatic Robot camera. The double Šolc filter has a spectral bandwidth of 3.5 Å. The two units in the double filter have been thoroughly tested and are compared with theoretically calculated transmission curves. Two new types of linear film polarizers for the uv region have been tested and used in the filter. A temperature control unit was developed which stabilized the filter temperature in flight to within ±0.2 °C. The instrument has been tested in vacuum and to the Aerobee 150 vibration specifications. It has been flown and successfully recovered three times and performed excellently during each fight.
Kerstin Fredga, "Rocket Spectroheliograph for the Mg II Line at 2802.7 Å," Appl. Opt. 8, 333-333 (1969)