Solar Spectrometer

Description

The experiment was designed to measure solar EUV radiation in the range of 10 to 400 A by a grating spectrometer. The spectral range was scanned every 8 min when the spacecraft was in sunlight. In operation, the spectrometer was pointed so that the sunlight fell perpendicularly on the front face of the instrument, passed through the entrance slit, and was dispersed by the grating. An aperture-defining slit just before the grating allowed light to strike only the 20-mm x 20-mm ruled portion. The edges of this slit were made very sharp to minimize light scattering. With this arrangement the angular aperture was 1.2 x 2.2 deg, which covered the sun and corona. The experiment worked during the period March 7 to May 15, 1962, and over 7000 spectra were obtained. Below 170 A, the data were difficult to interpret because of lower sensitivity and scattered radiation. Above 342 A, the second order images obscured the data. For more details, see W. E. Behring, Applied Optics, v. 9, p. 1006, 1970.