An Atlas of Extreme-Ultraviolet Spectroheliograms from OSO-IV

Abstract

The atlas contains a collection of far-ultraviolet solar spectroheliograms obtained by the Harvard College Observatory spectrometer on the fourth Orbiting Solar Observatory launched in 1967 October. An extended series of plates depicts composite spectroheliograms as a numerical matrix suitable for quantitative studies and is accompanied by pictorial representation in quasi-photographic form and in the form of contour maps. The necessary photometric conversion factors are contained on each plate to convert the numerical data into emergent solar flux and also flux received at the top of the Earth's atmosphere. Each spectroheliogram is a composite of the best data within the daylight portion of the orbits, and the series includes most of the stronger solar emission lines and continua in the wavelength region 3( A covering stages of ionixation from neutral species to species ionized fifteen times. The spectroheliograms have a spatial resolution of 1 minute of arc. The operational characteristics of the instrument are discussed, together with the wavelength sensitivity, telescope slit function, spectrometer line profile, photometric calibration, and calibration changes on the ground and in orbit.