UV Observational Techniques for the Extended Solar Corona

The SOHO Ultraviolet Coronagraph Spectrometer is being developed for spectroscopic determinations of temperatures, densities and flow velocities in the extended solar corona. Determinations of plasma parameters for the primary particles (electrons and protons) and for several minor ions are planned. The techniques and instrumentation to be used must overcome the relatively low intensity levels and potentially high stray light levels intrinsic to observations of the extended corona while also providing high radiometric and spectrometric accuracy and relatively high spectral and spatial resolution. This paper concentrates on the instrument characteristics that are required to observe the resonantly scatter HI Lyman-alpha line at heliocentric heights from 1 to 10 solar radii