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Coronal Observation 5

Purpose: This sequence is used at large heliocentric heights to determine proton temperature, outflow velocity, electron density, and OVI density. The primary observable quantities are Ly-alpha profile, OVI intensity, and visible polarized radiance. This mode is expected to be used 2.5% of the time.

Description: Duration 1 to 3 hours. There will be several versions with different dwell times, each one optimized for a particular target (streamers, quiet corona, coronal holes). Scan telescope mirror from radial position 3.5 to 10.0 R (TBC). There are 10 mirror positions, with step size ranging from 0.5 to 1.0 R (TBC).

This observation may involve offset pointing prior to the observation (but not during the observation). The purpose is to ``over-occult" and thus reduce stray light levels. In that case the ``Offset-Pointing" type of safety checking would be used rather than the ``Sun-center" type.

At each mirror position, measure resonantly scattered Ly-alpha profile. A series of exposures is obtained with slightly different grating positions (``dither motion"). There are 20 grating positions with steps of 0.01 Å (TBC). Dwell times increase with height in the corona. The OVI 1032/1037 Å intensities are also measured. Polarized visible radiance will be measured at one position along the slit for each mirror position.



Peter Smith
Fri Jan 17 12:11:15 EST 1997