5.2. Coalignment The ability to maintain coalignment of the…

5.2. Coalignment

          The ability to maintain coalignment of the four channels is dependent on knowledge of the thermal and mechanical
stability of the system, which affects the rotation of the telescope mirrors. Because of the mechanical instabilities described
above, observations in all but the LWRS aperture require multiple peakups per orbit in order to maintain a reasonable throughput.
Observations made through the LWRS aperture, where coalignment is much less critical, can typically be maintained for weeks
without interruption, with small adjustments of the FPAs and mirrors, as long as pointing angle constraints are followed.

          A number of tests have been executed to determine how to most efficiently implement observing in the MDRS and HIRS
apertures. Based on data taken for several different targets in the CVZ, the image motions are very repeatable with orbital phase.
Using this information allows a determination of when to perform peakups in the MDRS or HIRS aperture as a function of orbital
phase, and a prediction of how long we can observe before new peakups are necessary to keep the channels aligned. After more
data is obtained, and the shape of this channel motion is well calibrated, we are hopeful that only a single peakup at the beginning
of the target's visibility period will be necessary, and then the FPAs can be moved autonomously throughout the orbit in order
to keep the channels aligned, thus avoiding the necessity of performing time-consuming peakups throughout the orbit.

5.3. Spectrograph Resolution and Instrument Focus

           The resolution, R=