A study was made to look for possible improvements to the current
system. One conclusion from the report was that a significant
improvement could be made by changing the standby pick-off mirror
which has a reflectivity of only 62%. It was impossible to
remove the coating off the existing mirror so it was decided to
acquire a new one. Specification were defined and a mirror ordered.
The most obvious improvement to the instrument is a change of the very
low efficiency detector. A 2kx2k device with 15m pixels would be
the best solution in the current situation, providing the maximum 3.6
arcmin squared field-of-view with a sampling of 0.11 arcsec per pixel
compared to the current 3 arcmin squared sampled at 0.176 arcsec.
Depending on the device, the expected gain in efficiency with a new
CCD would be a factor
1.5 in the red and a factor
2 in the
blue.
Further improvements, allowing for a larger field-of-view would require modification of the filter mechanism and/or the pick-off mirror unit, were also specified in more detail.
Thomas Augusteijn 2006-02-02