IF-MOS trade-off study: Concerns and questions

During this study, the following concerns and questions about the MOS and IFS design concepts have arisen.

A micro-mirror or shutter array in the NGST focal plane will act as a diffraction grating. The ultimate fate of the diffracted light may have an adverse effect on the level of parasitic light within the instrument. How can this be predicted and controlled?
How will the MOS background subtraction actually be done: from the object slitlets themselves or from separate apertures (or both)?
What are the costs, in thermal dissipation and reliability, of the necessary mechanisms?
What are the failure modes of the MMA/MSA?
Will the target acquisition requirements preclude parallel observations?

Is a spectral resolution of R = 150 too low for doing the 'wide field' parts of the DRM?
What are the sources of parasitic light expected for the image-sliced IFS?
What are the costs, in thermal dissipation and achievability, of the large detector array required for the LR mode??
What is the expected degradation to the prism transmission after 10 years in the L2 radiation environment?

How realistic is it to assume that the optical throughputs of the two types of spectrograph are similar?
Which device gives the optimum performance for a single, faint source - galaxy and unresolved?

Modified by Bob Fosbury on July 20, 1999.
For more information, please send mail to Bob Fosbury.