What telescope performance (e.g. pointing and tracking, image quality) is required?
The telescope and instrument should contribute equally to the overall system wave front error budget. The pointing stability should therefore be approximately 0.”003 pixel (3 sigma). This stability need only be maintained no longer than a typical integration time (1000 s for the near-IR, 100 s for mid-IR). Carefully controlled dithering of the line of sight, accurate to 0″.003 with an amplitude of about 1″, should be required to extract diffraction limited spatial information from undersampled images, to veto cosmic ray contaminated pixels, and to replace data from dead pixels. Significant image motion between subsequent frames of the interferogram does not degrade spectral or spatial resolution. In particular, the FTS can obtain spectra of moving objects such as solar system targets.
