the survey a target list that requires no extra calibrations, provided the observations are not time critical, adds minimal extra cost to the operations.

Emphasis should be given to programs for which access to space significantly reduces the sky background for observations and to programs for which either high spatial resolution or large collecting area is important. The ATD/NTOT thus has a major advantage over other facilities for the following kinds of programs:

  • Programs in the near infrared (2 to 4 microns), where the difference in the sky background is reduced by several orders of magnitude (largely through reduction of H2O and other tropospheric species);

  • Programs in the far red (>0.7 micron), where the sky is reduced by up to one order of magnitude (OH emission); and

  • Programs that depend on the contrast between a point source and its neighborhood (either the sky background or its own astronomical environment) or that require subarc-second spatial resolution to reach interesting spatial scales or that are photon-starved, that is, receive little attention with the HST.


1. Thompson, R.I., “NICMOS: A Second Generation Infrared Instrument for the Hubble Space Telescope”, Advances in Space Research 13(12):509-519, 1993.

2. Space Science Board, National Research Council, Institutional Arrangements for the Space Telescope, National Academy of Sciences, Washington, D.C., 1976. Also see, Space Science Board, Institutional Arrangements for the Space Telescope: A Mid-Term Review , National Academy Press, Washington, D.C., 1985.

3. Space Studies Board, National Research Council, Lessons Learned from the Clementine Mission, National Academy Press, Washington, D.C., in preparation.

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