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W. Freudling (ST-ECF, ESO), S. Arribas (STScI, ESA), S. Cristiani (ST-ECF, ESO), R. Fosbury (ST-ECF, ESA), P. Jakobsen (ESTEC, ESA), N. Pirzkal (ST-ECF, ESO)
The Ad hoc Science Working Group has recommended (US-manufactured) micro-electronic mirrors or shutters (MEMS) as the preferred slit-generating system for the Next generation Space Telescope near-infrared multi-object spectrograph that will be supplied by the European Space Agency. Such MEMS devices will not be perfectly `binary' in the sense that elements which are in the `off' position will still deliver some light to the spectrograph from bright objects in the FoV via diffraction and scattering processes. These `spoilers' will appear as attenuated spectra on the detector and some of them will overlap the spectra of the faint target sources. We have used source counts, size and magnitude distributions derived from the deepest NICMOS observations of the Hubble Deep Fields to estimate the expected frequency and degree of such overlaps. We also simulated a deep exposure with a MEMs based spectrograph using SLIM - a multi-object spectroscopy simulator originally developed for the slitless spectroscopy modes of the HST Advanced Camera for Surveys - adapted to handle a mixture of targets and attenuated spoilers. The results are compared with estimates of this confusion problem discussed by several groups during the NGST spectrograph studies.
The author(s) of this abstract have provided an email address for comments about the abstract: wfreudli@eso.org