NICMOS Instrument Handbook for Cycle 11

Chapter 9: 
Exposure Time
Calculations

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In this chapter . . .

Overview Calculating NICMOS Imaging Sensitivities WWW Access to the Exposure Time Calculator

 

In this chapter we provide information needed to estimate exposure times for NICMOS Cycle 11 Phase I proposals. We provide some general comments about NICMOS imaging exposure time issues. We then describe how to use the Web-based NICMOS Exposure Time Calculator (ETC). Imaging is the only capability currently implemented in the ETC, which uses the expected instrument performance under NCS. This will be updated as more in-flight information becomes available. This ETC also uses measured values for HST primary and secondary mirror emissivities and temperatures, and throughput calculations are performed by the STSDAS SYNPHOT package's COUNTRATE task. With this approach, our estimation of the thermal background is in good agreement with observed values.

Reference sensitivity curves are also given in Appendix 1 for imaging, and in Chapter 5 for grism spectroscopy.