16927

We wish to use the STIS and WFC3-IR modes of HST to carry out spectroscopic observations of two NIRISS commissioning targets from roughly 0.5 to 1.7 microns to establish the spectra shape of one target and the spectral shape and (approximate) absolute calibration of the second target. The spectra will be used in the analysis of the NIRISS commissioning programs NIS-018 (APT 1092) and NIS-034 (APT 1541). Although these observations will cover only about half the spectral range of the NIRISS GR700XD grism comma it will provide the only available check on the quality of the NIRISS commissioning calibration products in this mode.