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Testing of the LSST's photometric calibration strategy at the CTIO 0.9 meter telescope
Author(s): Michael W. Coughlin; Susana Deustua; Augustin Guyonnet; Nicholas Mondrik; Joseph P. Rice; Christopher W. Stubbs; John T. Woodward
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Paper Abstract

The calibration hardware system of the Large Synoptic Survey Telescope (LSST) is designed to measure two quantities: a telescope's instrumental response function versus wavelength and atmospheric transmission. First of all, a "collimated beam projector," which projects monochromatic light, monitored with a NIST-traceable photodiode, through a mask and a collimating optic onto the telescope, is designed to measure the instrumental response function. This method does not suffer from stray light effects and the reflections/ghosting present when using a flat-field screen illumination, which has a systematic source of uncertainty from uncontrolled reflections. It allows for an independent measurement of the throughput of the telescope's optical train as well as each filter's transmission as a function of position on the primary mirror. Second, CALSPEC stars can be used as calibrated light sources to illuminate the atmosphere and measure its transmission. To produce spectrophotometry necessary to measure the atmosphere's transfer function, we use the telescope's imager with a Ronchi grating in place of a filter to configure it as a low resolution slitless spectrograph. In this paper, we describe this calibration strategy, focusing on results from this prototype system at the Cerro Tololo Inter-American Observatory (CTIO) 0.9 meter telescope. We compare the instrumental throughput measurements to nominal values from the vendor. We describe measurements of the atmosphere made via CALSPEC standard stars during the same run.

Paper Details

Date Published: 10 July 2018
PDF: 13 pages
Proc. SPIE 10704, Observatory Operations: Strategies, Processes, and Systems VII, 1070420 (10 July 2018); doi: 10.1117/12.2309582
Show Author Affiliations
Michael W. Coughlin, Caltech (United States)
Susana Deustua, Space Telescope Science Institute (United States)
Augustin Guyonnet, Harvard Univ. (United States)
Nicholas Mondrik, Harvard Univ. (United States)
LSSTC (United States)
Joseph P. Rice, National Institute of Standards and Technology (United States)
Christopher W. Stubbs, Harvard Univ. (United States)
John T. Woodward, National Institute of Standards and Technology (United States)


Published in SPIE Proceedings Vol. 10704:
Observatory Operations: Strategies, Processes, and Systems VII
Alison B. Peck; Robert L. Seaman; Chris R. Benn, Editor(s)

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