Space-based photometric precision from ground-based telescopes

Published

July 1, 2010

Author(s)

Peter C. Zimmer, John T. McGraw, Anthony B. Hull, Daniel C. Zirzow, Steven W. Brown, Claire E. Cramer, Gerald T. Fraser, Keith R. Lykke, Allan W. Smith, John T. Woodward IV, Christopher W. Stubbs, Mark R. Ackermann, Dean C. Hines

Abstract

Ground-based telescopes supported by lidar and spectrophotometric auxiliary instrumentation can attain space-based precision for all-sky photometry, with uncertainties dominated by fundamental photon counting statistics. Earth‟s atmosphere is a wavelength-, directionally- and time-dependent turbid refractive element for every ground-based telescope, and is the primary factor limiting photometric measurement precision. To correct accurately for the transmission of the atmosphere requires direct measurements of the wavelength-dependent transmission in the direction and at the time that the supported photometric telescope is acquiring its data. While considerable resources have been devoted to correcting the effects of the atmosphere on angular resolution, the effects on precision photometry have largely been ignored. We describe the facility-class lidar that observes the stable stratosphere, and a spectrophotometer that observes NIST absolutely calibrated standard stars, the combination of which enables fundamentally statistically limited photometric precision. This inexpensive and replicable instrument suite provides the lidar-determined monochromatic absolute transmission of Earth‟s atmosphere at visible and near-infrared wavelengths to 0.25% per airmass and the wavelength-dependent transparency to less than 1% uncertainty per minute. The atmospheric data are merged to create a metadata stream that allows throughput corrections from data acquired at the time of the scientific observations to be applied to broadband and spectrophotometric scientific data. This new technique replaces the classical use of nightly mean atmospheric extinction coefficients, which invoke a stationary and plane-parallel atmosphere. We demonstrate application of this instrument suite to stellar photometry, and discuss the enhanced value of routinely provably precise photometry obtained with existing and future ground-based telescopes.

Proceedings Title

Conference 7737 - Proceedings of SPIE Volume 7737

Volume

7735

Conference Dates

June 28-July 2, 2010

Conference Location

San Diego, CA, US

Conference Title

Proceedings of the SPIE Conference on Astronomical Telescopes and Instrumentation 2010

Pub Type

Conferences

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DOI Link

Keywords

absolute calibration, atmospheric extinction, atmospheric transmission, calibration, lidar, radiometry, photometry, spectrophotometry

Citation

Zimmer, P. , McGraw, J. , Hull, A. , Zirzow, D. , Brown, S. , Cramer, C. , Fraser, G. , Lykke, K. , Smith, A. , Woodward IV, J. , Stubbs, C. , Ackermann, M. and Hines, D. (2010), Space-based photometric precision from ground-based telescopes, Conference 7737 - Proceedings of SPIE Volume 7737, San Diego, CA, US, [online], https://doi.org/10.1117/12.857700 (Accessed December 6, 2024)