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Published November 1, 2005 | public
Journal Article

Broadband submillimeter measurements of the full Moon center brightness temperature and application to a lunar eclipse

Abstract

We report on observations of the full Moon brightness temperature covering the frequency range of 300–950 GHz, and also on observations of the lunar eclipse of July 16, 2000, though only covering the frequency range of 165–365 GHz due to poor atmospheric transmission at higher frequencies. All observations were performed from the summit of Mauna Kea (HI) using a Fourier Transform Spectrometer mounted on the Caltech Submillimeter Observatory and supplemented by measurements of the atmospheric opacity using a 183 GHz Water Vapor Monitor. The telescope was pointed to the center of the lunar disk (with a footprint of ∼45–15 km on the Moon at 300 through 900 GHz). In order to obtain the correct values of the Moon brightness temperatures at all frequencies we carefully corrected for the atmospheric absorption, which varies across the submillimeter domain. This correction is fully described. The measured pre-eclipse brightness temperature is around 337 K in the 165–365 GHz range. This temperature slightly increases with frequency to reach ∼353 K at 950 GHz, according to previous broader band data. The magnitude of the temperature drop observed during the eclipse at 265 GHz (central frequency of the band covered) was about ∼70 K, in very good agreement with previous millimeter-wave measurements of other lunar eclipses. We detected, in addition, a clear frequency trend in the temperature drop that has been compared to a thermal and microwave emission model of the lunar regolith, with the result of a good match of the relative flux drop at different frequencies between model and measurements.

Additional Information

© 2005 Elsevier. Received 13 December 2004; revised 16 February 2005. Available online 13 May 2005. We are grateful to Drs. M. De Petris and S.J. Keihm for providing their model calculations for comparison to our data. The authors wish to thank the CSO Hawaii staff for providing assistance during the observations. This work has been supported by NSF Grants ATM-9616766 and AST-9615025, and by Spanish MCyT Grants ESP2002-01627, AYA2002-10113-E and AYA2003-02785-E. CSO operations were supported by NSF Grant AST-9980846.

Additional details

Created:
August 22, 2023
Modified:
October 25, 2023