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Title: SARAS MEASUREMENT OF THE RADIO BACKGROUND AT LONG WAVELENGTHS

Abstract

SARAS is a correlation spectrometer connected to a frequency independent antenna that is purpose-designed for precision measurements of the radio background at long wavelengths. The design, calibration, and observing strategies admit solutions for the internal additive contributions to the radiometer response, and hence a separation of these contaminants from the antenna temperature. We present here a wideband measurement of the radio sky spectrum by SARAS that provides an accurate measurement of the absolute brightness and spectral index between 110 and 175 MHz. Accuracy in the measurement of absolute sky brightness is limited by systematic errors of magnitude 1.2%; errors in calibration and in the joint estimation of sky and system model parameters are relatively smaller. We use this wide-angle measurement of the sky brightness using the precision wide-band dipole antenna to provide an improved absolute calibration for the 150 MHz all-sky map of Landecker and Wielebinski: subtracting an offset of 21.4 K and scaling by a factor of 1.05 will reduce the overall offset error to 8 K (from 50 K) and scale error to 0.8% (from 5%). The SARAS measurement of the temperature spectral index is in the range −2.3 to −2.45 in the 110–175 MHz band and indicatesmore » that the region toward the Galactic bulge has a relatively flatter index.« less

Authors:
 [1]; ; ; ;
  1. University of California, Berkeley, CA (United States)
Publication Date:
OSTI Identifier:
22521758
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 801; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANTENNAS; BACKGROUND RADIATION; BRIGHTNESS; CORRELATIONS; COSMIC RADIO SOURCES; EMISSION SPECTRA; INDEXES; MHZ RANGE; MILKY WAY; RADIOWAVE RADIATION

Citation Formats

Patra, Nipanjana, Subrahmanyan, Ravi, Sethi, Shiv, Shankar, N. Udaya, and Raghunathan, A., E-mail: nipanjana@berkeley.edu. SARAS MEASUREMENT OF THE RADIO BACKGROUND AT LONG WAVELENGTHS. United States: N. p., 2015. Web. doi:10.1088/0004-637X/801/2/138.
Patra, Nipanjana, Subrahmanyan, Ravi, Sethi, Shiv, Shankar, N. Udaya, & Raghunathan, A., E-mail: nipanjana@berkeley.edu. SARAS MEASUREMENT OF THE RADIO BACKGROUND AT LONG WAVELENGTHS. United States. doi:10.1088/0004-637X/801/2/138.
Patra, Nipanjana, Subrahmanyan, Ravi, Sethi, Shiv, Shankar, N. Udaya, and Raghunathan, A., E-mail: nipanjana@berkeley.edu. Tue . "SARAS MEASUREMENT OF THE RADIO BACKGROUND AT LONG WAVELENGTHS". United States. doi:10.1088/0004-637X/801/2/138.
@article{osti_22521758,
title = {SARAS MEASUREMENT OF THE RADIO BACKGROUND AT LONG WAVELENGTHS},
author = {Patra, Nipanjana and Subrahmanyan, Ravi and Sethi, Shiv and Shankar, N. Udaya and Raghunathan, A., E-mail: nipanjana@berkeley.edu},
abstractNote = {SARAS is a correlation spectrometer connected to a frequency independent antenna that is purpose-designed for precision measurements of the radio background at long wavelengths. The design, calibration, and observing strategies admit solutions for the internal additive contributions to the radiometer response, and hence a separation of these contaminants from the antenna temperature. We present here a wideband measurement of the radio sky spectrum by SARAS that provides an accurate measurement of the absolute brightness and spectral index between 110 and 175 MHz. Accuracy in the measurement of absolute sky brightness is limited by systematic errors of magnitude 1.2%; errors in calibration and in the joint estimation of sky and system model parameters are relatively smaller. We use this wide-angle measurement of the sky brightness using the precision wide-band dipole antenna to provide an improved absolute calibration for the 150 MHz all-sky map of Landecker and Wielebinski: subtracting an offset of 21.4 K and scaling by a factor of 1.05 will reduce the overall offset error to 8 K (from 50 K) and scale error to 0.8% (from 5%). The SARAS measurement of the temperature spectral index is in the range −2.3 to −2.45 in the 110–175 MHz band and indicates that the region toward the Galactic bulge has a relatively flatter index.},
doi = {10.1088/0004-637X/801/2/138},
journal = {Astrophysical Journal},
number = 2,
volume = 801,
place = {United States},
year = {Tue Mar 10 00:00:00 EDT 2015},
month = {Tue Mar 10 00:00:00 EDT 2015}
}