CALIBRATION OF THE EDGES HIGH-BAND RECEIVER TO OBSERVE THE GLOBAL 21 cm SIGNATURE FROM THE EPOCH OF REIONIZATION

Raul A. Monsalve, Alan E. E. Rogers, Judd D. Bowman, Thomas J. Mozdzen
2017 Astrophysical Journal  
The EDGES High-Band experiment aims to detect the sky-average brightness temperature of the 21-cm signal from the Epoch of Reionization (EoR) in the redshift range 14.8 ≳ z ≳ 6.5. To probe this redshifted signal, EDGES High-Band conducts single-antenna measurements in the frequency range 90-190 MHz from the Murchison Radio-astronomy Observatory in Western Australia. In this paper, we describe the current strategy for calibration of the EDGES High-Band receiver and report calibration results for
more » ... the instrument used in the 2015-2016 observational campaign. We propagate uncertainties in the receiver calibration measurements to the antenna temperature using a Monte Carlo approach. We define a performance objective of 1 mK residual RMS after modeling foreground subtraction from a fiducial temperature spectrum using a five-term polynomial. Most of the calibration uncertainties yield residuals of 1 mK or less at 95% confidence. However, current uncertainties in the antenna and receiver reflection coefficients can lead to residuals of up to 20 mK even in low-foreground sky regions. These dominant residuals could be reduced by 1) improving the accuracy in reflection measurements, especially their phase 2) improving the impedance match at the antenna-receiver interface, and 3) decreasing the changes with frequency of the antenna reflection phase.
doi:10.3847/1538-4357/835/1/49 fatcat:5poyfbucrfcpfdetx36o62lxpu