Calibration of the EDGES High-Band Receiver to Observe the Global 21-cm Signature from the Epoch of Reionization

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 $14.8 \gtrsim z \gtrsim 6.5$. 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 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.Comment: Updated to match version accepted by Ap

VHF-band RFI in Geographically Remote Areas

The Experiment to Detect the Global EoR Signature (EDGES) is a radio spectrometer operating between 90 and 205 MHz using a single broadband dipole. The instrument recently completed a deep, three-month continuous measurement campaign in the Murchison Radio-astronomy Observatory (MRO) where it reached sufficient sensitivity to constrain the cosmological epoch of reionization (EoR). EDGES has also been used to conduct short, shallow RFI surveys in remote regions in the United States, including northern Maine and the Catlow Valley in southeast Oregon. Here, we show results on the RFI spectrum seen by EDGES at each of these locations and implications for upcoming low-frequency arrays such as MWA, LWA, LOFAR, and PAPER

Founder effect: assessment of variation in genetic contributions among founders

Journal ArticleWe present a Monte Carlo method for determining the distribution of founders' genetic contributions to descendant cohorts. The simulation of genes through known pedigrees generates the probability distributions of contributed genes in recent cohorts of descendants, their means, and their variances

Radio Astronomy

Contains reports on three research projects.National Aeronautics and Space Administration (Grant NsG-419)National Aeronautics and Space Administration (Grant NsG-250-62)U. S. Air Force under Contract AF 19(628)-500Lincoln Laboratory, Purchase Order DDL BB-10