High Fidelity Receiver for Low Signal-to-Noise Ratio Measurements of Cosmic Dawn

Project: Research project

Description

State clearly and concisely the objectives of your work and the expected deliverables. Develop and verify a receiver capable of detecting, at high fidelity, broadband signals in a low signal-tonoise ratio (SNR) environment, with a specific focus on detecting the highly-redshifted 21 cm hyperfine transition of neutral hydrogen during and before the formation of the first stars (Cosmic Dawn). This highly redshifted hydrogen signal is expected as a result of the interaction of the ultraviolet and X-ray radiation fields from the first stars and first accreting black holes with the surrounding neutral intergalactic medium. Cosmic Dawn was identified as a priority science theme for the decade in the recent New Worlds, New Horizons in Astronomy& Astrophysics Decadal Survey, and the highly-redshifted 21 cm signal provides a unique and unmatched window into the feedback processes from the formation of the first stars, galaxies, and black holes during the first 500 million years after the Big Bang (redshifts ~ 1050). The required science instrument is a radio spectrometer or radiometer, operating in the approximate frequency range between 30 and 120 MHz, with the specific challenge of producing an HF/VHF band radio receiver capable of detecting signals at the SNR level of than 10-510-6. Current designs attempt to achieve this level of fidelity by producing an instrumental frequency response that is extremely smooth between adjacent spectral sub-bands and capable of being modeled by a simple function (e.g., 3rd order polynomial in frequency). This requirement for spectral smoothness results because the expected redshifted 21 cm signal is expected to have a particular spectral shape (or a constrained range of shapes), and it is essential that the instrumental response not be able to be confused with or mask the expected science signal. Radiometers operating in this frequency range can be based on proven flight hardware, but this particular requirement on the instrumental frequency response is new. The instrumental frequency response and overall instrumental performance were identified as major weaknesses in both the Science Implementation Merit and Feasibility and Mission Implementation Feasibility Evaluations for a recent Explorer proposal (the Dark Ages Radio Explorer, DARE). The proposed SURP will contribute directly to retiring a key risk associated with a future Explorer proposal or Mission of Opportunity proposal for a science instrument on another space-based mission. Further, while our focus for this proposed SURP is for a future Astrophysics 2 mission targeting Cosmic Dawn, similar instrumental design principles may be relevant for future cosmic microwave background (CMB) or Earth Science missions, e.g., searching for weak, broadband signals against the combined thermal emission from the Earth and radio interference from urban areas. The expected deliverable from the proposed SURP is a prototype radiometer that will be tested both in the laboratory and in the field against the documented performance criteria.
StatusFinished
Effective start/end date4/20/127/11/13

Funding

  • National Aeronautics Space Administration (NASA): $47,184.00

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signal to noise ratios
receivers
radiometers
frequency response
proposals
stars
astrophysics
frequency ranges
radio receivers
radio frequency interference
broadband
Earth sciences
requirements
intergalactic media
hydrogen
thermal emission
astronomy
radiation distribution
horizon
hardware