Speaker
Description
Neutral hydrogen emits radiation at a wavelength of 21 cm (1420 MHz), providing a unique probe of the large-scale structure of the Universe. Because this emission is redshifted by cosmic expansion, observations at lower frequencies allow us to map matter distribution over much of cosmic history, including epochs before the first stars formed. However, the cosmological 21 cm signal is buried beneath astrophysical foregrounds that are several orders of magnitude brighter. Detecting it requires characterizing radio telescope beam patterns with sub-percent accuracy, a challenging task.
Global Navigation Satellite System (GNSS) satellites provide an attractive calibration source for beam mapping. Their precisely known orbits, well-defined pseudo-random noise (PRN) codes, and transmissions across multiple relevant frequency bands enable accurate measurements of telescope beam patterns, including far sidelobes. Moreover, it provides an avenue for real-time beam monitoring and obtaining relative calibration between antennas.
I previously demonstrated GNSS-based beam mapping using a commercial u-blox ZED-F9P receiver, showing that beam maps with a dynamic range of up to 80 dB are achievable. While effective, commercial receivers are not a scalable solution for radio telescope arrays consisting of hundreds of antennas. To address this limitation, I am developing a beam-mapping pipeline using the open-source GNSS-SDR, which adopts GNU Radio's signal processing framework. This talk will present the implementation and preliminary beam-mapping results, discuss the advantages and challenges of GNSS-based beam mapping with software-defined radio, and outline the next steps toward scalable calibration for next-generation 21 cm experiments.
| Talk Length | 30 Minutes |
|---|---|
| Link to Open Source Code | The project is currently in the early stages of development. I intend to release the source code as open source once the project is complete and sufficiently documented. |
| Acknowledge | Acknowledge In-Person |