Collaborative Research: Advanced Digital Calibrators for 21cm Cosmology

One of the greatest mysteries in modern cosmology is the Dark Energy-driven accelerating expansion of the Universe. Galaxy surveys have a unique capability to measure the expansion of the Universe that occurred long ago, enabling a sensitive measurement of the presence and characteristics of Dark Energy. Experiments have been undertaken with surveys of hundreds of thousands of galaxies using optical telescopes, but those surveys are still limited by the number of galaxies they can measure.

Radio surveys can get around this limitation but require precise understanding of the instrument making the measurement. This proposal will develop new radio signal technology and techniques to improve the capability of current instruments to do these experiments and thus enable a better understanding of the nature of Dark Energy. The project looks to expand interaction with school teachers to enhance their knowledge of radio astronomy techniques that can be relayed to students in schools.

The investigators will design, prototype, characterize, and deploy deterministic digital calibration signals for the purpose of improved calibration for 21 cm cosmology. New 21 cm interferometers require precise calibration, particularly of the instrument beam, to remove bright foregrounds and extract the cosmological signal of interest. Currently, the incoherent (power only) calibrators developed to address this challenge limit the dynamic range of the measurement and also have no direct sensitivity to instrument phase.

The calibration source proposed here addresses these critical gaps to make full-sky, high signal-to-noise measurements of the complex (real and imaginary) instrument beam. The calibration source will produce a precise signal that can be correlated in the radio interferometer correlator, yielding a deterministic signal that can be used to make measurements of the beam in both phase and amplitude.

The project includes an expansion of existing programs with educators in learning digital signal processing techniques.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.