Radio Camera Initiative

PI: Gregg Hallinan and Vikram Ravi (Division of Physics, Mathematics and Astronomy)
SASE: Mei-Ling Laures, Scholar

At the wavelengths of interest for radio astronomy, even the largest possible steerable mechanical radio dishes (∼ 100 m) have angular resolution barely comparable to the human eye. Radio interferometry combines signals from many antennas to synthesize a much larger aperture, with the angular resolution now defined by the longest ”baseline”, i.e., the largest physical separation between a pair of dishes. By this technique, radio telescopes spread across the globe have delivered the highest angular resolution images in astronomy, including the recent image of a black hole shadow with a resolution 1000 times better than the Hubble Space Telescope. This technique comes at a price. Each combination of antennas produces a complex number, called a visibility. The amount of visibility data produced by the telescope therefore scales as the square of the number of antennas and can rapidly dominate the cost of a radio telescope. Historically, this has favored the use of small numbers of large antennas, to ensure good sensitivity, while keeping the data rate manageable.

Caltech’s Owens Valley Radio Observatory (OVRO) has proposed a new approach. Rather than building large dishes, the observatory proposes to build very large numbers of small antennas, using low-cost commercial off-the-shelf (COTS) antennas where possible. This only serves to increase the volume of visibility data but allows us to approach a critical threshold. As the number of antennas grows very large (> 1000), the PSF proportionally improves, eventually becoming comparable to that of an optical telescope. This opens-up the possibility of building a complete deterministic pipeline that outputs images, rather than visibilities, to the end-user.

The Schmidt Academy is working with faculty, graduate students, and staff scientists from different disciplines -- from radio astronomy to computer science and applied mathematics -- on the “Radio Camera Initiative”. This groundbreaking project will provide framework tools not only for the DSA-2000 radio camera (Deep Synoptic Array with 2000 radio dishes), but other applications as well, including great improvements to the science output of the 352-dipole Long Wavelength Array (LWA-352). All software will be open source and available for adoption by other telescopes worldwide.

radio dishes