The Tianlai dish pathfinder array: design, operation, and performance of a prototype transit radio interferometer

The Tianlai Dish Pathfinder Array is a radio interferometer designed to test techniques for 21 cm intensity mapping in the post-reionization universe as a means for measuring large-scale cosmic structure. It performs drift scans of the sky at constant declination. We describe the design, calibration, noise level, and stability of this instrument based on the analysis of about 5% of 6200 h of on-sky observations through 2019 October. Beam pattern determinations using drones and the transit of bright sources are in good agreement, and compatible with electromagnetic simulations. Combining all the baselines, we make maps around bright sources and show that the array behaves as expected. A few hundred hours of observations at different declinations have been used to study the array geometry and pointing imperfections, as well as the instrument noise behaviour. We show that the system temperature is below 80 K for most feed antennas and that noise fluctuations decrease as expected with integration time, at least up to a few hundred seconds. Analysis of long integrations, from 10 nights of observations of the North Celestial Pole (NCP), yielded visibilities with amplitudes of 20-30 mK, consistent with the expected signal from the NCP radio sky with <10 mK precision for 1 MHz x 1 min binning. Hi-pass filtering the spectra to remove smooth spectrum signal yields a residual consistent with zero signal at the 0.5 mK level.

Automated summary

The Tianlai Dish Pathfinder Array is a radio interferometer designed for testing 21 cm intensity mapping techniques in the post-reionization universe. Analysis of on-sky observations up to October 2019 shows good agreement between beam patterns determined using drones and bright sources, and electromagnetic simulations. The system temperature was found to be below 80 K for most feed antennas, and noise fluctuations decreased as expected with integration time, up to a few hundred seconds.