Design, operation and performance of the PAON4 prototype transit interferometer

Abstract

PAON4 is an L-band (1250-1500 MHz) small interferometer operating in transit mode deployed at the Nançay observatory in France, designed as a prototype instrument for Intensity Mapping. It features four 5 meter diameter dishes in a compact triangular configuration, with a total geometric collecting area of ∼ 75m 2 , and equipped with dual polarisation receivers. A total of 36 visibilities are computed from the 8 independent RF signals by the software correlator over the full 250 MHz RF band. The array operates in transit mode, with the dishes pointed toward a fixed declination, while the sky drifts in front of the instrument. Sky maps for each frequency channel are then reconstructed by combining the time-dependent visibilities from the different baselines observed at different declinations. This paper presents an overview of the PAON4 instrument design and goals, as a prototype for dish arrays to map the Large Scale Structure in radio, using intensity mapping of the atomic hydrogen 21 cm line. We have operated PAON4 over several years and we have used data from observations in different periods to assess the array performances. We present preliminary analysis of a large fraction of this data and discuss crucial issues for this type of instrument, such as the calibration strategy, instrument response stability and noise behaviour.

Current status and future of cosmology with 21cm Intensity Mapping

“…Smaller instruments such as PAON4 63 and BMX 64 have also been built to explore specific technical aspects of dish arrays operating in transit mode. PAON4 is a small, 4-dish test interferometer located at the Nançay radio observatory in France, operational since end of 2015.…”

The Tianlai Cylinder Pathfinder array: System functions and basic performance analysis

“…Several dedicated instruments have been constructed, or are under development, to detect the 21 cm signal: CHIME [15], Tianlai [8,[16][17][18][19], HIRAX [20], OWFA [21], and BINGO [22]. Other instruments are being designed and built to test the technique, including BMX and PAON-4 [23,24]. With the exception of BINGO, they are all interferometer arrays with large numbers of receivers in order to provide enough mapping speed to detect the weak 21 cm signal; and all are laid out in a compact configuration in order to provide sensitivity at the relatively large scales (0.5 k 0.05) where the BAO features appear in the power spectrum.…”

The Tianlai Cylinder Pathfinder Array: System Functions and Basic Performance Analysis

“…Several dedicated instruments have been constructed, or are under development, to detect the 21 cm signal: CHIME [15], Tianlai [8,[16][17][18][19], HIRAX [20], OWFA [21], and BINGO [22]. Other instruments are being designed and built to test the technique, including BMX and PAON-4 [23,24]. With the exception of BINGO, they are all interferometer arrays with large numbers of receivers in order to provide enough mapping speed to detect the weak 21 cm signal; and all are laid out in a compact configuration in order to provide sensitivity at the relatively large scales (0.5 k 0.05) where the BAO features appear in the power spectrum.…”