Wide-field imaging with the Mauritius radio telescope.

Abstract

The Mauritius Radio Telescope (MRT) is a Fourier Synthesis T- shaped array operating at 151.5 MHz. The primary objective of the telescope is to produce a sky survey in the declination range –70° to –10°. A 512 channel digital complex correlation receiver is used to measure the visibility function. The visibilities have to be measured with four different delay settings to image the entire declination range, keeping the effects of bandwidth decorrelation to less than 20% on the longest baseline. To have a reasonable surveying sensitivity this has to be done in one observation schedule. However the existing correlator system which can measure visibilities with only one presettable delay setting for each integration time, cannot meet this requirement. A recirculator system which enables visibility measurements with four different delay settings in one integration time using the existing correlator has been designed and installed to make the MRT an efficient surveying instrument. This paper describes the recirculator system, and the scheme that we use at MRT to caIibrate the visibilities mea- sured with different delay settings. The observations carried out for the full sky survey and a section of the wide field image made using the new system are described in this paper.