Wide-field imaging with the Mauritius Radio Telescope.

The Mauritius Radio Telescope (MRT) is a Fourier Synthesis T-shaped array o perating at 151.5 MHz. The primary objective of the telescope is to produce a sky survey in the declination range -70 degrees to -10 degrees. A 512 ch annel digital complex correlation receiver is used to measure the visibilit y function. The visibilities have to be measured with four different delay settings to image the entire declination range, keeping the effects of band width decorrelation to less than 20% on the longest baseline. To have a rea sonable surveying sensitivity this has to be done in one observation schedu le. However the existing correlator system which can measure visibilities w ith only one presettable delay setting for each integration time, cannot me et this requirement. A recirculator system which enables visibility measure ments with four different delay settings in one integration time using the existing correlator has been designed and installed to make the MRT an effi cient surveying instrument. This paper describes the recirculator system, a nd the scheme that we use at MRT to calibrate the visibilities measured wit h different delay settings. The observations carried out for the full sky s urvey and a section of the wide field image made using the new system are d escribed in this paper.