Adding uGMRT to EVN observations

The Upgraded Giant Metrewave Radio Telescope (uGMRT) is an interferometric array consisting of 30 dishes of 45 m diameter each, located in the western part of India, providing nearly seamless coverage from 120 MHz to 1460 MHz. The uGMRT is being made available for L-band VLBI observations in concert with the EVN for the 1-June-2023 proposal submission deadline, strictly on a best-effort basis. Proposals requiring the uGMRT as part of their observations should include separate scientific and technical justifications (the latter would be required by NCRA to assess the technical feasibility of the uGMRT observations). Approved EVN proposals involving uGMRT would then be scheduled on a best- effort basis subject to availability of suitable empty slots in the uGMRT schedule. 

The uGMRT works simultaneously as an interferometer as well as a beamformer. The VLBI data is derived from the beamformer output. To ensure the best performance, only the central 15 antennas will be phased-up. The visibilities from the uGMRT as an interferometer will be available from the uGMRT archive per request, provided there are no conflicting GMRT programs running for the same target. For detailed specifications and additional features please contact Viswesh Marthi (vrmarthi@ncra.tifr.res.in), preferably well before the proposal deadline. 

The table below lists the current specifications and feature availability of the GMRT for VLBI. As a corollary to the table, it is emphasized that adding antennas beyond the central square could have a negative impact on the stability of the antenna phases over time, necessitating less-than-ideal intervals between rephasing scans. The overall impact is negative in the form of extended slewing and rephasing overheads.

*PASV - Phased Array Spectral Voltage