Motivated by the need for rapid localisation of newly discovered faint millisecond pulsars ( MSPs ) we have developed a coherently dedispersed gating correlator .
This gating correlator accounts for the orbital motions of MSPs in binaries while folding the visibilities with best-fit topocentric rotational model derived from periodicity search in simultaneously generated beamformer output .
Unique applications of the gating correlator for sensitive interferometric studies of MSPs are illustrated using the Giant Metrewave Radio Telescope ( GMRT ) interferometric array .
We could unambiguously localise five newly discovered Fermi MSPs in the on-off gated image plane with an accuracy of \pm 1 ^ { \prime \prime } .
Immediate knowledge of such precise position allows the use of sensitive coherent beams of array telescopes for follow-up timing observations , which substantially reduces the use of telescope time ( \sim 20 \times for the GMRT ) .
In addition , precise a-priori astrometric position reduces the effect of large covariances in timing fit ( with discovery position , pulsar period derivative and unknown binary model ) , which in-turn accelerates the convergence to initial timing model .
For example , while fitting with precise a-priori position ( \pm 1 ^ { \prime \prime } ) , timing model converges in about 100 days , accounting the effect of covariance between position and pulsar period derivative .
Moreover , such accurate positions allows for rapid identification of pulsar counterpart at other wave-bands .
We also report a new methodology of in-beam phase calibration using the on-off gated image of the target pulsar , which provides the optimal sensitivity of the coherent array removing the possible temporal and spacial decoherences .