Upgrade of legacy ORT for pulsar observations

Ooty Radio Telescope (Swarup et al. 1971) is 530-m long and 30-m wide cylindrical paraboloid equatorially mounted radio telescope located in southern India. With its large collecting area and low frequency of observations (326.5 MHz), it is a sensitive instrument suitable for steep spectrum sources, such as radio pulsars, which are bright at these frequencies. In the early 2000, pulsar observations at the ORT had stopped due to unavailability of a state-of-art backend. We started a project to upgrade the legacy ORT by equipping it with a new receiver and a state-of-art digital backend specifically designed for pulsar observations. This receiver, called Pulsar Ooty radio telescope New Digital Efficient Receiver (PONDER), is capable of real-time time-series observations of pulsars, inter-planetary scintillations and very long baseline interferometer (VLBI). It was designed and commissioned between 2008 - 2012 and significantly upgraded the science capability of the instrument. In this presentation, this instrument and the resulting science results are described.