Delta differential One-way ranging (DDOR) transmitter onboard Mars Orbiter Mission (MOM)

Delta Differential One-way ranging (DDOR) is an interferometer technique used in deep space missions to calculate the angular position of a satellite with reference to a well known source which is usually a quasar. A Transmitter has been used in Mars Orbiter Mission (MOM) for DDOR measurement to improve the accuracy of orbit determined by other techniques. The Transmitter operates at S-band with carrier phase modulated by a single tone at around 4 MHz approximately. This paper discusses the principle of DDOR measurement, how the specifications for the Transmitter were arrived at, the design & realization using the available components and its on-orbit performance.