In-flight contour radiometric performance

This paper provides a detailed description of the flight experience obtained during the first operational use of a noncoherent Doppler and ranging system. This experience was gained from the Comet Nucleus TOUR (CONTOUR) spacecraft between its launch on July 3 and the solid rocket motor firing on August 15, 2002. The data obtained during these 43 days include Doppler velocities and range measurements made through NASA’s Deep Space Network. Onboard the CONTOUR spacecraft was an X-Band transceiver system. In order to support Doppler velocity measurements that are not affected by bias and drift of the spacecraft frequency reference, the spacecraft carried a small amount of additional hardware that placed radiometric data directly into the telemetry stream. A software process on the ground used this telemetry to convert the Doppler observables to those that would have been obtained with a transponder. In order to support ranging measurements, the uplink Doppler effects were removed through the use of programmed uplink fi-equency ramps. This paper describes the process of performing Doppler and range measurements and presents samples of the results obtained. Additional information, such as precise spacecraft oscillator monitoring and receiver fi-equency monitoring that are provided by such a system, is also presented. 0-7803-7651-X/03/$17.00