Gravitational wave searches with ground tracking networks
Long-term experiments designed to search for gravitational waves (GW) have been performed with the Pioneer 10 and 11 spacecraft, and are planned for NASA's Galileo and ESA's Ulysses spacecraft. The result of a passing monochromatic GW is a sinusoidal modulation of the Doppler series that depends on the round-trip light time (RTLT) to a spacecraft and on the angle between the radiation propagation direction and the spacecraft link. Thus, an ideal experiment must have coverage and monitoring of interplanetary spacecraft during cruise that must be continuous as the earth turns to permit observation of complete three-pulse responses over the RTLT. To achieve this goal, an international 40-day Joint Tracking Experiment (JTE) is planned for the fall of 1987 for continuous tracking of the two spacecraft, when both will be near solar opposition. A diagram of the tracking geometry during the JTE and diagrams illustrating theoretical GW properties are included.