Before revision: Satellite-to-Satellite Tracking (SST) – The SST experiment consisted of , the ground-based ATS ranging system, the wideband communication transponder on the ATS-6 geosynchronous spacecraft, and the ranging transponder on the LEO satellite.
After revision: Satellite-to-Satellite Tracking (SST) – The SST experiment consisted of , the ground-based ATS ranging system, the wideband communication transponder on the ATS-6 geosynchronous spacecraft, and the ranging transponder on the GEOS-3 satellite.