Andert, Thomas P. In September Rosetta was placed into bound orbits with an initial distance of 30 km and a decreasing distance until the end October. After lander delivery, bound orbits were maintained again at 20 km and 30 km. One of the objectives of the Rosetta Radio Science Investigations RSI is to address the dielectric properties, small-scale roughness, and rotational state of the nucleus of the comet, which can be determined by means of a surface scattering experiment, also known as Bistatic Radar.
The radio subsystem transmitter located on board the Rosetta spacecraft beams right circularly polarized radio signals at two wavelengths Part of the impinging radiation is then scattered toward a receiver at a ground station on Earth and recorded. On September 29th, the first Bistatic Radar experiment ever at a comet was successfully conducted.
The ultra-stable oscillator USO on board Rosetta served during the experiment as a very stable reference frequency source.
The direct and reflected signal were separated during the experiment by only a fraction of 1 Hz. The extreme stability of the USO allowed a detection and separation of the weak signals even on the required long integration times. Five additional Bistatic Radar experiments were conducted successfully between mid-October and mid-December with the m DSN ground stations in Goldstone and Canberra at different distances to the comet 10 km, 20 km and 30 km and reflected signals were observed in each case.
Andert, T. The radio transmitter and high gain antenna HGA on the spacecraft beamed right circularly polarized RCP radio signals at two wavelengths - 3.
