Speaker
Description
The GENESIS satellite, scheduled for launch in 2028, will contribute to the improvement of the International Terrestrial Reference Frame (ITRF), by combining the four major space geodetic techniques, namely GNSS, DORIS, SLR and VLBI, onboard a single platform at an altitude of 6000 km. The VLBI transmitter (VT) is one of the key instruments, designed to operate in two distinct transmission modes. In the primary mode, the VT will mimic quasar sources with a Gaussian signal, enabling conventional geodetic operations through cross-correlation of signals between two ground stations. In the secondary mode, a periodic signal is transmitted, allowing for single-station operation by correlating the received signal with a locally generated digital replica. In this case, the measured delay relates directly to the propagation time between the satellite and the station. The selected waveform for the second mode is a binary offset carrier (BOC) modulation applied to a pseudo-random noise (PRN) spreading code, similar to Galileo satellites. BOC parameters, however, have not been fixed yet.
Single-station measurements are expected to benefit from a higher signal-to-noise ratio (SNR), since the local replica is noiseless. While the primary mode will require the use of four different frequency bands (S, C, low X and high X bands) compatible with VLBI Global Observing System (VGOS), the secondary mode is expected to rely on only one or two of those four allocated bands.
In this poster, we compare the performance between the two modes in terms of delay resolution and secondary peak levels under realistic assumptions. Different BOC parameters are being evaluated to identify the most suitable configuration for the GENESIS mission.
