Ground Station Segmented Architecture
"Ground Station Segmented Architecture" is the second in a series of white papers by Jim Springett of NeoComm, to describe how to implement tracking stations for advanced Space VLBI missions in a low-cost manner. The first paper in the series is "Achieving Future SVLBI Gbps Data Rates"[pdf:296KB].
The secret of the low-cost success is to segment the communication requirements between spacecraft and earth into two parallel links: a wide-band high-power one-way Ka-band (37 to 38 GHz) down-link for the VLBI science data and a narrow-band low-power two-way (37-38 GHz down, 40 GHz up) link for the phase transfer, Doppler compensation, and telemetry. On-board there is a separate set of low-power "pilot tones" for the narrow-band link. On the ground the wide-band link relies on a large ground station; the narrow-band link relies on a small (nominally 3-m) separate ground antenna. The ground-based components are well-understood and can rely on a single design common to all tracking sites. The designs all scale easily with data rate from 128 Mbps to the 1 to 4 Gbps regime.
(Joel Smith, 05-mar-2002)