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Three ground stations in Toronto, Vancouver and Vienna are
used to download data from MOST. The primary control station
is in Toronto while the secondary stations (Vancouver and
Vienna) are controlled and coordinated over the Internet.
Although the basic mission can be accomplished with just one
ground station, additional science data can be acquired using
the secondary stations.
The
stations used for MOST communications are based on an amateur
radio core station operating at VHF and UHF frequencies. They
are upgraded with S-band transverters and BPSK transceivers
connected to a 2-m parabolic antenna (downlink) and a 45 element
loop yagi (uplink). The antennas are mounted on a heavy-duty,
precisely controlled rotator located atop a 20-foot tower.
The
ground station radios are connected to a custom terminal node
controller (combination modem and serial communications controller)
which is in turn connected to a computer that coordinates
multiple terminals each running interface software for specific
components on the satellite. Through this system, terminal
users have a virtual link to their satellite hardware of interest.
The terminal node controller also generates "firecodes"
or emergency commands to reset satellite hardware. A "timing
tick" generator is used to maintain knowledge of clock
drift in the instrument computers so as to accurately time
tag science observations.
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MOST