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The MOST satellite design originates from trying to fit as
large a telescope as possible, all the electronics to interface
with the telescope, the satellite bus equipment that allows
the storage and transmission of the science data to the ground,
the ACS hardware that is required to maintain better than
25 arcsecond pointing accuracy for the telescope, and a power
system to provide enough power to the satellite, all into
a package that can meet the requirements for launch as a secondary
payload on a Delta II launch vehicle (with Radarsat-2 as the
primary payload). It probably bears little resemblance to
the satellite design that would have resulted had a launch
on the Rockot been planned from Day 1. However, that is the
nature of microsatellite design.
 The
telescope is a 15cm diameter aperture Maksutov telescope.
A periscope mirror allows the long axis of the telescope to
lie perpendicular to the aperture of the telscope and therefore
fit into the Delta II secondary payload physical constraints.
Attached to the telescope, separate from the satellite bus
structure, is a two stage passive cryocooler that is capable
of maintaining the focal plane of the telescope at a temperature
of -40°C. Covering the aperture of the telescope is a
door that is designed to actively close to protect the instrument
focal plane from direct sunlight.
The
satellite structure is based on a tray stack design. The structure
consists of aluminum trays that house the satellite's electronics,
battery, radios, and attitude actuators. These trays are stacked
forming the structural backbone of the satellite. To this
backbone, the telescope is mounted with its barrel parallel
to the axis of the stack. Six aluminum honeycomb panels, acting
as substrates for solar cells and carriers for attitude sensors,
enclose the tray stack/telescope assembly. An actuated telescope
door mounted on the star facing side of the satellite protects
the telescope focal plane from direct stares at the Sun should
the satellite tumble or lose attitude lock.
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MOST