Satellite Configuration Design - Finite Element Analysis for Satellite Structures - page 23

of the coaxial cables. Brackets are used to mount all antennas except the X-band
antenna, because the wave pattern is affected by the distance between the antenna
and its mounting surface.
2.6.4 Platform Command & Data Handling
Subsystem
The electronic modules of PCDHS in Small Sat, especially on-board digital
computing complex (ODCC), are important for the configuration designer. These
modules are dense and therefore heavy, so the best location for mounting them is
near the aft end. PCDHS equipment will be electrically connected to virtually all
of the satellite's nonstructural components. By grouping electronics, cabling losses
and mass can be minimized.
2.6.5 Power Subsystem
Small Sat configuration is strongly influenced by the power subsystem compo-
nents, especially the solar arrays. The design of solar arrays is based on the
satellite's power requirements, the orbit altitude, sun-angle conditions, the method
of attitude control, and mission and payload requirements. For Small Sat, fixed
solar panels mounted on the satellite body surfaces are not used, because Small Sat
needs relatively high power with respect to the available surface area. Heat
rejection can be another problem of using fixed solar panels. Therefore, four
deployed-fixed solar panels are used to supply power for Small Sat. A deployed-
fixed solar panel is one that is stowed in one location for launch, and then deployed
to a fixed position in space. Rotation mechanisms are used to rotate solar panels
and provide fixation into specific positions in space. Locking and releasing
mechanisms are needed to fix the solar panels during launch, and then release them
at space.
In defining deployed locations for solar panels, shadows from other components
should be avoided. Therefore, in Small Sat, solar panels and rotation mechanisms
are mounted at the aft end. This also reduces the overall structural loading by
keeping the mass of both solar panels and rotation mechanisms near the launch
vehicle interface. This minimizes the cable runs to battery, which is also mounted
near the aft end of the satellite. Flat solar arrays made of lightweight honeycomb
sandwich are the most common and easiest to manufacture. Solar arrays are major
contributors to a deployed satellite's modes of vibration, so these should be very
light and stiff, with natural frequencies high enough to avoid interaction with the
control system. During launch, acoustics combined with transient loads usually
cause the highest loads in the solar panels and mechanisms.