Defense Intelligence Reference Document Laser Lightcraft Nanosatellites

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Because configuration (2) has a much smaller overall energy balance than configuration
(1), it is much more sensitive to MLI properties and to internal power dissipation.
However, eclipse performance improves. During the ~ 8 hour eclipse, internal
temperatures drop by only 20°C, a marked improvement, with end-of-eclipse
temperatures well within the range of most spacecraft components. It should be noted
that the solar arrays, since they are now isolated from the body of the nanosat, drop to
temperatures of about -1l0°C. Even these solar array temperatures should not pose a
problem. For example, the solar arrays of many geosynchronous satellites drop
routinely to temperatures of about -150°C during the 72 minute eclipse experienced by
these spacecraft at each equinox season.
The key feature of configuration (3) is that the equipment is coupled to an external
radiator only with a two-phase heat transport device, such as a capillary pumped loop
(CPL) or loop heat pipe (LHP). Operational temperatures are again maintained to
temperatures of about 20°C nominal with a properly sized radiator. However, the
temperature is also totally dependent on the proper operation of the two-phase "loop."
The two-phase heat transport device can be made redundant by the addition of a
second loop if single fault tolerance is desired. Note that redundancy is not a
consideration for the other two configurations. During the ~ 8 hour eclipse, further
improvement is realized, with internal temperatures dropping by as little as 6°C if the
internal payload is well insulated from the exterior of the nanosat. As in configuration
(2), the solar array temperatures drop to about -110°C. For certain equipment or
science instruments, the temperature control afforded by this type of "active" design
may be necessary.
A moderate amount of technology development has been underway since 2000 to
enable a two-phase heat transport system for use in a nanosat. The small size and low
heat transport requirements of the nanosat will necessitate significant downsizing of
today's flight qualified two-phase systems. This reduction will be accomplished by
leveraging recent successful tests of a small cryogenic two-phase CPL.
RF COMMUNICATIONS
The onboard RF subsystem must be small, low mass, and low power. The system
specifications are:
• Mass: 0.5 kg.
• Power consumption: 0.5 watt.
• Transmission data rate: up to 100 kbits/sec.
• Command reception data rate: 1 kbit/sec.
• Range: 3 to 5 Earth radii.
• Channel type: BPSK.
• Effective isotropic radiated power: 0.15 watt (-8.2 dbW).
• Carrier frequency: 8,470 MHz.
The tracking system should be coupled with this communication subsystem to maximize
efficiency in mass and power.
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