Defense Intelligence Reference Document Laser Lightcraft Nanosatellites

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These array functions can be made coherent over very great distances. RF antennas
with sizes of hundreds of kilometers and optical telescopes of hundreds of meters
diameter can be formed. These systems can enable new capabilities not possible with
single spacecraft either acting alone, as a proliferated but non-coherent constellation,
or as relays for each other. Formed of nanosats and picosats, such swarms will contain
so many spacecraft that the economics of true mass production will come into play in
space for the first time, greatly reducing the cost of producing the system. In addition,
these systems feature the advantages of truly distributed satellite systems, including
fault tolerance, robustness, survivability, reconfigurability by software, and the ability
to be incrementally emplaced and upgraded as budgets are available.
These swarms can be implemented in a cost effective manner using laser propulsion for
both launch and orbital insertion. However, the system designs described in the
following sections are flexible enough to allow for the use of alternative conventional
launch vehicle technologies. The technologies to produce these swarms and their
constituent nanosats or picosats probably can be demonstrated by 2015 and deployed
in space by 2020.
The following concepts were provided via the voluminous research notes, lectures, and
briefings provided courtesy of I. Bekey.
ROTATING PICOSAT SWARM ARRAY RADIO FREQUENCY COLLECTOR
An unconventional, large sparse antenna array RF collector spacecraft with a small
surface footprint even when deployed in geosynchronous Earth orbit (GEO) separates
different sources in proximity and also detects weak signals. Its implementation would
result in a highly desirable, long dwell RF emitter detection capability.
At the heart of this system is a large antenna that is formed by a swarm of tiny
elements that make up the lens of a space-fed array with no structure. The antenna is
a sparse, self-cohering array formed from a large number of picosats rotating (in
relative coordinates) in a plane around a central orbital point in GEO. The picosats are
self-contained repeater spacecraft. Each one receives the ground signal, delays it, and
retransmits the signal so that it arrives at the feeds at the same time as a direct ray
through the center of the array. The time delay of each picosat is self computed based
on its location in the swarm, as measured by a local differential global positioning
system (DGPS)-like navigation signal, to compensate for its deviation from its assigned
ideal location. Each picosat digitizes, delays, frequency shifts, and retransmits its
received signals independently, causing an in-phase composite signal from the ground
to be received at the feeds.
The relative positions of these picosat elements change slowly, and only small and
infrequent propulsive maneuvers are needed for constellation maintenance. A tether
along the local vertical at the central point holds the receivers and DGPS-like reference
at the focus against a counterweight. A pseudorandom distribution of the picosats
suppresses the antenna grating lobes, and intensive computation greatly reduces much
of the remaining sidelobes, creates multiple beams, and steers the ensemble of the
individual beams anywhere on Earth. The antenna system will function with far fewer
elements as a more sparse array, though with limited sensitivity. This system can be
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