Defense Intelligence Reference Document Laser Lightcraft Nanosatellites

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Miniaturized solid propellant gas generators could be used as ACS thrusters. Forty-
eight SO mN-sec pulses are required to reorient the nanosat after it achieves the
required orbital altitude. Although this could be achieved either by a monopropellant or
a cold gas thruster, it could also be achieved using an array of gas generators. Such
miniaturized gas generators have already been successfully built and commercialized by
companies such as MOOG and Lockheed-Martin Space Systems. By incorporating
micro-electromechanical systems (MEMS) techniques, the devices have been produced
relatively inexpensively. Miniaturized electric propulsion ACS thrusters, such as pulsed
plasma and MEMS field-emission electric propulsion (MEMS FEEP) thrusters, have been
developed and are now emerging into widespread commercialization.
GUIDANCE, NAVIGATION AND CONTROL
Guidance Navigation and Control (GN&C) subsystem key technologies and concepts
have been identified to enable successful altitude determination of spin-stabilized and
three-axis-stabilized nanosats for future missions. They include miniaturization of a
sun sensor and horizon crossing indicator. The miniature precision "fan" sun sensor will
pinpoint the sun virtually everywhere in the entire celestial sphere with every satellite
rotation. The sun sensor will be required to weigh less than 0.25 kg, draw less than 0.1
watt, operate on no greater than a 3.3 volt bus, and meet a 0.1° resolution
requirement. The miniature horizon crossing indicator has a small bore-sight field of
view that is mounted at an angle off the spin axis. As the spacecraft rotates, a cone of
coverage is formed. The sensor must be capable of detecting Earth over a range of
orbital radii with a pointing accuracy of 0.05°. Total horizon crossing indicator weight
and power will be less than 0.2 kg and 0.1 watt, respectively.
Of particular interest to Constellation missions is the incorporation of GPS onboard the
nanosats, to eliminate ground-based ephemeris generation. This allows for increased
autonomy and simpler, more accurate time resolution onboard the spacecraft. For GPS
to fit within the constraints of a nanosat, the receiver electronics need to be
miniaturized into a layer within the C&DH module.
COMMAND AND DATA HANDLING
Developing the C&DH subsystem for a nanosat presents some unique challenges, with
low mass (0.25 kg) and low power (0.5 W) requirements being the biggest drivers.
Advanced microelectronic solutions are being developed to meet these challenges. The
microelectronics developed must be modular and of scalable packaging to both reduce
cost and meet the requirements of various missions. This development will utilize the
most cost effective approach, whether infusing commercially driven semiconductor
devices into spacecraft applications or partnering with industry in the design and
development of high capacity data processing devices. The major technologies will
include: lightweight, low power electronics packaging; radiation hard, low power
processing platforms; high capacity, low power memory systems; and radiation hard,
reconfigurable, field programmable gate arrays (RHrFPGA).
The C&DH requirements are as follows:
• Power: 0.5 watts.
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