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Solar and Space Physics: A Science for a Technological Society
APPENDIX B
339
Small satellites in the 1- to 20-kg range enable the possibility of large constellations. The utility of
multipoint observations in heliophysics has been demonstrated by NASA’s Time History of Events and
Macroscale Interactions during Substorms (THEMIS) mission, a constellation of five 100-kg probes. The
Space Technology 5 (ST5) spacecraft, at ~25 kg each, were flown under the New Millennium program
before it was terminated.
To enable future missions, it would be wise to accelerate the development of spacecraft technologies
for supporting small satellites, including constellation operations and inter-spacecraft coordination. Also
useful would be investigating system engineering tradeoffs for designing a large constellation of small,
scientific satellites, including balancing the risk of using modern, low-power electronics in space versus
spacecraft lifetime.
Propulsion
Propulsion—Solar Sails
Heliophysics can benefit from observations of the Sun, Earth, and heliosphere from orbits requiring
continuous propulsive activity to maintain or reach in a timely fashion. Vantage points above Earth’s poles,
at sub-L1 locations, and at high ecliptic latitudes have unique properties that enable important observations. Six community white papers advocated science enabled by this technology, and previous strategic
studies have advocated solar sails. Past heliophysics mission concepts include a solar polar imager, a
stationary Earth polar observatory, upstream solar wind monitoring at a sub-L1 location, an L5 mission,
Solar Sentinels, and Interstellar Probe.
Significant investments have already been made in the United States and abroad. The Japan Aerospace
Exploration Agency (JAXA) and NASA carried out dedicated tests of solar sailing for primary thrust using
the IKAROS spacecraft and NanoSail-D2. Without an appropriate demonstration mission that goes beyond
the small-scale, heavy-sail tests to date, the possibility of using this technology in the future will remain in
doubt. NASA’s Office of the Chief Technologist has suggested a technology demonstration line that could
cover 75 percent of the cost of a $200 million solar sail demonstration mission. The committee strongly
urges that this potential opportunity be pursued to demonstrate a 25 g m –2 , ~40-m solar sail. 1
Propulsion—High Drag
Heliophysics system science requires an understanding of plasma-neutral coupling, global composition, and structure of Earth’s upper atmosphere (< 300 km altitude). Long-term in situ observations in this
relatively high-drag region are required to develop scientific understanding of this coupling region between
space and Earth’s upper atmosphere. Reaching this altitude requires increased performance propulsion
systems, innovative ways to reduce dependence on expendables, and use of aerodynamic effects to enable
satellite operations in high-drag regions. The concept of using “dipper” satellites that maneuver in and out
of high-drag regions is the conventional approach, but it does not significantly increase the observational
time. Capable but “disposable” (very small, very-low-cost) satellites for the exploration of high-drag regions
is an approach that has yet to be studied in detail. Such observational platforms could be deployed from
the ISS or another host spacecraft if a propulsion system were developed to enable the deployment and
maintenance of small satellite constellations in and above these high-drag environments.
1 See Section 2.4.4.4 of NASA, In-Space Transportation Capability Portfolio, 2005.
Solar and Space Physics: A Science for a Technological Society
APPENDIX B
339
Small satellites in the 1- to 20-kg range enable the possibility of large constellations. The utility of
multipoint observations in heliophysics has been demonstrated by NASA’s Time History of Events and
Macroscale Interactions during Substorms (THEMIS) mission, a constellation of five 100-kg probes. The
Space Technology 5 (ST5) spacecraft, at ~25 kg each, were flown under the New Millennium program
before it was terminated.
To enable future missions, it would be wise to accelerate the development of spacecraft technologies
for supporting small satellites, including constellation operations and inter-spacecraft coordination. Also
useful would be investigating system engineering tradeoffs for designing a large constellation of small,
scientific satellites, including balancing the risk of using modern, low-power electronics in space versus
spacecraft lifetime.
Propulsion
Propulsion—Solar Sails
Heliophysics can benefit from observations of the Sun, Earth, and heliosphere from orbits requiring
continuous propulsive activity to maintain or reach in a timely fashion. Vantage points above Earth’s poles,
at sub-L1 locations, and at high ecliptic latitudes have unique properties that enable important observations. Six community white papers advocated science enabled by this technology, and previous strategic
studies have advocated solar sails. Past heliophysics mission concepts include a solar polar imager, a
stationary Earth polar observatory, upstream solar wind monitoring at a sub-L1 location, an L5 mission,
Solar Sentinels, and Interstellar Probe.
Significant investments have already been made in the United States and abroad. The Japan Aerospace
Exploration Agency (JAXA) and NASA carried out dedicated tests of solar sailing for primary thrust using
the IKAROS spacecraft and NanoSail-D2. Without an appropriate demonstration mission that goes beyond
the small-scale, heavy-sail tests to date, the possibility of using this technology in the future will remain in
doubt. NASA’s Office of the Chief Technologist has suggested a technology demonstration line that could
cover 75 percent of the cost of a $200 million solar sail demonstration mission. The committee strongly
urges that this potential opportunity be pursued to demonstrate a 25 g m –2 , ~40-m solar sail. 1
Propulsion—High Drag
Heliophysics system science requires an understanding of plasma-neutral coupling, global composition, and structure of Earth’s upper atmosphere (< 300 km altitude). Long-term in situ observations in this
relatively high-drag region are required to develop scientific understanding of this coupling region between
space and Earth’s upper atmosphere. Reaching this altitude requires increased performance propulsion
systems, innovative ways to reduce dependence on expendables, and use of aerodynamic effects to enable
satellite operations in high-drag regions. The concept of using “dipper” satellites that maneuver in and out
of high-drag regions is the conventional approach, but it does not significantly increase the observational
time. Capable but “disposable” (very small, very-low-cost) satellites for the exploration of high-drag regions
is an approach that has yet to be studied in detail. Such observational platforms could be deployed from
the ISS or another host spacecraft if a propulsion system were developed to enable the deployment and
maintenance of small satellite constellations in and above these high-drag environments.
1 See Section 2.4.4.4 of NASA, In-Space Transportation Capability Portfolio, 2005.