Download CubeSats in Heliophysics Research Charles Swenson, Utah State

CUBESATS IN HELIOPHYSICS RESEARCH
Charles Swenson, Utah State University, [email protected]
David Klumpar, University of Montana, [email protected]
Robert Lin, University of California Berkeley [email protected]
Aaron Ridley, University of Michigan, [email protected]
Gary Swenson, University of Illinois, [email protected]
Miguel Larson, Clemson University, [email protected]
Geoff Crowley, Astraspace, [email protected]
Rick Doe, SRI, [email protected]
Douglas Rowland, NASA Goddard, [email protected]
Vassilis Angelopoulos, University of California Los Angeles, [email protected]
Ennio Sanchez, SRI, [email protected]
Scott Palo, University of Colorado, [email protected]
Gregory Earle, University of Texas Dallas, [email protected]
Chad Fish, Utah State University Space Dynamics Laboratory, [email protected]
The most significant advances in solar and space physics, or Heliophysics, over the next decade are
most likely to derive from new observational techniques. The connection between advances in
scientific understanding and technology has historically been demonstrated across many
disciplines and time. There are clear ties between advances in our understanding of Heliophysics
processes and the deployment of new sensing techniques, from new vantage points, which fuel new
discoveries. Sensors such as X-ray and UV-imaging, GPS based measurements, energetic neutral
atom imagers and others along with the ability to place these sensors above the atmosphere and
within regions of interest have revolutionized Heliophysics science. The study of the Heliophysics
system requires multipoint observations to develop understanding of the coupling between
disparate regions: solar-wind, magnetosphere, ionosphere, thermosphere, mesosphere on a
planetary scale. Multipoint measurements are also needed to develop understanding of the various
scalars or vector field signatures (i.e gradients, divergence) that arise from coupling processes that
occur across temporal and spatial scales within localized regions. Such multipoint scientific
investigations have been presented in the most recent NASA Roadmap and it is likely that these and
other science objectives will be expanded upon in the current decadal study process. It is clear that
the Heliophysics community now needs multi-point measurements from within the space
environment to make progress on important scientific questions.
Therefore significant attention must be paid to maintaining the many satellites of and the continued
development of the Heliophysics System Observatory under NASA’s care. In addition it is imperative
that promising new technologies that will enable multipoint measurements from the space vantage
point be further developed.
Remote imaging is one source of multi-point measurements of Heliophysics systems but not all
measurement parameters of interest can be observed through remote sensing techniques. Some
examples that are not well observed by remote imaging are electric field patterns and currents
flowing along magnetic field lines both of which are important quantities for understanding the
coupling of regions. It is also clear that significant scientific advances can be made by placing
remote imaging sensors at multiple points to make distributed observations of globally coherent
phenomena such as atmospheric tides and auroral storms, or to improve the observations through
advanced signal processing methods such as tomography or improved temporal/spatial
resolutions. The development of platforms and the required infrastructure which enables both in
situ and remote sensing from multiple points within the space environment must now be a high
priority for the advancement of the science of Heliophysics.
The resources that will be available over the next decades for all areas of Heliophysics research
have limits and it is therefore important that the community find ways to leverage the costs of
developing new technologies to advance science. The high cost of access to space, at first review, is
a serious impediment to making multipoint measurements within the space environment or in
other words in deploying constellations of traditional satellites. It is therefore desirable to develop
much smaller and lower-cost sensor/satellite systems such that the largest number of distributed
measurements can be economically made in the space environment. The smaller the mass and
volume of the sensor/satellite the larger the number will be that can be deployed from a single
launch vehicle. The prospect of creating miniaturized sensors and satellite systems is good given
the enormous investment of commercial, medical, and defense industries in producing highly
capable, portable and low-power battery-operated consumer electronics, in-situ composition probes,
and novel reconnaissance sensors. The advancement represented by these technologies has direct
application in developing small sensor/satellite system for Heliophysics research. The application
of portable consumer electronics technology for Heliophysics exploration must be well represented
in the current decadal survey process.
Affordable constellations are not the only observational tool enabled by smaller and lower-cost
sensor/satellite systems. With them it becomes feasible to put "almost disposable" platforms into
heretofore sparsely or un-sampled locations or regions where it is currently not economical to
place a larger more expensive satellites. Deployed into very low Earth orbit, these small low-cost
platforms could carry instruments into the lower ionosphere/thermosphere, for example. The
region between 100 km and about 250 km in the Earth’s atmosphere is not conducive to long
lifetime orbits but could be monitored nearly continuously by periodically deploying small satellites
from the International Space Station, for instance. The region is currently explored in part by
remote sensing methods and has been punctured by sounding rockets. Similarly in the solar
chromosphere it is difficult to get closer than about 10 solar radii (e.g. Solar Probe Plus) since the
harsh environmental conditions limit the satellite's lifetime. With low cost, disposable satellites,
direct entry missions into the solar atmosphere could be conceived. Large missions tasked to
explore comets, asteroids or planets could take along a number of small sub-satellites that could be
deployed on arrival at these bodies to provide multipoint observations while communicating with
the "mother ship" to relay the data to Earth. These are but a few examples of short lifetime targeted
missions with potentially high scientific value. Small low-cost satellites can be placed into short
lifetime trajectories lasting only a few days or a few weeks for scientific purposes which would not
be feasible for larger more-expensive satellites.
The CubeSat standard for picosatellites was developed in the late 1990’s for the use of the academic
community in teaching space systems engineering to the next generation. It has since become
widely accepted both internationally and by a broad spectrum of organizations due to the low-costs
and relatively easy access to launch services which promoting the standard have engendered. The
distinguishing characteristic of CubeSats is the mechanical standard for containerized launch
services and how the picosatellites are opportunistically paired with those launch vehicles that
provide deployment containers. The Poly Picosatellite Orbital Deployer (P-POD) developed by Cal
Poly is an example of a widely accepted containerized launch system for secondary payloads. Most
launch vehicles in the United States have designed support for multiple P-Pod containers which
each delivering a 3 liter (10 x 10 x 30 cm) volume weighing no more that 4 kg to orbit. CubeSats
have developed a significant industrial base with several aerospace companies providing
subsystems to entire spacecraft busses of varying capabilities. Current estimates place the number
of CubeSat developers at over 100 worldwide including governments, industry and academia. The
NASA Flight Projects Office has promoted the launch of CubeSats on NASA vehicles though the
Education Launch of Nanosatellite (ELaNA) program in cooperation with the NASA Office of
Education. The NSF has supported the scientific development of picosatellites through the CubeSatbased Science Missions for Space Weather and Atmospheric Research program since 2008. As of
Fall 2010, six NSF CubeSat missions are in development spanning remote detection and in-situ
investigations of critical space weather state variables. Several commercial sector companies and labs
have demonstrated miniaturized optical, particle, and RF sensors purpose-built for CubeSat-based
research missions. CubeSat technologies, including standards based launch containers for secondary
payloads, represent a significant opportunity both for developing the required technology and for
achieving multipoint observations from within the space environment.
The advancement of solar and space physics, or Heliophysics, requires a skilled and trained pool of
experimentalists, engineers and managers in addition to scientific modelers and theorists. The
Heliophysics science community must give consideration to the organization and training of the
human elements which drive scientific progress. “Doing” is the key element in developing the
experimental, engineering and management skills for a scientific community. Therefore it is
important to have a spectrum of experimental programs with differing costs and expectations such
that these skills can be affordably developed. Small CubeSat missions are one way to develop
scientific teams such that they are better prepared to manage and accomplish larger programs. It is
important that these missions have strong scientific purposes and leadership such that the
community fully reaps the training benefits as well as the scientific benefit of the investment.
Experimental programs that are strongly driven by scientific objectives provide significantly
different training experiences than those driven merely as technical demonstrations. Secondary
payloads such as CubeSat represent not only an important platform for scientific investigations but
also a platform to develop the experimental skills of the community, but only if these programs are
strongly tied into the Heliophysics scientific agenda.
The application of CubeSats or a proposed standard for larger scale nanosats, 6 to 12 liter volume
spacecraft, for multipoint measurement in support of Heliophysics science will require technology
development and policy evolution. We strongly suggest that the technologies be developed with strong
coupling to the Heliophysics scientific community.
1) Constellation deployment and maintenance: technologies and strategies need to be
developed for deploying a large number of CubeSats or nanosats in a cost effective way
to achieve the required constellation configuration. It is apparent that some scientific
objectives can be achieved with a large constellation of essentially uncontrolled
spacecraft orbits where as other studies would benefit from semi or fully controlled
orbits, via propulsion capabilities, within the constellation. The development of a lowcost capability to launch or position individual CubeSats to specific LEO destinations is
also desirable and would enable a number of targeted scientific studies.
2) Communications: In order for CubeSats or nanosats to become a significant contributor
scientifically they must provide downlink capabilities similar to existing scientific
satellites. The architectures for offloading data from a large number of spacecraft,
frequency regulatory frameworks and ground station infrastructures must be
developed.
3) Sensors: miniature space sensors suitable for deployment on CubeSats and appropriate
for the scientific investigation need to be developed. The model developed by NASA’s
Planetary Instrument Development Program may be appropriate for developing
scientific sensors for CubeSats or nanosats. The scientific community must learn how to
make use of the commercial and defense-related technologies enabling low-power,
compact systems and apply them to instrumentation for Heliophysics.
4) Risk Culture: CubeSat or nanosat-based constellations may achieve significant scientific
breakthroughs despite failures associated with individual sensors or spacecraft due to the
large number of elements that continue to function. The constellation, when considered as a
whole, would therefore still be a very low risk scientific endeavor. An acceptance of
increased risk tolerance for individual spacecraft within a constellation will need to emerge
within NASA to fully realize the promise of low-cost CubeSat constellations.