Last month, the Keck Institute for Space Studies (KISS) at the California Institute of Technology released a report titled, “Small Satellites: A Revolution in Space Science,” which examines the sorts of missions types of missions that could be with rapidly evolving small satellites. The potential missions described in the report cover planetary science (moons, asteroids, etc.), astrophysics and heliophysics.
The planetary science missions include the use of mother ships that would deploy CubeSats and impactors to explore Jupiter’s moon Europa, tens of thousands of ChipSats to characterize Saturn’s rings, landing vehicles to explore asteroids, and small spacecraft that would map the moon’s interior and search for volatiles and organics.
The report says that a number of the missions are years away because new technologies for small satellites will need to be developed first. The document includes five recommendations for how NASA can go forward on developing the technologies and pursuing the missions.
NASA is already pursuing deep-space CubeSat missions, including a series that will be launched as secondary payloads in the first flight of the Space Launch System (SLS) in 2007. In May, the space agency also announced the selection of nine Small Business Innovation Research (SBIR) Phase I awards to fund deep-space CubeSat technologies. NASA also has funded Draper Laboratory to develop a satellite to deploy ChipSats to explore surface of Europa.
What follows are excerpts from the Keck report listing the potential missions with additional information about the planetary science ones. The five recommendations are listed at the end.
|MISSION CONCEPT||SCIENCE OBSERVATION||OBSERVING STRATEGY||PAYLOAD TECHNOLOGIES|
|C/entinel||In-situ and proximity operations around small bodies including surface, deep interior, and origins of these systems.||Multiple fly-by and insitu landers, deployed as CubeSats with support from larger host spacecraft.||Thermal and mineralogical sensors, spectrometers, entry descent-landing.|
|CHAMPAGNE: Planetary Ring Explorers||Characterizing the composition and physical structure of Saturn’s rings, including determining the spatial and velocity distributions, physical properties, size distribution of the ring particles and their location variations across the rings.||Insert tens of thousands of ‘smart particles’ ChipSats|
of a similar scale to ring particles into the rings permitting very close inspection and characterization.
|ChipSat/TF-SLR based smart particles.|
|ExCSITE||Characterization of Europa’s surface via high-resolution imaging, gravity field mapping, and chemical characterization of dust ejecta.||Multiple deployed flyby systems as CubeSats and/or SmallSats, including impactors for surface experiments, with support from host spacecraft.||Dust detectors, deployable impactor shields, fast high resolution imaging cameras, particle and fields instrumentation, and proximity operations.|
|Lunar Cube Vibrations||Mapping and characterization of the lunar interior and the search for volatiles and organics.||Multiple fly-by and insitu landers, deployed as CubeSats and/or ChipSats with support from larger host spacecraft.||Seismometers, thermal sensors, magnetic field and dust sensors.|
|L5 Space Weather Sentinels (L5SWS)||Space weather monitoring from the Sun-Earth L5 point: observe Earth-directed CMEs, monitor solar wind stream structure, see solar active regions before visible from Earth.||Combine remote sensing and in-situ instruments at Earth-Sun L5 using solar sails. Fractionate the mission into multiple 6U CubeSats for insitu fields and particles, heliophysics imager, magnetograph and telecom building up observation capability incrementally.||Propulsion capability and station keeping at L5, relay communication, instrument packaging and miniaturization, arc-minute pointing stability.|
|RELIC||Understanding energy transport from black holes to the intergalactic medium.||Aperture synthesis imaging with a 1 km diameter spherical array of 30+ 3U CubeSats imaging doubled-lobed active galaxies at freq. below 30 MHz.Deployment at Earth-Sun L2 or low gravity gradient environment beyond the Moon.||5-meter dipole antennas in all 6-axes. Formation flying, constellation management, data downlink, antenna deployment, in situ data analysis and correlation management.|
|Soft-X||Measurement of the low-energy diffuse background from the interstellar medium||X-ray spectroscopy mission in sun-sync orbit observing away from Earth at 1-2 deg spatial resolution over the entire sky.||X-ray spectrometer detector from 100-1000 eV with a single collimator. Collimated CCD or CMOS detector and on-board processor for X-ray photon counting.|
|UVIP-UV Reionization Probe||Understanding the source and mechanisms for reionization in the universe.||UV coarse spectral wide area survey imaging in LEO with a graduated “A-train style” constellation of ESPA-class small satellites.||Arc-second resolution, 912-2400 AA band, ~25cm aperture optics with CCD UV detectors. Pointing stability, UV coatings, high efficiency UV detectors.|
|Ionosphere Magnetosphere Coupling Constellation (IMCC)||Global electrodynamics of Earth’s magnetosphereionosphere coupling.||In situ measurements by 60 nanosatellites on 6 high inclination orbital planes supported by existing ground assets.||DC magnetometer, AC magnetometer, Langmuir probe, low-energy plasma instrument, energetic particle and electric field instrument.|
|Solar Polar Constellation||First dedicated solar polar constellation mission for understanding variability, dynamo, and Solar System effects.||Constellation of 6-12 identical CubeSats in high inclination solar orbit.||Heliophysics imager, DC magnetometer, low-energy plasma instrument, energetic particle detector, magnetograph.|
DESCRIPTIONS OF POTENTIAL MISSIONS
The investigation of small-body objects, including asteroids and comets, offers multiple attractive mission opportunities, with benefits in the scientific, exploration and defense realms. For mission safety, and conservation of resources, most missions so far have limited their closest approach of small bodies to several tens of kilometers – with the notable exceptions of the orbiter-turned-landers NEAR and Hayabusa. The NEO-probe architecture introduces a new paradigm to reduce cost and risk taking advantage of nano-spacecraft (e.g., CubeSat) as a low-cost platform for close-in and in situ exploration of small bodies. This platform would carry instrumentation to obtain measurement of key strategic knowledge gaps identified by the NRC study “Defending Planet Earth” (2010): internal structure, mass, size shape, geology (morphology, collisional history), elemental and mineralogical composition, rotational properties, near surface mechanical and thermal properties, and variations of these properties at all scales. Missions to perform these measurements would in turn contribute to a more general understanding of small body interiors and origin reservoirs that ties to key science themes (“Building Blocks”, “Processes”) emphasized in the Planetary Science Decadal Survey. Most importantly, close proximity and in situ observations would provide ground truth information to calibrate our understanding of remote observations (e.g., ground-based RADAR, space observatories).
Once the probe is separated from the mothership, challenging operations must occur, including descent and landing (hard or soft), communications, and basic survivability. Similar to the proposed Minerva 2 mission on Hayabusa 2, these small probes must deploy from the mothership, head to the surface (either controlled or uncontrolled), and survive. Simulations have provided promising results (Tardivel and Scheeres 2012) indicating that passive orbits are readily available to guarantee surface impact, and even limited targeting may be available. This class of probes is even amenable to surface mobility (Minerva, Hedgehog) once landed. Harder impacts might serve to disturb the body, or at least provide seismic events for remote characterization.
CHAMPAGNE: Planetary Ring Explorers
The composition and physical structure of Saturn’s rings are not well understood. Science objectives of the CHAMPAGNE (CubeSat / ChipSat High Agility Multi Probe and Grid Network Explorer) mission concept include determining the spatial and velocity distributions, physical properties, size distribution of the ring particles and their location variations across the rings.
The mission would insert tens of thousands of ‘smart particles’ of a similar scale to ring particles into the rings permitting very close inspection and characterization. CubeSat/ESPA-scale motherships would enter orbit within 100,000 km of Saturn’s rings using their own on-board propulsion from Earth or piggybacking on another outer solar system mission. ChipSat / TF-SLR based smart particles, also possibly with on board propulsion, would be deployed into the rings in waves, with data from each smart particle wave downlinked and stored on in-range motherships.
Each smart particle would be tracked while in range of a mothership until destruction or until its maximum expected survival time is reached. Data would be locally processed and transmitted to Earth infrequently by the motherships via large thin film high gain antenna / solar arrays using high power burst transmissions limited by available energy harvesting and on board battery storage. Mission investigations would be complete within several weeks, but extended operations of motherships may last for years.
Simultaneous communication and position tracking of many (~100’s at a time) smart particles and multiple motherships would be required. A mixture of smart particle types including ‘drift through until destruction’, ‘ping pong balls’ and ‘sticky landers’ would be inserted into the rings to make different classes of measurement including their rate of attrition – a useful measurement in its own right. Multiple deployment events are preferred unless a one shot deployment during a flyby piggyback ride is necessary.
Technology issues include the development of small scale (3U to 24U) CubeSat motherships with propulsion and high gain thin film antenna / solar arrays, tracking and relay at up to 100,000 km for smart particle/mothership communications; the development of efficient infrequent ‘bursty’ communication systems (both ring probe to mothership and mothership to Earth); relay via other missions; on-board processing to cope with energy harvesting with storage type power systems to manage the power budget limitations of small motherships and smart particles at 9AU; Smart particle systems and instrumentation (accelerometers, transmitter, mm scale camera with fisheye lens, etc.) capable of surviving long cruise times will be required. Development of a heavily instrumented universal ChipSat / mass customizable TF-SLR with sufficient flexibility to allow the non-recurring engineering costs to be spread across a wide range of planetary science missions plus automated management systems for swarm missions will be important.
The Explorer Cubesat for Student Involvement in Travels to Europa (ExCSITE) is meant as a smart instrument to be deployed from the Europa Clipper mission as it flies by Jupiter’s ocean-moon Europa. Depending on the launch vehicle available to the Clipper mission, the mothership may have enough mass margin to carry a dozen of small- and nanosatellites (Europa Project Study Report 2012). The ExCSITE platform would provide a pathfinder for university exploration of deep space through the deployment of science instruments accomplishing key objectives highlighted in the science traceability matrix for Clipper. These include high-resolution imaging of the surface with the Cubesat getting very close to Europa’s surface; particle and field (magnetic/gravity) mapping through the deployment of several assets that would sample multiple regions of Europa’s induced field and track its temporal variations as a means to constrain the properties (salinity, geometry) of the deep ocean; chemistry characterization of dust ejecta from Europa with a dust spectrometer performing a shallow flyby in very close proximity (
Small instruments could be transported to low altitudes by a Cubesat derived platform providing shielding, batteries, and on-board autonomy. Several deployable instruments on Cubesat platforms could be carried by the Clipper mothership, contained within deployers providing further shielding and telecom relay. Hence, deployed experiments could be performed independently with minimal impact to other science planned for Clipper, and with little dependence on mothership resources except for power and data forwarding.
Lunar Cube Vibrations
The science driver for the Lunar Cube Vibrations mission concept is mapping and characterization of the interior structure of the moon and the search for volatiles and organics. These objectives are directly aligned with the interests of the Lunar Exploration Analysis Group (LEAG) and the Planetary Science Decadal Survey. The latter includes a lunar geophysical network as part of its New Frontiers mission concept portfolio.
Multiple low cost CubeSats, augmented with ChipSat/Thin-Film Spacecraft/Lander/Rover (TF-SLR) scale hard landing capable instruments with analytical and geotechnical sensors, would be widely and precisely distributed over the lunar surface. (TF-SLRs are postage-stamp to handkerchief-sized spacecraft at the gram to milligram-scale.)
Orbiting motherships, both dedicated and pre-existing would relay data to earth, with direct to earth telecommunications as an alternative data transport mechanism. When ridesharing to the moon, a single mothership would deploy all the surface packages. If solar sail or electric propulsion from geosynchronous transfer orbit (GTO) is used, multiple smaller motherships with a few sensors per mothership are preferred. A rideshare to low lunar orbit is expected to comprise approximately 50kg as seven 3U CubeSats on a system such as Mini-Surveyor or an ESPA ring.
KECK made series of policy recommendations on how to further develop small-satellite technology and to pursue deep-space missions.
|Beyond LEO SmallSat Science Exploration Program||A means to establish a roadmap and set of scientific objectives tailored specifically to unique small satellite observations in astrophysics, heliophysics, and planetary science. This would include an expansion of the SMEX and mission of opportunity programs to include development of a robust set of small satellite constellation survey missions.|
|Beyond LEO SmallSat Technology Maturation Program||The means to advance hardware and software technologies, including instruments, to enable long duration and resilient small spacecraft systems compatible with deep space scientific exploration.|
|Small Spacecraft as Secondaries on All Beyond LEO Missions||Establishing this capability adds value to flagship mission science observation, specifically where measurements are desired in extreme environments or high risk circumstances to the primary, with manageable risk at low cost.|
|Dedicated SmallSat Launch and Operations Program||A program targeted to this recommendation for beyond LEO small spacecraft systems. This includes investments in ground station capabilities and associated infrastructure to support beyond LEO deployment, telecom, and tracking.|
|Targeted “Class D” Proposal Opportunities for Beyond LEO SmallSat Missions||The current peer-review process can impede the ability to propose single small satellite missions, as they must compete against higher-class instruments and spacecraft within the same scientific guidelines. This recommendation would support a means to assess how innovative approaches could target specific scientific advances using new platforms.|