D

Heliophysics Science Division Missions

The committee requested data on the following heliophysics missions: Aeronomy of Ice in the Mesosphere (AIM), Interstellar Boundary Explorer (IBEX), Interface Region Imaging Spectrograph (IRIS), Van Allen Probes, Solar Terrestrial Relations Observatory (STEREO), Magnetospheric Multiscale (MMS), and the Voyager Interstellar Mission. No data were provided on Voyager.

AERONOMY OF ICE IN THE MESOSPHERE

The AIM mission is an Explorer-class spacecraft launched into a polar orbit by a Pegasus XL rocket in 2007. The objective of the mission was to monitor noctilucent ice clouds over Earth’s poles. The mission cost $37.6 million in 2006.

Scientific Productivity

There are 88 news articles and press releases as well as 8 special sessions at the American Geophysical Union that featured AIM science.

AIM sponsored more than 15 education and public outreach events, and more than 9 NASA Heliophysics Guest Investigator proposals used AIM data. Five AIM papers were in the top 25 most cited papers in the Journal of Atmospheric and Solar-Terrestrial Physics during 2014. Over the course of the mission, many news organizations have published articles on AIM (e.g., CBSnews.com, the New York Times, USA Today, Discovery Channel TV in Canada, SpaceNews, BBC World News, Cosmos magazine in Australia, Forbes, MSNBC, Washington Post, KAALTV [ABC affiliate Rochester Mason City-Austin, Iowa-Minnesota], and KSL-TV [NBC affiliate Salt Lake City, Utah]). AIM science continues to be featured in the media and in NASA news releases and announcements. Since the mission was launched in 2007, there have been 8 AIM Science@NASA web articles with accompanying videos as well as several Spaceweather.com articles. Indicative of the growing scientific and public interest in noctilucent clouds, AIM observations of long-term change in the mesopause region were described in the March 18, 2016, NASA Science Mission Directorate weekly highlights; in the April 2016 NASA Advisory Committee minutes; in a July 1, 2016, Spaceweather.com article; and in an August 16, 2016, Science@NASA nowcast. In addition, the AIM team announcement of an early start to the 2016 Southern Hemisphere Polar Mesospheric Cloud (PMC) season received worldwide media attention, appearing on 25 science websites including the Christian

Science Monitor, NatureWorldNews, Science Magazine online, NPR, and Rava Tech Insider (Pakistan’s premier video curation website), for example. Indicative of the utility of the data, Spaceweather.com publishes daily AIM/Cloud Imaging and Particle Size (CIPS) images during the PMC seasons. In 2014 the Journal of Atmospheric and Solar-Terrestrial Physics reported that 5 of its top 25 cited papers of the previous 5 years were based on AIM observations.

Impact on the Current and Future Health of the Relevant Scientific Communities

AIM supports the Laboratory for Atmospheric Space Physics Mission Operation Center infrastructure, including voice and data lines, command and control software, planning and scheduling software (including Tracking and Data Relay Satellite System [TDRSS] scheduling software), data processing software, and so on. The AIM team has developed numerous scientific software applications that are freely available on the Internet. These include models of optics and radiative transfer, an equilibrium PMC model, and a variety of routines to access and analyze satellite data. The team was able to share the cost of maintaining Solar Radiation and Climate Experiment (SORCE) ground spacecraft simulator.

Contributions to Development and Demonstration of Technology Applicable to Future Missions

Technology developed to mitigate AIM onboard S-band receiver failure early in the mission, including the development of autonomous operations and use of Morse code to command the spacecraft through the TDRSS, has the potential for salvaging future missions with similar problems. AIM has successfully proven the use of autonomous-state vector generation and autonomous instrument operations. AIM/TDRSS scheduling technology will be used for the Imaging X-ray Polarimetry Explorer mission. The Solar Occultation for Ice Experiment (SOFIE) instrument used commercial off-the-shelf silicon carbide detectors on orbit for the first time and demonstrated that it has excellent reliability and high performance for future missions. Finally, the Mars Atmosphere and Volatile Evolution (MAVEN)/Imaging Ultraviolet Spectrograph instrument drew heritage from AIM’s CIPS instrument.

The AIM spacecraft bus is the same as SORCE, built on heritage from the Solar Anomalous and Magnetospheric Particle Explorer (SAMPEX), Submillimeter Wave Astronomy Satellite (SWAS), Tropical Rainfall Measuring Mission (TRMM), and other satellites. The spacecraft bus allowed use of the SORCE ground spacecraft simulator and leverage of operational experience (database and procedures). The SORCE battery experience was useful in resolving potential issue on AIM. The AIM/SOFIE instrument was built on heritage from the NASA Upper Atmosphere Research Satellite (UARS)/Halogen Occultation Experiment (HALOE) instrument.

Conclusions

One of the smallest missions conducted by NASA’s Heliophysics Science Division, AIM continues to provide new insights into the properties and origins of polar mesospheric clouds and their possible connection to climate change. Initial observations revealed that the clouds appear every day and are highly variable of a variety of time- and spatial scales. They contain small ice particles responsible for strong radar echoes of the summertime mesosphere, and mesospheric ice occurs in a single continuous layer from a main peak at ~83-km altitude to over 90 km, while the cloud structures exhibit complex features not unlike those in tropospheric clouds. With the most recent mission extension now having enabled a decade of observations of these clouds, AIM has now shown that the clouds have been continuously increasing, rather than waxing and waning with the solar cycle, a trend that could be related to increasing concentrations of greenhouse gases in the atmosphere. AIM has confirmed that the seed particles of the ice crystals that form the clouds are meteoritic smoke particles, produced by the incineration of meteors in Earth’s atmosphere. AIM has revealed that heat movement in the atmosphere is more likely linked to mesospheric circulation than directly to solar radiation and has provided new insights into the dynamics of planetary waves in the atmosphere, which can influence weather on a global scale.

INTERSTELLAR BOUNDARY EXPLORER

The Interstellar Boundary Explorer (IBEX) mission is an Explorer-class spacecraft launched in 2005. IBEX’s mission is to map the boundary between the solar system and interstellar space. The mission cost $110.1 million between 2006 and 2008. The mission featured some international cooperation. The University of Bern performed design, fabrication, testing documentation, and delivery of IBEX-Hi and -Lo Pre-collimators and Lo ESA.

Impact on the Current and Future Health of the Relevant Scientific Communities

IBEX has made many contributions to the scientific community with the discovery of the IBEX Ribbon and many other fundamental discoveries about the heliosphere—our home in the galaxy.

Contributions to Development and Demonstration of Technology Applicable to Future Missions

The Energetic Neutral Atom (ENA) imaging capability from IBEX basically enables these observations on the Interstellar Mapping Probe mission, which is the next major heliophysics mission. The team’s innovative launch capability can fly a small (~100 kg) payload out of Earth’s gravitational well to pretty much anywhere in the solar system, given enough time, using a NASA-supplied Pegasus XL rocket.

There were no flight spares, but IBEX was built on general technology from prior missions with a lot of innovation from IBEX’s small principal investigator (PI)-led team.

Conclusions

From its vantage point near Earth, IBEX has opened an entirely new perspective on the distant interaction between the heliosphere and Very Local Interstellar Medium (VLISM). By providing ENA imaging spectroscopy of this far region, IBEX’s imaging of the ENA “Ribbon” has provided new constraints on the orientation of the local interstellar magnetic field and, by comparing energy spectra with those of the ionized energetic particles in situ observed by the Voyagers, new constraints on the properties of the interaction region itself. As a new tool now through multiple extended missions, IBEX is also providing information on potential temporal variations in these far regions, and the success of this new technique has motivated the selection of the Interstellar Mapping Probe in the most recent Heliophysics Decadal Survey as the next strategic mission to implement.

INTERFACE REGION IMAGING SPECTROGRAPH

The Interface Region Imaging Spectrograph (IRIS) is a small Explorer-class spacecraft launched in 2013 into a polar orbit. The mission’s objective is to study the chromosphere of the Sun.

Technology developed for IRIS feeds forward in many different ways to reduce risk and cost for future missions, including the following:

• Low-cost satellite bus with very stable three-axis solar pointing;
• Advanced Camera for Surveys (ACS) control software;
• Solc filter for broadband UV imaging;
• Novel primary mirror heat dump, avoiding thermal problems of traditional solar telescopes;
• Combined image-stabilizing and scanning system with no additional mirrors; and
• Spacecraft including X-band transmitter and precision magnetometer.

Scientific Productivity

This mission was scientifically productive, enabling the construction of a powerful observatory at the cost of a small Explorer (SMEX):

• The Guide telescope and ACS solar pointing design came from the Transition Region and Coronal Explorer and Solar Dynamics Observatory (SDO) missions.
• Flight spare camera electronics came from SDO.
• Mechanisms (front door, filter wheels, shutters, wedge motors) rely on design, qualification, and life tests from Hinode, SDO, and the Solar Ultraviolet Imager.
• Flight spare instrument computer came from SDO.
• SDO electrical, electronic, and electromechanical parts and the majority of instrument control electronics and thermal control designs came from Hinode and SDO.
• Data compression firmware and flight software were reused from SDO. Optics mounts came from the Near Infrared Camera and primary and secondary mirror mounts came from the Atmospheric Imaging Array (AIA).
• Gravity Recovery and Interior Laboratory (GRAIL) flight spare battery, GRAIL designed reaction wheels, BroadReach avionics, and S-band transponder from the Lunar Atmospheric and Dust Environment Explorer were used.

Impact on the Current and Future Health of the Relevant Scientific Communities

At Lockheed Martin Solar and Astrophysics Laboratory, it was very important to maintain critical scientific and engineering capabilities. Critical capabilities were created and maintained at Goddard Space Flight Center (GSFC) in the areas of microcalorimeter fabrication and applications, low-temperature systems technology, high-spectral-resolution X-ray calibration technology, and atomic physics as applied to X-ray astronomy.

IRIS results have also been the subject of extensive media coverage, with press releases or social media coverage in just the last 19 months alone for the first detection of resonant absorption (August 2015), the Mercury transit (May 2016), solar flare models (June 2016), coronal rain observations (August 2016), collaboration with Atacama Large Millimeter/Submillimeter Array (ALMA; September 2016), tracking solar waves in sunspots (October 2016), estimating heating from shock waves in the chromosphere (November 2016), and new solar coronal heating insights (December 2016). These stories received widespread, international coverage by a variety of news sources, magazines, television (e.g., BBC Click), and websites. This is illustrated by a Google news search for “IRIS AND solar AND interface,” which reveals 4,660+ hits. In addition, IRIS is active in social media, with the IRIS Facebook page receiving semiweekly updates of movies and science nuggets, and 10,400 “likes.”

Conclusions

IRIS is a SMEX mission designed to probe the flow of energy from the solar photosphere into the corona remotely from Earth. IRIS probes the condition in and flow of energy through the dynamic chromosphere and transition region of the Sun by obtaining high-resolution UV spectra and images in that region, which are sensitive to nonthermal energy flow, at high temporal resolution.

Observations have revealed a new layer of complexity of the interplay of fibril structures characterized by large contractions in density and temperature in the transition region. The region has been shown to be extremely active, driven by nonthermal processes associated with rapidly evolving twisted magnetic fields and magnetic loops.

VAN ALLEN PROBES

The Van Allen Probes are two spacecraft launched into Earth orbit in 2012. Their mission is to study the radiation belts that surround Earth.

Contributions to Development and Demonstration of Technology Applicable to Future Missions

Van Allen Probes advanced our ability to design for high-radiation environments, in terms of analysis and modeling, materials testing, and circuit design.

Van Allen Probes did not use any existing flight spares. In general, Van Allen Probes used the existing base of spacecraft engineering design and body of knowledge and built on it. There was not a specific precursor technology that emerged that enabled the Van Allen Probes mission to kick-off. Energetic Particle, Composition, and Thermal Plasma Suite (ECT) instruments drew heritage both in terms of design and concept from earlier flight instruments, though not to the extent of build-to-print or use of flight spares. Rather, detection techniques, detector types, and advanced electronics developed through other NASA and non-NASA flight programs were used to guide and/or implement the ECT instrumentation. The Electric and Magnetic Field Instrument Suite and Integrated Science sensors—that is, the search coil and the magnetometer that are out on the ends of the booms—have heritage from several prior missions but had some redesign to accommodate the high-radiation environment of the Van Allen Probes. Some of the mechanical materials were somewhat different, and the details of the Magnetic Search Coil preamps were designed using high-radiation-tolerance parts. Electric Field and Waves Suite instruments drew their heritage from Time History of Events and Macroscale Interactions during Substorms (THEMIS), Polar, and Cluster.

The “hockey puck” Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) instrument inherits a long-existing knowledge base of measuring low-energy space plasma particles. Early versions were flown on Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) and New Horizons (PEPSSI). This particular hockey puck design has been flown three times, on Van Allen Probes (RBSPICE), Juno Jupiter Energetic Particle Detector Instrument (JEDI), and MMS Energetic Ion Spectrometer (EIS), with minor variations specific to those implementations.

Examples of international collaboration or contribution include the following:

• Korea Astronomy and Space Science Institute (KASI)—NASA provides the expertise required for the initial setup of the data system to store, use, and disseminate the science-quality SDO data, which will be provided to KASI for the duration of the mission.
• Brazilian Space Agency—Collects space weather data when Radiation Belt Storm Probe (RBSP) spacecraft pass over Brazil antenna site.
• Czech Republic—Receives RBSP space weather beacon data and transmits to the RBSP Mission Operations Center via the Internet. NASA transmits RBSP space weather beacon data and provides beacon-mode data from RBSP.
• Argentina’s National Committee of Space Activities (CONAE)—Collects RBSP space weather data when spacecraft is over Argentina (Brazil AER/CONAE/Czech Republic/KASI—mainly space weather stations).

This mission maintains both scientific and engineering capabilities such as the handling of data, the generation of higher level science products and distribution products for immediate practical use, and the enhancement of capabilities and methodologies to design for and analyze hostile environments.

As of February 2017 the Van Allen Probes bibliography contains over 350 publications,¹ including several articles in high-profile journals that have received substantial press interest, such as Nature (6 articles), Nature Physics (2 articles), Nature Communications (3 articles), Science (2 articles), and Physical Review Letters (2 articles). The publications also include one special issue of Space Science Reviews (18 articles), one special issue of Geophysical Research Letters (26 articles), and two special issues of the Journal of Geophysical Research (42 and 21 articles). The Van Allen Probes yearly publication rate has been growing every year since the mission launch. This remarkable growth in productivity is attributed largely to the accessibility of the Van Allen Probes data to the international scientific community enabled by the Science Gateway;² over 50 percent of Van Allen Probes publications were led by first authors not directly affiliated with the instrument teams.

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¹ Johns Hopkins University Applied Physics Laboratory, Van Allen Probes Science Gateway, “Bibliography,” http://rbspgway.jhuapl.edu/ biblio, accessed February 2017.

² Johns Hopkins University Applied Physics Laboratory, Van Allen Probes Science Gateway, http://rbspgway.jhuapl.edu, accessed February 2017.

Conclusions

The twin Van Allen Probes spacecraft were launched into Earth orbits on August 30, 2012, to provide understanding of how populations of relativistic and penetrating ions in space form and change in response to variable inputs of energy. The probes confirmed the existence of a third radiation belt as a predictable consequence of the protection from losses that the plasmasphere provides to a part of the outer radiation belt because the wave environments are so different inside. The probes showed that particle energization is due to a source of nonadiabatic energization within the interior of the radiation belts, as opposed to adiabatic energization from transport-induced compression, and that global acceleration of particles by drift resonance with ultra-low frequency is ubiquitous. The probes continue to provide new data on the energization and dynamics of Earth’s radiation belts.

SOLAR TERRESTRIAL RELATIONS OBSERVATORY

The Solar Terrestrial Relations Observatory (STEREO) mission consists of two spacecraft launched into orbit around the Sun in 2006. The goal of the mission was to conduct stereoscopic observations of the Sun. One spacecraft remains in operation. STEREO cost $64.5 million in 2006.

Scientific Productivity

There are regular media releases related to STEREO. On the NASA STEREO portal site, there were six science story-type releases from 2015 to 2017. The mission also had web releases and media interviews related to the STEREO 10th anniversary in October 2016 and to recovery efforts for STEREO-B, also in fall 2016. STEREO images are available through NASA websites (in public-friendly formats) and through services like Helioviewer.³ Sometimes this interest is off topic (“UFO” spotters and such), but there are clearly members of the public who download the data. There are also apps incorporating STEREO data of the far side of the Sun.⁴

Contributions to Development and Demonstration of Technology Applicable to Future Missions

STEREO is a pathfinder for future missions to the Sun-Earth Lagrange points (L5 and L4). STEREO demonstrated how to operate twin satellites. The Heliospheric Imagers helped reduce risk (and raised the technology readiness levels) for the Solar Orbiter Heliospheric Imager (SoloHI) and particularly for the Wide-Field Imager for Parker Solar Probe (WISPR) on the Parker Solar Probe mission (which has two telescopes like the Heliospheric Imagers). The design work and tests for COR2 led directly to the compact coronagraph (CCOR) development. COR2 is, in essence, the blueprint for operational coronagraphs of the future (e.g., fields of view, spatial resolution, and cadence). The Sun-Earth Connection Coronal and Heliospheric Investigation (SECCHI) charge-coupled devices (CCDs) were the basis for the AIA CCDs (just a larger form factor).

The same design (build to print) from the STEREO Solar Wind Electron Analyzer (SWEA) instrument was used on the MAVEN program. Generally, instruments evolve from one project to the next due to a combination of different requirements, improved technology, and new ideas. SWEA used the design as is, which was a cost and schedule savings for MAVEN. The technology and infrastructure developed at the University of New Hampshire (UNH) for Plasma and Supra-Thermal Ion Composition (PLASTIC) has been used in the ion optics of the SoloHIs (expected launch in 2018) and was also used for the IBEX-Lo instrument on IBEX (2008), thus reducing instrument development costs on those missions, at least for the UNH portions.

The Stereo Waves Experiment (SWAVES) instrument was/is a forerunner of, for example, the Parker Solar Probe WAVES instrument (even many of the same team members). In addition, many spare pieces of previous instruments (parts of flight spares, parts of engineering units), much flight software, and a great deal of ground support equipment were used to construct and improve STEREO instruments.

STEREO instruments also inherited their designs from previous missions, improved upon them, and then

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³ Helioviewer Project, Helioviewer.org, last updated March 10, 2017, https://www.helioviewer.org/.

⁴ See, for example, the EducationalAppStore.com, “3D Sun,” http://www.educationalappstore.com/app/3d-sun-1, accessed February 2017.

passed those ideas and lessons learned onto the next projects. The thermal isolators developed for STEREO (originally from an MPE heritage on Cluster, but further developed by UNH for STEREO and now available through UNH), have also been used in these other missions. COR2 is a direct derivative of Large Angle and Spectrometric Coronagraph (LASCO)/C3, and the coronagraph test facility at the U.S. Naval Research Laboratory was maintained thanks to SECCHI and then used for SoloHI and WISPR. The STEREO team used some concepts from Ulysses’ Solar Wind Ion Composition Spectrometer, Cluster’s Composition and Distribution Function (CODIF) analyzer, and FAST (Fast Auroral Snapshot) teams’ instruments for use in PLASTIC. These experiences then further trained people who played major roles in RBSP and MAVEN project support. The SWAVES instrument built on Wind Experiment (WIND)/Waves Experiment (WAVES), Ulysses/Unified Radio and Plasma Wave Experiment, and (especially) Cassini/Radio and Plasma Wave Science.

Conclusions

The twin STEREO spacecraft provided new synoptic views of the Sun and solar phenomena, while allowing for the direct viewing of coronal mass ejections (CMEs) and their propagation to Earth. By combining CME images with in situ field and particle measurements at the two platforms simultaneously, the STEREO mission has enabled increased understanding of the three-dimensional structure of CMEs as they propagate through the inner heliosphere from the Sun to Earth and under what conditions the impact of these plasma and energetic particle environments give rise to varying impacts on the Earth geospace environment, effects collectively now known as “space weather.”

MAGNETOSPHERIC MULTISCALE

The Magnetospheric Multiscale (MMS) mission was launched in 2015. The mission consists of four spacecraft flying in formation. The goal of the mission is to gather information about the microphysics of magnetic reconnection, energetic particle acceleration, and turbulence. MMS was a large strategic mission costing $999.2 million between 2006 and 2015.

Scientific Productivity

The MMS mission is still relatively new. Its scientific productivity has not been fully realized.

Impact on the Current and Future Health of the Relevant Scientific Communities

MMS is the most ambitious space plasma physics mission ever, and employed a large fraction of the heliophysics research and engineering communities both within and outside GSFC.

Contributions to Development and Demonstration of Technology Applicable to Future Missions

There is substantially reduced risk for future formation-flying missions owing to the experience gained with MMS. This experience feeds into future missions being proposed by Goddard and others working with Goddard.

All instruments benefited greatly from experience with prior versions. The Hot Plasma Composition Analyzer instruments pioneered a new radio frequency filtering technique, and the Fast Plasma Investigation instrument pioneered in the areas of multiplicity of sensors, fast-stepping high-voltage power supplies, and flexible data compression, among others. The balance of those instruments was based on prior versions and experience.

Conclusions

By providing extremely high cadence measurements on four identically instrumented spacecraft with significant maneuverability and capability for controlled formation flying, MMS has enabled the first in situ microscale plasma physics laboratory within Earth’s magnetosphere.

Still in its primary mission, MMS has allowed for conclusive fundamental tests of magnetic reconnection, a long-studied but not well understood aspect of collisionless plasma physics in a magnetized plasma. The results are likely to lead to paradigm shifts across space plasma physics from Earth’s magnetosphere to galactic, astrophysical scales.

The MMS mission may be indicative of future heliophysics missions that will consist of multiple spacecraft flying in formation. It may provide numerous lessons learned for the development of future missions.