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Solar and Space Physics: A Science for a Technological Society
REPORT OF THE PANEL ON SOLAR AND HELIOSPHERIC PHYSICS
309
• Hard X-ray imaging spectroscopy, full-disk, 64-150 keV;
• Solar and interplanetary energetic particles, 0.05- to 100-MeV/nuc, and electrons;
• Solar wind ion composition and electrons; and
• Magnetometer.
Two science phases are envisioned: drift to L5 at about 38° per year with continuous collection of
science data and orbit around L5, 45°-90° from the Sun-Earth line. A long extended mission is possible.
Goddard Space Flight Center has studied a similar concept called Earth-Affecting Solar Causes Observatory 17 (EASCO), featuring about a 2-year low-thrust trajectory to L5 and using solar-electric propulsion,
saving more than 200 kg compared with hydrazine.
In summary, the L5 mission concept promises important breakthroughs in both helioseismology and
space weather (motivation M2). It would make major advances toward SHP panel science goals 1 and 3,
including, in particular, actions 1b and 3d. The panel encourages NASA, NOAA, and the Department of
Defense (DOD) to carry out an interagency study of an L5 mission (see §10.5.5.7).
10.5.2.6 Solar Polar Imager Mission
Current understanding of the Sun, its atmosphere, and the heliosphere is severely limited by a lack
of good observations of the Sun’s polar regions. The Solar Polar Imager (SPI) mission concept, 18 a NASA
vision mission with strong international interest, would go into a 0.48-AU circular orbit with 60° inclination
to conduct extended (many days per orbit) observations of the polar regions, enabling the determination
of polar flows down to the tachocline, where the solar dynamo is thought to originate. The rapid 4-month
orbit, combined with in situ and remote-sensing instrumentation, will enable unprecedented studies of the
physical connections between the Sun, the solar wind, and SEPs.
Instrumentation could include a Doppler magnetograph, white-light coronagraph, EUV imager, UV
spectrograph, TSI monitor, energetic-particle spectrometer, solar wind composition spectrometer, and magnetometer and could provide studies of the polar magnetic field over the solar cycle, the three-dimensional
global structure of the corona, and solar wind, energetic-particle, and TSI variations with latitude. Most
important, SPI would measure the temporal evolution of time-varying flows, differential rotation, and
polar-region meridional circulation down to the tachocline, addressing SHP science goal 1. Finally, SPI
would explore how space weather forecasts can benefit from a polar perspective (SHP science goal 3 and
motivation M2).
Solar-sail propulsion is proposed to place SPI into its orbit. Recent advances demonstrate that solar
sails are technically feasible and effective for maneuvering in the heliosphere. A technology-readiness
plan is outlined in Section 10.5.2.8. The SHP panel strongly encourages NASA to develop the propulsion
technology needed to launch SPI during the 2023-2033 decade.
10.5.2.7 Interstellar Probe Mission Concept
Recent in situ measurements by the Voyagers, combined with all-sky heliospheric images from IBEX
and Cassini, have made outer-heliospheric science one of the most exciting and fastest-developing fields
of heliophysics. The measurements have transformed knowledge of the boundaries of the heliosphere. The
17 N. Gopalswamy et al., Earth-Affecting Solar Causes Observatory (EASCO): A New View from Sun-Earth L5, white paper submitted
to the Decadal Strategy for Solar and Space Physics (Heliophysics), Paper 99.
18 P. Liewer et al., Solar Polar Imager: Observing Solar Activity from a New Perspective, white paper submitted to the Decadal
Strategy for Solar and Space Physics (Heliophysics), Paper 156.
Solar and Space Physics: A Science for a Technological Society
REPORT OF THE PANEL ON SOLAR AND HELIOSPHERIC PHYSICS
309
• Hard X-ray imaging spectroscopy, full-disk, 64-150 keV;
• Solar and interplanetary energetic particles, 0.05- to 100-MeV/nuc, and electrons;
• Solar wind ion composition and electrons; and
• Magnetometer.
Two science phases are envisioned: drift to L5 at about 38° per year with continuous collection of
science data and orbit around L5, 45°-90° from the Sun-Earth line. A long extended mission is possible.
Goddard Space Flight Center has studied a similar concept called Earth-Affecting Solar Causes Observatory 17 (EASCO), featuring about a 2-year low-thrust trajectory to L5 and using solar-electric propulsion,
saving more than 200 kg compared with hydrazine.
In summary, the L5 mission concept promises important breakthroughs in both helioseismology and
space weather (motivation M2). It would make major advances toward SHP panel science goals 1 and 3,
including, in particular, actions 1b and 3d. The panel encourages NASA, NOAA, and the Department of
Defense (DOD) to carry out an interagency study of an L5 mission (see §10.5.5.7).
10.5.2.6 Solar Polar Imager Mission
Current understanding of the Sun, its atmosphere, and the heliosphere is severely limited by a lack
of good observations of the Sun’s polar regions. The Solar Polar Imager (SPI) mission concept, 18 a NASA
vision mission with strong international interest, would go into a 0.48-AU circular orbit with 60° inclination
to conduct extended (many days per orbit) observations of the polar regions, enabling the determination
of polar flows down to the tachocline, where the solar dynamo is thought to originate. The rapid 4-month
orbit, combined with in situ and remote-sensing instrumentation, will enable unprecedented studies of the
physical connections between the Sun, the solar wind, and SEPs.
Instrumentation could include a Doppler magnetograph, white-light coronagraph, EUV imager, UV
spectrograph, TSI monitor, energetic-particle spectrometer, solar wind composition spectrometer, and magnetometer and could provide studies of the polar magnetic field over the solar cycle, the three-dimensional
global structure of the corona, and solar wind, energetic-particle, and TSI variations with latitude. Most
important, SPI would measure the temporal evolution of time-varying flows, differential rotation, and
polar-region meridional circulation down to the tachocline, addressing SHP science goal 1. Finally, SPI
would explore how space weather forecasts can benefit from a polar perspective (SHP science goal 3 and
motivation M2).
Solar-sail propulsion is proposed to place SPI into its orbit. Recent advances demonstrate that solar
sails are technically feasible and effective for maneuvering in the heliosphere. A technology-readiness
plan is outlined in Section 10.5.2.8. The SHP panel strongly encourages NASA to develop the propulsion
technology needed to launch SPI during the 2023-2033 decade.
10.5.2.7 Interstellar Probe Mission Concept
Recent in situ measurements by the Voyagers, combined with all-sky heliospheric images from IBEX
and Cassini, have made outer-heliospheric science one of the most exciting and fastest-developing fields
of heliophysics. The measurements have transformed knowledge of the boundaries of the heliosphere. The
17 N. Gopalswamy et al., Earth-Affecting Solar Causes Observatory (EASCO): A New View from Sun-Earth L5, white paper submitted
to the Decadal Strategy for Solar and Space Physics (Heliophysics), Paper 99.
18 P. Liewer et al., Solar Polar Imager: Observing Solar Activity from a New Perspective, white paper submitted to the Decadal
Strategy for Solar and Space Physics (Heliophysics), Paper 156.