Heliophysics Community Support for Continued Measurements by NASA’s New Horizons Mission
The Issue
TO: Dr Nicola Fox, Associate Administrator, SMD
Dr Joseph Westlake, Director, Heliophysics Division
Dr Louise Prockter, Director, Planetary Science Division
It is our understanding that continued New Horizons heliophysics measurements are threatened unless NASA finds a way for the Heliophysics Division to fund the data collection and downlink. The Heliophysics Decadal states “New Horizons will fill a major gap in the understanding of the plasma physics of the outer heliosphere …” (Priority Science Goal 4).
Therefore, we the undersigned science community, are expressing the critical need for continued heliophysics measurements by the New Horizons mission and respectfully ask NASA to ensure future data collection and downlink of all the mission’s data.
Projected to operate until 2050 (~135 au), New Horizons is currently observing the radial evolution of the solar wind, Pick-Up Ions (PUIs), propagating solar disturbances, energetic particles, Galactic Cosmic Rays (GCRs) and dust throughout the entire heliosphere. In particular, the SWAP and PEPSSI instruments are making historically unique measurements of H+ and He+ interstellar PUIs that the Voyager Mission was not equipped to do. Owing to New Horizons, we now know that PUIs control the behavior of the solar wind past 10 astronomical units. These PUIs dominate the thermodynamics at the heliospheric boundary that shields the inner heliosphere from Galactic Cosmic Rays (GCRs), one of the most severe threats to long-term human presence in space.
Understanding GCR shielding mechanisms is not yet possible due to the complete lack of PUI measurements in the heliosheath that are needed to derive energy diffusion coefficients for PUI-driven turbulent processes. Soon (2027 - mid 2030’s), New Horizons is estimated to encounter and cross the heliospheric Termination Shock (TS), where its new measurements will be crucial to uncover the physics at this important boundary. This will be a historical milestone for NASA and the Heliophysics Division.
As the only spacecraft now in the outer heliosphere, New Horizons is therefore an essential element of the Heliophysics System Observatory. In particular, New Horizons will make in-situ measurements of the PUI source population that the Interstellar Mapping and Acceleration Probe (IMAP) observes remotely as energetic neutral atoms. This New Horizons-IMAP partnership provides a unique opportunity that will never again arise and must be fully exploited.
In summary, the heliophysics measurements by SWAP and PEPSSI onboard New Horizons are unique and must continue uninterrupted. These measurements will enable dramatic progress in understanding the boundary of our habitable astrosphere with the concurrent remote imaging by IMAP. If these measurements were to cease, as currently planned, without the Heliophysics Division funding in FY27 and beyond it would signal that NASA cedes the farthest frontier of space exploration.
Sincerely,
Name:
Affiliation:
283
The Issue
TO: Dr Nicola Fox, Associate Administrator, SMD
Dr Joseph Westlake, Director, Heliophysics Division
Dr Louise Prockter, Director, Planetary Science Division
It is our understanding that continued New Horizons heliophysics measurements are threatened unless NASA finds a way for the Heliophysics Division to fund the data collection and downlink. The Heliophysics Decadal states “New Horizons will fill a major gap in the understanding of the plasma physics of the outer heliosphere …” (Priority Science Goal 4).
Therefore, we the undersigned science community, are expressing the critical need for continued heliophysics measurements by the New Horizons mission and respectfully ask NASA to ensure future data collection and downlink of all the mission’s data.
Projected to operate until 2050 (~135 au), New Horizons is currently observing the radial evolution of the solar wind, Pick-Up Ions (PUIs), propagating solar disturbances, energetic particles, Galactic Cosmic Rays (GCRs) and dust throughout the entire heliosphere. In particular, the SWAP and PEPSSI instruments are making historically unique measurements of H+ and He+ interstellar PUIs that the Voyager Mission was not equipped to do. Owing to New Horizons, we now know that PUIs control the behavior of the solar wind past 10 astronomical units. These PUIs dominate the thermodynamics at the heliospheric boundary that shields the inner heliosphere from Galactic Cosmic Rays (GCRs), one of the most severe threats to long-term human presence in space.
Understanding GCR shielding mechanisms is not yet possible due to the complete lack of PUI measurements in the heliosheath that are needed to derive energy diffusion coefficients for PUI-driven turbulent processes. Soon (2027 - mid 2030’s), New Horizons is estimated to encounter and cross the heliospheric Termination Shock (TS), where its new measurements will be crucial to uncover the physics at this important boundary. This will be a historical milestone for NASA and the Heliophysics Division.
As the only spacecraft now in the outer heliosphere, New Horizons is therefore an essential element of the Heliophysics System Observatory. In particular, New Horizons will make in-situ measurements of the PUI source population that the Interstellar Mapping and Acceleration Probe (IMAP) observes remotely as energetic neutral atoms. This New Horizons-IMAP partnership provides a unique opportunity that will never again arise and must be fully exploited.
In summary, the heliophysics measurements by SWAP and PEPSSI onboard New Horizons are unique and must continue uninterrupted. These measurements will enable dramatic progress in understanding the boundary of our habitable astrosphere with the concurrent remote imaging by IMAP. If these measurements were to cease, as currently planned, without the Heliophysics Division funding in FY27 and beyond it would signal that NASA cedes the farthest frontier of space exploration.
Sincerely,
Name:
Affiliation:
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Petition created on 27 July 2026