Spaceflight Insider

New Horizons to remain a planetary mission through decade’s end

NASA’s New Horizons mission spacecraft. Credit: NASA

NASA’s New Horizons mission spacecraft. Credit: NASA

NASA’s New Horizons mission, which flew by Pluto in 2015 and Kuiper Belt Object (KBO) Arrokoth in 2019, will remain funded as a planetary mission through the end of the decade, according to a recent announcement by the agency’s Science Mission Directorate.

The decision reverses an April announcement that proposed transferring the spacecraft solely to heliophysics starting in fiscal year 2025, a move that would have taken the mission away from the team that has run it since its 2006 launch.

Many planetary scientists argued the initial decision made little sense as New Horizons will be traversing the Kuiper Belt through 2028 or 2029 and is the only spacecraft there for the foreseeable future. Approximately 25 planetary and space scientists sent a formal letter to NASA in June objecting to the decision.

Among the signatories were Jim Bell, former chair of the Planetary Society board; astrophysicist and Queen lead guitarist Brian May, and author Homer Hickham.

More than 7,000 people signed a petition organized in August by the National Space Society asking NASA to maintain New Horizons as a planetary mission until it exits the Kuiper Belt.

“All of us on New Horizons are happy that NASA has decided to continue its exploration of the Kuiper Belt,” said mission principal investigator Alan Stern.

Mission scientists hope to find yet another KBO for the spacecraft to fly by while it is in this region though this is far from certain.

Even if another target is not found, “We’re studying new, more distant KBOs from angles and closer ranges that you can’t get from Earth to determine their surface properties, their satellite counts and shapes, things that cannot be done well except by a spacecraft in the Kuiper Belt,” Stern said. The spacecraft is healthy and has sufficient fuel to function into the mid-2050s, he added.

Within days of NASA’s latest announcement, a separate team of scientists announced they may have discovered 12 massive KBOs around 60 astronomical units (AU, with one AU equal to the average Earth-Sun distance of 93 million miles) from the Sun. The Kuiper Belt has been thought to extend to 50 AU. If confirmed, these objects, which could be massive enough to qualify as dwarf planets, could indicate the presence of a second Kuiper Belt in the distant outer solar system or simply that the Kuiper Belt is larger than previously thought.

New Horizons is currently 57 AU from the Sun. Stern said the spacecraft continues to detect dust that could indicate collisions of objects further out.

“The number of impacts is not declining. And the simplest explanation for that is that there is more stuff out there that we haven’t detected,” Stern said.


Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.

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