Space and Physics
PUBLISHED
A NASA spacecraft nearing the edge of the Solar System may have two of its instruments shut down next month due to a lack of funding. If that happens, it would come not long before the spacecraft reached a particularly interesting part of space, where it was to study one of the most severe threats to humans in space.
Back in 2006, US space agency NASA launched New Horizons on a journey to study dwarf planet Pluto, over 5 billion kilometers (3.1 billion miles) from Earth. The spacecraft first headed to Jupiter for a gravity assist, imaging Jupiter's moons Io, Europa, and Ganymede, before hurtling towards everyone's favorite not-planet at a new speed of around 300 million miles per year. Arriving in 2015, the spacecraft provided our best and closest view of Pluto.
"Data from New Horizons clearly indicated that Pluto and its satellites were far more complex than imagined, and scientists were particularly surprised by the degree of current activity on Pluto’s surface," NASA explains of the mission.
"The atmospheric haze and lower than predicted atmospheric escape rate forced scientists to fundamentally revise earlier models of the system."
After seeing Pluto, New Horizons continued its tour of the Solar System, this time being redirected to Arrokoth, a two-lobed object in the Kuiper Belt, far beyond the orbit of Neptune. As with many other NASA spacecraft, it still wasn't done with its work, and in 2023 the space agency announced it was extending the spacecraft's mission, with a new focus on collecting data on the heliosphere, the massive bubble that surrounds the Sun and Solar System.
"The New Horizons mission has a unique position in our Solar System to answer important questions about our heliosphere and provide extraordinary opportunities for multidisciplinary science for NASA and the scientific community,” Nicola Fox, associate administrator for NASA’s Science Mission Directorate in Washington, said in a statement at the time.
“The agency decided that it was best to extend operations for New Horizons until the spacecraft exits the Kuiper Belt, which is expected in 2028 through 2029."
We have two years to go, so why are we talking about instrument shutdowns?
Data on our solar wind has been collected by two key instruments on board: the Pluto Energetic Particle Spectrometer Science Investigation (known by the distressing acronym PEPSSI), and Solar Wind Around Pluto (SWAP).
While the instruments continue to collect and transmit data, unaffected by budget constraints, back on Earth, NASA has withheld $2 million in funding for the last two years, which was used to pay the scientists and researchers who download and analyze the data on the ground.
Without that funding, New Horizons’ principal investigator Alan Stern told Science that there was no choice but to shut the instruments down. This would be senseless at the best of times, but is particularly galling when New Horizons is about to reach an interesting part of the Solar System, equipped with instruments that Voyager 1 and 2 did not have on their own journey away from the Sun.
"In particular, the SWAP and PEPSSI instruments are making historically unique measurements of H+ and He+ interstellar PUIs [Pick-Up Ions] that the Voyager Mission was not equipped to do," a petition from former NASA Chief Scientist James L. Green explains.
"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."
The spacecraft is due to cross the heliospheric "termination shock" sometime from 2027 to the mid-2030s. This is the area of the Solar System where the solar wind begins to interact with the local interstellar medium, slowing it down.
Though Voyager 1 and 2 have both made it further out into the Solar System, they did so in a different direction, and without New Horizons' instruments. While the spacecraft is thought to be healthy and fully functional, with a lifespan which could take it into the 2050s, funding on Earth will need to be sorted if we want to study the termination shock and beyond.
It isn't looking good, with the instruments due to go offline next month, but it isn't necessarily a done deal either.
"We have heard from a few members of the community on this and indicated we are looking into it. The big dollars were already invested in New Horizons, so generally supportive of generating high-quality scientific returns for low-dollar spend," NASA Administrator Jared Isaacman wrote on X on Tuesday.
"This mission aside, at NASA, we do spend a large portion of the SMD budget maintaining missions well beyond their initial design life and scientific returns do diminish. If we can consolidate, ensure continuity of the science, and free up more resources for new breakthrough missions, like whatever comes after Dragonfly, we should, and I suspect we will."
