New Horizons is now nearly twice the distance from Pluto, the exoplanets are rapidly receding, and interstellar space is illuminated by the vast expanse of the Milky Way ahead. But spacecraft research is not over yet. Its instruments are all working and responsive, and the New Horizons team has been working hard to advance the spacecraft’s capabilities for new missions.
Since its launch in January 2006, the New Horizons spacecraft has traveled more than 5 billion miles, passed Jupiter’s moons, and surveyed the frozen methane ice on its target planet, Pluto. In January 2019, it flew around the planet Arrokoth, which lies another billion miles from Pluto and is the farthest object ever visited by a spacecraft. The data they brought back from these intact remnants of our solar system’s formation has given us important new insights into how this process occurred.
But New Horizons’ mission is far from over. Although there may never be another close encounter with an orbiting object, the team managing the spacecraft is working on ways to put its instruments to new uses.
Budgets and energy budgets
As New Horizons approaches the Sun, piloting the spacecraft requires not only patience, but also refined focus. Led by Alice Bowman – the mission’s version of Star Trek’s Scotty – engineers start building a command load three months in advance, then run it on a simulator in the Applied Physics Laboratory to make sure it’s sound. Transmitting commands currently takes eight hours to reach the vehicle from Earth and requires reserving a spot on NASA’s Deep Space Network, three massive radio dishes located in California, Australia and Spain, which handle communications on multiple space missions. So, like getting a table at a popular restaurant, reservations are required months in advance unless there is an emergency.
New Horizons spins as it races through space, and while some instruments (such as particle detectors) work best in spin mode, to use its imagers, the craft must be detached and steered using precious fuel. The power comes from a radioisotope thermoelectric generator, essentially a nuclear battery made of plutonium-238, which has a half-life of 87.7 years. It is currently unknown how long this force will last.
The two Voyager spacecraft, which left the solar system before New Horizons, are still operational but had to turn off some instruments, including their onboard cameras, which were “energy hogs”, so they now only operate a few instruments Using low power demand, then send the data back. As with Voyagers, New Horizons’ most power-hungry instruments (e.g., imagers) that need heaters to keep them at operating temperatures will likely be shut down first. It’s hard to predict when that will happen, because the RTG’s lifespan is constantly being extended by the engineering team, which keeps inventing ever more ingenious modifications to gain power.
The mission also needs to continue paying these engineers. Fortunately, NASA recently announced that funding for New Horizons will continue until at least 2028 or 2029.
A new vision for KBOs
One of the spacecraft’s missions is to continue exploring the Kuiper Belt, which extends from Neptune’s orbit at 30 AU to beyond 50 AU from the Sun. It consists of pieces of rock, ice, comets and dust. Since the largest Kuiper Belt Object (KBO) left Pluto behind, the geology team has used the spacecraft’s designed capabilities to study other KBOs, so far finding more than 100 new objects and passing nearly 20 KBOs close enough to reveal their properties. Surface, shapes and objects. Rotation periods, and moons in close orbits.
The Kuiper Belt holds the key to a big mystery. Why did all the planets pile up from clouds of interstellar dust and gas instead of colliding with each other in mutual annihilation? Asteroids are hit so hard and reshaped by multiple collisions that they no longer retain traces of their formation. So, when the geology team learned that the spacecraft would fly by a large Kuiper Belt object, they were very excited.
Sweeping past Bilateral communication Arrokoth Only 3,500 kilometers (2,198 miles) away in 2019, the images returned by New Horizons looked to the untrained eye to resemble an unspectacular, lumpy potato. But its single location in the outer Kuiper Belt has kept Arrokoth intact, essentially a fossil from the early days of the solar system’s formation. Detailed data modeling obtained by New Horizons for this 36 km (22 mi) long, 20 km (13 mi) wide object shows that the larger side was assembled from 8 to 10 smaller components, all of which had to move together. Very slowly until it “docks” successfully. “If they had come together faster, their outlines would have been affected by the collision,” said Will Grundy, head of the mission’s planetary geology team at Lowell Observatory, where Pluto was discovered in 1930.
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