– New Horizons is a long, long, long way home.
Fifteen years after launching from Earth at record speeds and six years since it became the world’s first spacecraft to fly from Pluto, New Horizons is on track to reach a mile mark that only four other robotic probes in history have surpassed.
On Saturday (April 17) at 20:42 EDT (1242 GMT, April 18), New Horizons will reach 50 AU (astronomical units) from the sun – or 50 times the distance of the Earth from the sun. That’s 4.65 billion miles (7.5 billion kilometers). At 50 AU, it takes more than 6.5 hours for the signals sent by New Horizons to reach Earth, while traveling at the speed of light.
New Horizons is the fifth most distant spacecraft on Earth.
Pioneer 10, which was launched in 1972 and was the first probe to pass through the asteroid belt and fly from Jupiter, reached 50 AU on September 22, 1990. Today it is about 129 AU from Earth.
Its sister ship, Pioneer 11, reached 50 AU a year later in 1991. It was launched in 1973 and, in addition to flying from Jupiter, was the first to make direct observations of Saturn. It is now about 105 AU from Earth.
NASA launched Voyager 1 on September 5, 1977, 16 days after its twin, Voyager 2. Voyager 1 studied Jupiter and Saturn, while Voyager 2 also collided with Uranus and Neptune. Voyager 1 today is 152 AU from Earth. Voyager 2 is at 127 AU. While the Pioneer 10 and Pioneer 11 stopped working years ago, both Voyager remain active today.
Today, pioneers and travelers are so far away that none of them is the closest probe to New Horizons. At this point, NASA’s Juno spacecraft, orbiting Jupiter, is closer.
“In the very distant future, we will be so far away from everyone else that we will be closer to the Voyagers and the Pioneers, but we will never miss them because three of the four are going faster than us,” Stern said. “We are currently at almost 100 AU from Voyager 1.”
To highlight how far Voyager 1 has traveled, NASA directed the probe’s camera back to the inner solar system in 1990, when it was about 40.11 AU from Earth. The resulting mosaic image, now known as the Family Portrait, captured six planets – Venus, Earth, Jupiter, Saturn, Neptune and Uranus – as only a few pixels of light each.
At 50 AU from the sun, the New Horizons couldn’t do the same.
“Mathematics tells us that this would burn our camera because we would be focused on the sun,” Stern said, noting that even at such a great distance, the sun remains too bright for its long-range reconnaissance device, which is calibrated for low light. meeting with Pluto. “So we don’t want to do that until we cross the Kuiper belt years later.”
Instead, Stern and his team directed New Horizons to Voyager 1, noting for the first time a spacecraft in the Kuiper Belt captured the location of an even more distant spacecraft that now travels through interstellar space.
“Of course, we didn’t see Voyager 1 because it’s too weak, but we did paint the star field,” Stern told collectSPACE. “We looked with the camera at the farthest spacecraft and took a picture of this star field from our position in the Kuiper belt. For me, it’s just terribly beautiful, even though it’s just a picture of stars.”
“This is a tribute to Voyager’s pioneering mission, in addition to celebrating what we do,” he said.
More than just a round stage, reaching 50 AU means that everything New Horizons is doing now exceeds the planned lifespan of the project.
“One of the first things you do when designing a spaceship is set requirements, and one thing we had to set was the maximum distance we designed the spacecraft to run,” Stern said. “Now you’re always building the fields so you can do better, but we had to have a number, so if we cross that goal line, we can declare victory – that the spacecraft has fulfilled its design goals.”
“That goal line was 50 AU,” Stern said.
New Horizons flew from Pluto, taking a closer look at the world and its moons in July 2015, when the spacecraft was 39.2 AU from the sun. Four years later on New Year’s Eve 2019, New Horizons made the most distant flight in history (to date), capturing the first close-up observations of an object from the Kuiper Belt (“Arrokoth”) at a distance of 43.4 AU from the sun.
“We’re still getting data from this flight,” Stern said. “Meanwhile, as we fly through the Kuiper Belt, we do three other things: we study the heliosphere, plasma, dust and gas; we study other objects in the Kuiper Belt, we know that there are more than 30 that we have observed in ways that are not you can from Earth or any other spacecraft, and we use the Hawaii Subaru Telescope, one of the largest telescopes in the world, to find new Kuiper Belt objects to explore and hopefully to find a flight because we still have fuel in the tank and we are able to make another flight. “
The hope is to find another target before New Horizons runs out of power. Although it draws its electricity from a nuclear battery (radioisotope thermoelectric generator or RTG), its plutonium supply generates 33 watts less each decade. By the end of the 2030s, when New Horizons will be at or near 100 AU from the sun, it may be too weak to operate.
Even if New Horizons doesn’t reach 100 AU, Stern is impressed with how far the mission has come, and even more with how far his team has come.
“When the Voyagers were flying, their team was 450 people. New Horizons did this with about 50 buttons, which is about 10 times less,” he said.
“When you think about what our team has accomplished in those 15 years with a spaceship and without a backup, going there for the first time to explore Pluto for the first time, the Kuiper belt for the first time and now passing the 50 AU marker, where it’s designed to be its maximum distance, it just sounds like science fiction to me, “Stern said. “I have to press that this group of people have actually managed to do this thing that is much bigger than life.”