Until recently, scientists could only speculate about the materials that make up the surface of Pluto, located more than 3 billion miles from Earth.
It is now known that Pluto has a wide variety of terrain of different ages and colors, and consists of water, methane, nitrogen and carbon monoxide ices—thanks in large part to a sophisticated device conceived by Dennis Reuter and Donald Jennings, and developed by Reuter and his team at NASA’s Goddard Space Flight Center in Maryland.
“Dennis and his team spent decades developing this instrument that has changed our view of the outer solar system and its components,” said Lucy-Ann McFadden, a physical scientist at Goddard.
The New Horizons spacecraft carried the instrument, an imaging spectrometer named LEISA, as it flew past Pluto in July 2015. The instrument looked at infrared wavelengths of light to study the different materials on the surface. It was part of a larger system that took spectacular images of the dwarf planet. The resulting data allowed scientists to make detailed maps of Pluto’s surface for the first time, and it will shape the fields of astronomy and astrophysics for years to come.
“We basically had these blurry pictures of Pluto. It is so far away and we had no information on the details of the geology,” said Paul Mahaffy, director of NASA’s Solar System Exploration Division. “The data is telling us what Pluto is like. It is opening our eyes to a place in the solar system that took decades to reach.”
As an astrophysicist, Reuter not only has “great scientific vision, he also is an effective leader,” said McFadden. “He figures out what skills he needs and pulls together an outstanding team.”
In the space business, it’s not enough to know the science, said Keith Noll, chief of NASA’s Planetary Systems Laboratory. “You’ve got to know how to work with engineers, budget people and project people to get things done. It’s a real art, and Dennis is terrific at it.”
Reuter and team, with help from industrial partners and the support of Alan Stern, the New Horizons Mission principal investigator from Southwest Research Institute, worked for nearly 15 years to design and build the instrument and then had to wait another nine years for it to reach Pluto to see if it worked.
Getting to Pluto, which is more than 30 times farther from the sun than Earth, is a major challenge, said Lori Glaze, deputy director of NASA’s Solar System Exploration Division.
“When we send things out into space, they have to survive for a long time in a very cold environment and withstand exposure to radiation. It’s difficult to build an instrument that will last that long and still work when it gets there,” Glaze said.
“Dennis did a fabulous job” building such an instrument, Glaze said. “He is THE lead person on how to design and build it (an infrared spectrometer) so it can do that particular science.”
Until last year, knowledge of Pluto was scant. “To think there would be more than just a dirty ice ball was an incredible thought,” said Chris Scolese, the center director of Goddard. “Dennis wasn’t the only one to think that, but he came up with the concept for the instrument that could measure properties they thought were there. And he convinced others it could be done.”
As a result, Scolese added, LEISA and the other instruments on the New Horizons spacecraft “have told us about a totally different planet than anyone expected.”
NASA Administrator Charles Bolden said the continuing treasure trove of data will keep analysts busy for years. “I look at the impact it will have on the next generation of scholars,” he said.
The challenge was daunting: design and build an instrument that doesn’t weigh a lot and doesn’t use much power but can operate flawlessly in the severe conditions of outer space, where the temperature is minus 455 degrees Fahrenheit and the amount of light available to cameras is 1,000 times less than that on Earth.
The instrument had to be extremely sensitive to pick up light far from the sun and needed adequate resolution to separate out different compounds. Reuter’s design accomplished that, revealing the surprisingly complex distribution of water, methane, nitrogen, and carbon monoxide ices on Pluto’s surface.
The LEISA array was part of an instrument called RALPH, which weighed less than 23 pounds and consumed only 6.3 watts of power. Importantly, LEISA had no moving parts that could break down.
“Having no moving parts was an incredible innovation,” said Glaze. “An elegant design.”
Reuter and team wanted to explore where no one had before. “Pluto was just sitting out there, still unexplored,” he said. As an astrophysicist “this is exactly what you want to do: find out what things are made of, and how we came about.”
Growing up in the era of the Mercury space flights, “I thought it would be really cool to be an astronaut,” Reuter said. “But having these instruments go into space . . . it’s beyond cool.”