First spacecraft to visit Pluto carries software and equipment developed at Stanford

Artist’s depiction shows the New Horizons spacecraft passing Pluto and its largest moon, Charon. Stanford’s contribution, the REX instrument, utilizes the spacecraft’s large antenna. (Image credit: NASA illustration)

An instrument designed by Stanford researchers is on board NASA’s New Horizons spacecraft, scheduled to soar past Pluto and its five moons on July 14.

The Stanford instrument, designed to measure Pluto’s atmosphere and surface, will deliver much-needed data to the Stanford researchers who have been waiting decades to thaw some of the frozen world’s most enduring mysteries.

“It’s this tiny rock on the edge of our solar system,” said Stanford senior scientist and astronomer Ivan Linscott. “But it still has the ability to capture the public’s imagination.”

Once considered a planet, astronomers now recognize Pluto as one of probably dozens of Pluto-size “dwarf planets” that have some – ­but not all – of the characteristics of the larger and more massive eight planets like Earth and Jupiter. Planetary scientists are eager to learn more about Pluto to understand how this diminutive world evolved in the solar system and if it is similar to other icy objects far from the Sun.

To that end, as it speeds by at 30,000 miles per hour, New Horizons will use its seven instruments to drink up information about Pluto’s composition, surface features, atmosphere and moons.

“Even though it’s just this one moment, there’s a richness there that will bring this wealth of information,” Linscott said. “It’s like Disneyland, but you’re getting one ride.”

The New Horizons instrument that Stanford scientists helped design is REX (radio science experiment), which was developed under the direction of Len Tyler, a Stanford electrical engineering professor and New Horizons principal investigator before his retirement.

Since then, Linscott has assumed some of Tyler’s roles with the New Horizons mission and is part of the team managing the spacecraft’s final approach toward Pluto. Tyler and Linscott developed REX in a partnership between Stanford and Johns Hopkins University’s Applied Physics Laboratory.

“It is definitely Stanford’s biggest contribution to New Horizons,” said Stanford electrical engineering graduate student William Woods, who has studied preliminary data from New Horizons as part of his dissertation research.

REX will use radio transmissions from Earth to gather information about Pluto. As New Horizons passes behind Pluto on July 14, Earth-based stations will beam radio waves toward the fast-moving spacecraft. Particles in Pluto’s atmosphere will modify the radio waves. REX will allow New Horizons to detect and record these changes and transmit the data back to Earth. Linscott and other members of the REX instrument team can use this information to learn about the temperature, pressure and composition of Pluto’s atmosphere and surface conditions.

“It takes an entire year before that dataset will be downloaded,” Linscott said. “We’ll be getting it back in stages.”

Tyler, Linscott and a small army of Stanford scientists and graduate students spent years perfecting REX and its operating software before New Horizons launched in 2006. For example, one graduate student, Kamakshi Sivaramakrishnan, came up with the software code that tells REX how to keep track of complex radio wave data and help New Horizons store and transmit this information with a minimum of data corruption.

“There was simply no easy way to do that,” Linscott said. “But she took it on with a great deal of commitment and dedication and found a way to do it.”

This large and important role for REX belies its diminutive size. The two circuit boards that make up REX are by far the smallest of the seven scientific instruments on board the 1,000-pound spacecraft. Each weighing in at 3.5 ounces, the circuit boards are integrated into the spacecraft’s communications systems and make use of New Horizons’ nearly 7–foot-wide antenna dish.

During New Horizons’ nearly 10-year journey to the outer solar system, scientists have been testing the spacecraft’s instruments – including REX – to make sure they are ready for the encounter.

“So far, it has worked flawlessly,” Linscott said.

The New Horizons spacecraft’s glimpse of Pluto will help scientists understand its origins and how conditions on the dwarf planet change during its nearly 250-year orbit. Unlike the eight planets, Pluto makes an erratic journey around the Sun, approaching closer than Neptune before shooting 2 billion miles out toward the solar system’s edge. This skewed pathway may subject Pluto to extremes in temperature. Some scientists even believe its atmosphere might freeze and “collapse” onto the surface as it travels far from the sun, Linscott said. Pluto made its most recent close approach to the Sun in 1989, and NASA launched New Horizons in 2006 to capture this glimpse of Pluto before it got too far out in its current quarter-millennial circuit.

After New Horizons passes by Pluto, mission scientists plan to propose an extended mission for the spacecraft to travel to the Kuiper Belt. This region, far beyond Pluto, contains numerous small icy objects that New Horizons could study to gather new information about the solar system’s origins and evolution. If NASA approves such an extended mission, the REX instrument may be called upon again to gather basic information about distant celestial bodies.

James Urton is an intern with Stanford News Service