Juno spacecraft breaks solar power distance record

Launched from Earth in 2011, the Juno spacecraft will arrive at Jupiter in 2016 to study the gas giant from an elliptical, polar orbit. Juno will repeatedly dive between the planet and its intense belts of charged particle radiation, coming only 5,000 kilometers (about 3,000 miles) from the cloud tops at closest approach. (Click to enlarge.) Image Credit: NASA/JPL-Caltech

NASA’s Juno mission has broken the record for distance traveled by a solar-powered spacecraft. Juno reached this milestone at 11 a.m. PST (2 p.m. EST/ 19:00 GMT) on Wednesday, Jan. 13, 2016, when the spacecraft was approximately 493 million miles (793 million kilometers) from the Sun.

The record was previously held by the European Space Agency’s (ESA) Rosetta spacecraft, whose orbit peaked at the 492 million-mile (792-million kilometer) mark in October 2012, during its approach to comet 67P/Churyumov-Gerasimenko.

Juno should arrive at its destination later this year. Image Credit: NASA

“Juno is all about pushing the edge of technology to help us learn about our origins,” said Scott Bolton, Juno principal investigator at the Southwest Research Institute in San Antonio. “We use every known technique to see through Jupiter’s clouds and reveal the secrets Jupiter holds of our Solar System’s early history. It just seems right that the Sun is helping us learn about the origin of Jupiter and the other planets that orbit it.”

Juno is the first solar-powered spacecraft designed to operate so far from the Sun. Generating sufficient power to operate the spacecraft requires a very large area of solar cells. The four-ton Juno spacecraft carries three 30-foot (9-meter) solar arrays festooned with 18,686 individual solar cells. At Earth’s distance from the Sun, the cells can generate about 14 kilowatts of electric. The further away from the Sun the spacecraft is, the lower the power its solar cells will be able to generate.

“Jupiter is five times farther from the Sun than Earth, and the sunlight that reaches that far out packs 25 times less punch,” said Rick Nybakken, Juno‘s project manager from NASA’s Jet Propulsion Laboratory. “While our massive solar arrays will be generating only 500 watts when we are at Jupiter, Juno is very efficiently designed, and it will be more than enough to get the job done.”

All eight previous spacecraft that operated as far out in the Solar System as Jupiter have used nuclear power. Solar power is possible on the Juno mission because of improved solar-cell performance, energy-efficient scientific instruments and spacecraft systems, a mission design that avoids Jupiter’s shadow and a polar orbit that minimizes total radiation. Juno‘s maximum distance from the Sun during its 16-month long scientific mission at Jupiter will be approximately 517 million miles (832 million kilometers), a nearly 5 percent increase in the record for solar-powered spacecraft.

“It is cool we got the record and that our dedicated team of engineers and scientists can chalk up another first in space exploration,” said Bolton. “But the best is yet to come. We are achieving these records and venturing so far out for a reason – to better understand the biggest world in our Solar System and thereby better understand where we came from.”

Juno was launched atop an Atlas V rocket from Space Launch Complex 41 at Cape Canaveral Air Force Station in Florida on August 5, 2011.  The spacecraft will arrive at Jupiter on July 4. Over the next year, Juno will orbit Jupiter 33 times, skimming to within 3,100 miles (5,000 kilometers) of the planet’s cloud tops every 14 days. During its mission, Juno will probe beneath the cloud cover of Jupiter and study Jupiter’s aurorae to learn more about the planet’s origins, structure, atmosphere, and magnetosphere.

Technicians stow for launch a solar array on NASA’s Juno spacecraft. Each of Juno‘s three solar arrays is 9 feet (2.7 meters wide), by 29 feet (8.9 meters long). Photo Credit: NASA/JPL-Caltech/KSC

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Jim Sharkey

Jim Sharkey is a lab assistant, writer and general science enthusiast who grew up in Enid, Oklahoma, the hometown of Skylab and Shuttle astronaut Owen K. Garriott. As a young Star Trek fan he participated in the letter-writing campaign which resulted in the space shuttle prototype being named Enterprise. While his academic studies have ranged from psychology and archaeology to biology, he has never lost his passion for space exploration. Jim began blogging about science, science fiction and futurism in 2004. Jim resides in the San Francisco Bay area and has attended NASA Socials for the Mars Science Laboratory Curiosity rover landing and the NASA LADEE lunar orbiter launch.