NASA’s Juno spacecraft inserted into orbit above Jupiter
PASADENA, Calif. — NASA’s Juno spacecraft completed the final step of its nearly five-year voyage to Jupiter, successfully entering orbit around the giant planet on Monday, July 4. Jupiter Orbit Insertion (JOI) was achieved following a 35-minute burn that began at 8:18 p.m. PDT (11:18 p.m. EDT / 03:18 GMT on July 5).
The spacecraft traveled nearly 1.8 billion miles (2.8 billion kilometers) during its long, looping journey which included a flyby of Earth on October 9, 2013, to gain a gravity-assisted 70 percent boost in speed. As Juno approached Jupiter over its north pole, the spacecraft was accelerated to a velocity of 130,000 miles per hour (209,215 kilometers per hour) by the planet’s massive gravity well, making it one of the fastest objects in the Solar System.
Monday’s activities began with a 9:00 a.m. PDT (12:00 p.m. EDT) mission briefing at NASA’s Jet Propulsion Laboratory located near Pasadena, California. By this time, Juno had already crossed the orbits of the two outermost Galilean moons – Callisto and Ganymede.
“What a wonderful day to celebrate! You know, this is a milestone for our country, but it’s a wonderful day for planetary science,” said Jim Green, Director, Planetary Science Division NASA Headquarters. “We’ve had a number of probes fly by Jupiter; Galileo was our last probe to go [to] Jupiter, [which] orbited it for several years. It studied Jupiter, but only surface deep and looked [at] all the moons. And now with Juno, we have a chance to go back and study the planet in its own right.”
His excitement about now having the opportunity to explore the largest planet in Solar System in even greater detail was echoed by other team members.
“As planned, we are deep in the gravity well of Jupiter and accelerating,” said Rick Nybakken, Juno project manager from NASA’s Jet Propulsion Laboratory in Pasadena, California. “Even after we begin firing our rocket motor, Jupiter will continue to pull us, making us go faster and faster until we reach the time of closest approach. The trick is, by the end of our burn, we will slow down just enough to get into the orbit we want.”
Nybakken told SpaceFlight Insider that two days ago Juno was moving at 9.8 km/s, yesterday it was going 12.1 km/s, and today it’s going 50+ km/s during the start of the engine burn. The trajectory put Juno “ahead of Jupiter; Jupiter was coming up behind us. And it’s actually going to stop all of our forward progress and pull us backwards around it as it’s coming up […] then loop us around, and if we don’t slow down just a little bit, we need to slow down 0.4 km/s” then Jupiter would slingshot Juno adding 10 km/s to its velocity. Rick added that “[t]he absolute speeds are incredible”.
“Standing on the shoulders of giants, we build on the same techniques for missions like Voyager, which are still operating,” Nybakken told SpaceFlight Insider. “We take the additional challenges we have to face to operate at Jupiter, and we apply a whole different set of design and test techniques for parts, materials, coatings, filters, cable wraps, micrometeoroid protection, all sorts of things that we need to worry about at Jupiter.”
Following the briefing, Juno crossed the orbit of Europa at 10:30 a.m. PDT (1:30 p.m. EDT) and Io at 2:15 p.m. PDT (5:15 p.m. EDT). Jupiter’s four largest moons are called the Galilean moons because they were discovered in 1609 by Galileo Galilei. By 4:17 p.m. PDT (7:17 p.m.), Juno was within 200,000 miles (322,000) kilometers of the Giant Planet itself.
The primary hazard to the spacecraft as it approached Jupiter was the giant planet’s radiation belts, which Juno Primary Investigator Scott Bolton described as being “[t]he equivalent idea of Earth’s Van Allen Belts, but on steroids.” The spacecraft approached the planet from above to reduce its exposure from the most dangerous part of these radiation belts. Another hazard is the rings of dust and debris around Jupiter. Even a small particle of dust could do serious damage, so Scott said the engineering team built Juno “like an armored tank”.
“There will be a tremendous sense of relief once we know we’ve successfully entered orbit with no anomalies,” said Kenny Starnes, Juno program manager and leader of the Mission Support Area at Lockheed Martin Space Systems near Denver. “It’s kind of like winning a late-round tournament game – you can celebrate for a moment, but you know there’s still plenty of work to do in the near future. Soon after JOI, we continue our preparation of command sequences for the science mission to begin.”
The sports analogy is an apt one because the Juno spacecraft is about the same size as an NBA basketball court. The spacecraft has three solar panels, which are 8.9 feet (2.7 meters) wide and 29 feet (8.9 meters) long. It is the first solar-powered spacecraft to visit Jupiter and it’s operating farther from the Sun than any other solar-powered spacecraft in history.
Juno is equipped with radiation-hardened electrical wiring and shielding around its many sensors. The spacecraft’s main computers are housed inside a specially designed half-inch thick titanium vault that provides protection against Jupiter’s harsh radiation, whereas the scientific instruments and detectors require additional shielding as they are mounted around the spacecraft. Heidi Becker, Juno Radiation Monitoring Investigation Lead, worked on shielding scientific instruments located outside of the vault. The star tracker/detector has “a block of heavy metal around it to keep down the radiation; when the radiation hits the detector, it creates, kind of like what you see when you don’t get TV reception, snow on the image. And if it’s high enough, you can’t see the stars,” she told SpaceFlight Insider.
During Juno’s orbit insertion, the spacecraft performed a series of operations to prepare for the main engine burn that would slow its speed, allowing it to be captured in orbit around Jupiter. At 6:16 p.m. PDT (9:16 p.m. EDT), Juno began to slowly turn away from the Sun. At 7:28 p.m. PDT (10:28 p.m. EDT), the spacecraft made a faster turn into the proper position for orbit insertion. The spacecraft also started a faster spin at 7:56 pm which stabilizes the vehicle during the burn making attitude control easier through gyroscopic effects.
At 8:18 p.m. PDT (11:18 p.m. EDT), Juno began the 35-minute main engine burn. Applause filled the auditorium and mission control while the gathered audience breathed a sigh of relief that the engine had lit. The burn was performed in view of Earth, allowing its progress to be monitored by the mission teams at NASA’s Jet Propulsion Laboratory in Pasadena, California, and Lockheed Martin Space Systems in Denver, via signal reception by Deep Space Network antennas in Goldstone, California, and Canberra, Australia. As the primary antennas were turned away from Earth during the burn, a series of tones were transmitted to keep mission control appraised of the status, via a secondary antenna, with different frequencies indicating various milestones.
At 8:54 p.m., mission control at JPL and Lockheed Martin erupted in applause as the tones indicating successful completion of the main engine burn were received by the Deep Space Network and NASA TV announced: “Welcome to Jupiter.” The burn puts Juno in its desired initial orbit, and the burn duration was within 1 second of pre-burn predictions. About the successful JOI, Scott Bolton said that this was “a dream coming true”. Talking with Spaceflight Insider after the successful burn, Jim Green says he is relieved “recognizing how hard it is everyone’s worked to make this happen and then watching it come off pretty flawlessly, is really a tremendous satisfaction”.
At the post JOI briefing, an amazing movie was shown from the approach where the movements of the Galilean moons can be seen orbiting Jupiter over 17 days. This is the first time the harmony of nature and celestial movement at this scale has been seen on video. It led to some new science as well: Callisto was dimmer than the other moons at this phase angle, which was not expected. Scott Bolton talked with Spaceflight Insider about this discovery saying “you had to go out in space and look sideways” to see this effect. Scott also emphasized that the next movie sequence from JunoCam will not stop at five days out, but will continue on right over the pole saying “it will be a great ride”.
Juno’s first orbit of Jupiter will take 53.5 days. The spacecraft conserved fuel by going into a longer capture orbit rather than going directly for a 14-day orbit. Over the next few months, Juno’s science and mission teams will perform testing and calibrations on the spacecraft’s subsystems and science instruments and collect some data. Juno will begin making 14-day science orbits after the final burn of the spacecraft’s main engine on October 19.
“Our official science collection phase begins in October, but we’ve figured out a way to collect data a lot earlier than that,” said Bolton. “Which, when you’re talking about the single biggest planetary body in the Solar System, is a really good thing. There is a lot to see and do here.”
Juno’s scientific mission has several objectives: to investigate whether Jupiter has a solid core, to determine the amount of water and ammonia in the atmosphere, and to study the planet’s powerful magnetic fields. As our primary example of a giant planet, Jupiter may provide insight into the formation of planetary systems around other stars.The spacecraft’s nine scientific instruments will increase our understanding of the Solar System by providing data about the origin and evolution of Jupiter.
To honor the historic event, a Google Doodle includes an 8-bit animation which sent readers to more information about the historic event.
This article was produced by SpaceFlight Insider contributors Matthew Kuhns and Jim Sharkey.
Video courtesy of NASA/JPL
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.