Like countless others before it, the data packet rode a radio signal more than 500 million miles from the New Horizons spacecraft to Earth, filtering through NASA's largest antennas late last week to mission and science operations center computers in Maryland and Colorado.
But this particular data – infrared scans of Jupiter's day-night boundary – were special for another reason: they were the last to be sent to Earth from the New Horizons Jupiter flyby, which took place in February and March.
"All of the data from our Jupiter close-approach encounter is on the ground," says mission Principal Investigator Alan Stern, of NASA Headquarters, Washington, D.C. "The data are better and richer than we ever expected. The Jupiter system is spectacular and New Horizons performed superbly to observe it. Our team couldn't be happier."
The dataset – about 36 gigabits, gathered from Feb. 24-March 7 and stored on the spacecraft's digital recorders – includes the bulk of New Horizons' 700-plus observations of Jupiter's atmosphere, rings and closest moons. Mission scientists have been poring through these images and spectral measurements since the spacecraft began transmitting them, and are reviewing the early results of this work at a New Horizons science team meeting this week in Boulder, Colo.
"From the first close-up look at the Little Red Spot storm, to the best views ever of Jupiter's rings, to sequences of a volcanic eruption on the Jovian moon Io, we've seen some amazing things," says New Horizons Project Scientist Hal Weaver, of the Johns Hopkins University Applied Physics Laboratory (APL), Laurel, Md. "It's fair to say we met or surpassed nearly all of our scientific objectives."
To get the science, though, the team had to meet its main objective: keep the spacecraft safe as it flew through an "aim point," 1.4 million miles from Jupiter, that set its course for an encounter with Pluto in July 2015. The flight past Jupiter was also a chance to test the spacecraft's systems and operators under real-world conditions. "From the operations standpoint, it was a flawless encounter," says Alice Bowman, New Horizons mission operations manager at APL. "The performance of the spacecraft and operations team really bodes well for what we'll do at Pluto."
Since passing Jupiter on Feb. 28, New Horizons has sped nearly 100 million miles down the long, dynamic tail of Jupiter's magnetosphere, measuring charged particles in this previously uncharted environment. The observations will continue until late June. "The particle spectrometer teams are very excited about what they're seeing so far," Stern says. "There is a lot more complexity and organization in the magnetotail than they expected. But that's the way exploration works – once we visit a place for the first time, our knowledge is changed by the reality of what we find!"