Cameras aboard NASA’s OSIRIS-REx spacecraft snapped portraits of Jupiter and its moons as the University of Arizona-led team prepared to look for more elusive targets.
On Feb. 9, the OSIRIS-REx spacecraft, then 75 million miles from Earth, turned its cameras toward Jupiter and began snapping the first images taken since September’s launch.
The giant planet first appeared, overexposed and fuzzy, in an image taken with MapCam, the medium-range camera, but Jupiter wasn’t really the focus of that exercise. The team was more concerned about the stars in the background, as a test of “stellar optical navigation.”
The mission specialists navigate by the stars to find their way to asteroid Bennu, where they plan to grab a sample and return it to Earth.
On Feb. 12, the craft’s long-range camera, known as PolyCam, produced a much clearer image of Jupiter and its moons.
Two pictures were taken and overlaid, resulting in the final image. The first was exposed for 1.2 seconds to collect light from the Galilean moons Callisto, Io and Ganymede. The second was exposed for only 4 milliseconds to capture the giant planet.
The images were taken to test the on-board cameras and to exercise the team on the ground as it prepares to search for Earth’s Trojan asteroids, said Sara Knutson, the mission’s lead science operations engineer.
“We started building the command products in November and rushed to finish before Christmas,” she said. “We broke for the holidays, and a month and a half later, we finally get to see the images from something we’ve built.”
The OSIRIS-REx mission team has been busy bringing down the data from the spacecraft and analyzing it.
“This is really exciting, especially for me because this is my first mission,” Knutson said. “There was lots of anticipation leading up to this.”
Since then, the team has turned its cameras toward Earth’s Trojan point — a spot in Earth’s orbit where asteroids are gravitationally trapped in a stable position.
All planets have Trojan asteroids tailing or leading in their orbit around the sun. But, because of the location of Trojans in the sky, astronomers would have to point their telescopes near the horizon during dusk and dawn when it’s much too bright to see small, faint objects. Even space telescopes cannot point their cameras that close to the sun.
OSIRIS-REx will have a much better view of the Trojans, according to mission leader Dante Lauretta, of the UA’s Lunar and Planetary Laboratory.
Whether the Trojans are actually there or not, scientists don’t know. If they are there, they could tell us about the earliest building blocks of the Earth. If they’re not there, that would be interesting too, said UA regents’ professor Renu Malhotra.
That might mean they’ve eroded over time or, more interestingly, signal that Earth’s orbit has changed dramatically sometime in the past, she said.
Preparation will pay off when OSIRIS-REx finally reaches Bennu in 2018. “This exercise is important for the safety of the spacecraft,” Knutson said. Knowing what’s in the area is important to avoid collisions.
Before approaching Bennu to collect a sample, the team will perform a similar scan to see if the asteroid has natural satellites that could pose a threat to the craft.