OSIRIS-APEX, a
The mission team confirmed that the spacecraft indeed had come out of the experience unscathed after downloading stored telemetry data in mid-March. The team also tested OSIRIS-APEX’s instruments in early April, once the spacecraft was far enough from the Sun to return to normal operations. Between December 2023 and March, OSIRIS-APEX was inactive, with only limited telemetry data available to the team on Earth.
Innovative Engineering Solutions
The spacecraft’s clean bill of health was due to creative engineering. Engineers placed OSIRIS-APEX in a fixed orientation with respect to the Sun and repositioned one of its two solar arrays to shade the spacecraft’s most sensitive components during the pass.
The spacecraft is in an elliptical orbit around the Sun that brings it to a point closest to the Sun, called a perihelion, about every nine months. To get on a path that will allow it to meet up with its new target Apophis in 2029, the spacecraft’s trajectory includes several perihelions that are closer to the Sun than the spacecraft’s components were originally designed to withstand.
“It’s phenomenal how well our spacecraft configuration protected OSIRIS-APEX, so I’m really encouraged by this first close perihelion pass,” said Ron Mink, mission systems engineer for OSIRIS-APEX, based at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
Unexpected Benefits and Ongoing Challenges
Besides confirming that the January perihelion worked out according to predictions, engineers found surprises while testing spacecraft components. A couple of instruments came out better than expected after exposure to higher temperatures.
A camera that helped map asteroid Bennu and will do the same at Apophis, saw a 70% reduction in “hot pixels” since April 13, 2023, the last time it was tested. Hot pixels, which are common in well-used cameras in space, show up as white spots in images when detectors accumulate exposure to high-energy radiation, mostly from our Sun.
“We think the heat from the Sun reset the pixels through annealing,” said Amy Simon, OSIRIS-APEX project scientist, based at NASA Goddard. Annealing is a heat process that can restore function of instruments and is often done intentionally through built-in heaters on some spacecraft.
Captured on October 20, 2020, as NASA’s