Upper Half of Osprey Boulder

This image shows the upper portion of the largest boulder in the crater where sample site Osprey is located. The crater is near asteroid Bennu’s equator, and its northern rim is visible in the lower half of the image. The sample site itself is located below the boulder and to the right (outside of the image frame). The image was taken by the PolyCam camera on NASA’s OSIRIS-REx spacecraft on February 11 from a distance of 0.4 miles (0.6 km). The field of view is 29 ft (8.8 m). For reference, the boulder’s prominent fracture is 11 ft (3.2 m) long, which is about the length of a paddle board. The image was obtained during the mission’s Reconnaissance B phase. When it was taken, the spacecraft was over the northern hemisphere, pointing PolyCam north and to the west. During this flyover, the spacecraft’s OLA instrument was scheduled to provide ranging data to PolyCam in order to focus the camera. However, due to an anomaly that occurred with OLA, the PolyCam images from this flyover are slightly out of focus.

The small, horizontal streaks on the bottom left of the image are caused by short exposure times (less than three milliseconds). Short exposure times are required for imaging areas near Bennu’s equator, since they are brightly illuminated by the sun. The duration between images is so short that the imaging system does not always have time to process all the data generated by the previous exposure, which results in icicle-like patterns.

Date Taken: February 11, 2020

Instrument Used: OCAMS (PolyCam)

Credit: NASA/Goddard/University of Arizona

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