OSIRIS-REx’s landing spot on the asteroid Bennu


Genesis cover

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Bennu, annotated
Click for full resolution unlabeled image.

The OSIRIS-REx science team today released another image of the asteroid Bennu, this time showing the planned Nightingale touch-and-go sample grab landing site.

The image to the right, reduced, cropped, and annotated by me, is that image. From the caption:

The crater where sample site Nightingale is located can be seen near the top, center of the image – it is a small region containing dark, fine-grained material. Bennu’s prime meridian boulder, Simurgh Saxum , is also visible in the lower left of the image, near the asteroid’s limb. Directly east of Simurgh is Roc Saxum . The field of view is 0.3 miles (0.5 km). For reference, Simurgh is 125 ft (38 m) across, which is about the size of a commercial airliner.

Nightingale is only about 50 feet across, which is about a third the size of the kind of smooth areas they had designed their grab-and-go equipment around. This global image illustrates the difficulties they face with that sample grab. Though there appear to be larger areas in this photo that seem smooth, they really are not. The asteroid has no dust, and the sample grab equipment is designed to suck up particles smaller than 0.8 inches in diameter. Most of the surface is covered with pebbles and gravel larger than this.

Thus they needed to find a spot where the bulk of the material is “fine-grained.” Nightingale fits that bill, though it has a small footprint and also has larger particles that pose a risk to the sample grab because they could damage the spacecraft, or clog the sample grab equipment.

Either way, for the spacecraft to autonomously guide itself accurately down to this small spot, surrounded as it is by much larger boulders, will be challenging, and is why they have done one dress rehearsal already, getting as close as 213 feet, and will do a second in June, getting down to 82 feet.

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