Youn some ways, the last place you’d want to put the James Webb Space Telescope is, well, in space. If you owned a $10 billion car, you wouldn’t leave it out in a hail storm, and while there’s no hail in space, there are plenty of micrometeoroids—high speed debris no bigger than a dust grain but moving so fast they can pack a true destructive wallop. Millions of these fragments fall on Earth every day. However, they burn in the atmosphere well before reaching the ground. Webb, which is located in space at an approximate distance of 1.6million km (1,000,000 mi. The Webb is protected by no protection from Earth. And as NASA and others have reported in the past week, its mirror—the heart of the space telescope—has already been dinged five times by tiny space flecks, the most recent of which has done real, but correctable, damage.
The Webb’s mirror is an exquisite piece of engineering. It measures 6.5m (4 in. ), and is 21 ft. long. across, it’s made up of 18 hexagonal segments, each of which can be moved along seven different axes to allow controllers to focus the overall instrument. Each segment, which is made from beryllium has a surface area of 25 sq. It measures 269 square meters ft.). Each one is covered with reflective golden, though it’s a thin film that would be no larger than a golfball if it was peeled away and compacted into a sphere. The beryllium’s surface is smooth and polished to the point that its largest imperfection, at 7.6 cm (3 inches) in size, would not be visible if the material were extended to the dimensions of the United States. That’s a heck of a piece of hardware to leave exposed to the space elements. But if you’re going to do your work where Webb does, it’s a risk you have to take.
This is what makes the micrometeoroid strike particularly troubling. Although NASA scientists simulate these collisions on ground, they found that the impacts that actually occurred were larger than the models. “With Webb’s mirror exposed to space, we expected that occasional micrometeoroid impacts would gracefully degrade telescope performance over time,” Lee Feinberg, a Webb telescope optical manager, said in a statement. “This one…is larger than our degradation predictions assumed.”
However, this does not necessarily mean that the telescope has been seriously damaged and cannot go on doing its work. The position of the mirror segments can be moved in increments measured in nanometers—or billionths of a meter—allowing a damaged segment to be precisely refocused to cancel out the effect of the ding. Ground crews have adjusted the damaged segment in accordance with the plan, keeping the telescope on course to release its first images on July 12.
Webb can defend itself. NASA is able to predict the approaching of micrometeoroid rains, and Webb can move its telescope so that it faces away from the path of the debris. It is certain that the telescope will continue to receive high-speed dust and grains over its lifetime. The Webb is expected to return spectacular science within the same decade. This, however, cannot be denied. Space is a dangerous place to do business—but it’s a very rich one as well.
Original publication of this article was TIME Space. Register here.
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