Rotational modulation collimator
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Rotational Modulation Collimators (or RMCs), invented by Minuro Oda, are used to create images of high energy x-rays. Since high energy x-rays are not easily focused therefore x-ray lenses or mirrors do not exist, RMCs selectively block and unblock x-rays in a way which depends on their incoming direction.
RHESSI is the first mission to make use of Rotational Modulation Collimators in space.