All Nine Grids Rotating:
Point Source Located Exactly on the Spin Axis

Next we consider how the grid-pair collimators modulate this parallel beam of X-ray photons. It is helpful to imagine yourself riding along on one of the photons in the beam being emitted from the solar event. The accompanying animation shows what you would see assuming you were traveling exactly along the HESSI spin axis.

Only the slats of the front grid would block your view of the detectors – the thermal insulation blankets and the cryostat cover used to keep the instrument cool are transparent to all but the lowest energy X-rays.