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.