Apollo Lunar Module Crewman Optical Alignment Sight (COAS) for aiding the astronaut in rendezvous, docking, and navigation.
Flown to earth orbit as part of the Apollo 9 Lunar Module (LM-3) in the first manned flight of the LM, March 3-13, 1969.
Displays a graduated circle reticle on the combiner (angled glass plate) that appears to be at infinite distance,
superimposed over the target in view.
Could be mounted and set for use at the left window (“LW”), overhead window (“OW”), and right
Large knob controls the reticle light intensity; small knob is pulled to rotate the barrel to set the window position.
A similar unit was used in the Apollo Command Module, and a follow-on design has been used in the
This version (-0009) included a built-in neutral density (dimming) filter that reduced the maximum lamp brightness, to
accommodate star sightings. During docking operations on the Apollo 9 flight, the reticle image viewed through this artifact was not visible for a time because of the bright sunlit Command Module.
The lamp brightness was increased on later versions (-0021, -0025), used on Apollo 10 and later, with the removal of the built-in filter in favor of an external detachable filter.
Utilized during the Apollo 9 mission in demonstrations of normal and contingency flight operations.