1-20. SYSTEM FUNCTIONAL DESCRIPTION (cont)
(c) The shutter assembly provides a protective overlapping cover to the
nightside optical assembly.
A rotary solenoid drives an arm to rotate the shutter
Rotation of the ring pulls open the seven shutter vanes, and a coiled spring
Two mechanical stops are mounted on the bottom of the ring to limit
Two optical sensors provide shutter open and shutter closed signals to the
motor control CCAs.
(d) The sensor mount assembly uses a locking handle to secure the nightside
sensor assembly UUT.
The forward position of the handle (toward the nightside optical
assembly) unlocks the UUT by retracting the four locking cams.
In the rear position
(away from the nightside optical assembly) the four locking cams are extended to the
Two optical sensors are used to sense the open and closed positions.
(e) The secondary heat source (c) provides an IR source for the wider field-
of-view of the PNVS UUT.
Sources B and C are always referenced to the precision (A)
Only one source (B or C) can be selected at a time.