The spacecraft center of pressure (cp) shall be within 18 cm of the center of mass (cg) for any attitude with the instrument cover off and the hydrogen tanks empty.
A cp/cg offset this small enables the attitude control system to maintain control down to 400 km with the worst-case solar flux assumed. The limiting case is safehold which uses only torque rods for control. This is an end-of-life scenario, so empty tanks are used.
Vic Untalan/Mike Fennell analysis "Maximum WIRE Aerodynamic Torque Analysis" dated February 14, 1996 (document incorrectly labled 1995).
Mechanical modeling and mass properties measurement.
This requirement impacts the orbit (SYS.REQ.2) requirement. This requirement should be revisited prior to the addition of any balance weights.
Revision: April 11, 1996