parallel to the axis of the prism. A high-gain fixed dish antenna was
at one end of the prism, and the 489 N thruster at the other end.
The sensor openings were all located together on one of the eight
panels, 90 degrees from the solar panels, and protected in flight by
a single sensor cover. The spacecraft propulsion system consisted
of a nonpropellant hydrazine system for attitude control and a bi-
propellant nitrogen tetraoxide and monomethyl hydrazine system
for the maneuvers in space. The bipropellant system had a total
capability of about 1900 m/s with about 550 m/s required for lunar
insertion and 540 m/s for lunar departure. Attitude control was
achieved with 12 small attitude control jets, two star tracker
cameras, and two inertial measurement units. The spacecraft was
three-axis stabilized in lunar orbit via reaction wheels with a
precision of 0.05 Deg. in control and 0.03 Deg. in knowledge.
Power was provided by gimbaled, single axis, GaAs/Ge solar 
1750A computer (1.7 million instructions per second) for savemode,
attitude control, and housekeeping operations, a RISC 32-bit
processor (18 million ips) for image processing and autonomous
operations, and an image compression system provided by the
French Space Agency CNES. A data handling unit sequenced
the cameras, operated the image compression system, and
directed the data flow. Data was stored in a 2 Gbit dynamic solid
state data recorder. 

The mission had two phases. After two Earth flybys, lunar insertion
was achieved approximately one month after launch. Lunar map-
ping took place over approximately two months, in two parts. The
first part consisted of a five hour elliptical polar orbit with a periapsis
of about 400 Km at 30 degrees south latitude and an apoapsis of
8300 Km. Each orbit consisted of an 80 minute lunar mapping
phase near periapsis and 139 minutes of downlink at apoapsis.