Genesis maintains its orientation in space, or "attitude,"
by continuously spinning in space. The attitude control
system will keep Genesis spinning at a rate of 1.6 revolutions
per minute. During the science mission, the axis of spin
pointed 4 degrees ahead of the Sun, so that ion and electron
monitors would face directly into the oncoming solar wind.
The slow spin helps maintain inertial pointing at the
Sun, and minimizes pointing errors due to solar radiation
pressure torques. Genesis determines its orientation at
any given time using a star tracker and Sun sensors.
Genesis is the first robotic spacecraft to fly this
particular system to determine its orientation, or "attitude."
The star tracker can track stars of third magnitude
or fainter; in combination with the digital Sun sensor,
it can identify stars and generate information on the
spacecraft's attitude. Using both the angles of the
Sun and of nearby stars, on-board software can determine
the spacecraft's orientation and spin rate. As long
as the spacecraft is spinning between 1.6 and 2 revolutions
per minute, it can identify stars. During the maneuvers
when the spacecraft is spinning faster than 2 rpm, the
spacecraft will use its spinning Sun sensors to determine
its orientation. There are two star trackers, two digital
sun sensor and two spinning sun sensors onboard as redundant
The guidance, navigation and control subsystem weighs
10.0 kilograms (22.0 pounds).