The First To...
ION will be among the first CubeSats to be actively stabilized
on all three-axes. The onboard magnetometer and sun sensors are
used to provide the necessary information for attitude
determination. Torque coils are then used to orient the
spacecraft in the nadir pointing direction and perform any
station keeping maneuvers. In addition to the magnetic torque
ION is equipped with four micro-vacuum arc thrusters capable of
rotating the satellite around the x and y-axis and translation
it in the z-axis.
It's Purely "Attitude"!!!
to processor and engineering schedule limitations, most of the
data processing for the ACS is done on the ground. This "open
loop" system relies on the downloaded magnetometer and solar
sensor data to estimate the attitude and rotational rate at a
known time and position during any given orbit. Accurate orbit
propagators as well as detailed Earth magnetic field models have
been used to achieve the desired accuracy of these calculations.
The computed attitude information is fed into a simulation that
uses an asymptotic period linear quadratic regulator (LQR) to
find the optimum magnetic torque needed to achieve a specific
In addition, the satellite's dynamics and kinematics have also
been modeled and added to this simulation creating a feedback
loop. Starting with the initial attitude, the controller finds
the optimum torque sequence and applies it to the simulated
satellite. The response of the system is calculated and the new
attitude and rotational rate are fed back into the LQR to find
new optimum torque sequence. The system response is thus
calculated after each torque and it is used to find an overall
torque profile. Once the satellite
is oriented correctly, the simulation is stopped and
the entire profile is uploaded to the satellite during the next
pass for execution.
40 micro gauss accuracy
30 loops each, of
Traced on a PCB board
Alameda Applied Sciences Corporation Micro-Vacuum Arc
3-axis control of the satellite will be maintained using three
orthogonal torque coils. One coil will outline the perimeter of
the +x face, another will outline the perimeter of the +y face,
and the third will outline the perimeter of the -z face.
All three torque coils are of equal dimensions.