Overview:
The purpose of these tests is to ensure the ADCS module is able to execute slew maneuvers and achieve certain angular velocities about any axis. Since it is difficult to accurately measure small angular velocities, we verify that the ADCS module is capable of providing the torque necessary to achieve various velocities.
In this procedure, the (x, y, z) axes are those that align with the edges of Helmholtz cage, with z-axis pointing in the vertical direction.
Set-up:
- Attach the satellite on the air bearing. Align the CM of the satellite with the center of the air bearing (or else we’ll have to recalculate inertia tensor of the air bearing).
- Stabilize Module on air bearing.
- align the principal axis of the satellite satellite along the (x, y, z) axis.
- Verify system alignment/sensor readings
Magnetic field:
- These tests will be repeated for 2 magnetic fields: 0.032*(1, 1, 1) and 0.048*(1, 1, 1). Units for both are mT. They represent the maximum and minimum magnetic field strength that the magnetorquer experiences in orbit.
Procedure:
- In the fine-pointing modes, command the satellite to execute the following rotations: Also, command the OBC to store the data from accelerometers.
| Description |
Quaternion |
Notes |
| 180 degree rotation about z-axis |
<0, 0, 0, 1> |
These two tests must be done on an air bearing since the fishing line would produce a torque. |
| -180 degree rotation about z-axis |
<0, 0, 0, -1> |
|
| 20 degree rotation about x-axis |
<0.98, 0.17, 0, 0> |
|
| -20 degree rotation about x-axis |
<0.98, -0.17, 0, 0> |
|
| 20 degree rotation about y-axis |
<0.98, 0, 0.17 0, 0> |
|
| -20 degree rotation about y-axis |
<0.98, 0, 0.17 0, 0> |
|
| a 13 degree rotation about an arbitrary axis (1, 1, 0) |
<0.98, 0.12, 0.12, 0> |
|
- After each maneuver, or after the OBC storage is full, download accelerometer data from the OBC.
- Use accelerometer data and inertia tensor to calculate torque on the satellite during maneuver. Account for drag
- Verify that the direction of the torque produced aligns with the rotational axis.
- Verify that the torques produced produced had a wide range of magnitude. (0 to 10^-3 N/m)