Push Broom Sensors

Many satellites and aircraft have sensors or instruments that sweep back and forth across the Earth. These sweeping sensors are often called Push Broom Sensors. As the sensor moves back and forth, it sweeps in a plane perpendicular to the vehicle's velocity vector. You can model this type of motion using a spinning sensor.

Use the following steps as a guideline for modeling a push broom sensor. The first two steps allow you to define the Spin Axis for the sensor. The subsequent steps allow you to reproduce the sweeping motion of the push broom.

1. Set the Cone Angle to 90 degrees so that the boresight is perpendicular to the Spin Axis.
2. Set the Azimuth and Elevation angles for the Spin Axis so that they are aligned with the velocity vector.

   The velocity vector location depends on the vehicle's selected attitude profile. Satellites typically use the Nadir aligned with ECF velocity constraint or Nadir aligned with ECI velocity constraint profile. Both of these constrain the velocity vector with the satellite's +X axis. In this case, the correct Spin Axis angles consist of an Azimuth of 0 degrees and an Elevation of 0 degrees. The same is true for an aircraft with either of its two common attitude profiles.

3. Set the Scan Mode to Bidirectional.
4. Adjust the Start and Stop Angles so that the sensor remains on the Earth at all times during the sweep.

For geostationary satellites, Start and Stop Angles of -5 degrees and +5 degrees are sufficient. For low-Earth orbiting (LEO) satellites and aircraft you can increase these angles to get the desired sweep width.