Skip to main content
Version: 4.9

Reference Vectors

In the Reference Vectors board, you can create local direction vectors and vectors from the spacecraft to celestial bodies and targets. These vectors are used in other parts of the model to define behaviors such as pointing, condition compliance, targeting(/agentbranch/targets), and attitude determination. Reference vectors fall into four categories: Celestial, Local, Target, and Target Group.

Celestial Vectors​

Celestial Vectors point to the center of natural bodies such as the Earth and those outside of the Earth's atmosphere, like the Sun and Moon.

Local Vectors​

Local vectors are uniquely determined relative to the position, velocity, and orientation of the spacecraft. The available options are as follows:

  • Nadir - directly towards the center of Earth from the satellite.
  • Zenith - vector in the direction opposite nadir
  • Positive Cross Track - out of plane at right angle to position and velocity vectors (cross product of position and velocity, parallel to orbital angular momentum)
  • Negative Cross Track - out of plane at right angle to position and velocity vectors (negative direction of the cross product of position and velocity)
  • Positive Along Track - "forward", at right angle to position vector
  • Negative Along Track - "aft", at right angle to position vector
  • Ram - velocity direction
  • Anti-Ram - vector in the direction opposite ram
  • Magnetic Field - local magnetic field vector

Target Vectors​

If you have defined a Target, you can create a Target Vector which points from the spacecraft to that Target.

Target Group Vectors​

If you have defined a Target Group, you can create a Target Group Vector which points to the Active Target of a Target Group. The Active Target is determined based on which targets satisfy the Conditions associated with the Active Operational Mode and tiebroken by Target Priority.