Skip to main content
Version: 4.9

Geometry

In the Geometry View, you can create properties related to the local geometry of your spacecraft: Body Frame Vectors, External Surfaces, and Fields of View.

Take care when establishing your principal directions and origin. If you have a CAD model of your satellite, align your Sedaro body frame with the coordinate system in the CAD model - this will make extracting key vectors straightforward.

Body Frame Vectors​

Body Frame Vectors are unit vectors fixed relative to the spacecraft body. Body Frame Vectors are used to drive Pointing Modes, define the orientation of sensor boresights and comm antennas, and to describe exterior geometry.

Create a Body Frame Vector by clicking the "+" button beneath the list of vectors. You can define a Body Frame Vector in either Cartesian or spherical polar (with the z-axis as the polar axis) coordinates of the principal axes.

Surfaces​

Surfaces are used as the mounting location for solar panels and used to compute atmospheric drag, radiative heat transfer, and solar radiation pressure perturbations.

Create Surface by clicking the "+" button beneath the list of surfaces. You will be prompeted to define the area (m²) of the surface.

Motion Type​

Each surface must be given a motion type, which defines how they articulate relative to the spacecraft body.

  • Fixed Surfaces are fixed with respect to the satellite's local/body reference frame
  • Sun Tracking Surfaces rotate about an axis that is fixed in the satellite's local/body reference frame. These surfaces maintain a rotation angle that maximimizes alignment with the sun vector. Surfaces associated with a solar panel are often Sun Tracking.
  • Anti-Sun Tracking surfaces rotate about an axis that is fixed in the satellite's local/body reference frame. These surfaces maintain a rotation angle that minimizes alignment with the sun vector. This type is useful for creating the "back" side of a Sun Tracking Surface.

Surface Materials​

In the Surface creation dialog, you can choose an existing or create a new Surface Material. Just as with other forms of hardware, you can specify a part number, manufacturer, temperature rating, etc. You will also define the radiative properties of the surface.

  • IR Emissivity - Percent of thermal energy radiated at IR wavelengths from this surface relative to a black body of the same temperature.
  • Solar Absorptivity - Percent of energy absorbed and trapped as heat by the surface at solar (visible) wavelengths.
  • Diffuse Solar Reflectivity - Percent of light diffusely reflected from the surface, used for solar radiation pressure calculations. Diffuse refers to light that is scattered on impact.
  • Specular Solar Reflectivity - Percent of light specularly reflected from the surface, used for solar radiation pressure calculations. Specular refers to light that is coherently reflected on impact.

Fields of View​

Fields of View (FoVs) are defined based on a direction (Body Frame Vector) and either a circular or rectangular sensor plane. These can be linked to Sensors or Directed Energy Devices and used to create FoV Conditions. When defining a Rectangular Field of View, you will choose a second vector which specifies the "Height" direction.