Table of Contents

Getting Started: Configuring Orbits

Defining the Orbit

To modify a spacecraft's orbit, press the Spacecraft tab in the Properties panel. The orbit can be described using any of the methods described below. The path will be visualized constantly in the Viewport around the spacecraft’s primary body (Earth by default). In this example, a polar orbit described with Keplerian Orbital Elements is used.

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Orbit Options

In Nominal Studio, there are multiple ways to define the orbit of a spacecraft. Each method has drawbacks and benefits, however, they can be alternated at any time.

Note

It can be helpful to utilize multiple methods at once, such as placing a spacecraft in the correct geodetic coordinates and then modifying the velocity through the Cartesian elements.

Cartesian: These coordinates are the most direct way to define the position and velocity of a spacecraft. This is relative to the primary body of the spacecraft in the PCI (planet-centered inertia) frame, which is about the J2000 frame. These are defined in units of m and m/s respectively.

Keplerian: These classical elements are a more practical method for describing an orbit. The orbit visualization is based on these Keplerian elements and is made up of 6 components:

  1. Semi-Major Axis: The average of the innermost and outermost distances of the orbit.
  2. Eccentricity: Defines how elliptical the orbit is; zero being circular, 1 being linear.
  3. Inclination: The verticality of the orbit toward the planet's poles.
  4. Right Ascension of the Ascending Node: Rotates the orbit around the planet's poles.
  5. The argument of Periapsis: Rotates the orbit along the plane of the orbit as defined by the inclination.
  6. True Anomaly: How far along the orbit the spacecraft currently sits.

Geodetic: These coordinates allow for the alignment of the spacecraft to latitude, longitude and altitude. The resulting orbit will be circular, however, these parameters can be used before switching back to a Keplerian orbit. The orbital inclination will be dependent on the latitude value specified, assuming that the spacecraft is at the peak of its orbit when initialized.

Two Line Elements (TLE): TLEs are a standard for specifying the orbit of a spacecraft, along with other information. TLEs can be pasted into the UI, or imported from a file. When importing from a file with multiple TLE sets, use the index to specify which TLE set should be used for this spacecraft.

Warning

Certain orbits may not translate to all input methods, for example, hyperbolic or other irregular paths can be defined which may not have a valid Keplerian description, these are still valid conditions however.

Importing TLEs

This section allows the import of a TLE file to describe the orbit of the spacecraft. If a TLE file is available, select an existing spacecraft, then go to the TLE tab in the Properties Panel, and select Import TLE. Import the appropriate file and the spacecraft will update, including the name of the spacecraft and the shown TLE lines. By switching back to the other orbit formats, the position and velocity, or orbital elements, of the spacecraft will be shown.

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Custom Orbits

Spacecraft motion does not need to be simulated in real time. If a spacecraft or other Entity is required to follow a predefined path this can be achieved with Custom Orbits. A csv file with a list of timestamped coordinates can be imported to make the spacecraft follow any path.

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