Basilisk Astrodynamics Simulation Framework  0.8.0 Open-Source Spacecraft Simulation Environment.
Vizard - Unity Based Basilisk Visualization

## Overview

The Vizard Unity-based Basilisk visualization is able to display in a three-dimensional view the Basilisk simulation data. The intent of the visualization is to show what states are being simulated. If a planet is being modeled as a gravitational simulation element then it is visible in the simulation. If the planet or moon is not modeled then it is not shown. Similarly for the sun. If there is a sun being modeled then the light comes from this sun direction and the sun is visible. However, if no sun is being modeled then a default lighting from a fixed direction is modeled, but no sun is visible in the visualization. Vizard can also show some panels illustrating spacecraft device states, or show the spacecraft device in a heads-up display (HUD) mode. If not device or sensor is being modeled, then none will show up as options in the Vizard menu bar.

In the above Vizard window interface illustration, the slider on the lower-left allows the user to skim forwards and backwards through the simulation data. The Play/Pause button at the bottom-center allows for the Visualization to be paused and resumed. The +/- buttons on the lower-right allow the simulation to speed and and slow down. Note that with 1x the visualization is moving through the data with 1 frame per simulation time step. To see a video of the interface, click on the image above.

## Vizard Startup

When starting up the Vizard software the user is presented with a resolution and graphics setting option panel as shown above. There is an option on the lower portion of this panel to turn off this plane on start-up and only show it if the program is started while pressing the option key. Note that the Vizard screen size can be dynamically changed after startup as well.

Vizard Startup Panel

Next Vizard presents a panel where the user can select which simulation to visualize. To play back a previously recorded BSK simulation press the Select button and navigate to the binary BSK recording file. After a file has been selected press the Start Visualization button.

Vizard Simulation Selection Panel

## View Modes

To engage with the visualization, the view point can be rotated and the user can zoom in and out. There are three view modes available:

• Spacecraft-Centric View Mode (default): Here the spacecraft is drawn 1:1 while showing other celestial objects about it. When rotating the center of the spacecraft is the center of rotation. The spacecraft trajectory is not shown in this view. You can zoom in and out locally, but if you zoom out too far then the view mode switched to a planet-centric view mode.
• Planet-Centric View Mode: Here a planet-wide view is presented. When rotating the view point this is about with the center of the planet as the center of rotation. The spacecraft trajectory is shown. The spacecraft is drawn at an exaggerated size so it is visible as a 3D object in this view. To return to a spacecraft-centric view mode double click on the spacecraft. If you zoom out far enough then the mode switches to a heliocentric view.
• Heliocentric View Mode: Here a solar system wide view is shown. The planets are drawn enlarged to make them visible, and the planet trajectories are shown as well. If the spacecraft is orbiting a planet it is not visible in this view. If the spacecraft is on a heliocentric trajectory it is shown, also enlarged, in this view. Double clicking on a planet returns the user to a planet-centric view.

## Space Vehicle States

### Basic Position and Orientation

Vizard is able to show the position and orientation of the spacecraft being simulated. If one or more planets are being modeled, then the spacecraft is show relative to the nearest planet.

### Reaction Wheel States

If Reaction Wheels or RWs are modeled, then a RW panel can be opened from within the Actuator menu bar item. Here the RW wheel speeds and motor torques are shown.

Illustration of RW Panel

### Thruster States

If thrusters are being simulated then a range of visualizations can be enables within the Actuator menu item. The options include to open a Thruster Panel which shows the thruster firings as bar charts. The thruster HUD uses a particle engine to illustrate if a thruster is firing. Here the length and density of the particles is related to the strength and duty cycle of the thruster. The thruster geometry option draws small cones where the thrusters are modeled to be. This is useful when debugging that a thruster configuration is being properly modeled. Finally, the thruster normals option illustrates the thrust axes being modeled.

Illustration of Thruster Panel and HUD

## Vizard Configuration Options

### View Menu Item

The View menu tab contains a range of Vizard options. A range of coordinate frames can be toggled on or off.

Illustration of spacecraft and planet Coordinate frame Axes

This allows a line to be drawn from the spacecraft aimed at another celestial body such as the sun, a planet, etc. The spacecraft location is referred to as "Inertial". The purpose of these lines is to have a quick visual reference in what direction another body is located. The lines can be hidden or removed as needed. Some celestial bodies come with default colors such as yellow for sun heading, or red for Mars heading, etc. However, each line color can be customized as needed.

Illustration of Pointing Vectors to Mars and the Sun

This feature allows for a cone to be added relative to the spacecraft which indicates if a cone about a particular body-fixed axis intersects with a celestial object. For example, this can be used to add a cone to validate that the sensor axis doesn't get too close to the sun (keep out cone), or if the solar panel normal axis stays within some cone to the sun (keep in cone). If the cone in/out condition is not triggered, then the cone is opaque. If the in/out condition is triggered, then the cone becomes solid.

Illustration of Pointing Vectors to Mars and the Sun

### Camera Menu Item

The Camera menu item allows for custom camera views to be created into the visualization.

#### Inertial Planet Camera

This is a camera whose view always points relative to a particular celestial body. The user can set the field of view value, as well as grab a screen shot if needed. The user can select relative to which planet the camera should point, and if the camera should point along orbit axis, along track or orbit normal.

Illustration of Inertial Planet Camera Window

#### Inertial Camera

Up to two custom views can be generated that look out of the spacecraft +/- x-, y- and z-axis. Again the field of view can be configured, and a screen grab button is present.

Illustration of Inertial Camera Window

#### Skybox Menu Item

The default star field is a realistic NASA star field. The alternate option is an ESO Milky Way star field that is more visually pleasing, but less realistic.

Illustration of Skybox Option with Milky Way Star Field