Collision Check

Collision Check is a calculator for estimating the probability of collision between two conjuncting satellites, using information found in a standard Conjunction Summary Message (CSM). This is accomplished via Monte Carlo simulation; employing the Cholesky decomposition of the conjuncting satellites' dispersion adjusted covariance matrices sampled over a random Gaussian distribution.

The program can be downloaded in the releases tab.

Screenshots

Building

To download the required dependencies and build the Collision Check program using Leiningen, run the following command while in the project root directory:

lein uberjar

The program will packaged as a standalone JAR file in the ./target directory.

Usage

This program requires an installed Java Runtime Environment, version 7 or higher.

For 64-bit Linux operating systems, the FORTRAN runtime library must be installed. This can be accomplished in Debian/Ubuntu by running:

sudo apt-get install libgfortran3

To run the program, double click the collision-check-XXX-standalone.jar (if your operating system's file manager is configured to launch Java programs), or enter the following in your terminal (replacing XXX with the version number):

java -jar collision-check-XXX-standalone.jar

Once the application has started;

• Enter the UVW coordinates from the CSM in the Asset Position and Satellite Position fields.
• Enter the 3x3 UVW covariance matrices from the CSM in the Asset Covariance and Satellite Covariance fields.
• Enter the combined radii (in meters) of the satellites in the Combined Radii field, to define the collision space. The radar cross-section from the CSM is not a reliable measure of the actual satellite cross section. It is safer to over-estimate, than under-estimate.
• Enter a standard deviation in the Sigma field, to define the conjunction space. A low sigma (e.g. 1) will result in a small search space, with high fidelity in a close approach. A high sigma (e.g. 3) will increase the search space, but will dilute the collision probability.
• Enter the number of samples to take in the conjunction space. This number should be fairly large (many tens of thousands).
• Click the Run button.

Once the Run button is pressed, the program will check to ensure that the entered position and covariance appear valid. If values seem invalid, an alert will appear indicating the incorrect field(s). If any values cannot be parsed, relatively sane defaults will be used in the calculation; an alert will appear indicating the default value.

If all values are determined to be valid, the progress bar above the Run button will begin to increment as the conjunction space is sampled. Upon sampling completion, several charts will be created:

• Miss-Distance Cumulative Distribution: Shows the cumulative distribution of the miss distances calculated during the simulation. A vertical bar is also included to indicate the collision space boundary. Also contained in the chart are the CSM Miss Distance, to compare with the miss distance found in the CSM, and the Collision Probability.
• UVW-Axis Conjunction Space: Several charts showing a subset of the points sampled in the conjunction space. This provides a visual representation of the position and covariance in the Radial, In-Track, and Cross-Track planes. The asset's sampled points will appear blue, and the satellite's sampled points will appear red.

The charts can be saved or manipulated by right-clicking inside the chart area and selecting from the available options. Zooming in is accomplished by highlighting a area on the chart with the mouse cursor; clicking and dragging up will reset the chart's zoom.

A Collision Avoidance (ColA) Maneuver should probably be considered when the Collision Probability is calculated to be above some threshold. An industry standard threshold is 1e-04, a 1 in 10,000 chance of colliding.

Credits

• Collision Check program icon obtained from IconArchive.

License

The MIT License (MIT)

Copyright (c) 2014 David RC Dayton
Copyright (c) 2014 John W Harms

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.