iPhone apps

Princeton Satellite Systems has one iPhone application available for download on the Apple App Store. ChessNotePad and Outer Space Defense are currently retired.


QuaternionCalc is a utility for performing mathematical operations involving quaternions. Included quaternion operations are:

  • Quaternion transpose
  • Forward transformation of a vector
  • Backward transformation of a vector
  • Conversion of a quaternion to 3-2-1 Euler angles
  • Creation of a quaternion from two unit vectors
  • Conversion of a quaternion into a transformation matrix

For more information go to QuaternionCalc help on our support site. QuaternionCalc uses the Princeton Satellite Systems MatrixLib framework for iOS.


Image of app on iPhone

ChessNotePad is a chess recording and playback application. It can be used anywhere you would use paper and pencil to record chess games. ChessNotePad records games in PGN format as you and your opponent play. Forget pen and pencil! Once a game is complete, you can save it for later viewing and optionally email it to yourself and the opponent. You can also download or paste PGN games from the Internet and save them for later viewing.

Questions? Check out ChessNotePad Frequently Asked Questions page on our support site.

Outer Space Defense

Outer Space Defense is a game designed to teach relative orbit dynamics. This game poses a test of skill pitting your mastery of spacecraft orbital control and prowess with a laser against multiple attacking enemy satellites. See how long you last against a relentless enemy that launches satellites designed to take you out at a faster and faster pace!

Picture of iPhone appInterested in learning about the theory behind the game? Click here to download a brief
description of the coordinate systems, equations of motion, relative orbit dynamics, and control methods used in the game.