Operations comparison of deep space ranging types: Sequential tone vs. pseudo-noise

NASA's Deep Space Network currently has a ranging system that uses a sequence of square wave tones to determine spacecraft distance. This ranging system correlates tones received from the spacecraft with those it transmitted. The phase shift that maximizes the correlation value is then related to the round trip light time distance. A new ranging system is being developed that can be configured to use sequential square wave tones or to use repeating pseudonoise tones. This allows more flexibility and possibly better performance. The tradeoffs between the two types of ranging are presented. A detailed derivation of the ranging performance as a function of configuration, signal strength, and other variables is given. The ranging performance for the two ranging types is compared. A configuration for pseudo-noise ranging that provides better performance is provided. Operational issues and simplifications resulting from using pseudo-noise ranging are also discussed.