Navigation system
Radiometric Navigation
Measuring a spacecraft's distance and velocity from its radio signal — range from the round-trip signal time, and line-of-sight velocity from the Doppler shift. Combined over time from the ground stations, these fix a spacecraft's trajectory across the Solar System.
Related
Sources
The primary and reference sources this topic draws on.
- NASANational Aeronautics and Space Administration
Mission data, planetary science, space telescopes, and public-domain imagery.
Most NASA-produced imagery is in the public domain; individual items are checked for usage terms before publication.
- NASA JPLJet Propulsion Laboratory / Solar System Dynamics
Orbital data, ephemerides, and small-body parameters for planets, asteroids, and comets.