// ORBITAL LOGISTICS AND PROPULSION TERM
Phase Angle
The angle between the light source (like the Sun), the observed object (like a planet or moon), and the observer (like a spacecraft or telescope).
TECHNICAL DEFINITION
Phase angle is the angle formed by the vectors from an observer to an illuminated object and from the illuminated object to the light source (e.g., Sun-object-observer angle), critical for determining the object's illumination, apparent brightness, and surface feature visibility in remote sensing and planetary science.
BACKGROUND
China has one of the most active space programs in the world. With launch vehicles of the Long March rocket family and four spaceports, China conducts the most or second most orbital launches each year. China's fleet of over 1,300 Earth orbit satellites serves communication, navigation, reconnaissance and scientific research. China Manned Space Program operates Tiangong, one of two active space stations alongside the International Space Station (ISS). China National Space Administration (CNSA) has achieved robotic rover, lander, and orbiter missions to the Moon and Mars.
READ MORE ON WIKIPEDIASYNONYMS & ALIASES
- Illumination angle
- solar phase angle
- viewing angle
USAGE NOTE
High phase angles can make observing surface features difficult due to backscattering and shadows.
DEVELOPERS
Organizations developing technology related to Phase Angle.
A U.S. government agency that designs and executes complex space missions. The calculation of phase angles is fundamental to their work, determining launch windows for interplanetary travel (e.g., to Mars) and enabling rendezvous and docking procedures with the International Space Station (ISS).
Managed by Caltech for NASA, JPL specializes in robotic interplanetary missions. Their trajectory and navigation teams are experts in astrodynamics, developing software and techniques to calculate the precise phase angles required for gravity assists and targeting celestial bodies across the solar system.
Ansys develops engineering simulation software, including the Systems Tool Kit (STK), originally created by AGI. STK is an industry-standard physics-based software platform used for analyzing and visualizing assets in space. It provides core tools for calculating and optimizing trajectories based on phase angles for rendezvous, station-keeping, and interplanetary missions.
An intergovernmental organization dedicated to the exploration of space. ESA's mission operations and flight dynamics teams develop and use advanced software to plan complex trajectories for missions like JUICE (JUpiter ICy moons Explorer), which rely on precise phase angle calculations for multiple gravity-assist maneuvers over many years.
A private aerospace company that designs, manufactures, and launches rockets and spacecraft. SpaceX's operations, from the precise orbital insertion of Starlink satellites to maintain constellation phasing, to the Crew Dragon's rendezvous and docking with the ISS, are all dependent on a mastery of phase angle calculations and management.
A global aerospace and defense technology company. Through its SpaceLogistics subsidiary, the company operates the Mission Extension Vehicle (MEV) to service satellites in orbit. These rendezvous and docking operations require extremely precise guidance, navigation, and control (GNC) systems that actively manage the phase angle with the target satellite.
A commercial provider of space situational awareness (SSA) data and services. LeoLabs uses a global network of phased-array radars to track objects in low Earth orbit. Their platform calculates and predicts orbital paths, which inherently involves determining the relative phasing of satellites to identify and prevent potential collisions.