Solar radiation pressure

Solar radiation pressure is the force sunlight exerts on an object by transferring momentum when its photons are absorbed or reflected. Its strength depends on the object’s distance from the Sun and how it interacts with light.

Photon momentum: The momentum carried by a photon, proportional to its energy and inversely proportional to the speed of light. Absorption or reflection transfers this momentum from sunlight to the object.
Solar sail: A spacecraft propulsion system that uses sunlight’s momentum to accelerate a large reflective sail. It is designed to turn solar radiation pressure into sustained thrust.
Mariner 10: A NASA spacecraft that flew past Mercury three times in 1974 and 1975. Solar pressure disturbed its attitude, prompting a correction to its trajectory model.
Solar gravity: The gravitational attraction exerted by the Sun on bodies in the Solar System. It pulls matter toward the Sun, while radiation pressure pushes illuminated matter away.
Radiation pressure: Pressure exerted on a surface by electromagnetic radiation transferring momentum. Solar radiation pressure is the pressure from sunlight acting on an object.
LightSail 2: A CubeSat mission that demonstrated orbit changes using a reflective solar sail. Its flight provided an in-space demonstration of propulsion by sunlight.
IKAROS: A Japanese spacecraft that demonstrated solar-sail propulsion during its 2010 interplanetary mission. Its sail’s acceleration made solar radiation pressure a measured propulsion effect.
Yarkovsky effect: A force caused by anisotropic thermal emission from a rotating body heated by sunlight. Unlike direct radiation pressure, it arises from reradiated heat rather than incident photon momentum alone.
Reflectivity: The fraction of incident radiation a surface reflects rather than absorbs or transmits. Reflection transfers more momentum than absorption, changing the force from sunlight.
Spacecraft attitude control: Methods for controlling a spacecraft’s orientation in space. Uneven solar pressure can create torque that missions must predict or exploit.

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