Earth orbit

Earth orbit
Name	Earth orbit

Earth orbit is the set of trajectories taken by objects under the gravitational influence of the planet while revolving around the Sun and bound primarily by Newton's laws of motion and Universal gravitation. Orbital paths around the planet are governed by historic formulations from Isaac Newton, refined by Pierre-Simon Laplace and modern celestial mechanics applied by agencies such as NASA, European Space Agency and Roscosmos. Human activity in these trajectories includes missions by Apollo program, International Space Station operations, and commercial launches by SpaceX and Arianespace.

Overview

Orbiting objects range from natural bodies like Moon to artificial satellites launched by organizations such as Indian Space Research Organisation and Japan Aerospace Exploration Agency. Characteristic regimes include low-altitude trajectories used by the International Space Station and high-altitude paths exploited by Global Positioning System and Inmarsat. Key historical milestones include the launch of Sputnik 1 and crewed flights of Vostok 1, which transformed strategic uses through programs like Mercury program and programs of China National Space Administration.

Orbital mechanics and parameters

Fundamental parameters are semi-major axis, eccentricity, inclination, ascending node, argument of perigee and true anomaly, developed from work by Johannes Kepler and formalized via Kepler's laws of planetary motion. Perturbations arise from nonspherical gravity described by the J2 perturbation (Earth oblateness), third-body effects from Moon and the Sun, and atmospheric drag at low altitudes modeled using standards from Committee on Space Research and datasets from National Oceanic and Atmospheric Administration. Mission design uses patched conic approximations from Konstantin Tsiolkovsky-inspired rocketry and numerical propagation techniques used by Jet Propulsion Laboratory and European Space Operations Centre.

Types of Earth orbits

Common classifications include low Earth orbit (LEO) used by Hubble Space Telescope and crewed platforms like Skylab, medium Earth orbit (MEO) employed by Global Positioning System and Glonass, geostationary orbit (GEO) occupied by communications satellites such as those from Intelsat and Eutelsat, and highly elliptical orbits exemplified by Molniya satellites. Sun-synchronous and polar inclinations serve Earth observation missions by agencies like Landsat and Copernicus Programme. Transfer orbits such as the Hohmann transfer are routinely used in launches by providers including United Launch Alliance.

Natural satellites and debris

Natural companions include the Moon and transient co-orbitals like quasi-satellites observed in surveys by institutions such as Pan-STARRS and LINEAR. Anthropogenic objects range from functioning spacecraft by Iridium Communications to defunct rocket stages cataloged by United States Strategic Command. Space debris incidents, including collisions like 2009 satellite collision and fragmentation events, are tracked by entities such as Space Surveillance Network and mitigated by guidelines from Inter-Agency Space Debris Coordination Committee. Cataloged debris influences conjunction assessment protocols used by operators including SpaceX and OneWeb.

Launching and orbital insertion

Launch vehicles such as Saturn V, Soyuz and Falcon 9 provide delivery into target orbits via staging and guidance systems developed by corporations like Boeing and Lockheed Martin. Insertion maneuvers employ burns planned at facilities including Kennedy Space Center and Baikonur Cosmodrome, with orbital phasing and plane change strategies based on trade studies by Aerospace Corporation and mission control centers such as TsUP. Legal and regulatory frameworks involve entities like Federal Aviation Administration and international agreements including the Outer Space Treaty.

Orbital decay and lifetime

Atmospheric drag, solar activity modulated by the 11-year solar cycle and geomagnetic storms from Solar Dynamics Observatory influence decay rates for low-altitude objects, with reentry risk assessments conducted by agencies such as European Space Agency and China Aerospace Science and Technology Corporation. Long-term orbital lifetime projections for debris require modeling tools used by NASA Orbital Debris Program Office and mitigation practices prescribed by United Nations Office for Outer Space Affairs. Techniques for lifetime extension include altitude-raising maneuvers by operators like Intelsat and end-of-life disposal to graveyard orbits used by GEO satellite operators including SES.

Applications and impacts

Earth-centered orbits enable services from Global Positioning System, remote sensing by missions such as Sentinel and meteorology by platforms like Geostationary Operational Environmental Satellite. Scientific investigations by observatories including Chandra X-ray Observatory and experiments on International Space Station inform disciplines advanced at institutions such as Smithsonian Astrophysical Observatory and Max Planck Society. Societal and economic impacts involve telecommunications by companies like Telesat, navigation sectors relying on European Union programs, and environmental monitoring tied to initiatives by United Nations Environment Programme.

Category:Orbits