![[Pasted image 20241217005329.png]] ## LEO **Low Earth Orbit (LEO)** **Altitude**: 160 – 2,000 km **Characteristics**: Short orbital periods (~90–120 minutes), low latency for communications, ideal for Earth observation, and less costly to reach. **Examples**: - **International Space Station (ISS)** – Crew and research platform. - **Starlink Satellites** ([[SpaceX]]) – Broadband internet constellation. - **[[Planet Labs]] Dove Satellites** – Earth observation and imaging. ## GEO **Geostationary Orbit (GEO)** **Altitude**: ~35,786 km above Earth's equator **Characteristics**: Satellites in GEO match Earth's rotation, appearing fixed over a single location. Ideal for communications, weather monitoring, and broadcasting due to constant coverage. **Examples**: - **GOES Satellites** – U.S. weather monitoring. - **Intelsat Satellites** – Global communications and broadcasting. - **Inmarsat Satellites** – Satellite communications for maritime and aviation sectors. ## GSO **Geosynchronous Orbit (GSO)** **Altitude**: ~35,786 km above Earth's equator. **Characteristics**: Satellites in GSO have an orbital period that matches Earth's rotation (24 hours). Unlike [[🌍 Orbits#GEO|GEO]], these orbits are inclined or elliptical, so the satellite appears to move in a figure-eight (analemma) relative to the ground. **Examples**: - **Inmarsat-3 F1** – Communication satellite for global coverage. - **GOES (Geostationary Operational Environmental Satellites)** – Weather monitoring satellites. - **QZSS (Quasi-Zenith Satellite System)** – Japanese satellite system providing regional positioning services. ## MEO **Medium Earth Orbit (MEO)** **Altitude**: ~2,000 km to 35,786 km **Characteristics**: Offers a balance between coverage area and signal latency. Commonly used for navigation, communication, and some Earth observation systems. **Examples**: - **GPS Satellites** – U.S. Global Positioning System (20,200 km). - **Galileo Satellites** – European navigation system. - **GLONASS Satellites** – Russian navigation system. ## SSO **Sun-Synchronous Orbit (SSO)** **Altitude**: ~600-800 km above Earth's surface (a subset of [[🌍 Orbits#LEO|LEO]]). **Characteristics**: A near-polar orbit where the satellite passes over the same region at roughly the same local solar time each day, ensuring consistent lighting conditions for imaging. Ideal for Earth observation and remote sensing. **Examples**: - **Sentinel-2** – ESA's Copernicus Earth observation satellites. - **Landsat** – NASA's Earth observation program. - **Planet Labs' Dove Satellites** – High-frequency imaging for Earth monitoring. ## Polar **Polar Orbit** - **Altitude**: Typically 200–1,000 km (Low Earth Orbit range), but can extend higher. - **Characteristics**: Satellites in polar orbits pass over Earth's poles, allowing them to observe the entire planet over time as Earth rotates. They have near-90° inclination and are often sun-synchronous for consistent lighting. - **Examples**: - **NOAA POES (Polar Operational Environmental Satellites)** – Weather and environmental monitoring. - **Terra (NASA)** – Earth observation for climate and environmental data. - **CryoSat-2** – ESA's satellite for ice thickness monitoring. ## GTO **Geostationary Transfer Orbit (GTO)** **Altitude**: Highly elliptical orbit with a low perigee (~200 km) and a high apogee (~35,786 km). **Characteristics**: A transitional orbit used to move satellites from Low Earth Orbit ([[🌍 Orbits#LEO|LEO]]) to Geostationary Orbit ([[🌍 Orbits#GEO|GEO]]). The orbit is elliptical, and satellites use onboard propulsion to circularize at GEO altitude. **Examples**: - **Communications Satellites** – Initial placement for satellites like SES and Intelsat before reaching GEO. - **Weather Satellites** – Launch stages for satellites such as GOES before they circularize at GEO. - **Commercial Launch Missions** – Many rockets like [[SpaceX]]'s Falcon 9 or Rocket Lab's Electron place payloads in GTO as a transfer stage. ## TLI **Trans-Lunar Injection (TLI)** TLI is a maneuver that propels a spacecraft from Earth orbit onto a trajectory toward the Moon. This orbit provides the necessary velocity to escape Earth's gravity and enter a lunar transfer trajectory. TLI is typically performed after a spacecraft is positioned in a parking orbit, such as low Earth orbit (LEO). Examples of Missions Using TLI: - Apollo Program: NASA's historic lunar missions used TLI to send crewed spacecraft toward the Moon. - CAPSTONE Mission: A small CubeSat operated by Advanced Space, launched to test lunar orbit dynamics for NASA's Artemis program. - Artemis I: NASA's uncrewed mission as part of the Artemis program utilized TLI to send the Orion spacecraft into a lunar orbit.