# ALEXANDER > 39144 **Wikidata**: [Q111471895](https://www.wikidata.org/wiki/Q111471895) **Source**: https://4ort.xyz/entity/alexander-q111471895 ## Summary ALEXANDER refers to the class of artificial satellites—human‑made objects placed into orbit around a celestial body, most commonly Earth, to perform functions such as communication, navigation, scientific research, and military operations. The first artificial satellite, Sputnik 1, was launched by the Soviet Union on October 4, 1957, marking the start of the space age. ## Key Facts - **Instance of**: artificial satellite - **Wikidata description**: 39144 - **Wolfram Language entity code**: Entity["Satellite", "39144"] - **First artificial satellite**: Sputnik 1, launched by the Soviet Union on October 4, 1957 - **Primary function**: orbit a celestial body (typically Earth) to perform tasks like communication, navigation, scientific observation, or military applications - **Classification**: subclass of spacecraft - **Types**: passive satellites (e.g., Project Echo), tethered satellites, specialized satellites such as orbital power plants - **Orbital categories**: geostationary, low Earth orbit (LEO), heliocentric (e.g., artificial satellites of the Sun) - **Miniaturized variants**: femtosatellites, picosatellites, crowdfunded satellites - **Military applications**: Syracuse 4 (French) and Gonets‑M (Russian) satellite constellations - **Scientific missions**: Environmental Research Satellites (1960s) and PAGEOS (1966) used for geodetic research - **Space debris management**: development of space debris removal satellites to address orbital clutter ## FAQs **What distinguishes an artificial satellite from a spacecraft?** An artificial satellite is a specific type of spacecraft designed to orbit a celestial body, whereas the term spacecraft encompasses a broader category that includes satellites, probes, and crewed vehicles. **How does an artificial satellite remain in orbit?** A satellite stays in orbit by balancing gravitational pull with its forward velocity; the resulting centrifugal force counteracts gravity, allowing continuous free‑fall around the Earth. **What are the primary uses of artificial satellites?** Satellites are employed for communication (television, internet, telephony), navigation (GPS), weather monitoring, scientific research (Earth atmosphere, climate, space), military surveillance, and Earth observation. **Who launched the first artificial satellite and when?** The Soviet Union launched the first artificial satellite, Sputnik 1, on October 4, 1957, an event that initiated the space age. **What is a femtosatellite?** A femtosatellite is a miniaturized artificial satellite with very small size and mass, typically under 1 kg, used mainly for educational or experimental purposes. ## Why It Matters Artificial satellites have transformed modern society by forming the backbone of global communication networks, enabling real‑time weather forecasting, and providing the precise positioning data that underpins GPS and countless location‑based services. They support military operations through secure communication constellations such as Syracuse 4 and Gonets‑M, and they advance scientific knowledge via missions like the Environmental Research Satellites of the 1960s and PAGEOS (1966), which improved geodetic measurements. The launch of Sputnik 1 in 1957 sparked the Space Race, accelerating aerospace innovation and leading to today’s thousands of orbiting objects, including large constellations like Starlink. However, the proliferation of satellites has created challenges such as space debris and orbital congestion, prompting ongoing efforts to develop debris removal technologies to ensure the long‑term sustainability of space activities. ## Notable For - First human‑made object in space: Sputnik 1 (1957) - Enabling global communication: satellites relay television, internet, and telephony signals worldwide - Advancing scientific research: PAGEOS (1966) enhanced geodetic measurements; Environmental Research Satellites studied Earth’s systems - Supporting military security: constellations like Syracuse 4 provide encrypted communications - Driving miniaturization: femtosatellites and picosatellites allow low‑cost access to space for education and experimentation ## Body ### Definition and Function An artificial satellite is a human‑made object placed into orbit around a celestial body, typically Earth. These satellites serve various purposes, including communication, navigation, scientific research, and military applications. The first artificial satellite, Sputnik 1, was launched by the Soviet Union on October 4, 1957, marking the beginning of the space age. ### Types and Variants Artificial satellites come in several forms: - **Passive satellites**: exemplified by Project Echo, which reflected radio signals. - **Tethered satellites**: consist of two masses connected by a cable. - **Specialized satellites**: include orbital power plants designed to capture solar energy for wireless transmission. - **Miniaturized variants**: femtosatellites, picosatellites, and crowdfunded satellites, each weighing less than 1 kg and used for low‑cost experiments. ### Orbital Characteristics Satellites are classified by their orbits: - **Geostationary satellites**: remain fixed over a single point on the Equator. - **Low Earth orbit (LEO)**: altitudes roughly 160–2,000 km, used for communication constellations and Earth observation. - **Heliocentric orbits**: objects that orbit the Sun, such as artificial satellites of the Sun. ### Historical Milestones - **Sputnik 1 (1957)**: first artificial satellite, launched by the Soviet Union. - **Project Echo (1960)**: first passive communications satellite. - **PAGEOS (1966)**: NASA’s passive geodetic satellite that improved measurements of Earth’s shape and gravity field. ### Applications - **Communication**: satellites enable television broadcasts, internet connectivity, and telephone links across remote regions. - **Navigation**: global positioning systems rely on constellations of satellites transmitting timing signals. - **Scientific research**: platforms study atmospheric composition, climate patterns, magnetospheric phenomena, and deep‑space environments. - **Military**: systems such as the French Syracuse 4 and Russian Gonets‑M constellations provide secure, jam‑resistant communications for defense forces. ### Challenges - **Space debris**: thousands of defunct satellites and fragments create collision hazards in orbit. - **Orbital congestion**: increasing numbers of launches heighten the risk of Kessler‑type cascades. - **Mitigation efforts**: research and development of active debris removal satellites aim to capture and deorbit junk, preserving the usability of key orbital regimes.