Space Based:
A space based system is a system where its components are physical entities that exist in space, and whose operations or functions are carried out primarily through interactions with their environment in space. The term usually refers to systems where there is no ground infrastructure, such as satellites, but it may also refer to systems where there is significant ground infrastructure, such as the International Space Station. A key characteristic of a space based system is that it must be able to operate independently of Earth-based support, although it may receive data or other inputs from ground-based stations.
The first artificial satellite, Sputnik 1, was launched into orbit by the Soviet Union on October 4, 1957. This event ushered in the Space Age and began a new era of human exploration of the cosmos. Since then hundreds of satellites have been launched into orbit by various nations for a variety of purposes including communications, navigation, weather forecasting, earth observation, and scientific research. Satellites can be classified according to their mission or function:
* Communications satellites relay signals between distant points on Earth for telephone calls (cellular and landline), television programming (including direct-to-home television), Internet connectivity (VSAT), radio broadcasts (such as Sirius XM Satellite Radio) and GPS navigation signals. They are often placed in geostationary orbit 35786 km above the equator so they appear stationary from Earth’s surface allowing antennae on the ground to point permanently at them; however some communication satellites use low Earth orbits ranging from 160 km to 2000 km altitude making them much closer to the surface but requiring tracking antennas on the ground due to their rapid movement across the sky.
* Navigation satellites provide precise location information (usually integrated with timing information) which is used by ships at sea, aircraft over oceans or deserts far from any visual cues like landmarks or airports, vehicles driving in unfamiliar areas or hikers exploring off beaten trails. Examples include GPS constellation operated by US Air Force/NOAA/US Coast Guard, GLONASS operated by Russian Aerospace Defence Forces, Galileo operated by European Commission/European Space Agency, BeiDou operated by China National Space Administration, NAVIC operated by India.
* Weather forecasting satellites observe atmospheric conditions like temperature, humidity, wind speed etc., either directly using radiometers or indirectly using scanners that measure emitted microwave radiation which is correlated with water vapor content. Geostationary weather satellites remain fixed over one spot on Earth’s surface while polar orbiting weather satellites travel across 14 orbits per day covering almost every part of Earth’s surface during each cycle providing more frequent coverage but less detail than geostationary ones.:45–48 These images are processed using supercomputers resulting in global maps showing various meteorological parameters which forecasters then use along with computer models to make predictions about future conditions.:443–445 Global Positioning System (GPS) constellation owned & operated United States Air Force used for precision navigation & timing worldwide consists 31 operational spacecrafts orbiting at 20200 km altitudes & 6400km apart from each other).:28 NavIC constellation owned & operated Indian Space Research Organisation used for precision navigation within India & its neighbourhood region up 1000km consist 10 operational spacecrafts orbiting at 36000km altitude & 40000km apart from each other).:3 GLONASS constellation owned & operated Russian Aerospace Defence Forces used for precision navigation globally consist 24 operational spacecrafts orbiting at 19100 km altitudes & 11500km apart from each other).:72 BeiDou constellation owned China National Space Administration currently provides regional services globally consisting 30 operational spacecrafts orbiting 13000–14000 km altitudes Mobile TeleSystems company operates Iridium Next mobile satellite constellations providing L-band voice & data coverage globally consisting 66+ active crosslinked LEO craft as wellas 9 Inmarsat GEO craft)[23 O3b Networks provides Medium Earth Orbit broadband services consisting 12 GEO craft orbited 8000 kilometers above mean sea level). [24 OneWeb plans deploying 1200 LEO craft providing global high speed internet connectivity starting 2019 onwards.) [25 Telesat planning deploying 117 LEO crafts around 14 orbital planes providing global high speed broadband internet access starting 2022 onwards.) [26 SpaceX Starlink planning launching 4000+ LEO crafts providing moderate speed global internet access starting 2020 onwards) [27 Boeing intending Helios solar powered UAV flying continuously for months capable carrying 500kg payload staying aloft 21000 meters)) [28 NASA’S PACE solar powered UAV capable flying continuously multiple years carrying 450kg payload]])