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Inmarsat-4A F4
Inmarsat-4A F4, also known as Alphasat and Inmarsat-XL, is a large geostationary communications I-4 satellite operated by United Kingdom-based Inmarsat in partnership with the European Space Agency. Launched in 2013, it is used to provide mobile communications to Africa and parts of Europe and Asia. Inmarsat-4A F4 has been constructed by EADS Astrium and Thales Alenia Space based on the Alphabus satellite bus. It was the first Alphabus spacecraft to be launched, and as such it carries several experimental communications systems in addition to its commercial payload. The spacecraft had a launch mass of , and is expected to operate for at least fifteen years. Arianespace had been contracted to launch Inmarsat-4A F4, with an Ariane 5ECA rocket, flight number VA-214, delivering it and INSAT-3D into geosynchronous transfer orbit. The rocket lifted off from ELA-3 at Kourou at 19:54:07 UTC on 25 July 2013, with Inmarsat-4A F4 separating from the rocket around 27 minutes later. The sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Communications Satellite
A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a Transponder (satellite communications), transponder; it creates a communication channel between a source transmitter and a Radio receiver, receiver at different locations on Earth. Communications satellites are used for television, telephone, radio, internet, and military applications. Many communications satellites are in geostationary orbit above the equator, so that the satellite appears stationary at the same point in the sky; therefore the satellite dish antennas of ground stations can be aimed permanently at that spot and do not have to move to track the satellite. Others form satellite constellations in low Earth orbit, where antennas on the ground have to follow the position of the satellites and switch between satellites frequently. The radio waves used for telecommunications links travel by Line-of-sight propagation, line of sight and so are obstructe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Satellite Bus
A satellite bus (or spacecraft bus) is the main body and structural component of a satellite or spacecraft, in which the payload and all scientific instruments are held. Bus-derived satellites are less customized than specially-produced satellites, but have specific equipment added to meet customer requirements, for example with specialized sensors or transponders, in order to achieve a specific mission. They are commonly used for geosynchronous satellites, particularly communications satellites, but are most commonly used in spacecraft which occupy low Earth orbit missions. Examples Some satellite bus examples include: * Boeing DS&S 702 * Lockheed Martin Space Systems A2100 * Moog Inc. SL-OMV, Meteor, Meteorite * * INVAP ARSAT-3K * Airbus D&S Eurostar * ISRO's I-1K, I-2K, I-3K, I-4K, I-6K, and Indian Mini Satellite bus * NASA Ames MCSB * SSL 1300 * family * Orbital ATK Star Bus family, inc GEOStar * Mitsubishi Electric DS2000 * Spacecraft bus of the Jam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spacecraft Launched In 2013
A spacecraft is a vehicle that is designed to fly and operate in outer space. Spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, planetary exploration, and transportation of humans and cargo. All spacecraft except single-stage-to-orbit vehicles cannot get into space on their own, and require a launch vehicle (carrier rocket). On a sub-orbital spaceflight, a space vehicle enters space and then returns to the surface without having gained sufficient energy or velocity to make a full Earth orbit. For orbital spaceflights, spacecraft enter closed orbits around the Earth or around other celestial bodies. Spacecraft used for human spaceflight carry people on board as crew or passengers from start or on orbit (space stations) only, whereas those used for robotic space missions operate either autonomously or telerobotically. Robotic spacecraft used to support scientific research are space prob ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ka Band
The Ka band (pronounced as either "kay-ay band" or "ka band") is a portion of the microwave part of the electromagnetic spectrum. The designation "Ka-band" is from Kurz-above, which stems from the German word ''kurz,'' meaning "short". There is no standard definition of Ka-band. IEEE Standard letter designations for Radar Bands define the nominal frequency range for Ka band in the range 27–40 gigahertz (GHz) in Tables 1 and 2 of IEEE Standard 521 i.e. wavelengths from slightly over one centimeter down to 7.5 millimeters. The ITU however approves Ka-band satellite networks in the 17.3-31 GHz frequency range, with most Ka-band satellite networks having uplinks in the 27.5–31 GHz and downlinks in the 17.7–21.2 GHz range. The band is called Ka, short for "K-above" because it is the upper part of the original (now obsolete) NATO K band, which was split into three bands because of the presence of the atmospheric water vapor resonance peak at 22.24 G ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sentinel-1A
Sentinel-1A is a European radar imaging satellite launched in 2014. It is the first Sentinel-1 satellite launched as part of the European Union's Copernicus programme. The satellite carries a C-band Synthetic Aperture Radar which will provide images in all light and weather conditions. It analyzes many phenomena occurring on Earth, from detecting and tracking oil spills and mapping sea ice to monitoring movement in land surfaces and mapping changes in the way land is used. Program Copernicus is the long-term European Union Earth observation and monitoring programme. It used to be called GMES (Global Monitoring for Environment and Security) and was established by a Regulation that entered into force in 2014. It is a user-driven programme under civil control. Activities conducted under the programme included the launch of six families of dedicated, EU-owned earth observation satellites and instruments—the so-called Sentinels—and the ramp-up of the 6 Copernicus Services in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
European Data Relay System
The European Data Relay System (EDRS) system is a European constellation of GEO satellites that relay information and data between satellites, spacecraft, UAVs, and ground stations. The first components (a payload and dedicated GEO satellite) were launched in 2016 and 2019. Purpose and context The designers intend the system to provide almost full-time communication, even with satellites in low Earth orbit that often have reduced visibility from ground stations. It makes on-demand data available to, for example, rescue workers who want near-real-time satellite data of a crisis region. There are a number of key services that will benefit from this system's infrastructure: * Earth Observation applications in support of time-critical and/or data-intensive services; e.g., change detection, environmental monitoring. * Government and security services that need images from key European space systems such as Global Monitoring for Environment and Security. * Emergency response and cris ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orbital Period
The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets, exoplanets orbiting other stars, or binary stars. It may also refer to the time it takes a satellite orbiting a planet or moon to complete one orbit. For celestial objects in general, the orbital period is determined by a 360° revolution of one body around its primary, ''e.g.'' Earth around the Sun. Periods in astronomy are expressed in units of time, usually hours, days, or years. Its reciprocal is the orbital frequency, a kind of revolution frequency, in units of hertz. Small body orbiting a central body According to Kepler's Third Law, the orbital period ''T'' of two point masses orbiting each other in a circular or elliptic orbit is: :T = 2\pi\sqrt where: * ''a'' is the orbit's semi-major axis * ''G'' is the gravitationa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orbital Eccentricity
In astrodynamics, the orbital eccentricity of an astronomical object is a dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values between 0 and 1 form an elliptic orbit, 1 is a parabolic escape orbit (or capture orbit), and greater than 1 is a hyperbola. The term derives its name from the parameters of conic sections, as every Kepler orbit is a conic section. It is normally used for the isolated two-body problem, but extensions exist for objects following a rosette orbit through the Galaxy. Definition In a two-body problem with inverse-square-law force, every orbit is a Kepler orbit. The eccentricity of this Kepler orbit is a non-negative number that defines its shape. The eccentricity may take the following values: * Circular orbit: * Elliptic orbit: * Parabolic trajectory: * Hyperbolic trajectory: The eccentricity is given by e = \sqrt where ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semimajor Axis
In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the longest semidiameter or one half of the major axis, and thus runs from the centre, through a focus, and to the perimeter. The semi-minor axis (minor semiaxis) of an ellipse or hyperbola is a line segment that is at right angles with the semi-major axis and has one end at the center of the conic section. For the special case of a circle, the lengths of the semi-axes are both equal to the radius of the circle. The length of the semi-major axis of an ellipse is related to the semi-minor axis's length through the eccentricity and the semi-latus rectum \ell, as follows: The semi-major axis of a hyperbola is, depending on the convention, plus or minus one half of the distance between the two branches. Thus it is the distance from the c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orbital Inclination
Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Earth directly above the Equator, the plane of the satellite's orbit is the same as the Earth's equatorial plane, and the satellite's orbital inclination is 0°. The general case for a circular orbit is that it is tilted, spending half an orbit over the northern hemisphere and half over the southern. If the orbit swung between 20° north latitude and 20° south latitude, then its orbital inclination would be 20°. Orbits The inclination is one of the six orbital elements describing the shape and orientation of a celestial orbit. It is the angle between the orbital plane and the plane of reference, normally stated in degrees. For a satellite orbiting a planet, the plane of reference is usually the plane containing the planet's equator. For pla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apsis
An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides pertaining to orbits around different bodies have distinct names to differentiate themselves from other apsides. Apsides pertaining to geocentric orbits, orbits around the Earth, are at the farthest point called the ''apogee'', and at the nearest point the ''perigee'', like with orbits of satellites and the Moon around Earth. Apsides pertaining to orbits around the Sun are named ''aphelion'' for the farthest and ''perihelion'' for the nearest point in a heliocentric orbit. Earth's two apsides are the farthest point, ''aphelion'', and the nearest point, ''perihelion'', of its orbit around the host Sun. The terms ''aphelion'' and ''perihelion'' apply in the same way to the orbits of Jupiter and the other planets, the comets, and the asteroids of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Longitude
Longitude (, ) is a geographic coordinate that specifies the east- west position of a point on the surface of the Earth, or another celestial body. It is an angular measurement, usually expressed in degrees and denoted by the Greek letter lambda (λ). Meridians are imaginary semicircular lines running from pole to pole that connect points with the same longitude. The prime meridian defines 0° longitude; by convention the International Reference Meridian for the Earth passes near the Royal Observatory in Greenwich, south-east London on the island of Great Britain. Positive longitudes are east of the prime meridian, and negative ones are west. Because of the Earth's rotation, there is a close connection between longitude and time measurement. Scientifically precise local time varies with longitude: a difference of 15° longitude corresponds to a one-hour difference in local time, due to the differing position in relation to the Sun. Comparing local time to an absol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
