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Pass (spaceflight)
An orbital pass (or simply pass) is the period in which a spacecraft is above the local horizon, and thus available for line-of-sight communication with a given ground station, receiver, or relay satellite, or for visual sighting. The beginning of a pass is termed ''acquisition of signal'' (AOS); the end of a pass is termed ''loss of signal'' (LOS). The point at which a spacecraft comes closest to a ground observer is the ''time of closest approach'' (TCA). Timing and duration The timing and duration of passes depends on the characteristics of the orbit a satellite occupies, as well as the ground topography and any occulting objects on the ground (such as buildings), or in space (for planetary probes, or for spacecraft using relay satellites). The longest duration ground pass will be experienced by an observer directly on the ground track of the satellite. Path loss is greatest toward the start and end of a ground pass, as is Doppler shifting for Earth-orbiting satellites. S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coverage (telecommunication)
In telecommunications, the coverage of a radio station is the geographic area where the station can communicate. Broadcasters and telecommunications companies frequently produce coverage maps to indicate to users the station's intended service area. Coverage depends on several factors, such as orography (i.e. mountains) and buildings, technology, radio frequency and perhaps most importantly for two-way telecommunications the sensitivity and transmit efficiency of the consumer equipment. Some frequencies provide better regional coverage, while other frequencies penetrate better through obstacles, such as buildings in cities. The ability of a mobile phone to connect to a base station depends on the strength of the signal. That may be boosted by higher power transmissions, better antennas, taller antenna masts or alternative solutions like in-building picocells. Normal Macro-Cell signals need to be boosted to pass through buildings, which is a particular problem designing networks f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Universe Today
Universe Today (U.T.) is a North American-based non-commercial space and astronomy news website founded by Fraser Cain. The domain was registered on December 30, 1998, and the website went live in March 1999. ''Universe Today'' assumed its current form on July 24, 2003, featuring astronomy news and other space-related content. In early September 2005, the website’s forum section merged with '' Bad Astronomy'' to create a combined site with the BAUT forum. During April 2011, the Association of British Science Writers noted that ''Universe Today'' decided not to make preparations for reporting on embargoed stories until they are public knowledge. Emily Lakdawalla said that she relies on ''Universe Today'' and '' Bad Astronomy'' to "give ... an independent look at big news stories". Publications ''Universe Today'' has published two books, which are available both as e-books and on physical media: * * See also * '' Astronomy Cast'' * ''Space.com Space.com is an on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Space University
The International Space University (ISU) is a higher education institute headquartered in Illkirch-Graffenstaden, a suburb of Strasbourg, France. It is dedicated to the discovery, research, and development of outer space and its applications for peaceful purposes, through international and multidisciplinary education and research programs. ISU was founded in 1987 and is registered in France and in the United States as a non profit organisation. As of April 2020, there were over 5000 ISU alumni from 109 countries. The Chancellor of the International Space University is Pascale Ehrenfreund, Chair of the German Aerospace Center (DLR) Executive Board and President of the International Astronautical Federation (IAF). Previous chancellors have included Buzz Aldrin, Jean-Jacques Dordain, and Arthur C. Clarke. The sixth President of the International Space University is Juan de Dalmau who succeeded Walter Peeters in September 2018. History In 1985, space enthusiasts Peter Diama ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Satellite Watching
Satellite watching or satellite spotting is a hobby which consists of the observation and tracking of artificial satellites that are orbiting Earth. People with this hobby are variously called satellite watchers, trackers, spotters, observers, etc. Since satellites outside Earth's shadow reflect sunlight, those especially in low Earth orbit may visibly glint (or "flare") as they traverse the observer's sky, usually during twilight. History Amateur satellite spotting traces back to the days of early artificial satellites when the Smithsonian Astrophysical Observatory launched the Operation Moonwatch program in 1956 to enlist amateur astronomers in an early citizen science effort to track Soviet Union, Soviet ''sputniks''. The program was an analog to the World War II Ground Observer Corps citizen observation program to spot enemy bombers. Moonwatch was crucial until professional stations were deployed in 1958. The program was discontinued in 1975. The people who had been invo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Satellite Revisit Period
The satellite revisit period is the time elapsed between observations of the same point on Earth by a satellite. It depends on the satellite's orbit, target location, and swath of the sensor. "Revisit" is related to the same ground trace, a projection of the satellite's orbit on to the Earth. Revisit requires a very close repeat of the ground trace. In the case of polar orbit or highly inclined low-Earth-orbit reconnaissance satellites, the sensor must have the variable swath, to look longitudinally (east-west, or sideways) at a target, in addition to direct overflight observation, looking nadir. In the case of the Israeli EROS Earth observation satellite, the ground trace repeat is 15 days, but the actual revisit time is 3 days, because of the swath ability of the camera payload. See also * Orbit period * Satellite watching Satellite watching or satellite spotting is a hobby which consists of the observation and tracking of artificial satellites that are orbiting Ea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ground Track
A satellite ground track or satellite ground trace is the path on the surface of a planet directly below a satellite's trajectory. It is also known as a suborbital track or subsatellite track, and is the vertical projection of the satellite's orbit onto the surface of the Earth (or whatever body the satellite is orbiting). A satellite ground track may be thought of as a path along the Earth's surface that traces the movement of an imaginary line between the satellite and the center of the Earth. In other words, the ground track is the set of points at which the satellite will pass directly overhead, or cross the zenith, in the frame of reference of a ground observer.. The ground track of a satellite can take a number of different forms, depending on the values of the orbital elements, parameters that define the size, shape, and orientation of the satellite's orbit, although identification of the always reliant upon the recognition of the physical form that is in motion; This ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jet Propulsion Laboratory
The Jet Propulsion Laboratory (JPL) is a Federally funded research and development centers, federally funded research and development center (FFRDC) in La Cañada Flintridge, California, Crescenta Valley, United States. Founded in 1936 by California Institute of Technology (Caltech) researchers, the laboratory is now owned and sponsored by NASA and administered and managed by Caltech. The primary function of the laboratory is the construction and operation of planetary robotic spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating the NASA Deep Space Network (DSN). Among the major active projects at the laboratory, some are the Mars 2020 mission, which includes the ''Perseverance (rover), Perseverance'' rover; the Mars Science Laboratory mission, including the ''Curiosity (rover), Curiosity'' rover; the ''Mars Reconnaissance Orbiter''; the ''Juno (spacecraft), Juno'' spacecraft orbiting Jupiter; the ''Soil Moisture Active P ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Venus
Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker and denser than Earth and any other rocky body in the Solar System. Its atmosphere is composed of mostly carbon dioxide (), with a global sulfuric acid cloud cover and no liquid water. At the mean surface level the atmosphere reaches a temperature of and a pressure 92 times greater than Earth's at sea level, turning the lowest layer of the atmosphere into a supercritical fluid. Venus is the third brightest object in Earth's sky, after the Moon and the Sun, and, like Mercury, appears always relatively close to the Sun, either as a "morning star" or an "evening star", resulting from orbiting closer ( inferior) to the Sun than Earth. The orbits of Venus and Earth make the two planets approach each other in synodic periods of 1.6 years ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apparent Magnitude
Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), extinction of the object's light caused by interstellar dust along the sightline, line of sight to the observer. Unless stated otherwise, the word ''magnitude'' in astronomy usually refers to a celestial object's apparent magnitude. The magnitude scale likely dates to before the ancient Ancient Greek astronomy#Astronomy in the Greco-Roman and Late Antique eras, Roman astronomer Ptolemy, Claudius Ptolemy, whose Star catalogue, star catalog popularized the system by listing stars from First-magnitude star, 1st magnitude (brightest) to 6th magnitude (dimmest). The modern scale was mathematically defined to closely match this historical system by Norman Robert Pogson, Norman Pogson in 1856. The scale is reverse logarithmic scale, logarithmic: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Space Station
The International Space Station (ISS) is a large space station that was Assembly of the International Space Station, assembled and is maintained in low Earth orbit by a collaboration of five space agencies and their contractors: NASA (United States), Roscosmos (Russia), European Space Agency, ESA (Europe), JAXA (Japan), and Canadian Space Agency, CSA (Canada). As the largest space station ever constructed, it primarily serves as a platform for conducting scientific experiments in microgravity and studying the space environment. The station is divided into two main sections: the Russian Orbital Segment (ROS), developed by Roscosmos, and the US Orbital Segment (USOS), built by NASA, ESA, JAXA, and CSA. A striking feature of the ISS is the Integrated Truss Structure, which connect the station’s vast system of solar panels and Spacecraft thermal control, radiators to its pressurized modules. These modules support diverse functions, including scientific research, crew habitation, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Satellite Flare
Satellite flare, also known as satellite glint, is a satellite pass visible to the naked eye as a brief, bright "flare". It is caused by the reflection toward the Earth below of sunlight incident on satellite surfaces such as solar panels and antennas (e.g., synthetic aperture radar). Streaks from satellite flare are a form of light pollution that can negatively affect ground-based astronomy, stargazing, and indigenous people. Many satellites flare with magnitudes bright enough to see with the unaided eye, i.e. brighter than magnitude +6.5. Smaller magnitude numbers are brighter, so negative magnitudes are brighter than positive magnitudes, ''i.e.'' the scale is reverse logarithmic . The Iridium constellation was one of the first anthropogenic sources of near-space light pollution to draw criticism. Larger satellite constellations, like OneWeb and Starlink, have received increased criticism. Scientific and policy analyses have raised questions about which regulatory ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
