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Launch Window
In the context of spaceflight, launch period is the collection of days, and launch window is the time period on a given day, during which a particular rocket A rocket (from , and so named for its shape) is a vehicle that uses jet propulsion to accelerate without using any surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely ... must be launched in order to reach its intended target. If the rocket is not launched within a given window, it has to wait for the window on the next day of the period. Launch periods and launch windows are dependent on both the rocket's capability and the orbit to which it is going. A launch ''period'' refers to the days that the rocket can launch to reach its intended orbit. A mission could have a period of 365 days in a year, a few weeks each month, a few weeks every 26 months (e.g. Exploration of Mars#Launch_windows, Mars launch periods), or a short period time that won' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exploration Of Mars
The planet Mars has been explored remotely by spacecraft. Uncrewed spacecraft, Probes sent from Earth, beginning in the late 20th century, have yielded a large increase in knowledge about the Martian system, focused primarily on understanding Geology of Mars, its geology and Planetary habitability, habitability potential. Engineering Interplanetary spaceflight, interplanetary journeys is complicated and the exploration of Mars has experienced a high failure rate, especially the early attempts. Roughly sixty percent of all spacecraft destined for Mars failed before completing their missions, with some failing before their observations could begin. Some missions have been met with unexpected success, such as the twin Mars Exploration Rovers, ''Spirit (rover), Spirit'' and ''Opportunity (rover), Opportunity'', which operated for years beyond their specification. Current status There are two functional rovers on the surface of Mars, the Curiosity (rover), ''Curiosity'' and Persever ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Animation Of InSight Trajectory
Animation is a filmmaking technique whereby still images are manipulated to create moving images. In traditional animation, images are drawn or painted by hand on transparent celluloid sheets to be photographed and exhibited on film. Animation has been recognised as an artistic medium, specifically within the entertainment industry. Many animations are either traditional animations or computer animations made with computer-generated imagery (CGI). Stop motion animation, in particular claymation, has continued to exist alongside these other forms. Animation is contrasted with live action, although the two do not exist in isolation. Many moviemakers have produced films that are a hybrid of the two. As CGI increasingly approximates photographic imagery, filmmakers can easily composite 3D animations into their film rather than using practical effects for showy visual effects (VFX). General overview Computer animation can be very detailed 3D animation, while 2D computer an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neptune
Neptune is the eighth and farthest known planet from the Sun. It is the List of Solar System objects by size, fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times the mass of Earth. Compared to Uranus, its neighbouring ice giant, Neptune is slightly smaller, but more massive and denser. Being composed primarily of gases and liquids, it has no well-defined solid surface. Neptune orbits the Sun once every 164.8 julian year (astronomy), years at an orbital distance of . It is named after Neptune (mythology), the Roman god of the sea and has the astronomical symbol representing Trident of Poseidon, Neptune's trident. Neptune is not visible to the unaided eye and is the only planet in the Solar System that was not initially observed by direct empirical observation. Rather, unexpected changes in the orbit of Uranus led Alexis Bouvard to hypothesise that its orbit was subject to gravitational Pe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orbital Maneuver
In spaceflight, an orbital maneuver (otherwise known as a burn) is the use of propulsion systems to change the orbit of a spacecraft. For spacecraft far from Earth, an orbital maneuver is called a ''deep-space maneuver (DSM)''. When a spacecraft is not conducting a maneuver, especially in a transfer orbit, it is said to be ''coasting''. General Rocket equation The Tsiolkovsky rocket equation, or ideal rocket equation, can be useful for analysis of maneuvers by vehicles using rocket propulsion. A rocket applies acceleration to itself (a thrust) by expelling part of its mass at high speed. The rocket itself moves due to the conservation of momentum. Delta-v The applied change in velocity of each maneuver is referred to as delta-v (\Delta\mathbf\,). The delta-v for all the expected maneuvers are estimated for a mission are summarized in a delta-v budget. With a good approximation of the delta-v budget designers can estimate the propellant required for planned maneuve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polar Orbit
A polar orbit is one in which a satellite passes above or nearly above both poles of the body being orbited (usually a planet such as the Earth, but possibly another body such as the Moon or Sun) on each revolution. It has an inclination of about 80–90 degrees to the body's equator. Launching satellites into polar orbit requires a larger launch vehicle to launch a given payload to a given altitude than for a near-equatorial orbit at the same altitude, because it cannot take advantage of the Earth's rotational velocity. Depending on the location of the launch site and the inclination of the polar orbit, the launch vehicle may lose up to 460 m/s of Delta-v, approximately 5% of the Delta-v required to attain Low Earth orbit. Usage Polar orbits are used for Earth-mapping, reconnaissance satellites, as well as for some weather satellites. The Iridium satellite constellation uses a polar orbit to provide telecommunications services. Near-polar orbiting satellites commo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sun-synchronous Orbit
A Sun-synchronous orbit (SSO), also called a heliosynchronous orbit, is a nearly polar orbit around a planet, in which the satellite passes over any given point of the planet's surface at the same local mean solar time. More technically, it is an orbit arranged so that it Precession, precesses through one complete revolution each year, so it always maintains the same relationship with the Sun. Applications A Sun-synchronous orbit is useful for imaging satellite, imaging, reconnaissance satellite, reconnaissance, and weather satellites, because every time that the satellite is overhead, the surface illumination angle on the planet underneath it is nearly the same. This consistent lighting is a useful characteristic for satellites that image the Earth's surface in visible or infrared wavelengths, such as weather and spy satellites, and for other remote-sensing satellites, such as those carrying ocean and atmospheric remote-sensing instruments that require sunlight. For example, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earth Observation Satellite
An Earth observation satellite or Earth remote sensing satellite is a satellite used or designed for Earth observation (EO) from orbit, including spy satellites and similar ones intended for non-military uses such as environmental monitoring, meteorology, cartography and others. The most common type are Earth imaging satellites, that take satellite images, analogous to aerial photographs; some EO satellites may perform remote sensing without forming pictures, such as in GNSS radio occultation. The first occurrence of satellite remote sensing can be dated to the launch of the first artificial satellite, Sputnik 1, by the Soviet Union on October 4, 1957. Sputnik 1 sent back radio signals, which scientists used to study the ionosphere. The United States Army Ballistic Missile Agency launched the first American satellite, Explorer 1, for NASA's Jet Propulsion Laboratory on January 31, 1958. The information sent back from its radiation detector led to the discovery of the Earth's Van ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orbital Plane (astronomy)
The orbital plane of a revolving body is the geometric plane in which its orbit lies. Three non-collinear points in space suffice to determine an orbital plane. A common example would be the positions of the centers of a massive body (host) and of an orbiting celestial body at two different times/points of its orbit. The orbital plane is defined in relation to a reference plane by two parameters: inclination (''i'') and longitude of the ascending node (Ω). By definition, the reference plane for the Solar System is usually considered to be Earth's orbital plane, which defines the ecliptic, the circular path on the celestial sphere that the Sun appears to follow over the course of a year. In other cases, for instance a moon or artificial satellite orbiting another planet, it is convenient to define the inclination of the object's orbit as the angle between its orbital plane and the planet's equatorial plane. The coordinate system defined that uses the orbital plane a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Space Rendezvous
Space is a three-dimensional continuum containing positions and directions. In classical physics, physical space is often conceived in three linear dimensions. Modern physicists usually consider it, with time, to be part of a boundless four-dimensional continuum known as '' spacetime''. The concept of space is considered to be of fundamental importance to an understanding of the physical universe. However, disagreement continues between philosophers over whether it is itself an entity, a relationship between entities, or part of a conceptual framework. In the 19th and 20th centuries mathematicians began to examine geometries that are non-Euclidean, in which space is conceived as '' curved'', rather than '' flat'', as in the Euclidean space. According to Albert Einstein's theory of general relativity, space around gravitational fields deviates from Euclidean space. Experimental tests of general relativity have confirmed that non-Euclidean geometries provide a bet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geocentric Orbit
A geocentric orbit, Earth-centered orbit, or Earth orbit involves any object orbiting Earth, such as the Moon or artificial satellites. In 1997, NASA estimated there were approximately 2,465 artificial satellite payloads orbiting Earth and 6,216 pieces of space debris as tracked by the Goddard Space Flight Center. More than 16,291 objects previously launched have undergone orbital decay and entered Earth's atmosphere. A spacecraft enters orbit when its centripetal acceleration due to gravity is less than or equal to the centrifugal acceleration due to the horizontal component of its velocity. For a low Earth orbit, this velocity is about ; by contrast, the fastest crewed airplane speed ever achieved (excluding speeds achieved by deorbiting spacecraft) was in 1967 by the North American X-15. The energy required to reach Earth orbital velocity at an altitude of is about 36 MJ/kg, which is six times the energy needed merely to climb to the corresponding altitude. Spa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Delta-v
Delta-''v'' (also known as "change in velocity"), symbolized as and pronounced , as used in spacecraft flight dynamics, is a measure of the impulse per unit of spacecraft mass that is needed to perform a maneuver such as launching from or landing on a planet or moon, or an in-space orbital maneuver. It is a scalar that has the units of speed. As used in this context, it is not the same as the physical change in velocity of said spacecraft. A simple example might be the case of a conventional rocket-propelled spacecraft, which achieves thrust by burning fuel. Such a spacecraft's delta-''v'', then, would be the change in velocity that spacecraft can achieve by burning its entire fuel load. Delta-''v'' is produced by reaction engines, such as rocket engines, and is proportional to the thrust per unit mass and the burn time. It is used to determine the mass of propellant required for the given maneuver through the Tsiolkovsky rocket equation. For multiple maneuvers, delta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Porkchop Plot
In orbital mechanics, a porkchop plot (also pork-chop plot) is a chart that shows level curves of equal characteristic energy (C3) against combinations of launch date and arrival date for a particular interplanetary flight. The chart shows the characteristic energy ranges in zones around the local minima, which resembles the shape of a porkchop slice. By examining the results of the porkchop plot, engineers can determine when a launch opportunity exists (a 'launch window') that is compatible with the capabilities of a particular spacecraft. A given contour, called a porkchop curve, represents constant C3, and the center of the porkchop the optimal minimum C3. The orbital elements of the solution, where the fixed values are the departure date, the arrival date, and the length of the flight, were first solved mathematically in 1761 by Johann Heinrich Lambert, and the equation is generally known as Lambert's problem (or theorem). Math The general form of ''characteristic energy'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
