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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 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 very 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. Mars launch periods), or a short period time that won't be repeated. A launch window indicates the time frame on a given day in the launch period that the rocket can launch to reach its intended orbit. This can be as short as a second (referred to as an instantaneous window) or even the entire day. For operational reasons, the window almost ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Animation Of InSight Trajectory
Animation is a method by which still figures are manipulated to appear as moving images. In traditional animation, images are drawn or painted by hand on transparent celluloid sheets to be photographed and exhibited on film. Today, most animations are made with computer-generated imagery (CGI). Computer animation can be very detailed 3D animation, while 2D computer animation (which may have the look of traditional animation) can be used for stylistic reasons, low bandwidth, or faster real-time renderings. Other common animation methods apply a stop motion technique to two- and three-dimensional objects like paper cutouts, puppets, or clay figures. A cartoon is an animated film, usually a short film, featuring an exaggerated visual style. The style takes inspiration from comic strips, often featuring anthropomorphic animals, superheroes, or the adventures of human protagonists. Especially with animals that form a natural predator/prey relationship (e.g. cats and mice, coyo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
European Space Agency
, owners = , headquarters = Paris, Île-de-France, France , coordinates = , spaceport = Guiana Space Centre , seal = File:ESA emblem seal.png , seal_size = 130px , image = Views in the Main Control Room (12052189474).jpg , size = , caption = , acronym = , established = , employees = 2,200 , administrator = Director General Josef Aschbacher , budget = €7.2 billion (2022) , language = English and French (working languages) , website = , logo = European Space Agency logo.svg , logo_caption = Logo , image_caption = European Space Operations Centre (ESOC) Main Control Room The European Space Agency (ESA; french: Agence spatiale européenne , it, Agenzia Spaziale Europea, es, Agencia Espacial Europea ASE; german: Europäische Weltraumorganisation) is an intergovernmental organisation of 22 member states dedicated to the exploration of space. Established in 1975 and headquartered ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Low Earth Orbit
A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, with an altitude never more than about one-third of the radius of Earth. The term ''LEO region'' is also used for the area of space below an altitude of (about one-third of Earth's radius). Objects in orbits that pass through this zone, even if they have an apogee further out or are sub-orbital, are carefully tracked since they present a collision risk to the many LEO satellites. All crewed space stations to date have been within LEO. From 1968 to 1972, the Apollo program's lunar missions sent humans beyond LEO. Since the end of the Apollo program, no human spaceflights have been beyond LEO. Defining characteristics A wide variety of sources define LEO in terms of altitude. The altitude of an object in an elliptic orbit can vary significantly along the ... [...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 (for example those in orbits around the Sun) an orbital maneuver is called a ''deep-space maneuver (DSM)''. The rest of the flight, especially in a transfer orbit, is called ''coasting''. General Rocket equation The Tsiolkovsky rocket equation, or ideal rocket equation is an equation that is useful for considering vehicles that follow the basic principle of a rocket: where a device that can apply acceleration to itself (a thrust) by expelling part of its mass with high speed and moving due to the conservation of momentum. Specifically, it is a mathematical equation that relates the delta-v (the maximum change of speed of the rocket if no other external forces act) with the effective exhaust velocity and the initial and final mass of a rocket (or other reaction engine.) For any such maneuver (or journ ... [...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 60 - 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.Science Focus 2nd Edition 2, pg. 297 The Iridium satellite constellation uses a polar orbit to provide telecommunications services. Near- ... [...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 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, 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, a satellite in Sun-synchronous orbit might ascend ac ... [...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 ... [...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 Moon's orbit as the angle between its orbital plane and the planet's equatorial plane. Artificial satellites around the Earth For launch vehicles a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Space Rendezvous
A space rendezvous () is a set of orbital maneuvers during which two spacecraft, one of which is often a space station, arrive at the same orbit and approach to a very close distance (e.g. within visual contact). Rendezvous requires a precise match of the orbital velocities and position vectors of the two spacecraft, allowing them to remain at a constant distance through orbital station-keeping. Rendezvous may or may not be followed by docking or berthing, procedures which bring the spacecraft into physical contact and create a link between them. The same rendezvous technique can be used for spacecraft "landing" on natural objects with a weak gravitational field, e.g. landing on one of the Martian moons would require the same matching of orbital velocities, followed by a "descent" that shares some similarities with docking. History In its first human spaceflight program Vostok, the Soviet Union launched pairs of spacecraft from the same launch pad, one or two days apart ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earth Orbit
Earth orbits the Sun at an average distance of 149.60 million km (92.96 million mi) in a counterclockwise direction as viewed from above the Northern Hemisphere. One complete orbit takes days (1 sidereal year), during which time Earth has traveled 940 million km (584 million mi). Jean Meeus, ''Astronomical Algorithms'' 2nd ed, (Richmond, VA: Willmann-Bell, 1998) 238. See Ellipse#Circumference. The formula by Ramanujan is accurate enough. Ignoring the influence of other Solar System bodies, Earth's orbit is an ellipse with the Earth-Sun barycenter as one focus and a current eccentricity of 0.0167. Since this value is close to zero, the center of the orbit is relatively close to the center of the Sun (relative to the size of the orbit). As seen from Earth, the planet's orbital prograde motion makes the Sun appear to move with respect to other stars at a rate of about 1° eastward per solar day (or a Sun or Moon diameter every 12 hours).Our planet takes abo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Delta-v
Delta-''v'' (more known as " change in velocity"), symbolized as ∆''v'' and pronounced ''delta-vee'', 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 the vehicle. As a simple example, take a conventional rocket-propelled spacecraft which achieves thrust by burning fuel. The spacecraft's delta-''v'' is 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-''v'' ... [...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 contours of equal characteristic energy (C3) against combinations of launch date and arrival date for a particular interplanetary flight. 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'' can be computed as: C_3 = v_\infty^2\,\! where v_\infty \, is the orbital velocity when the orbital distance tends to infinity. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
