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Lunar Laser Communication Demonstration
LADEE's Lunar Laser Communication Demonstration (LLCD) was a payload on NASA's Lunar Atmosphere and Dust Environment Explorer lunar orbiter. The LLCD pulsed laser system conducted a successful test on October 18, 2013, transmitting data between the spacecraft and its ground station on Earth at a distance of . This test set a downlink record of 622 megabits per second (Mbps) from spacecraft to ground, and an "error-free data upload rate of 20 Mbps" from ground station to spacecraft. Tests were carried out over a 30-day test period. The LLCD is a free-space optical communication system. It was NASA's first attempt at two-way space communication using an optical laser instead of radio waves. It is expected to lead to operational laser systems on future NASA satellites. The next iteration of the concept will be the Laser Communications Relay Demonstration scheduled for 2017. Also, it has been proposed as payload for the Phobos And Deimos & Mars Environment (PADME) orbiter. See al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LADEE
The Lunar Atmosphere and Dust Environment Explorer (LADEE; ) was a NASA lunar exploration and technology demonstration mission. It was launched on a Minotaur V rocket from the Mid-Atlantic Regional Spaceport on September 7, 2013. During its seven-month mission, LADEE orbited the Moon's equator, using its instruments to study the lunar exosphere and dust in the Moon's vicinity. Instruments included a dust detector, neutral mass spectrometer, and ultraviolet-visible spectrometer, as well as a technology demonstration consisting of a laser communications terminal. The mission ended on April 18, 2014, when the spacecraft's controllers intentionally crashed LADEE into the far side of the Moon, which, later, was determined to be near the eastern rim of Sundman V crater. Planning and preparations LADEE was announced during the presentation of NASA's budget in February 2008. It was initially planned to be launched with the Gravity Recovery and Interior Laboratory (GRAIL) satellite ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pulsed Laser
Pulsed operation of lasers refers to any laser not classified as continuous wave, so that the optical power appears in pulses of some duration at some repetition rate. This encompasses a wide range of technologies addressing a number of different motivations. Some lasers are pulsed simply because they cannot be run in continuous mode. In other cases the application requires the production of pulses having as large an energy as possible. Since the pulse energy is equal to the average power divided by the repetition rate, this goal can sometimes be satisfied by lowering the rate of pulses so that more energy can be built up in between pulses. In laser ablation for example, a small volume of material at the surface of a work piece can be evaporated if it is heated in a very short time, whereas supplying the energy gradually would allow for the heat to be absorbed into the bulk of the piece, never attaining a sufficiently high temperature at a particular point. Other applications rely ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Downlink
In a telecommunications network, a link is a communication channel that connects two or more devices for the purpose of data transmission. The link may be a dedicated physical link or a virtual circuit that uses one or more physical links or shares a physical link with other telecommunications links. A telecommunications link is generally based on one of several types of information transmission paths such as those provided by communication satellites, terrestrial radio communications infrastructure and computer networks to connect two or more points. The term ''link'' is widely used in computer networking to refer to the communications facilities that connect nodes of a network. Sometimes the communications facilities that provide the communication channel that constitutes a link are also included in the definition of ''link''. Types Point-to-point A point-to-point link is a dedicated link that connects exactly two communication facilities (e.g., two nodes of a network, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Megabit
The bit is the most basic Units of information, unit of information in computing and digital communication. The name is a portmanteau of binary digit. The bit represents a truth value, logical state with one of two possible value (computer science), values. These values are most commonly represented as either , but other representations such as ''true''/''false'', ''yes''/''no'', ''on''/''off'', or ''+''/''−'' are also widely used. The relation between these values and the physical states of the underlying Data storage device, storage or computing device, device is a matter of convention, and different assignments may be used even within the same device or computer program, program. It may be physically implemented with a two-state device. A contiguous group of binary digits is commonly called a ''bit string'', a bit vector, or a single-dimensional (or multi-dimensional) ''bit array''. A group of eight bits is called one ''byte'', but historically the size of the byte is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Free-space Optical Communication
Free-space optical communication (FSO) is an optical communication technology that uses light propagating in free space to wirelessly transmit data for telecommunications or computer networking over long distances. "Free space" means air, outer space, vacuum, or something similar. This contrasts with using solids such as optical fiber cable. The technology is useful where the physical connections are impractical due to high costs or other considerations. History Optical communications, in various forms, have been used for thousands of years. The ancient Greeks used a coded alphabetic system of signalling with torches developed by Cleoxenus, Democleitus and Polybius. In the modern era, semaphores and wireless solar telegraphs called heliographs were developed, using coded signals to communicate with their recipients. In 1880, Alexander Graham Bell and his assistant Charles Sumner Tainter created the photophone, at Bell's newly established Volta Laboratory in Washington, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word ''laser'' originated as an acronym for light amplification by stimulated emission of radiation. The first laser was built in 1960 by Theodore Maiman at Hughes Research Laboratories, based on theoretical work by Charles H. Townes and Arthur Leonard Schawlow and the optical amplifier patented by Gordon Gould. A laser differs from other sources of light in that it emits light that is coherence (physics), ''coherent''. Spatial coherence allows a laser to be focused to a tight spot, enabling uses such as optical communication, laser cutting, and Photolithography#Light sources, lithography. It also allows a laser beam to stay narrow over great distances (collimated light, collimation), used in laser pointers, lidar, and free-space optical communication. Lasers can also have high temporal coherence, which permits them to emit light ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Wave
Radio waves (formerly called Hertzian waves) are a type of electromagnetic radiation with the lowest frequencies and the longest wavelengths in the electromagnetic spectrum, typically with frequencies below 300 gigahertz (GHz) and wavelengths greater than , about the diameter of a grain of rice. Radio waves with frequencies above about 1 GHz and wavelengths shorter than 30 centimeters are called microwaves. Like all electromagnetic waves, radio waves in vacuum travel at the speed of light, and in the Earth's atmosphere at a slightly lower speed. Radio waves are generated by charged particles undergoing acceleration, such as time-varying electric currents. Naturally occurring radio waves are emitted by lightning and astronomical radio source, astronomical objects, and are part of the blackbody radiation emitted by all warm objects. Radio waves are generated artificially by an electronic device called a transmitter, which is connected to an antenna (radio), antenna, w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laser Communications Relay Demonstration
The Laser Communications Relay Demonstration (LCRD) is a NASA mission that will test laser communication in space for extremely long distances, between Earth and geosynchronous orbit. After being integrated into STPSat-6, a part of STP-3, LCRD launched on 7 December 2021 on an Atlas V 551. Results from LCRD's first year of experiments in orbit have been shared online and through a SPIE publication. Overview The LCRD mission was selected for development in 2011, with a launch on board a commercial satellite scheduled for 2019. The technology demonstration payload will be positioned above the equator, a prime location for line-of-sight to other orbiting satellites and ground stations. Space laser communications technology has the potential to provide 10 to 100 times higher data rates than traditional radio frequency systems for the same mass and power. Alternatively, numerous NASA studies have shown that a laser communications system will use less mass and power than a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phobos And Deimos & Mars Environment
Phobos And Deimos & Mars Environment (PADME) is a low-cost NASA Mars orbiter mission concept that would address longstanding unknowns about Mars' two moons Phobos and Deimos and their environment. The PADME mission competed for Discovery Program funding, but lost to the ''Psyche'' and ''Lucy'' missions. The Principal Investigator is Anthony Colaprete. Other principals include Pascal Lee (Deputy Principal Investigator) and Butler Hine (Project Manager). Objectives The origin of Mars' moons, which were discovered by astronomer Asaph Hall, remains unknown. PADME would advance the scientific understanding of the origin of Phobos and Deimos by studying: * Composition of surface and near-surface materials * Internal structure * Dynamics (transport) of surface materials on, and between, Deimos and Phobos. In addition, PADME would assess potential resources (water, organics, regolith) and potential hazards (dust) that Phobos and Deimos might present for future human exploration in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laser Communication In Space
Laser communication in space is the use of free-space optical communication in outer space. Communication may be fully in space (an inter-satellite laser link) or in a ground-to-satellite or satellite-to-ground application. The main advantage of using laser communications over Radio, radio waves is increased Bandwidth (computing), bandwidth, enabling the transfer of more data in less time. In outer space, the communication range of free-space optical communication is currently of the order of hundreds of thousands of kilometers. Laser-based optical communication has been demonstrated between the Earth and Moon and it has the potential to bridge interplanetary distances of millions of kilometers, using optical telescopes as beam expanders. Demonstrations and tests Before 1990 On 20 January 1968, the television camera of the Surveyor 7 lunar lander successfully detected two Ion laser, argon lasers from Kitt Peak National Observatory in Arizona and Table Mountain Observatory ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Space Science Experiments
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 better model f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
