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Submillimeter Wave Astronomy Satellite
Submillimeter Wave Astronomy Satellite (SWAS, also Explorer 74 and SMEX-3) is a NASA submillimetre astronomy satellite, and is the fourth spacecraft in the Small Explorer program (SMEX). It was launched on 6 December 1998, at 00:57:54 UTC, from Vandenberg Air Force Base aboard a Pegasus XL launch vehicle. The telescope was designed by the Smithsonian Astrophysical Observatory (SAO) and integrated by Ball Aerospace, while the spacecraft was built by NASA's Goddard Space Flight Center (GSFC). The mission's principal investigator is Gary J. Melnick. History The Submillimeter Wave Astronomy Satellite mission was approved on 1 April 1989. The project began with the Mission Definition Phase, officially starting on 29 September 1989, and running through 31 January 1992. During this time, the mission underwent a conceptual design review on 8 June 1990, and a demonstration of the Schottky receivers and acousto-optical spectrometer concept was performed on 8 November 1991. Developme ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Submillimetre Astronomy
Submillimetre astronomy or submillimeter astronomy (see spelling differences) is the branch of observational astronomy that is conducted at submillimetre wavelengths (i.e., terahertz radiation) of the electromagnetic spectrum. Astronomers place the submillimetre waveband between the far-infrared and microwave wavebands, typically taken to be between a few hundred micrometres and a millimetre. It is still common in submillimetre astronomy to quote wavelengths in 'microns', the old name for micrometre. Using submillimetre observations, astronomers examine molecular clouds and dark cloud cores with a goal of clarifying the process of star formation from earliest collapse to stellar birth. Submillimetre observations of these dark clouds can be used to determine chemical abundances and cooling mechanisms for the molecules which comprise them. In addition, submillimetre observations give information on the mechanisms for the formation and evolution of galaxies. From the g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Principal Investigator
In many countries, the term principal investigator (PI) refers to the holder of an independent grant and the lead researcher for the grant project, usually in the sciences, such as a laboratory study or a clinical trial. The phrase is also often used as a synonym for "head of the laboratory" or "research group leader". While the expression is common in the sciences, it is used widely for the person or persons who make final decisions and supervise funding and expenditures on a given research project. A co-investigator (Co-I) assists the principal investigator in the management and leadership of the research project. There may be a number of co-investigators supporting a PI. Federal funding In the context of United States federal funding from agencies such as the National Institutes of Health (NIH) or the National Science Foundation (NSF), the PI is the person who takes direct responsibility for completion of a funded project, directing the research and reporting directly to the fun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acousto-optical Spectrometer
An acousto-optical spectrometer (AOS) is based on the diffraction of light by ultrasonic waves. A piezoelectric transducer, driven by the RF signal (from the receiver), generates an acoustic wave in a crystal (the so-called Bragg-cell). This acoustic wave modulates the refractive index and induces a phase grating. The Bragg-cell is illuminated by a collimated laser beam. The angular dispersion of the diffracted light represents a true image of the IF-spectrum according to the amplitude and wavelengths of the acoustic waves in the crystal. The spectrum is detected by using a single linear diode array ( CCD), which is placed in the focal plane of an imaging optics. Depending on the crystal and the focal length of the imaging optics, the resolution of this type of spectrometer can be varied. See also * Acousto-optics * Acousto-optic modulator * Acousto-optic deflector * Nonlinear optics Nonlinear optics (NLO) is the branch of optics that describes the behaviour of light in ''n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Schottky Diode
The Schottky diode (named after the German physicist Walter H. Schottky), also known as Schottky barrier diode or hot-carrier diode, is a semiconductor diode formed by the junction of a semiconductor with a metal. It has a low forward voltage drop and a very fast switching action. The cat's-whisker detectors used in the early days of wireless and metal rectifiers used in early power applications can be considered primitive Schottky diodes. When sufficient forward voltage is applied, a current flows in the forward direction. A silicon p–n diode has a typical forward voltage of 600–700 mV, while the Schottky's forward voltage is 150–450 mV. This lower forward voltage requirement allows higher switching speeds and better system efficiency. History Walter H. Schottky (1886–1976) in 1914, discovered an irregularity in the emission of thermions in a vacuum tube, now known as the Schottky effect. Construction A metal–semiconductor junction is formed between a metal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cassegrain Reflector
The Cassegrain reflector is a combination of a primary concave mirror and a secondary convex mirror, often used in optical telescopes and radio antennas, the main characteristic being that the optical path folds back onto itself, relative to the optical system's primary mirror entrance aperture. This design puts the focal point at a convenient location behind the primary mirror and the convex secondary adds a telephoto effect creating a much longer focal length in a mechanically short system. In a symmetrical Cassegrain both mirrors are aligned about the optical axis, and the primary mirror usually contains a hole in the center, thus permitting the light to reach an eyepiece, a camera, or an image sensor. Alternatively, as in many radio telescopes, the final focus may be in front of the primary. In an asymmetrical Cassegrain, the mirror(s) may be tilted to avoid obscuration of the primary or to avoid the need for a hole in the primary mirror (or both). The classic Cassegrain ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microwave
Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ranges as microwaves; the above broad definition includes both UHF and EHF (millimeter wave) bands. A more common definition in radio-frequency engineering is the range between 1 and 100 GHz (wavelengths between 0.3 m and 3 mm). In all cases, microwaves include the entire SHF band (3 to 30 GHz, or 10 to 1 cm) at minimum. Frequencies in the microwave range are often referred to by their IEEE radar band designations: S, C, X, Ku, K, or Ka band, or by similar NATO or EU designations. The prefix ' in ''microwave'' is not meant to suggest a wavelength in the micrometer range. Rather, it indicates that microwaves are "small" (having shorter wavelengths), compared to the radio waves used prior to microwave te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Far Infrared
Far infrared (FIR) is a region in the infrared spectrum of electromagnetic radiation. Far infrared is often defined as any radiation with a wavelength of 15 micrometers (μm) to 1 mm (corresponding to a range of about 20 THz to 300 GHz), which places far infrared radiation within the CIE IR-B and IR-C bands. The long-wave side of the FIR spectrum overlaps with so named terahertz radiation. A.Glagoleva-Arkadiewa. (1924). "Short Electromagnetic Waves of wave-length up to 82 Microns". ''Nature'' 2844 113. do10.1038/113640a0/ref> Different sources use different boundaries for the far infrared; for example, astronomers sometimes define far infrared as wavelengths between 25 μm and 350 μm. Visible light includes radiation with wavelengths between 400 nm and 700 nm, meaning that far infrared photons have tens to hundreds of times less energy than visible light photons. Applications Astronomy Due to black-body radiation, objects with temper ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nebular Hypothesis
The nebular hypothesis is the most widely accepted model in the field of cosmogony to explain the formation and evolution of the Solar System (as well as other planetary systems). It suggests the Solar System is formed from gas and dust orbiting the Sun. The theory was developed by Immanuel Kant and published in his ''Universal Natural History and Theory of the Heavens'' (1755) and then modified in 1796 by Pierre Laplace. Originally applied to the Solar System, the process of planetary system formation is now thought to be at work throughout the universe. The widely accepted modern variant of the nebular theory is the solar nebular disk model (SNDM) or solar nebular model. It offered explanations for a variety of properties of the Solar System, including the nearly circular and coplanar orbits of the planets, and their motion in the same direction as the Sun's rotation. Some elements of the original nebular theory are echoed in modern theories of planetary formation, but most ele ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interstellar Cloud
An interstellar cloud is generally an accumulation of gas, plasma, and dust in our and other galaxies. Put differently, an interstellar cloud is a denser-than-average region of the interstellar medium, the matter and radiation that exists in the space between the star systems in a galaxy. Depending on the density, size, and temperature of a given cloud, its hydrogen can be neutral, making an H I region; ionized, or plasma making it an H II region; or molecular, which are referred to simply as molecular clouds, or sometime dense clouds. Neutral and ionized clouds are sometimes also called ''diffuse clouds''. An interstellar cloud is formed by the gas and dust particles from a red giant in its later life. Chemical compositions The chemical composition of interstellar clouds is determined by studying electromagnetic radiation that they emanate, and we receive – from radio waves through visible light, to gamma rays on the electromagnetic spectrum – that we receive from them. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Millitech Corporation
Proxim Wireless Corporation is a San Jose, California-based company that builds scalable broadband wireless networking systems for communities, enterprises, governments, and service providers. It offers wireless LAN, point-to-multipoint and point-to-point products through a channel network. The company is a product of many mergers and acquisitions over the years. History Proxim Corporation was founded in 1984, initially headquartered in Mountain View, California. Starting in 1989, it began to develop radio frequency modules using spread spectrum technology. Its first commercial product in 1990 used 900 MHz frequency bands. End-user products called RangeLAN were introduced in 1991 and 1992, reflecting their use as network interface controllers for local area networks (LANs). The first adapter using the Industry Standard Architecture bus and supported Novell NetWare. An initial public offering (IPO) on December 15, 1993 listed the company shares on NASDAQ under symbol PROX. In 1994 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
University Of Cologne
The University of Cologne (german: Universität zu Köln) is a university in Cologne, Germany. It was established in the year 1388 and is one of the most prestigious and research intensive universities in Germany. It was the sixth university to be established in Central Europe. It closed in 1798 before being re-established in 1919. It is now one of the largest universities in Germany with more than 48,000 students. The University of Cologne was a university of excellence as part of the German Universities Excellence Initiative from 2012 to 2019. As of 2021, 3 Nobel Prize winners have been affiliated with the university. Professors and former students have won 11 Leibniz Prizes, the most prestigious as well as the best-funded prize in Europe. History 1388–1798 The university of Cologne was established in 1388 as the fourth university in the Holy Roman Empire, after the Charles University of Prague (1348), the University of Vienna (1365) and the Ruprecht Karl University of H ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Critical Design Review
In the United States military integrated acquisition lifecycle the Technical section has multiple acquisition "Technical Reviews". Technical reviews and audits assist the acquisition and the number and types are tailored to the acquisition. Overall guidance flows from the Defense Acquisition Guidebook chapter 4, with local details further defined by the review organizations. Typical topics examined include adequacy of program/contract metrics, proper staffing, risks, budget, and schedule. In NASA's engineering design life cycle, design reviews are held for technical and programmatic accountability and to authorize the release of funding to a project. A design review provides an in-depth assessment by an independent team of discipline experts and managers that the design (or concept) is realistic and attainable from a programmatic and technical sense. Design review is also required of medical device developers as part of a system of design controls described in the US Food and D ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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