Extreme ultraviolet radiation (EUV or XUV) or high-energy ultraviolet radiation is electromagnetic radiation in the part of the electromagnetic spectrum spanning wavelengths from 124 nm down to 10 nm, and therefore (by the Planck–Einstein equation) having photons with energies from 10 eV up to 124 eV (corresponding to 124 nm to 10 nm respectively). EUV is naturally generated by the solar corona and artificially by plasma and synchrotron light sources. Since UVC extends to 100 nm, there is some overlap in the terms.
Neutral atoms or condensed matter cannot emit EUV radiation. Ionization must take place first. EUV light can only be emitted by electrons which are bound to multicharged positive ions; for example, to remove an electron from a +3 charged carbon ion (three electrons already removed) requires about 65 eV. Such electrons are more tightly bound than typical valence electrons. The existence of multicharged positive ions is only possible in a hot dense plasma. Alternatively, the free electrons and ions may be generated temporarily and instantaneously by the intense electric field of a very-high-harmonic laser beam. The electrons accelerate as they return to the parent ion, releasing higher energy photons at diminished intensities, which may be in the EUV range. If the released photons constitute ionizing radiation, they will also ionize the atoms of the harmonic-generating medium, depleting the sources of higher-harmonic generation. The freed electrons escape since the electric field of the EUV light is not intense enough to drive the electrons to higher harmonics, while the parent ions are no longer as easily ionized as the originally neutral atoms. Hence, the processes of EUV generation and absorption (ionization) strongly compete against each other.
EUV light can also be emitted by free electrons orbiting a synchrotron.
Continuously tunable narrowband EUV light can be generated by four wave mixing in gas cells of krypton and hydrogen to wavelengths as low as 110 nm. In windowless gas chambers fixed four wave mixing has been seen as low as 75 nm.
The response of matter to EUV radiation can be captured in the following equations: Point of absorption: EUV photon energy=92 eV=Electron binding energy + photoelectron initial kinetic energy; within 3 mean free paths of photoelectron (1–2 nm): reduction of photoelectron kinetic energy=ionization potential + secondary electron kinetic energy; within 3 mean free paths of secondary electron (~30 nm): 1) reduction of secondary electron kinetic energy=ionization potential + tertiary electron kinetic energy, 2)mNth generation electron slows down aside from ionization by heating (phonon generation), 3) final generation electron kinetic energy ~ 0 eV => dissociative electron attachment + heat, where the ionization potential is typically 7–9 eV for organic materials and 4–5 eV for metals. The photoelectron subsequently causes the emission of secondary electrons through the process of impact ionization. Sometimes, an Auger transition is also possible, resulting in the emission of two electrons with the absorption of a single photon.
Strictly speaking, photoelectrons, Auger electrons and secondary electrons are all accompanied by positively charged holes (ions which can be neutralized by pulling electrons from nearby molecules) in order to preserve charge neutrality. An electron-hole pair is often referred to as an exciton. For highly energetic electrons, the electron-hole separation can be quite large and the binding energy is correspondingly low, but at lower energy, the electron and hole can be closer to each other. The exciton itself diffuses quite a large distance (>10 nm). As the name implies, an exciton is an excited state; only when it disappears as the electron and hole recombine, can stable chemical reaction products form.
Since the photon absorption depth exceeds the electron escape depth, as the released electrons eventually slow down, they dissipate their energy ultimately as heat. EUV wavelengths are absorbed much more strongly than longer wavelengths, since their corresponding photon energies exceed the bandgaps of all materials. Consequently, their heating efficiency is significantly higher, and has been marked by lower thermal ablation thresholds in dielectric materials.
Certain wavelengths of EUV vary by as much as 2 orders of magnitude between solar minima and maxima, and therefore may contribute to climatic changes, notably the cooling of the atmosphere during solar minimum.
Like other forms of ionizing radiation, EUV and electrons released directly or indirectly by the EUV radiation are a likely source of device damage. Damage may result from oxide desorption or trapped charge following ionization. Damage may also occur through indefinite positive charging by the Malter effect. If free electrons cannot return to neutralize the net positive charge, positive ion desorption is the only way to restore neutrality. However, desorption essentially means the surface is degraded during exposure, and furthermore, the desorbed atoms contaminate any exposed optics. EUV damage has already been documented in the CCD radiation aging of the Extreme UV Imaging Telescope (EIT).
Radiation damage is a well-known issue that has been studied in the process of plasma processing damage. A recent study at the University of Wisconsin Synchrotron indicated that wavelengths below 200 nm are capable of measurable surface charging. EUV radiation showed positive charging centimeters beyond the borders of exposure while VUV (Vacuum Ultraviolet) radiation showed positive charging within the borders of exposure.
An earlier study showed that electrons produced by the 'soft' ionizing radiation could still penetrate ~100 nm below the surface, resulting in heating.
71 Tauri (71 Tau) is a faint star in the constellation Taurus. This is a yellow-white hued F-type main sequence star with an apparent magnitude of +4.48. Based upon parallax measurements made by the Hipparcos spacecraft, it is located approximately 160 light years from Earth.
This star has about 1.94 times the mass of the Sun. It has a projected rotational velocity of 192 km s−1, for an estimated rotation period of 14.2 days. Extreme ultraviolet flares have been observed coming from this star's hot corona.AEROS (satellite)
AEROS satellites were to study the aeronomy i. e. the science of the upper atmosphere and ionosphere, in particular the F region under the strong influence of solar extreme ultraviolet radiation. To this end the spectrum of this radiation was recorded aboard by one instrument (of type Hinteregger) on the one hand and a set of 4 other instruments measuring the most important neutral uand iononized parameters at the satellite's position on the other.
Aeros was built by Ball Aerospace for a co-operative project between NASA and the Bundesministerium für Foschung und Technologie (BMwF), Federal Republic of Germany.Named for the Greek god of the air at the suggestion of the BMwF .AEROS A and B carried identical instrumentation only the instrument measuring short scale variations of the electron density didn't work on A. A third Aeros C was planned for Earth Resources studies in a 3-axis spin-stabilized configuration, to be launched by a Shuttle in 1986.(Needs research)Apollo Telescope Mount
The Apollo Telescope Mount, or ATM, was a solar observatory attached to Skylab, the first American space station.
The ATM was manually operated by the astronauts aboard Skylab from 1973–74, yielding data principally as exposed photographic film that was returned to Earth with the crew. The film magazines had to be changed out by the crew during spacewalks.
The ATM was designed and construction was managed at NASA's Marshall Space Flight Center. It included eight major observational instruments, along with several lesser experiments. The ATM made observations at a variety of wavelengths, including X-Rays, Ultraviolet, and Visible light.
As of 2006, the original exposures were on file (and accessible to interested parties) at the Naval Research Laboratory in Washington, D.C.Array of Low Energy X-ray Imaging Sensors
The Array of Low Energy X-ray Imaging Sensors (ALEXIS) X-ray telescopes feature curved mirrors whose multilayer coatings reflect and focus low-energy X-rays or extreme ultraviolet light the way optical telescopes focus visible light. The satellite and payloads were funded by the United States Department of Energy and built by Los Alamos National Laboratory in collaboration with Sandia National Laboratories and the University of California-Space Sciences Lab. The satellite bus was built by AeroAstro, Inc. of Herndon, VA. The Launch was provided by the United States Air Force Space Test Program on a Pegasus Booster on April 25, 1993. The mission is entirely controlled from a small groundstation at LANL.CHIPSat
CHIPSat (Cosmic Hot Interstellar Plasma Spectrometer satellite) is a now-decommissioned, but still-orbiting, microsatellite. It was launched on January 12, 2003 from Vandenberg Air Force Base aboard a Delta II with the larger ICESat, and had an intended mission duration of one year. CHIPSat was the first of NASA's University-Class Explorers (UNEX) mission class. It performed spectroscopy from 90 to 250 angstroms (9 to 26 nm), extreme ultraviolet light.The primary objective of the science team, led by Principal Investigator Mark Hurwitz, was to study the million-degree gas in the local interstellar medium. CHIPSat was designed to capture the first spectra of the faint, extreme ultraviolet glow that is expected to be emitted by the hot interstellar gas within about 300 light-years of the Sun, a region often referred to as the Local Bubble. Surprisingly, these measurements produced a null result, with only very faint EUV emissions detected, despite theoretical expectations of much stronger emissions.
It was the first U.S. mission to use TCP/IP for end-to-end satellite operations control.
The University of California, Berkeley's Space Sciences Laboratory served as CHIPSat's primary groundstation and manufactured the CHIPS spectrograph, designed to perform all-sky spectroscopy. Other ground network support was provided by groundstations at Wallops Island, Virginia and Adelaide, Australia. CHIPSat's spacecraft platform was manufactured by SpaceDev.
In September 2005 the spacecraft was converted to a solar observatory. From April 3, 2006 to April 5, 2008 CHIPsat performed 1458 observations of the Sun.Satellite operations were terminated in April 2008.Caesium iodide
Caesium iodide or cesium iodide (chemical formula CsI) is the ionic compound of caesium and iodine. It is often used as the input phosphor of an X-ray image intensifier tube found in fluoroscopy equipment. Caesium iodide photocathodes are highly efficient at extreme ultraviolet wavelengths.Chang'e 3
Chang'e 3 ( ; Chinese: 嫦娥三号; pinyin: Cháng'é Sānhào; literally: "Chang'e No. 3") is an unmanned lunar exploration mission operated by the China National Space Administration (CNSA), incorporating a robotic lander and China's first lunar rover. It was launched in December 2013 as part of the second phase of the Chinese Lunar Exploration Program. The mission's chief commander was Ma Xingrui.The spacecraft was named after Chang'e, the goddess of the Moon in Chinese mythology, and is a follow-up to the Chang'e 1 and Chang'e 2 lunar orbiters. The rover was named Yutu (Chinese: 玉兔; literally: "Jade Rabbit") following an online poll, after the mythological rabbit that lives on the Moon as a pet of the Moon goddess.Chang'e 3 achieved lunar orbit on 6 December 2013 and landed on 14 December 2013, becoming the first spacecraft to soft-land on the Moon since the Soviet Union's Luna 24 in 1976. On 28 December 2015, Chang'e 3 discovered a new type of basaltic rock, rich in ilmenite, a black mineral.Extreme Ultraviolet Explorer
The Extreme Ultraviolet Explorer (EUVE) was a space telescope for ultraviolet astronomy, launched on June 7, 1992. With instruments for ultraviolet (UV) radiation between wavelengths of 7 and 76 nm, the EUVE was the first satellite mission especially for the short-wave ultraviolet range. The satellite compiled an all-sky survey of 801 astronomical targets before being decommissioned on January 31, 2001. It re-entered the atmosphere on January 30, 2002.Extreme ultraviolet Imaging Telescope
The Extreme ultraviolet Imaging Telescope (EIT) is an instrument on the SOHO spacecraft used to obtain high-resolution images of the solar corona in the ultraviolet range. The EIT instrument is sensitive to light of four different wavelengths: 17.1, 19.5, 28.4, and 30.4 nm, corresponding to light produced by highly ionized iron (XI)/(X), (XII), (XV), and helium (II), respectively. EIT is built as a single telescope with a quadrant structure to the entrance mirrors: each quadrant reflects a different colour of EUV light, and the wavelength to be observed is selected by a shutter that blocks light from all but the desired quadrant of the main telescope.
The EIT wavelengths are of great interest to solar physicists because they are emitted by the very hot solar corona but not by the relatively cooler photosphere of the Sun; this reveals structures in the corona that would otherwise be obscured by the brightness of the Sun itself. EIT was originally conceived as a viewfinder instrument to help select observing targets for the other instruments on board SOHO, but EIT is credited with a good fraction of the original science to come from SOHO, including the first observations of traveling wave phenomena in the corona, characterization of coronal mass ejection onset, and determination of the structure of coronal holes. Before mid-2010, EIT obtained an Fe XII (19.5 nm wavelength) image of the Sun about four times an hour, around the clock; these were immediately uplinked as time-lapse movies to the SOHO web site for immediate viewing by anyone who is interested. (Since the summer of 2010, when Thorpe commissioning of the Solar Dynamics Observatory was completed, its Atmospheric Imaging Assembly has been able to take much higher resolution solar images much more frequently. The white-light coronagraphs on SOHO are thus able to take images more frequently: they share a CPU and telemetry bandwidth with EIT. The images are used for long-duration studies of the Sun, for detailed structural analyses of solar features, and for real-time space weather prediction by the NOAA Space Weather Prediction Center.Extreme ultraviolet lithography
Extreme ultraviolet lithography (also known as EUV or EUVL) is a next-generation lithography technology using an extreme ultraviolet (EUV) wavelength, currently expected to be 13.5 nm. EUV is currently being developed for high volume use by 2020.Hinode (satellite)
Hinode (; Japanese: ひので, IPA: [çinode], Sunrise), formerly Solar-B, is a Japan Aerospace Exploration Agency Solar mission with United States and United Kingdom collaboration. It is the follow-up to the Yohkoh (Solar-A) mission and it was launched on the final flight of the M-V-7 rocket from Uchinoura Space Center, Japan on 22 September 2006 at 21:36 UTC (23 September, 06:36 JST). Initial orbit was perigee height 280 km, apogee height 686 km, inclination 98.3 degrees. Then the satellite maneuvered to the quasi-circular sun-synchronous orbit over the day/night terminator, which allows near-continuous observation of the Sun. On 28 October 2006, the probe's instruments captured their first images.
The data from Hinode are being downloaded to the Norwegian, terrestrial Svalsat station, operated by Kongsberg a few kilometres west of Longyearbyen, Svalbard. From there, data is transmitted by Telenor through a fibre-optic network to mainland Norway at Harstad, and on to data users in North America, Europe and Japan.Hisaki (satellite)
Hisaki, also known as the Spectroscopic Planet Observatory for Recognition of Interaction of Atmosphere (SPRINT-A) is a Japanese ultraviolet astronomy satellite operated by the Japan Aerospace Exploration Agency (JAXA). The first mission of the Small Scientific Satellite programme, it was launched in September 2013 on the maiden flight of the Epsilon rocket.
Hisaki remains operational as of 2017, and is performing joint observations with Juno orbiter.Hisaki was named after a cape Hisaki (火崎, literally Cape Fire) used by local fishermen to pray for safe travels in the eastern part of Kimotsuki, Kagoshima near the Uchinoura Space Center, but has the additional meaning of "beyond the Sun". An old name for the mission was EXCEED (Extreme Ultraviolet Spectroscope for Exospheric Dynamics).LYRA
LYRA (Lyman Alpha Radiometer) is the solar UV radiometer on board Proba-2, a European Space Agency technology demonstration satellite that was launched on November 2, 2009.LYRA has been designed and manufactured by a Belgian-Swiss-German consortium (ROB-SIDC, PMOD/WRC, IMOMEC, CSL, MPS and BISA) with additional international collaborations (Japan, USA, Russia, and France). Jean-François Hochedez (ROB) is Principal Investigator, Yves Stockman (CSL) is Project Manager, and Werner Schmutz (PMOD) is Lead co-Investigator.
LYRA will monitor the Solar irradiance in four UV passbands. They have been chosen for their relevance to solar physics, aeronomy and Space Weather:
the 115-125 nm Lyman-α channel,
the 200-220 nm Herzberg continuum channel,
the Aluminium filter channel (17-50 nm) including He II at 30.4 nm, and
the Zirconium filter channel (1-20 nm).The Radiometric calibration of the instrument is traceable to Synchrotron source standards, Physikalisch-Technische Bundesanstalt (PTB) and National Institute of Standards and Technology (NIST). Its stability will be monitored by onboard calibration light sources (light-emitting diodes), which allow distinguishing between potential degradations of the detectors and filters. Additionally, a redundancy strategy contributes to the accuracy and the stability of the measurements. LYRA will benefit from wide bandgap detectors based on diamond: it will be the first space assessment of a pioneering UV detectors program. Diamond sensors make the instruments radiation-hard and solar-blind: their high bandgap energy makes them quasi-insensitive to visible light (see also references in Marchywka Effect). The SWAP extreme ultraviolet (EUV) imaging telescope will operate next to LYRA on Proba-2. Together, they will establish a high performance solar monitor for operational space weather nowcasting and research. LYRA demonstrates technologies important for future missions such as the ESA Solar Orbiter mission.Mu Velorum
Mu Velorum (μ Vel, μ Velorum) is a binary star system in the southern constellation Vela. The two stars orbit each other with a semi-major axis of 1.437 arcseconds and a period of 116.24 years. (Wulff-Dieter Heintz (1986) lists a period of 138 years with his orbital elements.) The pair have a combined apparent visual magnitude of 2.69, making the system readily visible to the naked eye. From parallax measurements, the distance to this system is estimated to be 117 light-years (36 parsecs). The system is about 360 million years old.The primary component is a giant star with an apparent magnitude of 2.7 and a stellar classification of G5 III. It is radiating about 107 times the luminosity of the Sun from an expanded atmosphere about 13 times the Sun's radius. The mass of this star is 3.3 times that of the Sun. In 1998, the Extreme Ultraviolet Explorer space telescope detected a strong flare that released an X-ray emission nearly equal to the output of the entire star. The quiescent X-ray luminosity of Mu Velorum A is about 1.7 × 1030 erg s−1.The fainter companion, Mu Velorum B, is a main sequence star with an apparent magnitude of 6.4 and an assigned stellar classification of G2V. However, this classification is suspect. Closer examination of the spectrum suggests the star may actually have a classification of F4V or F5V, which suggests a mass of about 1.5 times the mass of the Sun. Such stars typically do not show a marked level of magnetic activity.Plasmasphere
The plasmasphere, or inner magnetosphere, is a region of the Earth's magnetosphere consisting of low energy (cool) plasma. It is located above the ionosphere. The outer boundary of the plasmasphere is known as the plasmapause, which is defined by an order of magnitude drop in plasma density. The plasmasphere was discovered in 1963 by Don Carpenter from the analysis of VLF whistler wave data. Traditionally, the plasmasphere has been regarded as a well behaved cold plasma with particle motion dominated entirely by the geomagnetic field and hence corotating with the Earth.
In 2014 satellite observations from the THEMIS mission have shown that density irregularities such as plumes or biteouts may form. It has also been shown that the plasmasphere does not always co-rotate with the Earth. The plasma of the magnetosphere has many different levels of temperature and concentration. The coldest magnetospheric plasma is most often found in the plasmasphere, a donut-shaped region surrounding the Earth. But plasma from the plasmasphere can be detected throughout the magnetosphere because it gets blown around by electric and magnetic field. Data gathered by the twin Van Allen Probes show that the plasmasphere also limits highly energetic ultrarelativistic electrons from cosmic and solar origin from reaching low earth orbits and the surface of the planet.STS-80
STS-80 was a Space Shuttle mission flown by Space Shuttle Columbia. The launch was originally scheduled for 31 October 1996, but was delayed to 19 November for several reasons. Likewise, the landing, which was originally scheduled for 5 December, was pushed back to 7 December after bad weather prevented landing for two days. The mission was the longest Shuttle mission ever flown at 17 days, 15 hours, and 53 minutes. Although two spacewalks were planned for the mission, they were both canceled after problems with the airlock hatch prevented astronauts Tom Jones and Tammy Jernigan from exiting the orbiter.Solar Dynamics Observatory
The Solar Dynamics Observatory (SDO) is a NASA mission which has been observing the Sun since 2010. Launched on February 11, 2010, the observatory is part of the Living With a Star (LWS) program.The goal of the LWS program is to develop the scientific understanding necessary to effectively address those aspects of the connected Sun–Earth system directly affecting life and society. The goal of the SDO is to understand the influence of the Sun on the Earth and near-Earth space by studying the solar atmosphere on small scales of space and time and in many wavelengths simultaneously. SDO has been investigating how the Sun's magnetic field is generated and structured, how this stored magnetic energy is converted and released into the heliosphere and geospace in the form of solar wind, energetic particles, and variations in the solar irradiance.Solar physics
Solar physics is the branch of astrophysics that specializes in the study of the Sun. It deals with detailed measurements that are possible only for our closest star. It intersects with many disciplines of pure physics, astrophysics, and computer science, including fluid dynamics, plasma physics including magnetohydrodynamics, seismology, particle physics, atomic physics, nuclear physics, stellar evolution, space physics, spectroscopy, radiative transfer, applied optics, signal processing, computer vision, computational physics, stellar physics and solar astronomy.
Because the Sun is uniquely situated for close-range observing (other stars cannot be resolved with anything like the spatial or temporal resolution that the Sun can), there is a split between the related discipline of observational astrophysics (of distant stars) and observational solar physics.
The study of solar physics is also important as it is believed that changes in the solar atmosphere and solar activity can have a major impact on Earth's climate. The Sun also provides a "physical laboratory" for the study of plasma physics.UVS (Juno)
UVS, known as the Ultraviolet Spectrograph or Ultraviolet Imaging Spectrometer is the name of an instrument on the Juno orbiter for Jupiter. The instrument is an imaging spectrometer that observes the ultraviolet range of light wavelengths, which is shorter wavelengths than visible light but longer than X-rays. Specifically, it is focused on making remote observations of the aurora, detecting the emissions of gases such as hydrogen in the far-ultraviolet. UVS will observes light from as short a wavelength as 70 nm up to 200 nm, which is in the extreme and far ultraviolet range of light. The source of aurora emissions of Jupiter is one of the goals of the instrument. UVS is one of many instruments on Juno, but it is in particular designed to operate in conjunction with JADE, which observes high-energy particles. With both instruments operating together, both the UV emissions and high-energy particles at the same place and time can be synthesized. This supports the Goal of determining the source of the Jovian magnetic field. There has been a problem understanding the Jovian aurora, ever since Chandra determined X-rays were coming not from, as it was thought Io's orbit but from the polar regions. Every 45 minutes an X-ray hot-spot pulsates, corroborated by a similar previous detection in radio emissions by Galileo and Cassini spacecraft. One theory is that its related to the solar wind. The mystery is not that there are X-rays coming Jupiter, which has been known for decades, as detected by previous X-ray observatories, but rather why with the Chandra observation, that pulse was coming from the north polar region.There is two main parts to UVS, the optical section and an electronics box. It has a small reflecting telescope and also a scan mirror, and it can do long-slit spectrography. UVS uses a Rowland circle spectrograph and a toroidal holographical grating. The detector uses a micro-channel plate detector with the sensor being a CsI photocathode to detect the UV lightUVS was launched aboard the Juno spacecraft on August 5, 2011 (UTC) from Cape Canaveral, USA, as part of the New Frontiers program, and after an interplanetary journey that including a swingby of Earth, entered a polar orbit of Jupiter on July 5, 2016 (UTC),For detection of following gasses in the far UV:
Acetylene (C2H2)UVS is similar to, but with a number of changes compared to instruments flown on New Horizons (Pluto probe), Rosetta (comet probe), as well as the Lunar Reconnaissance Orbiter. One of the changes is shielding to help the instrument endure Jupiter's radiation environment.The electronics are located inside the Juno Radiation Vault, which uses titanium to protect it and other spacecraft electronics. The UVS electronics include two power supplies and data processing. UVS electronics box uses an Actel 8051 microcontroller.UVS was developed at the Space Science Department at Southwest Research InstituteUVIS data in concert with JEDI observations detected electrical potentials of 400,000 electron volts (400 keV), 20-30 times higher than Earth, driving charged particles into the polar regions of Jupiter.There was a proposal to use Juno's UVS (and JIRAM) in collaboration with the Hubble Space Telescope instruments STIS and ACS to study Jupiter aurora in UV.