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  • 摘要:

    The LISA trio of satellites to detect gravitational waves from space has been selected as the third large-class mission in ESA’s Science programme, while the Plato exoplanet hunter moves into development.

    These important milestones were decided upon during a meeting of ESA’s Science Programme Committee today, and ensure the continuation of ESA’s Cosmic Vision plan through the next two decades.

    The ‘gravitational universe’ was identified in 2013 as the theme for the third large-class mission, L3, searching for ripples in the fabric of spacetime created by celestial objects with very strong gravity, such as pairs of merging black holes.

    Predicted a century ago by Albert Einstein's general theory of relativity, gravitational waves remained elusive until the first direct detection by the ground-based Laser Interferometer Gravitational-Wave Observatory in September 2015. That signal was triggered by the merging of two black holes some 1.3 billion light-years away. Since then, two more events have been detected.

    Furthermore, ESA’s LISA Pathfinder mission has also now demonstrated key technologies needed to detect gravitational waves from space. This includes free-falling test masses linked by laser and isolated from all external and internal forces except gravity, a requirement to measure any possible distortion caused by a passing gravitational wave.

    The distortion affects the fabric of spacetime on the minuscule scale of a few millionths of a millionth of a metre over a distance of a million kilometres and so must be measured extremely precisely.

    LISA Pathfinder will conclude its pioneering mission at the end of this month, and LISA, the Laser Interferometer Space Antenna, also an international collaboration, will now enter a more detailed phase of study. Three craft, separated by 2.5 million km in a triangular formation, will follow Earth in its orbit around the Sun.

    Following selection, the mission design and costing can be completed. Then it will be proposed for ‘adoption’ before construction begins. Launch is expected in 2034.

    ESA to Develop Gravitational Wave Space Mission with NASA Support

    In the same meeting Plato – Planetary Transits and Oscillations of stars – has now been adopted in the Science Programme, following its selection in February 2014.

    This means it can move from a blueprint into construction. In the coming months industry will be asked to make bids to supply the spacecraft platform.

    Following its launch in 2026, Plato will monitor thousands of bright stars over a large area of the sky, searching for tiny, regular dips in brightness as their planets cross in front of them, temporarily blocking out a small fraction of the starlight.

    The mission will have a particular emphasis on discovering and characterising Earth-sized planets and super-Earths orbiting Sun-like stars in the habitable zone – the distance from the star where liquid surface water could exist.

    It will also investigate seismic activity in some of the host stars, and determine their masses, sizes and ages, helping to understand the entire exoplanet system.

    Plato will operate from the ‘L2’ virtual point in space 1.5 million km beyond Earth as seen from the Sun.

    来源机构: 欧洲航天局 | 点击量:0
  • 摘要:

    ESO has signed a contract with the German company Physik Instrumente GmbH & Co. KG, based in Karlsruhe, to construct the position actuators (PACTs) that will adjust the positions of the 798 hexagonal segments of the primary mirror of ESO’s Extremely Large Telescope (ELT).

    The segments that make up the ELT’s enormous 39-metre main mirror will be connected to the main telescope structure via a support system (ann15003), of which the PACTs are fundamental components. Each segment, some 1.4 metres across and weighing 250 kg will be mounted on three PACTs — meaning 2394 in total. The PACTs will support the segment and actively control its position in three directions, known as piston, tip and tilt. The control system of the ELT primary mirror will initiate tiny adjustments to the PACTs to maintain the mirror’s overall shape, correcting for deformations which may be caused by changes in telescope elevation, temperature and wind forces, as well as limiting the effects of vibrations.

    More Information

    Physik Instrumente has worked with ESO before, providing the hexapods that align the subreflectors to the large main reflectors of the radio telescopes that make up the Atacama Large Millimeter/submillimeter Array (ALMA).

    来源机构: 欧洲南方天文台 | 点击量:49
  • 摘要:

    The team behind the Pale Red Dot campaign, who last year discovered a planet around the closest star to our Sun (eso1629), are resuming their search for Earth-like planets and launching another initiative today. The Red Dots campaign will follow the astronomers as they use ESO’s exoplanet-hunter to look for planets around some of our nearest stellar neighbours: Proxima Centauri, Barnard's Star and Ross 154. ESO is joining this Open Notebook Science experiment — real science presented in real time — that will give the public and the scientific community access to observational data from Proxima Centauri as the campaign unfolds.

    The scientific team [1] led by Guillem Anglada-Escudé from Queen Mary University of London will acquire and analyse data from ESO’s High Accuracy Radial velocity Planet Searcher (HARPS) and other instruments across the globe [2] over approximately 90 nights. Photometric observations began on 15 June and spectrographic observations start on 21 June.

    HARPS is a spectrograph with unrivalled precision — the most successful finder of low-mass exoplanets to date. Attached to the ESO 3.6-metre telescope at La Silla, HARPS searches nightly for exoplanets, looking for the minute wobbles in the star’s motion generated by the pull of an exoplanet in orbit. HARPS picks up motion which can be as little as a gentle walking pace — just 3.5 km/h — from trillions of kilometres away.

    Among the stars targeted by Red Dots will be Proxima Centauri, which scientists suspect has more than one terrestrial planet in orbit around it. Proxima Centauri is the closest star to our Sun, only 4.2 light-years away. It may be one of the most suitable places to look for life beyond our Solar System, as our instruments and technologies advance.

    Earlier this year, ESO announced a partnership with the Breakthrough Initiatives, which aims to demonstrate proof of concept for a new technology that will enable ultra-light unmanned space flight at 20% of the speed of light. Such nanocraft could be sent to the three stars of the Alpha Centauri system, of which Proxima Centauri is the closest to our Sun.

    The other two stars observed during the Red Dots campaign are Barnard's star, a low mass red dwarf almost 6 light-years away, and Ross 154, another red dwarf, 9.7 light-years away. Barnard’s star is a popular star in science fiction culture and has also been proposed as the target for future interstellar missions such as the Daedalus project.

    The telescope observations will be complemented by an outreach campaign supported by ESO and other partners [3]. The Pale Red Dot campaign revealed the methods and steps of doing science, but the results were presented only after the peer review process. This time, observational data from Proxima Centauri will be revealed, analysed and discussed in real time.

    Pro-am collaborations and contributions by interested citizens and scientists will be encouraged via social media and a forum tool, as well as via support tools from the American Association of Variable Star Observers (AAVSO).

    Any observations presented during this time will of course be preliminary only and they must not be used or cited in refereed literature. The team will not produce conclusive statements, nor claim any finding until a suitable paper is written, peer-reviewed and accepted for publication.

    The Red Dots campaign will keep the public informed via the reddots.space website, where weekly updates will be posted, together with supporting articles and highlights of the week including featured contributions by the community. Conversations will take place also on the Red Dots Facebook page, the Red Dots Twitter account and the hashtag #reddots.

    No one can say for sure what the outcome of the Red Dots campaign will be. After data acquisition and data analysis together with the community, the scientific team will submit the results for formal peer review. If exoplanets are indeed discovered around these stars, ESO’s Extremely Large Telescope, due to see first light in 2024, should be able to directly image them and characterise their atmospheres, a crucial step towards searching for evidence of life beyond the Solar System.

    Notes

    [1] The team of astronomers leading the observations and outreach campaign are: Guillem Anglada-Escudé, John Strachan, Richard P. Nelson, Harriet Brettle (Queen Mary University of London, UK), John Barnes (Open University, UK), Mikko Tuomi, Hugh R. A. Jones (University of Hertfordshire, UK), Cristina Rodríguez-Lopez, Eloy Rodriguez, Pedro J. Amado, María J. López-González, Nicolás Morales, José Luís Ortiz (Instituto de Astrofisica de Andalucia, Spain), Enric Pallé, Victor J. Sanchez Bejar, Felipe Murgas (Instituto de Astrofísica de Canarias, Spain), Ignasi Ribas, Enrique Herrero Casas (Institut de Ciències de l’Espai, Spain), Ansgar Reiners, Mathias Zechmeister, Stefan Dreizler, Lev Tal-Or, Sandra Jeffers (University of Goettingen, Germany), Yiannis Tsapras (Astronomisches Rechen-Institut, University of Heidelberg, Germany), Rachel Street (LCOGT.net), James Jenkins, Zaira Modroño Berdiñas (Universidad de Chile, Chile), Aviv Ofir (Weizmann Institute, Israel), Julien Morin (Université de Montpellier and CNRS, France), Gavin Coleman (University of Bern, Switzerland).

    [2] The facilities used during the Red Dots campaign are: HARPS/ESO in Chile (Spectroscopy/Doppler measurements and more); and an extended network of small telescopes for photometric monitoring including: Las Cumbres Global Observatory Telescope network; SpaceObs ASH2 in Chile; Observatorio de Sierra Nevada, in Spain; and Observatori Astronomic del Montsec, Spain. In addition to new data, the team will make extensive use of public observations of all three stars from the ESO archives (HARPS and UVES/VLT) and the ASAS photometric survey.

    [3] The outreach campaign is coordinated by members of the science team with support from the outreach departments of ESO, Queen Mary University of London, Instituto de Astrofisica de Andalucia/CSIC, Universidad de Chile and University of Goettingen.

    来源机构: 欧洲南方天文台 | 点击量:37
  • 摘要:

    Jerry Nelson, a pioneering astronomer known for his innovative designs for advanced telescopes, died June 10 at his home in Santa Cruz. He was 73.

    A professor emeritus of astronomy and astrophysics at UC Santa Cruz, Nelson was project scientist for the Thirty Meter Telescope (TMT) and had served as project scientist for the W. M. Keck Observatory in Hawaii from 1985 through 2012.

    Nelson conceived the revolutionary segmented mirror design of the Keck Observatory's twin 10-meter telescopes, and he developed new techniques to fabricate and control the mirror segments. Each telescope has an array of 36 hexagonal segments, precisely aligned to act as a single reflective surface. This design has since been used for other large ground-based telescopes, and the next-generation James Webb Space Telescope also has a segmented primary mirror design.

    Nelson also played an important role in the development of adaptive optics technology, which sharpens the images from ground-based telescopes by correcting for the blurring effect of Earth's atmosphere. As founding director of the Center for Adaptive Optics, a National Science Foundation Science and Technology Center based at UC Santa Cruz, Nelson helped pioneer the use of adaptive optics in astronomy.

    Claire Max, director of UC Observatories and the Bachman Professor of Astronomy and Astrophysics at UCSC, said Nelson was a renowned figure in the international astronomy community. "Jerry's impacts on the field of astronomy and astrophysics are legendary, and we will all benefit from his legacy for many years to come. He was a wonderful colleague and mentor to many of us," she said.

    Nelson earned his B.S. in physics at the California Institute of Technology and his Ph.D. in physics at UC Berkeley. From 1970 to 1981, he worked at Lawrence Berkeley National Laboratory, and he was a professor of astronomy at UC Berkeley from 1981 until 1994, when he moved to UC Santa Cruz.

    Much of Nelson's early research was in the area of high-energy physics and astrophysics. He analyzed the results of particle accelerator experiments and studied high-energy astrophysical phenomena such as pulsars using innovative astronomical instruments of his own design.

    Nelson presented the concepts that led to segmented-mirror telescopes in a series of papers and technical reports starting in 1977, often working with UC colleagues Terry Mast and Gary Chanan. The largest telescopes at that time had been fashioned by polishing a single glass "blank" to the requisite precision of a small fraction of the wavelength of visible light. In order to maintain that surface, the polished mirrors had to be very thick and were therefore heavy, which was a problem for larger mirrors. Nelson's idea was to create a single, high-precision optical surface by supporting individual hexagonal mirrors in a close-packed honeycomb configuration. Making this concept a reality required a series of innovative ideas for fabrication, measurement, and control of the mirror segments.

    Nearly twice the diameter and four times the light-gathering capacity of the previous largest ground-based telescopes, the twin Keck Telescopes had an enormous impact on astronomy and astrophysics research.

    "The segmented-mirror design will be seen as one of the major turning points in telescope technology and one that opened the path to much larger telescopes on the ground and in space in the coming decades," said Michael Bolte, a professor of astronomy and astrophysics at UC Santa Cruz. Bolte, who serves on the TMT Board of Directors, said the TMT's 30-meter primary mirror design is essentially a scaled up version of the Keck primary mirrors.

    After suffering a stroke in 2011, Nelson coped with significant physical limitations but remained deeply engaged in TMT design work. "He was a wonderful colleague. His endless curiosity always pushed the scientists around him to think more deeply, and his persistence and continued excellence after his stroke were inspirational to everyone," Bolte said.

    A symposium to honor Nelson was already planned for July 13 and 14 in Santa Cruz, featuring talks by many of the eminent astronomers who worked with him over the years. The gathering will now serve as a memorial celebration of his life, Bolte said.

    A member of the National Academy of Sciences, Nelson received many awards and honors for his achievements, including the 2010 Kavli Prize in Astrophysics, the Benjamin Franklin Medal in Electrical Engineering, the André Lallemande Prize of the French Academy of Sciences, and the Dannie Heineman Prize for Astrophysics of the American Astronomical Society.

    Nelson is survived by his wife, Jocelyn Nelson; his sister Jeanne Moat; two children from his first marriage, Leif and Alexandra; and three grandchildren. His first wife Victoria died in 1992.

    来源机构: 美国三十米望远镜(TMT) | 点击量:39
  • 摘要:

    An integral piece of the Thirty Meter Telescope’s Multi Segment Integration and Test facility (MSIT) has just been delivered to California. After leaving the port of Osaka, Japan on March 25, 2017, the Primary Mirror Cell prototype (MCP) arrived at the end of April 2017 and is now undergoing minor modifications prior to its final delivery to the Thirty Meter Telescope (TMT) laboratory in Monrovia. The TMT Primary Mirror System is comprised of 492 active mirror segments; the MSIT will enable integrated testing of up to seven primary mirror segments.

    The National Astronomical Observatory of Japan (NAOJ) has contracted with Mitsubishi Electric Company (MELCO) for the design of the Telescope Structure System. Hitachi Zosen Corporation, a major Japanese industrial and engineering corporation, is working with MELCO on its fabrication. Hitachi Zosen built the MCP for MELCO to determine if they can achieve the required dimensional accuracy and validate the proposed welding plan. In December 2016, TMT staff went to Osaka to perform an inspection of the MCP. Hitachi Zosen also designed and built a special container to transport the steel structure as well as a special frame to stabilize the MCP during its long journey to California.

    Meanwhile, in California, the concrete foundation for the MSIT was poured at the remodeled TMT Monrovia laboratory, located a few miles from the TMT Project Office. A jib crane is being installed at the laboratory to support the installation and removal of segments into the MSIT. “This is an important step for TMT,” said TMT Laboratory Manager Bob Anderson. “We have poured large foundations, more than four feet deep, to support the MSIT, which weighs over 9000 Kg, and the jib crane.”

    Multi Segment Integration and Test facility (MSIT) concept

    The MSIT will be used to verify form, fit and function of all TMT Primary Mirror System components and assemblies prior to full-scale production. In addition, the MSIT will verify the operation and performance of the M1 Control System (M1CS). The M1CS is responsible for turning the 492 TMT mirrors segments into the equivalent of a 30-meter diameter monolithic mirror. The M1CS must measure and control with nanometer precision to be successful. In addition, the MSIT has the ability to tilt the MCP – with seven segments installed – to 15 degrees, which is the tilt of the primary mirror at its perimeter when the telescope is pointing to the zenith. This allows the development team to work through the ergonomic challenges of working at the perimeter of the mirror cell.

    About the MSIT:

    The MSIT will include seven full-size - 1.44m - dummy aluminum segments (one central segment surrounded by the six others). The aluminum segments will be machined in the U.S. in the next several weeks. The aluminum segments may be replaced with actual TMT glass segments at a future date.

    Each segment will be mounted on a Segment Support Assembly (SSA) that supports the segment in translation and rotation while maintaining the optimal shape of its optical surface. Six of the seven SSAs were built in India under the direction of the India TMT Coordination Center. (ITCC).

    Twenty-one actuators (three for each segment) and twenty-four edge-sensors, both with nanometer precision, are used to control the height and tilts of the individual seven segments so as to make an equivalent monolithic mirror. Dust boots encase the sensors to keep them clean while a purge system maintains the humidity within the boot to an acceptable level. The actuators and sensors for the MSIT are fabricated in India under the direction of ITCC.

    Precision electronics for control and readout of the edge sensors and actuators are being designed by the Jet Propulsion Laboratory (JPL) in Pasadena. The electronics are distributed on the Segments, SSAs, and in “Node Wells” beneath the MCP floor. Although the electronics for the MSIT are initially being fabricated in the United States, the production electronics will be built in India also under the direction of ITCC.

    A Segment Lifting Jack System will be used to support segment installation and removal from the MSIT.

    The software that will control the MSIT is a small scale version of the Global Loop Controller (GLC), which controls the 492 TMT segments via 1476 actuators and 2772 sensors. The GLC includes complex algorithms that enable the 492 segments to act as a single mirror with nanometer precision while minimizing the effects of gravity when the telescope tracks a stellar object, temperature variations; and vibration, wind and seismic disturbances. The GLC is being developed and built by the Jet Propulsion Laboratory. The actuators, sensors, cabling, electronics and GLC are all part of the Primary Mirror Control System (M1CS).

    “The MSIT demonstrates the international aspect of TMT with contributions from Japan, India and the U.S.,” says Mark Sirota, manager of the Telescope Controls Group. “Tests will be carefully incremented as mirror segments are installed. The full scope of form, fit, and functionality will be verified. Initially we will start with a single segment to confirm the mechanical interfaces between SSA and the MCP. As we begin to install more segments we will continue to focus on mechanical interfaces and over time start to exercise the control aspects of the M1CS. The process will be very systematic, building up capability with time.

    “The MSIT will also provide an opportunity to understand the ergonomics of working in the mirror cell. We will be able to exercise our envisioned processes for removing and installing segments, replacing actuators, working at the perimeter of the mirror cell at a 15-degree angle, installing and replacing electronics and cables, and much more. We will be able to use the MSIT for training and even for troubleshooting problems that are encountered while commissioning the complete telescope. This is very exciting, as we’ve been developing this project for years; we surely will reduce risk by assembling these seven segments before assembling 492 of them.”

    来源机构: 美国三十米望远镜(TMT) | 点击量:82
  • 摘要:

    Up to now ESO’s giant telescope project has been referred to as the European Extremely Large Telescope or E-ELT, but this name, which was always intended to be interim and not final, is becoming less appropriate.

    To address this as the project moves rapidly forward into the construction phase, the organisation has decided on a shorter name. Instead of the European Extremely Large Telescope, the world’s biggest eye on the sky will now be known simply as the Extremely Large Telescope, the ELT.

    The new name, as well as being shorter and easier to say, reflects the growing number of ESO’s international partners, both at national level and as regards the commercial companies involved in the project, and also the fact that the telescope is located in Chile.

    Whilst older material may continue to refer to the telescope by its original name, ESO will be using the new name from now on and strongly encourages its use in all future material.

    来源机构: 欧洲南方天文台 | 点击量:75
  • 摘要:

    The company that has been developing MSE’s telescope structure is IDOM. IDOM designed many amazing structures including metros, large scientific facilities, stadia, as well as sustainable cities designed for a minimal carbon footprint. IDOM’s creations pair stunning architecture with unique solutions to solve challenging engineering problems, all done within a working culture guided by deep respect and care for the environment.

    Alexis Hill, MSE Deputy Project Engineer, likens IDOM's challenge - fitting an 11m telescope structure inside a building made for a 3.6 meter telescope while ensuring that telescope is balanced and moves with unrivaled precision and control - to "building a ship in a bottle".

    On March 16 and 17, engineers and scientists from Hawaii, Canada, France, Germany, and Spain got together in Bilbao, Spain to review IDOM’s conceptual design of MSE’s telescope structure. The goal of the review was to assess this initial design for performance, cost and risk. The expert panel looked for any showstoppers to the science objectives for MSE: to understand the properties of planet-hosting stars, to learn how our galaxy formed, make portraits of dark matter halos to unveil the nature of this mysterious substance that shapes the universe today, and to learn how supermassive black holes grow and transform their host galaxies. There were two essential questions addressed in the review:

    Will the telescope perform well enough to make the measurements needed to answer the science questions?

    Can it be built in the space allowed?

    IDOM's work impressed the reviewers, both because of their detailed analysis of every aspect of the design, as well as thorough explanations to questions, including a physical model of the telescope.

    IDOM’s design provides a mechanical framework supporting MSE’s wide field 11.25m aperture optics with exquisite precision while tracking the night sky, and coupling that to a bank of spectrographs capable of measuring more than 3000 objects at the same time. A particularly interesting aspect of the design challenge involves fitting this impressive framework into CFHT’s existing building - one that was built to hold the current 3.6m telescope!

    IDOM met this challenge, very well. Kei Szeto, the Chair of the review panel said IDOM passed the review with flying colors.

    Gaizka Murga, project manager at IDOM remarked on the collaboration with the MSE project office: "It has been a great pleasure for IDOM to collaborate with MSE Team in the preparation of the MSE Mount concept design. We have enjoyed very much the exercise of understanding the project needs and going to the basics to select the most suitable approach for the challenges of MSE. We are looking forward to moving forward to the next development phases of this unique project".

    In the immediate future IDOM will work closely with the MSE project office to find a way to increase the clearance between telescope and the surrounding dome. Several ideas are being explored which may provide relief while keeping the size of the observatory on Maunakea as close as possible to the current one.

    The MSE telescope, a ship-in-bottle technical wonder, will allow humanity to voyage through space and time through explorations of questions we share like: what are those bright dots in the night-sky, how were they formed and how will they evolve?

    来源机构: 加法夏望远镜(CFHT) | 点击量:107
  • 摘要:

    ESO has awarded a multi-million euro contract to the international company Teledyne e2v to design and produce a set of Large Visible Sensor Modules for use on the Extremely Large Telescope (ELT). Scheduled to see first light in 2024, the ELT is at the forefront of telescope technology. In order for the telescope to capture the Universe in exquisite detail, the ELT will use highly sophisticated adaptive optics systems which will enable it to adjust for changes in the atmosphere above it. These systems will require sensors of the highest quality.

    Each sensor, with a size of 800 x 800 pixels, will employ Teledyne e2v’s renowned CMOS technology. Their extreme sensitivity and fast response will permit the ELT’s adaptive optics systems to make tiny adjustments around 700 times a second to compensate for variations in Earth’s atmosphere. This will ensure that the resulting astronomical images — of exoplanets, distant galaxies and everything in between — will benefit from the highest resolution possible.

    The contract will last for four years, and consists of two stages. In the initial phase, sample sensors will be designed and manufactured to demonstrate proof of concept. Then a total of 28 sensors will be manufactured at Teledyne e2v’s site in Chelmsford, UK, most of which will be installed in planned ELT instruments and others will be deployed when needed.

    Teledyne e2v, the world leader in this field, has previously supplied ESO with high sensitivity CCD image sensors for the Multi-Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope (VLT), and their sensors will also be employed in the the forthcoming Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations (ESPRESSO).

    来源机构: 欧洲南方天文台 | 点击量:57
  • 摘要:

    NASA's James Webb Space Telescope has arrived at NASA’s Johnson Space Center in Houston, Texas, where it will undergo its last cryogenic test before it is launched into space in 2018.

    The telescope was loaded onto a trailer truck from NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and moved slowly down a highway by the Webb team to Joint Base Andrews in Maryland. At Andrews, the entire tractor-trailer, with telescope inside, was driven into a U.S. Air Force C-5C aircraft and flown to Ellington Field in Houston, Texas.

    When the C-5 landed at Ellington, the cargo was carefully unloaded and trucked to NASA Johnson, where inside a cleanroom the telescope was removed from its special shipping container. In the coming weeks it will be prepared for a key cryogenic test that will run nearly 100 days.

    To ensure the telescope's optics will operate at its frigid destination 1 million miles out in space, it must complete tests at cryogenic temperatures in a vacuum. The biggest and final cryogenic-vacuum test occurs in Johnson's Chamber A, the same vacuum chamber where Apollo spacecraft were tested. This test is critical in that it will verify the performance of the whole telescope as a system end-to-end at its extremely cold operating temperatures. Subsequently, the telescope will continue on its journey to Northrop Grumman Aerospace Systems in Redondo Beach, California, for final assembly and testing with the spacecraft bus and sunshield prior to launch in 2018.

    The James Webb Space Telescope is the world’s most advanced space observatory. This engineering marvel is designed to unravel some of the greatest mysteries of the universe, from discovering the first stars and galaxies that formed after the big bang to studying the atmospheres of planets around other stars. It is a joint project of NASA, ESA (the European Space Agency) and the Canadian Space Agency.

    The James Webb Space Telescope is pushed into the clean room of Building 32. Building 32 houses Chamber A, the thermal vacuum chamber where the telescope will have its final thermal vacuum testing.

    来源机构: 詹姆斯·韦伯空间望远镜(JWST) | 点击量:62
  • 摘要:

    The James Webb Space Telescope completed its environmental testing at NASA's Goddard Space Flight Center in Greenbelt, Maryland. The Webb telescope will be shipped to NASA's Johnson Space Center in Houston for end-to-end optical testing in a vacuum at its extremely cold operating temperatures.

    After undergoing rigorous environmental tests simulating the stresses of its rocket launch, the Webb telescope team at Goddard analyzed the results from this critical optical test and compared it to the pre-test measurements. The team concluded that the mirrors passed the test with the optical system unscathed.

    “The Webb telescope is about to embark on its next step in reaching the stars as it has successfully completed its integration and testing at Goddard. It has taken a tremendous team of talented individuals to get to this point from all across NASA, our industry and international partners, and academia,” said Bill Ochs, NASA’s Webb telescope project manager. “It is also a sad time as we say goodbye to the Webb Telescope at Goddard, but are excited to begin cryogenic testing at Johnson.”

    Rocket launches create high levels of vibration and noise that rattle spacecraft and telescopes. At Goddard, engineers tested the Webb telescope in vibration and acoustics test facilities that simulate the launch environment to ensure that functionality is not impaired by the rigorous ride on a rocket into space.

    Before and after these environmental tests took place, optical engineers set up an interferometer, the main device used to measure the shape of the Webb telescope’s mirror. An interferometer gets its name from the process of recording and measuring the ripple patterns that result when different beams of light mix and their waves combine or “interfere.”

    Waves of visible light are less than a thousandth of a millimeter long and optics on the Webb telescope need to be shaped and aligned even more accurately than that to work correctly. Making measurements of the mirror shape and position by lasers prevents physical contact and damage (scratches to the mirror). So, scientists use wavelengths of light to make tiny measurements. By measuring light reflected off the optics using an interferometer, they are able to measure extremely small changes in shape or position that may occur after exposing the mirror to a simulated launch or temperatures that simulate the subfreezing environment of space.

    During a test conducted by a team from Goddard, Ball Aerospace of Boulder, Colorado, and the Space Telescope Science Institute in Baltimore, temperature and humidity conditions in the clean room were kept incredibly stable to minimize fluctuations in the sensitive optical measurements over time. Even so, tiny vibrations are ever-present in the clean room that cause jitter during measurements, so the interferometer is a “high-speed” one, taking 5,000 “frames” every second, which is a faster rate than the background vibrations themselves. This allows engineers to subtract out jitter and get good, clean results on any changes to the mirror's shape.

    “Some people thought it would not be possible to measure beryllium mirrors of this size and complexity in a clean room to these levels but the team was incredibly ingenious in how they performed these measurements and the results give us great confidence we have a fantastic primary mirror,” said Lee Feinberg, Webb’s telescope optical element manager.

    The Webb telescope will be shipped to Johnson for end-to-end optical testing in a vacuum at its extremely cold operating temperatures. Then it will continue on its journey to Northrop Grumman Aerospace Systems in Redondo Beach, California, for final assembly and testing prior to launch in 2018.

    The James Webb Space Telescope is the world’s most advanced space observatory. This engineering marvel is designed to unravel some of the greatest mysteries of the universe, from discovering the first stars and galaxies that formed after the big bang to studying the atmospheres of planets around other stars. It is a joint project of NASA, ESA (the European Space Agency) and the Canadian Space Agency.

    来源机构: 詹姆斯·韦伯空间望远镜(JWST) | 点击量:66