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39-627: NIRCam is housed in the Integrated Science Instrument Module (ISIM), to which it is attached by struts. It is designed to operate at 37 K (−236.2 °C; −393.1 °F), so it can detect infrared radiation at this wavelength. It is connected to the ISIM by struts and thermal straps connect to heat radiators, which helps maintain its temperature. The Focal Plane Electronics operated at 290 K. NIRCam should be able to observe objects as faint as magnitude +29 with

78-410: A barium fluoride (BaF 2 ) and zinc selenide (ZnSe). The triplet lenses are collimating optics. The biggest lens has 90 mm of clear aperture. The observed wavelength range is broken up into a short wavelength and a long wavelength band. The short wavelength band goes from 0.6 to 2.3 μm and the long wavelength band goes from 2.4 to 5 μm; both have the same field of view and access to

117-511: A 10,000-second exposure (about 2.8 hours). It makes these observations in light from 0.6 to 5 μm (600 to 5000  nm ) wavelength. It can observe in two fields of view, and either side can do imaging, or from the capabilities of the wave-front sensing equipment, spectroscopy. The wavefront sensing is much finer than the thickness of an average human hair. It must perform at an accuracy of at least 93 nanometers and in testing it has even achieved between 32 and 52 nm. A human hair

156-674: A Delta 2 launch rocket. The design was cancelled at the end of 2000. At that time NGST/JWST was still a 8-meter (26 ft) design, with an area of 50 m (540 sq ft), a few years later this was reduced eventually to the 6.5-meter (21 ft) design, with an area of 25 m (270 sq ft). One part of JWST development was the production of the Optical Telescope Element Pathfinder. The OTE pathfinder uses two additional mirror segments, and additional secondary mirror, and puts together various structures to allow testing of various aspects of

195-494: A coronagraph. Each side of the NIRCam views a 2.2 arcminute by 2.2 arcminute patch of sky in both the short and long wavelengths; however, the short wavelength arm has twice the resolution. The long wavelength arm has one array per side (two overall), and the short wavelength arm has four arrays per side, or 8 overall. Side A and Side B have a unique field of view, but they are adjacent to each other. In other words,

234-457: A phase retrieval technique, to achieve designed wavefront error of less than 150 nm. To function as focusing mirror correctly the 18 main mirror segments need to be aligned very closely to perform as one. This needs to be done in outer space, so extensive testing on Earth is required to ensure that it will work properly. To align each mirror segment, it is mounted to six actuators that can adjust that segment in 5 nm steps. One reason

273-451: A single item can be used for different functions, or it may not be a physically created item at all, but rather a software simulation. The NEXUS space telescope was a complete space telescope, but essentially a scaled down JWST but with a number of changes including only three mirror segments with one folding out for a main mirror diameter of 2.8 meters (9.2 ft). It was lighter, so it was envisioned it could be launched as early as 2004 on

312-578: A total collecting surface of 27 square meters (290 sq ft). Secondary mirrors complete anastigmatic imaging optics with effective f / 20 focal ratio and focal length of 131.4 meters (431 ft). The main three-mirror telescope is a Korsch -type design, and it feeds into the Aft Optics Subsystem (part of OTE), which in turn feeds into the Integrated Science Instrument Module which holds

351-556: Is 3 meters (10 ft) long. The DTA tubes are made of graphite-composite carbon fiber, and it is intended that they will be able to survive the conditions in space. Achieving a working main mirror was considered one of the greatest challenges of JWST development. Part of the JWST development included validating and testing JWST on various testbeds of different functions and sizes. Some types of development items include pathfinders , test beds , and engineering test units . Sometimes

390-642: Is a radiator behind the main mirror, that helps keep the telescope cool. There are two ADIR's and they are made of high-purity aluminum. There is a special black coating on the radiators that helps them emit heat into space. Some major parts of the OTE according to NASA: The Aft Optics Subsystem includes the Tertiary mirror and the Fine Steering Mirror. One of the tasks for the Fine steering mirror

429-486: Is a component of the James Webb Space Telescope , a large international infrared space telescope launched on 25 December 2021 . ISIM is the heart of the JWST, and holds the main science payload which includes four science instruments and the fine guidance sensor. ISIM is the spacecraft chassis and instruments that take the light from the main mirror and convert that into the science data that

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468-471: Is called OTIS, which is the combination of these two regions. The ISIM Electronics Compartment (IEC) is a section of ISIM that houses computing and electrical resources for the instruments. The main electronics for each of the instruments is housed in this thermally wrapped box. In 2014 the electronics for NIRspec were installed in the IEC. The IEC is mounted to the cryogenic structure of the main telescope, and

507-490: Is designed to make the 18 segment primary mirror behave as a monolithic (single-piece) mirror, and it does this in part by actively sensing and correcting for errors. There are nine distance alignment processes that the telescope goes through to achieve this. Another important aspect to the adjustments is that the primary mirror backplane assembly is steady. The backplane assembly is made of graphite composite, invar , and titanium . The ADIR, Aft Deployable Infrared Radiator

546-547: Is extremely important to JWST, because it is not only a sensitive infrared camera, but it is also used to adjust the alignment of the main mirror segments. The tests were very positive because NIRcam showed it was very stable through vibration and thermal testing. NIRcam was installed into ISIM in March 2014, and then underwent integration and testing after that, as the telescope was readied for its originally planned 2019 launch. ISIM contains these instruments: ISIM also includes

585-423: Is image stabilization. The metal beryllium was chosen for a number of reasons including weight, but also for its low-temperature coefficient of thermal expansion compared to glass. Furthermore beryllium is not magnetic and a good conductor of electricity and heat. Other infrared telescopes that have used beryllium mirrors include IRAS , COBE , and Spitzer . The Subscale Beryllium Model Demonstrator (SBMD)

624-630: Is then sent back to Earth. The other two major sections of the JWST are the Optical Telescope Element (OTE) (mirrors and their structure) and the Spacecraft Element (SE), which includes the spacecraft bus and sunshield . ISIM has a mass of 1400 kg (3086 lb), about 23% of the mass of the JWST. The infrared camera instrument integrated with ISIM passed its thermal tests in early 2016. ISIM underwent intense thermal cold testing in late 2015 to early 2016. NIRcam

663-403: Is thousands of nanometers across. Wavefront sensor components include: Parts of NIRCam: NIRCam has two complete optical systems for redundancy. The two sides can operate at the same time, and view two separate patches of sky; the two sides are called side A and side B. The lenses used in the internal optics are triplet refractors . The lens materials are lithium fluoride (LiF),

702-511: The ISIM computer. The data between the FPE and the ISIM computer is transferred by SpaceWire connection. There are also Instrument Control Electronics (ICE). The Focal Plane Arrays contain 40 million pixels. The FPE provides or monitors the following for the FPA: NIRcam includes filter wheels that allow the light coming in from the optics to be sent through a filter before it is recorded by

741-567: The James Webb Space Telescope, including the Main mirror. It also has the fine steering mirror, which provides that final precise pointing, and it works in conjunction with the fine guidance sensor and other controls systems and sensors in the spacecraft bus . The main mirror segments are aligned roughly using a coarse phasing algorithm . Then for finer alignment, special optical devices inside NIRCam are used to conduct

780-571: The MIRI crycooler, which extends down into the spacecraft bus (on the hot side of the spacecraft). Relevant systems and subsystems the ISIM: Three regions to ISIM were defined by NASA to aid in its production. The three regions include the cryogenic instrument module (1), the electronics compartment (2), and finally the Command and Data Handling subsystem and MIRI crycooler (3), which is inside

819-585: The OTE to the spacecraft bus. It must expand to allow the Sunshield (JWST) to spread out, allowing the space between the five layers to expand. The sunshield segment has multiple components, including six spreaders at the outer edge to spread the layers out at the six extremities. During launch the DTA is shrunk down, but must extend at the right moment. The extended DTA structure allows the sun shield layers to be fully spread-out. The DTA must also thermally isolate

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858-678: The Optical Testing System (aka the OTS) which was created specifically to test the SBMD. The SBMD had to meet the requirements for a space-based mirror, and these lessons were important to the development of the JWST. The tests were conducted at the X-Ray Calibration Facility (XRCF) at Marshall Space Flight Center (MSFC) in the U.S. State of Alabama. The Optical Testing System (OTS) had to be developed to test

897-508: The back of the telescope or too close to the sunshield, but by using baffles and insulation, direct the heat out into space. The IEC box sits just below most of the instruments and behind it, but above the spacecraft bus. There is one side that is made of aluminum and the other sides are composite. It is wrapped in multiple layers of insulation including six layers of SLI (the JWST Single Layer Insulation). Some of

936-517: The camera looks at two 2.2 arcminute wide fields of view that are next to each other, and each of these views is observed at short and long wavelengths simultaneously with the short wavelength arm having twice the resolution of the longer wavelength arm. The builders of NIRCam are the University of Arizona, company Lockheed Martin , and Teledyne Technologies , in cooperation with the U.S. Space agency, NASA. Lockheed Martin tested and assembled

975-449: The cold section of the OTE from the hot spacecraft bus. The Sunshield will protect the OTE from direct sunlight and reduce the thermal radiation hitting it, but another aspect is the OTE's physical connection to the rest of the spacecraft. (see Thermal conduction and Heat transfer ) Whereas the sunshield stops the telescope getting hot due to radiated heat from the Sun, the DTA must insulate

1014-495: The degrees of freedom of the primary mirror alignment and phasing. The Subscale Beryllium Model Demonstrator (SBMD) was fabricated and tested by 2001 and demonstrated enabling technologies for what was soon Christened the James Webb Space Telescope, previously the Next Generation Space Telescope (NGST). The SBMD was a half-meter diameter mirror made from powdered beryllium. The weight of the mirror

1053-585: The device. Teledyne Technologies designed and manufactured the ten mercury-cadmium-telluride (HgCdTe) detector arrays. NIRCam was completed in July 2013 and it was shipped to Goddard Spaceflight Center, which is the NASA center managing the JWST project. NIRCam's four major science goals include: Data from the image sensors (Focal Plane Arrays) is collected by the Focal Plane Electronics and sent to

1092-416: The enclosure must maintain a much warmer temperature for the electronics inside, but not allow that heat to negatively affect the main telescope. The box can dissipate about 200 watts of electrical power. One of the considerations is to direct the majority of the heat (radiatively) in a roughly 20 degree angle in between the back of the main mirror structure and instruments and the sunshield. Not too close to

1131-417: The features for thermal (heat) management include a parasitic tray radiator and baffles. IEC constitutes region 2 of ISIM. Optical Telescope Element Optical Telescope Element ( OTE ) is a sub-section of the James Webb Space Telescope , a large infrared space telescope launched on 25 December 2021 , consisting of its main mirror , secondary mirrors , the framework and controls to support

1170-419: The mirror was divided into segments is that it cuts down on weight, because a mirror's weight is related to its size, which is also one of the reasons beryllium was chosen as the mirror material because of its low weight. Although in the essentially weightless environment of space the mirror will weigh hardly anything, it needs to be very stiff to maintain its shape. The Wavefront sensing and control sub-system

1209-534: The mirrors, and various thermal and other systems. The OTE collects the light and sends it to the science instruments in Webb's Integrated Science Instrument Module . The OTE has been compared to being the " eye " of the telescope and the backplane of it to being the " spine ". The primary mirror is a tiled assembly of 18 hexagonal elements, each 1.32 meters (4.3 ft) from flat to flat. This combination yields an effective aperture of 6.5 meters (21 ft) and

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1248-546: The overall risk of the program by practicing on something other than the actual flight spacecraft. Another testbed, the Test Bed Telescope, was a 1/6th scale model of the main mirror, with polished segments and working actuators, operating at room temperature, and used to test all the processes for aligning the segments of JWST. Another optics testbed is called JOST, which stands for JWST Optical Simulation Testbed, and uses an MEMS with hexagonal segments to simulate

1287-400: The science instruments and fine guidance sensor. The other two major sections of the JWST are the Integrated Science Instrument Module (ISIM) and the Spacecraft Element (SE), which includes the spacecraft bus and sunshield . The components of OTE were integrated by L3Harris Technologies to form the final system. The OTE combines a large amount of the optics and structural components of

1326-619: The section, including Ground Support Equipment. This supports the GSE being used on the JWST itself later on, and allows testing of mirror integration. OTE pathfinder as 12 rather than 18 cells compared to the full telescope, but it does include a test of the backplane structure. There are many test articles and developmental demonstrators for the creation of JWST. Some important ones were early demonstrators, that showed that many of fundamental technologies of JWST were possible. Other test articles are important for risk mitigation, essentially reducing

1365-447: The sensors. The filters have a certain range in which they allow light to pass, blocking the other frequencies; this allows operators of NIRCam some control over what frequencies are observed when making an observation with the telescope. By using multiple filters the redshift of distant galaxies can be estimated by photometry. NIRcam filters: Integrated Science Instrument Module Integrated Science Instrument Module ( ISIM )

1404-538: The spacecraft bus physically. MIRI needs to be colder than the other instruments so it has an additional cooler. MIRI is the mid-infrared instrument. The Command and Data Handling subsystem uses the spacecraft on-board communication standard called SpaceWire . SpaceWire was developed by the European Space Agency (ESA), and provides low-power data communication at up to 200 Mbits per second. Regions: In May 2016, OTE and ISIM were merged into what

1443-419: The telescope from the heat of the rest of the structure, similar to the way an insulated pan handle protects from the heat of a stove. The DTA extends by means of two telescoping tubes that can slide between each other on rollers. There is an inner tube and an outer tube. The DTA is extended by an electric motor that rotates a ball screw nut which pushes the two tubes apart. When the DTA is fully deployed it

1482-454: Was successfully tested at cryogenic temperatures, and one of the concerns was surface roughness at low kelvin numbers. The beryllium mirrors are coated with a very fine layer of gold to reflect infrared light. There are 18 hexagonal segments that are grouped together to create a single mirror with an overall diameter of 6.5 metres (21 ft). At the base of the OTE is the critical Deployable Tower Assembly (DTA). component which connects

1521-442: Was then reduced through a mirror-making process called "light-weighting", where material is removed without disrupting its reflecting ability, and in this case 90% of the SBMD mass was removed. It was then mounted to a rigid backplane with titanium bipod flexures and underwent various tests. This included freezing it down to the low temperatures required and seeing how it behaved optically and physically. The tests were conducted with

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