Mission type | Astronomy |
---|---|
Operator | ESA with contributions from NASA |
Website | ESA Europe Astrium Germany NASA United States |
Mission duration | 5 years (design) 10 years (goal) |
Spacecraft properties | |
Manufacturer | Astrium |
Launch mass | 196 kg (432 lb) [1] |
Start of mission | |
Launch date | December 25, 2021 |
Rocket | As part of JWST onboard Ariane 5 |
Launch site | Kourou ELA-3 |
Contractor | Arianespace |
Main telescope | |
Type | Spectrograph |
Wavelengths | 0.6 μm (orange) to 5.0 μm (near-infrared) |
The NIRSpec (Near-Infrared Spectrograph) is one of the four scientific instruments flown on the James Webb Space Telescope (JWST). [2] The JWST is the follow-on mission to the Hubble Space Telescope (HST) and is developed to receive more information about the origins of the universe by observing infrared light from the first stars and galaxies. In comparison to HST, its instruments will allow looking further back in time and will study the so-called Dark Ages during which the universe was opaque, about 150 to 800 million years after the Big Bang.
The NIRSpec instrument is a multi-object spectrograph and is capable of simultaneously measuring the near-infrared spectrum of up to 100 objects like stars or galaxies with low, medium and high spectral resolutions. The observations are performed in a 3 arcmin × 3 arcmin field of view over the wavelength range from 0.6 μm to 5.0 μm. It also features a set of slits and an aperture for high contrast spectroscopy of individual sources, as well as an integral-field unit (IFU) for 3D spectroscopy. [3] The instrument is a contribution of the European Space Agency (ESA) and is built by Astrium together with a group of European subcontractors. [4]
The James Webb Space Telescope's main science themes are: [5]
The NIRSpec instrument operates at −235 °C and is passively cooled by cold space radiators which are mounted on the JWST Integrated Science Instrument Module (ISIM). The radiators are connected to NIRSpec using thermally conductive heat straps. The mirror mounts and the optical bench base plate all manufactured out of silicon carbide ceramic SiC100. The instrument size is approximately 1900 mm × 1400 mm × 700 mm and weighs 196 kg (432 lb) including 100 kg of silicon carbide. The operation of the instrument is performed with three electronic boxes.
NIRSpec includes 4 mechanisms which are:
Further NIRSpec includes two electro-optical assemblies which are:
And finally the Integral Field Unit (IFU) image slicer, used in the instrument IFU mode.
The optical path is represented by the following silicon carbide mirror assemblies:
In order to achieve the scientific objectives NIRSpec has four operational modes: [3]
Multi-Object Spectroscopy (MOS) In MOS the total instrument field of view of 3 × 3 arcminutes is covered using 4 arrays of programmable slit masks. These programmable slit masks consist of 250 000 micro shutters where each can individually be programmed to 'open' or 'closed'. The contrast between an 'open' or 'closed' shutter is better than 1:2000. [7] If an object like e.g. a galaxy is placed into an 'open' shutter, the spectra of the light emitted by the object can be dispersed and imaged onto the detector plane. In this mode up to 100 objects can simultaneously be observed and the spectra be measured.
Integral Field Unit Mode (IFU) The integral field spectrometry will primarily be used for large, extended objects like galaxies. In this mode a 3 × 3 arcsecond field of view is sliced into 0.1 arcsecond bands which are thereafter re-arranged into a long slit. This allows to obtain spatially resolved spectra of large scenes and can be used to measure the motion speed and direction within an extended object. Since measured spectra in the IFU mode would overlap with spectra of the MOS mode it can not be used in parallel.
High-Contrast Slit Spectroscopy (SLIT)
A set of 5 fixed slits are available in order to perform high contrast spectroscopic observations which is e.g. required for spectroscopic observations of transiting extra-solar planets. Of the five fixed slits, three are 0.2 arcseconds wide, one is 0.4 arcsecond wide and one is a square aperture of 1.6 arcseconds. The SLIT mode can be used simultaneously with the MOS or IFU modes.
Imaging Mode (IMA)
The imaging mode is used for target acquisition only. In this mode no dispersive element is placed in the optical path and any objects are directly imaged on the detector. Since the microshutter array which is sitting in an instrument intermediate focal plan is imaged in parallel, it is possible to arrange the JWST observatory such that any to be observed objects fall directly into the center of open shutters (MOS-mode), the IFU aperture (IFU-mode) or the slits (SLIT mode).
The NIRSpec key performance parameters are: [3] [4] [8]
PARAMETER | VALUE |
---|---|
Wavelength range | 0.6 μm – 5.0 μm When operating in R = 1000 and R = 2700 mode, split in three spectral bands: 1.0 μm – 1.8 μm Band I 1.7 μm – 3.0 μm Band II 2.9 μm – 5.0 μm Band III |
Field of View | 3 × 3 arcmin |
Spectral resolution | R = 100 (MOS) R = 1000 (MOS + fixed Slits) R = 2700 (fixed Slits + IFU) |
Number of commendable open/ closed spectrometer slits | MEMS technology based on micro-shutter arrays with 4 times 365 × 171 = 250 000 individual shutters, each of them with a size of 80 μm × 180 μm |
Detector | 2 MCT Sensor Chip Assemblies (SCA's) of 2048 × 2048 pixels each. Pixel pitch = 18 μm × 18 μm |
Wavefront Error, including Telescope | Diffraction limited at 2.45 μm at MSA: WFE = 185 nm RMS (Strehl = 0.80) Diffraction limited at 3.17 μm at FPA: WFE = 238 nm RMS (Strehl = 0.80) |
Limiting sensitivity | * In R = 1000 mode, using one single 200 mas wide shutter or fixed slit, NIRSpec will be capable of measuring the flux in an unresolved emission line of 5.2×10−22 Wm−2 from a point source at an observed wavelength of 2 μm at SNR = 10 per resolution element in a total exposure of 105 s or less * In R = 100 mode, using one single 200 mas wide shutter or fixed slit, NIRSpec will be capable of measuring the continuum flux of 1.2×10−33 Wm−2Hz−1 from a point source at an observed wavelength of 3 μm at SNR = 10 per resolution element in a total exposure of 104 s or less |
NIRSpec optics envelope | Approximately 1900 mm × 1400 mm × 700 mm |
Instrument mass | 195 kg (430 lb) with about 100 kg silicon carbide parts, Electronic boxes: 30.5 kg (67 lb) |
Operating temperature | 38 K (−235.2 °C; −391.3 °F) |
.
NIRSpec has been built by Astrium Germany with subcontractors and partners spread over Europe and with the contribution of NASA from the US which provided the Detector Subsystem and the Micro-shutter Assembly.
The individual subcontractors and their corresponding contributions were: [9]
An optical spectrometer is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials. The variable measured is most often the irradiance of the light but could also, for instance, be the polarization state. The independent variable is usually the wavelength of the light or a closely derived physical quantity, such as the corresponding wavenumber or the photon energy, in units of measurement such as centimeters, reciprocal centimeters, or electron volts, respectively.
The Very Large Telescope (VLT) is an astronomical facility operated since 1998 by the European Southern Observatory, located on Cerro Paranal in the Atacama Desert of northern Chile. It consists of four individual telescopes, each equipped with a primary mirror that measures 8.2 meters in diameter. These optical telescopes, named Antu, Kueyen, Melipal, and Yepun, are generally used separately but can be combined to achieve a very high angular resolution. The VLT array is also complemented by four movable Auxiliary Telescopes (ATs) with 1.8-meter apertures.
The Large Binocular Telescope (LBT) is an optical telescope for astronomy located on 10,700-foot (3,300 m) Mount Graham, in the Pinaleno Mountains of southeastern Arizona, United States. It is a part of the Mount Graham International Observatory.
The W. M. Keck Observatory is an astronomical observatory with two telescopes at an elevation of 4,145 meters (13,600 ft) near the summit of Mauna Kea in the U.S. state of Hawaii. Both telescopes have 10 m (33 ft) aperture primary mirrors, and, when completed in 1993 and 1996, they were the largest optical reflecting telescopes in the world. They are currently the third and fourth largest.
The Gran Telescopio Canarias is a 10.4 m (410 in) reflecting telescope located at the Roque de los Muchachos Observatory on the island of La Palma, in the Canary Islands, Spain. It is the world's largest single-aperture optical telescope.
The James Webb Space Telescope (JWST) is a space telescope designed to conduct infrared astronomy. Its high-resolution and high-sensitivity instruments allow it to view objects too old, distant, or faint for the Hubble Space Telescope. This enables investigations across many fields of astronomy and cosmology, such as observation of the first stars and the formation of the first galaxies, and detailed atmospheric characterization of potentially habitable exoplanets.
The Multi-Unit Spectroscopic Explorer (MUSE) is an integral field spectrograph installed at the Very Large Telescope (VLT) of the European Southern Observatory (ESO). It operates in the visible wavelength range, and combines a wide field of view with a high spatial resolution and a large simultaneous spectral range. It is specifically designed to take advantage of the improved spatial resolution provided by adaptive optics, offering diffraction-limited performance in specific configurations. MUSE had first light on the VLT’s Unit Telescope 4 (UT4) on 31 January 2014.
The NASA Infrared Telescope Facility is a 3-meter (9.8 ft) telescope optimized for use in infrared astronomy and located at the Mauna Kea Observatory in Hawaii. It was first built to support the Voyager missions and is now the US national facility for infrared astronomy, providing continued support to planetary, solar neighborhood, and deep space applications. The IRTF is operated by the University of Hawaii under a cooperative agreement with NASA. According to the IRTF's time allocation rules, at least 50% of the observing time is devoted to planetary science.
International Ultraviolet Explorer, was the first space observatory primarily designed to take ultraviolet (UV) electromagnetic spectrum. The satellite was a collaborative project between NASA, the United Kingdom's Science and Engineering Research Council and the European Space Agency (ESA), formerly European Space Research Organisation (ESRO). The mission was first proposed in early 1964, by a group of scientists in the United Kingdom, and was launched on 26 January 1978 aboard a NASA Thor-Delta 2914 launch vehicle. The mission lifetime was initially set for 3 years, but in the end it lasted 18 years, with the satellite being shut down in 1996. The switch-off occurred for financial reasons, while the telescope was still functioning at near original efficiency.
A multi-object spectrometer is a type of optical spectrometer capable of simultaneously acquiring the spectra of multiple separate objects in its field of view. It is used in astronomical spectroscopy and is related to long-slit spectroscopy. This technique became available in the 1980s.
Donald F. Figer is an American astronomer and a professor in the College of Science of the Rochester Institute of Technology. He is also the director of RIT's Future Photon Initiative, Center for Detectors, and Rochester Imaging Detector Laboratory. His research interests include massive stars, massive star clusters, red supergiants, the Galactic Center, and the development of advanced technologies for astrophysics and a broad range of applications.
The Cosmic Origins Spectrograph (COS) is a science instrument that was installed on the Hubble Space Telescope during Servicing Mission 4 (STS-125) in May 2009. It is designed for ultraviolet (90–320 nm) spectroscopy of faint point sources with a resolving power of ≈1,550–24,000. Science goals include the study of the origins of large scale structure in the universe, the formation and evolution of galaxies, and the origin of stellar and planetary systems and the cold interstellar medium. COS was developed and built by the Center for Astrophysics and Space Astronomy (CASA-ARL) at the University of Colorado at Boulder and the Ball Aerospace and Technologies Corporation in Boulder, Colorado.
The Wide Field Camera 3 (WFC3) is the Hubble Space Telescope's last and most technologically advanced instrument to take images in the visible spectrum. It was installed as a replacement for the Wide Field and Planetary Camera 2 during the first spacewalk of Space Shuttle mission STS-125 on May 14, 2009.
IUCAA Girawali Observatory is an optical astronomy observatory run by the Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune, India. The Observatory is located about 80 km from Pune, off the Pune Nashik Highway in Girawali.
Advanced Telescope for High-ENergy Astrophysics (Athena) is an X-ray observatory mission selected by European Space Agency (ESA) within its Cosmic Vision program to address the Hot and Energetic Universe scientific theme. Athena will operate in the energy range of 0.2–12 keV and will offer spectroscopic and imaging capabilities exceeding those of currently operating X-ray astronomy satellites – e.g. the Chandra X-ray Observatory and XMM-Newton – by at least one order of magnitude on several parameter spaces simultaneously.
Integral field spectrographs (IFS) combine spectrographic and imaging capabilities in the optical or infrared wavelength domains (0.32 μm – 24 μm) to get from a single exposure spatially resolved spectra in a bi-dimensional region. The name originates from the fact that the measurements result from integrating the light on multiple sub-regions of the field. Developed at first for the study of astronomical objects, this technique is now also used in many other fields, such bio-medical science and Earth remote sensing. Integral field spectrography is part of the broader category of snapshot hyperspectral imaging techniques, itself a part of hyperspectral imaging.
The Visible Multi-Object Spectrograph (VIMOS) is a wide field imager and a multi-object spectrograph installed at the European Southern Observatory's Very Large Telescope (VLT), in Chile. The instrument used for deep astronomical surveys delivers visible images and spectra of up to 1,000 galaxies at a time. VIMOS images four rectangular areas of the sky, 7 by 8 arcminutes each, with gaps of 2 arcminutes between them. Its principal investigator was Olivier Le Fèvre.
Fine Guidance Sensor and Near Infrared Imager and Slitless Spectrograph (FGS-NIRISS) is an instrument on the James Webb Space Telescope (JWST) that combines a Fine Guidance Sensor and a science instrument, a near-infrared imager and a spectrograph. The FGS/NIRISS was designed by the Canadian Space Agency (CSA) and built by Honeywell as part of an international project to build a large infrared space telescope with the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA). FGS-NIRISS observes light from the wavelengths of 0.8 to 5.0 microns. The instrument has four different observing modes.
NIRCam is an instrument aboard the James Webb Space Telescope. It has two major tasks, as an imager from 0.6 to 5 μm wavelength, and as a wavefront sensor to keep the 18-section mirrors functioning as one. In other words, it is a camera and is also used to provide information to align the 18 segments of the primary mirror. It is an infrared camera with ten mercury-cadmium-telluride (HgCdTe) detector arrays, and each array has an array of 2048×2048 pixels. The camera has a field of view of 2.2×2.2 arcminutes with an angular resolution of 0.07 arcseconds at 2 μm. NIRCam is also equipped with coronagraphs, which helps to collect data on exoplanets near stars. It helps with imaging anything next to a much brighter object, because the coronagraph blocks that light.
MIRI, or the Mid-Infrared Instrument, is an instrument on the James Webb Space Telescope. MIRI is a camera and a spectrograph that observes mid to long infrared radiation from 5 to 28 microns. It also has coronagraphs, especially for observing exoplanets. Whereas most of the other instruments on Webb can see from the start of near infrared, or even as short as orange visible light, MIRI can see longer wavelength light.