Sentinel-4 is an imaging UVN (UV-VIS-NIR) spectrometer, developed by Airbus Defence and Space GmbH under ESA contract in the frame of the joint EU/ESA COPERNICUS program. The mission objective is the operational monitoring of trace gas concentrations for atmospheric chemistry and climate over Europe. Sentinel-4 will provide accurate measurements of key atmospheric constituents such as ozone, nitrogen dioxide, sulfur dioxide, methane, and aerosol properties. The instrument is a hyperspectral imager. It is composed of two imaging spectrometers covering the spectral ranges of 305 – 500 nm and 750 – 775 nm and a telescope which projects an image of the Earth onto the slits of the spectrometers. The instrument will be placed in a geostationary orbit, and a 3D spectral-spatial data-cube will be acquired thanks to the mirror scanning in East-West direction. The Telescope Spectrograph Assembly (TSA) represents the core of the optical system inside the Optical Instrument Module (OIM). It is composed of one common Telescope, two Spectrographs and two Focal Plane Assemblies integrated and aligned into a three-dimensional supporting structure. The TSA is later integrated into the main instrument structure which already includes the Scan Mirror Unit, Calibration Assembly and Front Baffle; thus completing the full optical chain. This paper gives an overview of the TSA integration and alignment activities for the Proto Flight Model (PFM) performed at the Airbus premises in Ottobrunn, Germany. It describes the alignment philosophy developed to meet the challenging optical requirements, including for example, the spatial co-registration between the two spectrometers and the spatial sampling distance on ground, after the transition from ambient laboratory conditions to the instrument operating conditions in geostationary orbit. The results of the optical tests in operating conditions produced by the Optical Ground Support Equipment are also included and discussed in this paper.
KEYWORDS: Contamination, Absorption, Transmittance, Space operations, Sensors, Signal to noise ratio, Signal attenuation, Modeling, Confocal microscopy
ESA Sentinel-4 mission will monitor trace gas concentrations and aerosols in the Earth’s atmosphere with a 1-hour revisit frequency and unprecedented spatial resolution. Initial performance predictions, relying on literature/historical values for optical absorption coefficients, revealed considerable losses at the end of the mission lifetime caused mainly by high levels of absorption of light due to molecular contamination spread over the 39 optical surfaces of the UVIS channel. This publication describes the significant effort undertaken by Sentinel-4 team to establish more reliable and accurate performance predictions, and the importance of performing measurements under representative conditions of the instrument’s contamination environment. The refined performance prediction analysis was the final step of the activity, demonstrating that the end of life performance requirements of Sentinel-4 will be met.
Sentinel-4 is an imaging UVN (UV-VIS-NIR) spectrometer, developed by Airbus Defence and Space as prime contractor under ESA contract in the frame of the joint EU/ESA COPERNICUS program. The mission objective is the operational monitoring of trace gas concentrations for atmospheric chemistry and climate applications. This paper gives an overview of the Sentinel-4 system architecture, its design & development status.
SENTINEL 4 is an imaging UVN (UV-VIS-NIR) spectrometer, developed by Airbus Defence and Space under ESA contract in the frame of the joint European Union (EU)/ESA COPERNICUS program. The mission objective is the operational monitoring of trace gas concentrations for atmospheric chemistry and climate applications. To this end SENTINEL 4 will provide accurate measurements of key atmospheric constituents such as ozone, nitrogen dioxide, sulfur dioxide, formaldehyde, as well as aerosol and cloud properties.
Sentinel-4 is an imaging UVN (UV-VIS-NIR) spectrometer, developed by Airbus Defence and Space under ESA contract in the frame of the joint EU/ESA COPERNICUS program. The mission objective is the operational monitoring of trace gas concentrations for atmospheric chemistry and climate applications – hence the motto of Sentinel-4 “Knowing what we breathe”. Sentinel-4 will provide accurate measurements of key atmospheric constituents such as ozone, nitrogen dioxide, sulfur dioxide, methane, and aerosol properties over Europe and adjacent regions from a geostationary orbit (see Fig. 1). In the family of already flown UVN spectrometers (SCIAMACHY, OMI, GOME and GOME 2) and of those spectrometers currently under development (Sentinel-5p and Sentinel-5), Sentinel-4 is unique in being the first geostationary UVN mission. Furthermore, thanks to its 60-minutes repeat cycle measurements and high spatial resolution (8x8 km2), Sentinel-4 will increase the frequency of cloud-free observations, which is necessary to assess troposphere variability. Two identical Sentinel-4 instruments (PFM and FM-2) will be embarked, as Customer Furnished Item (CFI), fully verified, qualified and calibrated respectively onto two EUMETSAT satellites: Meteosat Third Generation-Sounder 1 and 2 (MTG-S1 and MTG-S2), whose Flight Acceptance Reviews are presently planned respectively in Q4 2021 and Q1 2030. This paper gives an overview of the Sentinel-4 system1 architecture, its design and development status, current performances and the key technological challenges.
Sentinel-4 is an imaging UVN (UV-VIS-NIR) spectrometer, developed by Airbus DS under ESA contract in the frame of the joint EU/ESA COPERNICUS program. The mission objective is the operational monitoring of trace gas concentrations for atmospheric chemistry and climate applications – hence the motto of Sentinel-4 “Knowing what we breathe”.
Pierre Ferruit, Giorgio Bagnasco, Reiner Barho, Stephan Birkmann, Torsten Böker, Guido De Marchi, Bernhard Dorner, Ralf Ehrenwinkler, Massimo Falcolini, Giovanna Giardino, Xavier Gnata, Karl Honnen, Peter Jakobsen, Peter Jensen, Manfred Kolm, Hans-Ulrich Maier, Ralf Maurer, Markus Melf, Peter Mosner, Peter Rumler, Jean-Christophe Salvignol, Marco Sirianni, Paolo Strada, Maurice te Plate, Thomas Wettemann
The Near-Infrared Spectrograph NIRSpec is one of the four instruments of the James Webb Space Telescope (JWST).
NIRSpec will cover the 0.6-5.0 micron range and will be capable of obtaining spectra of more than 100 objects
simultaneously in its multi-object spectroscopy (MOS) mode. 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. We will first
show how these capabilities are linked to the four main JWST scientific themes. We will then give an overview of the
NIRpec modes and spectral configurations with an emphasis on the layout of the field of view and of the spectra. Last,
we will provide an update on the status of the instrument.
The Near Infrared Spectrograph (NIRSpec) is one of the four science instruments aboard the James Webb Space
Telescope (JWST) scheduled for launch in 2014. NIRSpec is sensitive in the wavelength range from ~ 0.6 to
5.0 μm and will be capable of obtaining spectra of more than a 100 objects simultaneously, as well as fixed slit
high contrast spectroscopy of individual sources. It also features an integral field unit for 3D spectroscopy. The
key scientific objectives of the instrument include studies of star formation and chemical abundances of young
distant galaxies and tracing the creation of the chemical elements back in time. In this paper, we present the
status of the NIRSpec instrument as it is currently being prepared for its extensive ground calibration campaign
later in 2010.
KEYWORDS: Sensors, James Webb Space Telescope, Electronics, Near infrared, Calibration, Infrared sensors, Space telescopes, Infrared telescopes, Infrared radiation, Astronomy
The James Webb Space Telescope, an infrared-optimized space telescope being developed by NASA for launch in 2014,
will utilize cutting-edge detector technology in its investigation of fundamental questions in astrophysics. JWST's near
infrared spectrograph, NIRSpec utilizes two 2048 × 2048 HdCdTe arrays with Sidecar ASIC readout electronics
developed by Teledyne to provide spectral coverage from 0.6 microns to 5 microns. We present recent test and
calibration results for the "pathfinder NIRSpec detector subsystem" as well as data processing routines for noise
reduction and cosmic ray rejection.
The James Webb Space Telescope (JWST) Near Infrared Spectrograph (NIRSpec) incorporates two 5 μm cutoff
(λco =5 μm) 2048×2048 pixel Teledyne HgCdTe HAWAII-2RG sensor chip assemblies. These detector arrays,
and the two Teledyne SIDECAR application specific integrated circuits that control them, are operated in space
at Τ ~ 37 K. This article focuses on the measured performance of the first flight-candidate, and near-flight
candidate, detector arrays. These are the first flight-packaged detector arrays that meet NIRSpec's challenging
6 e- rms total noise requirement. The current version of this paper has had a correction made to it at the request of the author. Please see the linked Errata for further details.
A novel cryogenic refocusing mechanism (RMA) has been designed by Galileo Avionica (GA) for the Near Infra-Red
Spectrograph (NIRSpec), one of the instruments of the James Webb Space Telescope (JWST). The RMA shall correct
possible in orbit focal length variations by a rigid translation of a set of two mirrors in a 6 mm range, with an accuracy of
50 microns and 15 microns step size. The RMA development has been driven by the operation at 30K temperature while
being still fully functional at room temperature, by the need to incorporate two mirrors with demanding quality as part of
the mechanism and by tight envelope constraints.
This paper reports details of the RMA opto-mechanical design and analysis and about the dedicated optical set-up
developed for its verification.
The James Webb Space Telescope (JWST) mission is a collaborative project between the National Aeronautics and
Space Administration (NASA), the European Space Agency (ESA) and the Canadian Space Agency (CSA).
JWST is considered the successor to the Hubble Space Telescope (HST) and although its design and science objectives
are quite different, JWST is expected to yield equivalently astonishing breakthroughs in infrared space science.
Due to be launched in 2013 from the French Guiana, the JWST observatory will be placed in an orbit around the anti-
Sun Earth-Sun Lagrangian point, L2, by an Ariane 5 launcher provided by ESA.
The payload on board the JWST observatory consists of four main scientific instruments: a near-infrared camera
(NIRCam), a mid-infrared camera/spectrograph (MIRI), a near-infrared tunable filter (TFI) and a near-infrared
spectrograph (NIRSpec). The instrument suite is completed by a Fine Guidance Sensor (FGS).
NIRSpec is a multi-object spectrograph capable of measuring the spectra of about 100 objects simultaneously at low
(R~100), medium (R~1000) and high (R~2700) resolutions over the wavelength range between 0.6 micron and 5.0
micron. It features also a classical fix-slits spectroscopy mode as well as a 3D-spectrography mode with spectral
resolutions up to 2700.
The availability of extensive and accurate calibration data of the NIRSpec instrument is a key element to ensure that the
nominal performance of the instrument will be achieved and that high-quality processed data will be made available to
the users. In this context, an on-ground calibration is planned at instrument level that will supplement the later in-flight
calibration campaign.
In this article we describe the overall on-ground instrument calibration campaigns and we provide an overview of the
main features and performances of the individual elements of the sophisticated cryogenic optical ground support
equipment (OGSE) used to calibrate NIRSpec.
The James Webb Space Telescope (JWST) mission is a collaborative project between the National Aeronautics and
Space Administration (NASA), the European Space Agency (ESA) and the Canadian Space Agency (CSA).
JWST is considered the successor to the Hubble Space Telescope (HST) and although its design and science objectives
are quite different, JWST is expected to yield equivalently astonishing breakthroughs in infrared space science.
Due to be launched in 2013 from the French Guiana, the JWST observatory will be placed in an orbit around the anti-
Sun Earth-Sun Lagrangian point, L2, by an Ariane 5 launcher, provided by ESA.
The payload on board the JWST observatory consists of four main scientific instruments: a near-infrared camera
(NIRCam), a combined mid-infrared camera/spectrograph (MIRI), a near-infrared tunable filter (TFI) and a nearinfrared
spectrograph (NIRSpec). The instrument suite is completed by a Fine Guidance Sensor (FGS).
Besides the provision of the Ariane 5 launcher, ESA, with EADS Astrium GmbH (D) as Prime Contractor, is fully
responsible for the funding and the furnishing of NIRSpec and, at the same time, for approximately half of MIRI costs
through special contributions from the ESA member states.
NIRSpec is a multi-object, spectrograph capable of measuring the spectra of about 100 objects simultaneously at low
(R=100), medium (R=1000), and high (R=2700) resolutions over the wavelength range between 0.6 micron and 5.0
micron. In this article we provide a general overview of its main design features and performances.
The NIRSpec instrument on the James Webb Space Telescope (JWST) is a multi-object spectrograph capable of measuring the near infrared spectrum of at least 100 objects simultaneously at various spectral resolutions. It operates under cryogenic conditions (T~ 35 K). NIRSpec is part of the JWST science instruments suite. Its main purpose is to provide low (R=100), medium (R=1000) and high resolution (R=2700) spectroscopic observations over the wavelength range 0.6 μm - 5.0 μm in support of the four JWST science programs. The NIRSpec instrument is being developed by the European Space Agency with EADS Astrium Germany GmbH as the prime contractor.
The Near-Infrared Spectrograph (NIRSpec) is the James Webb Space Telescope’s primary near-infrared spectrograph. NASA is providing the NIRSpec detector subsystem, which consists of the focal plane array, focal plane electronics, cable harnesses, and software. The focal plane array comprises two closely-butted λco ~ 5 μm Rockwell HAWAII-2RG sensor chip assemblies. After briefly describing the NIRSpec instrument, we summarize some of the driving requirements for the detector subsystem, discuss the baseline architecture (and alternatives), and presents some recent detector test results including a description of a newly identified noise component that we have found in some archival JWST test data. We dub this new noise component, which appears to be similar to classical two-state popcorn noise in many aspects, “popcorn mesa noise.” We close with the current status of the detector subsystem development effort.
In the frame of the XMM project, several test campaigns are accomplished to qualify the optical elements of the mission. The test described in this paper are performed on a XMM flight model mirror module added with a reflection grating assembly (RGA). The mirror module contains 58 x-ray optical quality shells, an x-ray baffle (XRB) to reduce the straylight. This complete XMM flight model mirror assembly (MA) is tested in a vertical configuration at CSL, in a full aperture or partial EUV collimated beam illumination, and with an x-ray pencil beam. One of the advantages of the EUV collimated beam is to verify the correct position of the RGA when integrated in flight configuration on the mirror module structure. This is not possible in x-ray with a finite source distance. The partial EUV illumination is performed to verify the correct integration of the RGA grating stacks. The pencil beam allows to make an accurate metrology of the XRB position, and to verify the positions of the 0, 1 and 2 diffraction order foci. In this paper, the tested module is first exposed, and the approach to qualify the instrument is described. The analysis of the results achieved over the different test configurations is presented. The impact of the environmental test on the reflection grating box is also diagnosed.
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