KEYWORDS: Space telescopes, James Webb Space Telescope, Aerospace engineering, Camera shutters, Sensors, Staring arrays, Electroluminescent displays, Acoustics, Instrument modeling, Spectroscopy
The Near-Infrared Spectrograph (NIRSpec) is one of the four instruments on the James Webb Space Telescope (JWST) which is scheduled for launch in 2018. NIRSpec is developed by the European Space Agency (ESA) with Airbus Defense and Space Germany as prime contractor. The instrument offers seven dispersers covering the wavelength range from 0.6 to 5.3 micron with resolutions from R ∼ 100 to R ∼ 2700. NIRSpec will be capable of obtaining spectra for more than 100 objects simultaneously using an array of micro-shutters. It also features an integral field unit with 3” x 3” field of view and a range of slits for high contrast spectroscopy of individual objects and time series observations of e.g. transiting exoplanets. NIRSpec is in its final flight configuration and underwent cryogenic performance testing at the Goddard Space Flight Center in Winter 2015/16 as part of the Integrated Science Instrument Module (ISIM). We present the current status of the instrument and also provide an update on NIRSpec performances based on results from the ISIM level test campaign.
Stephan Birkmann, Pierre Ferruit, Catarina Alves de Oliveira, Torsten Böker, Guido De Marchi, Giovanna Giardino, Marco Sirianni, Martin Stuhlinger, Peter Jensen, Peter Rumler, Massimo Falcolini, Maurice B. te Plate, Giovanni Cresci, Bernhard Dorner, Ralf Ehrenwinkler, Xavier Gnata, Thomas Wettemann
KEYWORDS: James Webb Space Telescope, Calibration, Mirrors, Sensors, Staring arrays, Aerospace engineering, Space telescopes, Camera shutters, Near infrared, Computer aided design
The Near-Infrared Spectrograph (NIRSpec) is one of the four instruments on the James Webb Space Telescope (JWST), scheduled for launch in 2018. NIRSpec has been designed and built by the European Space Agency (ESA) with Airbus Defense and Space Germany as prime contractor. The instrument covers the wavelength range from 0.6 to 5.3 micron and will be able to obtain spectra of more than 100 astronomical objects simultaneously by means of a configurable array of micro-shutters. It also features an integral field unit and a suite of slits for high contrast spectroscopy of individual objects. The extensive ground calibration campaign of NIRSpec was completed in Summer 2013, after which it was delivered to NASA for integration into the Integrated Science Instrument Module (ISIM). We highlight the major results from the instrument level calibration campaign which demonstrated full compliance with all opto-mechanical performance requirements. In addition, we present the current status of the instrument, describe the ongoing preparations for the Integrated Science Instrument Module (ISIM) test campaign to begin in June 2014, and briefly discuss plans for the pending exchange of the detector and micro-shutter assemblies following the first ISIM test cycle.
The Near-Infrared Spectrograph (NIRSpec) is one of the four science instruments of the James Webb Space Telescope. Its focal plane consists of two HAWAII-2RG sensors operating in the wavelength range of 0.6 to 5.0 µm and, as part of characterizing NIRSpec, the noise properties of these detectors under dark and illuminated conditions were studied. Under dark conditions, and as already known, 1/f noise in the detector system causes somewhat higher noise levels than can be accounted for by a simple model that includes white read noise and shot noise on integrated charge. More surprisingly, for high levels of accumulated charge, significantly lower total noise than expected was observed. This effect is shown to be due to pixel-to-pixel correlations introduced by signal-dependent interpixel crosstalk, with an interpixel coupling factor, α , that ranges from ∼0.01 for zero signal to ∼0.03 close to saturation.
KEYWORDS: Sensors, Interference (communication), Signal detection, James Webb Space Telescope, Cadmium sulfide, Infrared sensors, Quantum efficiency, Capacitance, Spectrographs, Signal processing
NIRSpec (Near Infrared Spectrograph) is one of the four science instruments of the James Webb Space Telescope
(JWST) and its focal plane consists of two HAWAII-2RG sensors operating in the wavelength range 0.6−5.0μm.
As part of characterizing NIRSpec, we studied the noise properties of these detectors under dark and illuminated
conditions. Under dark conditions, and as already known, 1/f noise in the detector system produces somewhat
more noise than can be accounted for by a simple model that includes white read noise and shot noise on
integrated charge. More surprisingly, at high flux, we observe significantly lower total noise levels than expected.
We show this effect to be due to pixel-to-pixel correlations introduced by signal dependent inter-pixel crosstalk,
with an inter-pixel coupling factor, α, that ranges from ~ 0.01 for zero signal to ~ 0.03 close to saturation.
Guido De Marchi, Stephan Birkmann, Torsten Böker, Pierre Ferruit, Giovanna Giardino, Marco Sirianni, Martin Stuhlinger, Maurice te Plate, Jean-Christophe Salvignol, Reiner Barho, Xavier Gnata, Robert Lemke, Michel Kosse, Peter Mosner
We present a detailed analysis of measurements collected during the first ground-based cryogenic calibration campaign
of NIRSpec, the Near-Infrared Spectrograph for the James Webb Space Telescope (JWST). In this paper we concentrate
on the performances of the NIRSpec grating wheel, showing that the magneto-resistive position sensors installed on the
wheel provide very accurate information on the position of the wheel itself, thereby enabling an efficient acquisition of
the science targets and a very accurate extraction and calibration of their spectra.
Stephan Birkmann, Pierre Ferruit, Torsten Böker, Guido De Marchi, Giovanna Giardino, Marco Sirianni, Martin Stuhlinger, Peter Jensen, Maurice B. J. te Plate, Peter Rumler, Bernhard Dorner, Xavier Gnata, Thomas Wettemann
KEYWORDS: Calibration, James Webb Space Telescope, Spectrographs, Spectral calibration, Camera shutters, Near infrared, Electroluminescent displays, Spectroscopes, Cryogenics, Mirrors
The Near Infrared Spectrograph (NIRSpec) is one of four science instruments aboard the James Webb Space
Telescope (JWST) scheduled for launch in 2018. NIRSpec is sensitive in the wavelength range from ~0.6 to 5.0
micron and will be capable of obtaining spectra from more than a 100 objects simultaneously by means of a
programmable micro shutter array. It will also provide an integral eld unit for 3D spectroscopy and xed slits
for high contrast spectroscopy of individual sources and planet transit observations. We present results obtained
during the rst cryogenic instrument testing in early 2011, demonstrating the excellent optical performance of
the instrument. We also describe the planning of NIRSpecs forthcoming second calibration campaign scheduled
for early 2013.
Stephan Birkmann, Torsten Böker, Pierre Ferruit, Giovanna Giardino, Peter Jakobsen, Guido de Marchi, Marco Sirianni, Maurice te Plate, Jean-Christophe Savignol, Xavier Gnata, Thomas Wettemann, Bernhard Dorner, Giovanni Cresci, Fabiàn Rosales-Ortega, Martin Stuhlinger, Richard Cole, Jason Tandy, Chris Brockley-Blatt
KEYWORDS: Calibration, Argon, James Webb Space Telescope, Lamps, Instrument modeling, Spectrographs, Data modeling, Space telescopes, Optical filters, Cryogenics
The Near Infrared Spectrograph (NIRSpec) is one of four science instruments aboard the James Webb Space
Telescope (JWST) that is to be launched later this decade. NIRSpec is sensitive in the wavelength range from 0.6
to 5.0 μm and operates at temperatures ≤ 40 K. It offers multi-object, fixed slit, and integral field spectroscopy
with seven selectable dispersers. The on-ground spectrophotometric calibration of the instrument is performed
by means of continuum and line emission lamps. NIRSpec also contains an internal calibration assembly (CAA)
that will provide the wavelength and radiometric calibration in orbit. Due to thermal constraints, the CAA
features low power tungsten filament lamps in combination with long-pass and Fabry-Perot-like interference
filters, which need to be calibrated at instrument level. We will report on the wavelength calibration of the
NIRSpec flight model and the CAA, carried out during the first cryogenic performance testing.
Guido De Marchi, Maurice B. te Plate, Stephan Birkmann, Torsten Böker, Pierre Ferruit, Giovanna Giardino, Peter Jakobsen, Marco Sirianni, Jean-Christophe Savignol, Xavier Gnata, Reiner Barho, Michel Kosse, Peter Mosner, Bernhard Dorner, Giovanni Cresci, Fabian Rosales-Ortega, Martin Stuhlinger, Torsten Gross, Thomas Leikert
The Near Infrared Spectrograph (NIRSpec) is one of four science instruments on board the James Webb Space
Telescope (JWST). NIRSpec offers multi-object, fixed slit, and integral field spectroscopy. There are eight optical
elements mounted on the grating wheel assembly (GWA), six gratings, a double-pass prism, and a mirror. The precise
knowledge of the position and tilt of these elements is critical for target acquisition and an accurate extraction and
calibration of science data. We present the concept of calibrating the position/tilt sensors during the NIRSpec flight
model ground calibration campaign, the performance of the sensors and first results concerning the GWA repeatability.
Since its launch in 1999, the European X-ray observatory XMM-Newton has suffered, 4 times, possible micro-meteoroid impacts believed to occur in the mirror shells, scattering debris toward the focal plane. The latest event, on 2005 March 09th, caused the loss of EPIC MOS1 CCD6, as well as small damage to MOS1 CCD1. This latter defect is leaking into the whole column that passes a few pixels from the nominal target position on CCD1 and affects a significant fraction of the on-axis source PSF (though the effects can be mitigated by suitable on-board offsetting of the signal from that column). We report on our investigations looking for possible pinholes in the XMM-Newton EPIC MOS1 filter created by micro-meteoroid generated debris. New simulation code allows modelling of pinhole patterns in real data sets. We will show the comparison between simulations and specially performed in-orbit detection measurements. These allow us to define the limiting size above which pinholes can be detected and to show if XMM-Newton's filters have suffered significantly from the micro-meteoroids.
On December 10th 2004 the XMM-Newton observatory celebrated its 5th year in orbit. Since the beginning of the mission steady health and contamination monitoring has been performed by the XMM-Newton SOC and the instrument teams. Main targets of the monitoring, using scientific data for all instruments on board, are the behaviour of the Charge Transfer Efficiency, the gain, the effective area and the bad, hot and noisy pixels. The monitoring is performed by combination of calibration observations using internal radioactive calibration sources with observations of astronomical targets. In addition a set of housekeeping parameters is continuously monitored reflecting the health situation of the instruments from an engineering point of view. We show trend behaviour over the 5 years especially in combination with events like solar flares and other events affecting the performance of the instruments.
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