Proceedings Volume 7808

Infrared Remote Sensing and Instrumentation XVIII

Marija Strojnik, Gonzalo Paez
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Proceedings Volume 7808

Infrared Remote Sensing and Instrumentation XVIII

Marija Strojnik, Gonzalo Paez
View the digital version of this volume at SPIE Digital Libarary.

Volume Details

Date Published: 25 August 2010
Contents: 10 Sessions, 46 Papers, 0 Presentations
Conference: SPIE Optical Engineering + Applications 2010
Volume Number: 7808

Table of Contents

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Table of Contents

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  • Front Matter: Volume 7808
  • IR Focal Plane and Detector Development I
  • IR Focal Plane and Detector Development II
  • Detection Technology and Materials Characterization
  • Thermal IR Imaging of Mercury: MERTIS
  • The Way Forward: FIRST to CLARREO
  • IR Instruments and Missions
  • Novel IR Device and Instrument Concepts
  • Radiometric Calibration and Standards
  • Poster Session
Front Matter: Volume 7808
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Front Matter: Volume 7808
This PDF file contains the front matter associated with SPIE Proceedings Volume 7808, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.
IR Focal Plane and Detector Development I
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Demonstration of 1Kx1K long-wave and mid-wave superlattice infrared focal plane arrays
Jet Propulsion Laboratory is actively developing the III-V based infrared detector and focal plane arrays (FPAs) for remote sensing and imaging applications. Currently, we are working on Superlattice detectors, multi-band Quantum Well Infrared Photodetectors (QWIPs), and Quantum Dot Infrared Photodetector (QDIPs) technologies suitable for high pixel-pixel uniformity and high pixel operability large area imaging arrays. In this paper, we will discuss the demonstration of long-wavelength 1Kx1K QDIP FPA, 1Kx1K QWIP FPA, the first demonstration of the megapixelsimultaneously- readable and pixel-co-registered dual-band QWIP FPA, and demonstration of the first mid-wave and long-wave 1Kx1K superlattice FPA. In addition, we will discuss the advantages of III-V material system in the context of large format infrared FPAs.
Barrier engineering in superlattices and quantum dots for higher operating temperature
The third generation of infrared detectors has seen a lot of emphasis been placed on Higher Operating Temperature (HOT) devices. In our research group, we are investigating barrier engineering in two promising material systems namely the type II strained layer superlattices and quantum dots in a well (DWELL) heterostructure. In this paper, we will outline some of our recent approaches to use barrier engineering to obtain a lower dark current and higher operating temperature in these devices.
Performance of InAsSb-based infrared detectors with nBn design
S. A. Myers, A. Khoshakhlagh, J. Mailfert, et al.
Our group is investigating nBn detectors based on bulk InAs(1-x)Sb(x) absorber (n) and contacts (n) with an AlAs(1-x)Sb(x) barrier (B). The wide-band-gap barrier material exhibits a large conduction band offset and small valence band offset with respect to the narrow-band-gap absorber material. An important matter to explore in this design is the barrier parameters (material, composition and doping concentration) and how they effect the operation of the device. This paper investigates AlAs(1-x)Sb(x) barriers with different compositions and doping levels and their effect on detector characteristics, in particular, dark current density, responsivity and specific detectivity.
Study of strain balance in long wavelength infrared InAs/GaSb superlattice materials
H. J. Haugan, G. J. Brown, S. D. Pacley, et al.
The epitaxial growth parameters optimized for mid wavelength infrared (MWIR) InAs/GaSb superlattice (SL) growth are not necessarily the best parameters for very long wavelength infrared (VLWIR) SL growth. While the cutoff wavelength of the SL structure can be easily extended from a MWIR to a VLWIR spectral range by increasing InAs layer thickness with a fixed GaSb layer thickness, the structural and optical properties of SLs are changing as well, and these changes are not necessarily beneficial to the material quality of VLWIR SLs. For instance, tensile strain in the SL rapidly increases as InAs layer thickness increases. This impacts the interface growth processes used to strain balance the average lattice constant of the SL to match the GaSb substrate, the interface engineering in a VLWIR SL is very different than that in a MWIR SL. Using a baseline SL design of 16 monolayers (MLs) InAs/7 MLs GaSb, a systematic study of controlling the Sb/As background pressure and shutter sequence during interface formation was performed in order to minimize tensile strain in the VLWIR SLs. The effect of various shutter sequences on the SL morphological quality and their impact on optical spectral response is reported. By inserting 0.5 MLs of InSb-like interfaces, using a migration-enhance-epitaxy technique, in the baseline SL design, while maintaining a total SL period of 23 MLs, we achieved a high structural quality, strain balanced LWIR SL with a photoresponse onset at 15 μm.
Intersubband transitions in GaN-based quantum wells: a new materials platform for infrared device applications
Roberto Paiella, Kristina Driscoll, Yan Li, et al.
Due to their large conduction-band offsets, GaN/AlGaN quantum wells can accommodate intersubband transitions at record short wavelengths throughout the mid-infrared and into the near-infrared spectral regions. As a result, they are currently the subject of extensive research efforts aimed at extending the spectral reach and functionality of intersubband optoelectronic devices. Here we review our recent work in this area, based on GaN/AlGaN quantum-well samples grown by molecular beam epitaxy on sapphire substrates. In particular, we have investigated the intersubband absorption properties of a wide range of structures, including isolated and coupled quantum wells. Furthermore, we have developed a new class of ultrafast all-optical switching devices, based on intersubband cross-absorption saturation in GaN/AlGaN quantum-well waveguides operating at fiber-optic communication wavelengths. Strong self-phase modulation of ultrafast optical pulses has also been measured in these waveguides, revealing a large refractive-index nonlinearity which is related to the same intersubband carrier dynamics. Finally, we have demonstrated optically pumped intersubband light emission from GaN/AlN quantum wells resonantly excited with a pulsed OPO. The measured room-temperature output spectra are peaked near 2 μm, which represents a new record for the shortest intersubband emission wavelength from any quantum-well materials system.
Single photon emission and detection at the nanoscale utilizing semiconductor nanowires
Michael E. Reimer, Maarten P. van Kouwen, Maria Barkelid, et al.
We report recent progress toward on-chip single photon emission and detection in the near infrared utilizing semiconductor nanowires. Our single photon emitter is based on a single InAsP quantum dot embedded in a p-n junction defined along the growth axis of an InP nanowire. Under forward bias, light is emitted from the single quantum dot by electrical injection of electrons and holes. The optical quality of the quantum dot emission is shown to improve when surrounding the dot material by a small intrinsic section of InP. Finally, we report large multiplication factors in excess of 1000 from a single Si nanowire avalanche photodiode comprised of p-doped, intrinsic, and n-doped sections. The large multiplication factor obtained from a single Si nanowire opens up the possibility to detect a single photon at the nanoscale.
IR Focal Plane and Detector Development II
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Performance improvement of AlN/GaN-based intersubband detectors thanks to quantum dot active regions
Daniel Hofstetter, Joab Di Francesco, Esther Baumann, et al.
Since the operating mode of 1.55 μm AlN/GaN-based intersubband photodetectors is based on optical rectification, both the excited state lifetime and the lateral displacement of the carriers play an important role for performance optimization. We thus show here results of an improved detector generation based on a novel type of active region. Thanks to the use of quantum dots instead of quantum wells, a factor of 60 could be gained in terms of maximum responsivity. In addition, the maximum performance was achieved at a considerably higher temperature of 160 K instead of 80 K as typically seen for quantum wells.
Infrared detectors for spaceborne laser receivers
NASA Goddard Space Flight Center is developing high-speed optical detectors that are sensitive in the near-infrared wavelength region. Applications include global 3D mapping, atmospheric gas measurements (e.g. carbon dioxide and methane) and laser communication and ranging.
Geiger-mode avalanche photodiode focal plane arrays for three-dimensional imaging LADAR
Mark A. Itzler, Mark Entwistle, Mark Owens, et al.
We report on the development of focal plane arrays (FPAs) employing two-dimensional arrays of InGaAsP-based Geiger-mode avalanche photodiodes (GmAPDs). These FPAs incorporate InP/InGaAs(P) Geiger-mode avalanche photodiodes (GmAPDs) to create pixels that detect single photons at shortwave infrared wavelengths with high efficiency and low dark count rates. GmAPD arrays are hybridized to CMOS read-out integrated circuits (ROICs) that enable independent laser radar (LADAR) time-of-flight measurements for each pixel, providing three-dimensional image data at frame rates approaching 200 kHz. Microlens arrays are used to maintain high fill factor of greater than 70%. We present full-array performance maps for two different types of sensors optimized for operation at 1.06 μm and 1.55 μm, respectively. For the 1.06 μm FPAs, overall photon detection efficiency of >40% is achieved at <20 kHz dark count rates with modest cooling to ~250 K using integrated thermoelectric coolers. We also describe the first evalution of these FPAs when multi-photon pulses are incident on single pixels. The effective detection efficiency for multi-photon pulses shows excellent agreement with predictions based on Poisson statistics. We also characterize the crosstalk as a function of pulse mean photon number. Relative to the intrinsic crosstalk contribution from hot carrier luminescence that occurs during avalanche current flows resulting from single incident photons, we find a modest rise in crosstalk for multi-photon incident pulses that can be accurately explained by direct optical scattering.
Detection Technology and Materials Characterization
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Infrared spectroscopy of thin layers under ultra-high vacuum conditions
We summarize recent results from in-situ infrared spectroscopic studies of nanofilm growth. These studies, performed under ultra-high vacuum conditions with sub-monolayer sensitivity, exploited the relationship between morphology and structure on the one side and, on the other side, vibrational excitations and plasmonic ones. The studies were performed within various projects ranging from astronomy and high-energy physics to organic electronics and plasmonics. The results represent examples the description of which needs theoretical models beyond the use of Fresnel's formulae, the assumption of abrupt interfaces, and the use optical databases for bulk materials. For example, at the SiO-Si interface Si- O-Si bridges with Si-O bonds longer than in the bulk are formed which can be identified via their special vibration signals at unusually low vibration frequencies. From a thickness of about 1 nm on, the infrared spectra show typical SiObulk features. The lowered vibrational frequencies are attributed to changes in the average distribution of Si-O bond length close to the interface. On the diamond (100) surface, during Cr deposition, we observed the formation of a conducting nanocrystalline fcc phase of chromium. At a certain thickness, the nanocrystalline phase makes a phase transition to the typical bulk chromium phase. Cr is a preferred material for electric contacts in single-crystal diamond detectors the performance of which sensitively depends on the conductivity of the deposited Cr contact. On organic semiconductor layers metallization may be accompanied by an intermixing at the metal-semiconductor interface. Such intermixing can be observed as the appearance of new excitation features.
cQED enhanced light detection and emission in electrically contacted quantum dot micropillars
S. Reitzenstein, C. Kistner, T. Heindel, et al.
The quest for efficient light sources and light detectors is a driving force in the development of semiconductor quantum dot (QD) devices. Self assembled QDs in bulk material are characterized by high quantum efficiency and can act as single photon emitters. However, they suffer from a poor light in- and outcoupling efficiency. We demonstrate highly efficient QD-micropillar based light detectors and single photon emitters exploiting cavity quantum electrodynamics (cQED) effects. An advanced fabrication technique allows us to realize ultra sensitive and wavelength selective light detectors as well as triggered, electrically driven single photon sources with photon outcoupling efficiencies exceeding 60 %.
Thermal IR Imaging of Mercury: MERTIS
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MERTIS-thermal infrared imaging of Mercury: advances in mid-IR remote sensing technology for planetary exploration
Gabriele E. Arnold, Harald Hiesinger, Jörn Helbert, et al.
MERTIS (MErcury Radiometer and Thermal infrared Imaging Spectrometer) is part of ESA's BepiColombo Mercury Planetary Orbiter mission to the innermost planet of the Solar system. MERTIS is designed to identify rock-forming minerals, to map the surface composition, and to study the surface temperature variations with an uncooled microbolometer detector in the hot environment of Mercury. MERTIS is an advanced IR instrument combining a pushbroom IR grating spectrometer (TIS) with a radiometer (TIR) sharing the same optics, instrument electronics and in-fight calibration components for a wavelength range of 7-14 and 7-40 μm, respectively. First results of the ongoing MESSENGER project at Mercury have shown a more complex geology and higher variability of features than previously thought. The MESSENGER studies have demonstrated the need to gain global high-resolution mid-IR spectral and temperature data to achieve a better understanding of the planetary genesis. The MERTIS measurements will acquire this currently missing data set. This article gives a summary of the instrument requirements and its design. We are reporting on the actual instrument development progress, and the status of system and subsystem qualification efforts.
MERTIS: understanding Mercury's surface composition from mid-infrared spectroscopy
Jörn Helbert, Harald Hiesinger, Ingo Walter, et al.
The Mercury Radiometer and Thermal Infrared Imaging Spectrometer MERTIS on the joint ESA-JAXA mission BepiColombo to Mercury is combining a spectrometer using an uncooled microbolometer in a pushbroom mode with a highly miniaturized radiometer. A full development model of MERTIS is now available. So, after three flybys of Mercury by the MESSENGER mission and with the Planetary Emissivity Laboratory at DLR in Berlin that can routinely obtain infrared emission spectra at high temperatures it is a good time to review the MERTIS science requirements and the performance in perspective of our new knowledge of Mercury.
MERTIS: shutterless background signal removal
Thomas Säuberlich, Carsten Paproth, Jörn Helbert
MERTIS (MERcury Thermal infrared Imaging Spectrometer) is an advanced infrared remote sensing instrument that is part of the ESA mission BepiColombo to planet Mercury. The enabling technology that allows sending the first spectrometer for the thermal infrared spectral range to Mercury is an uncooled microbolometer. One of the challenges is the calibration of the instrument. Radiometric and spectroscopic breadboard models of MERTIS were used to develop proper calibration methods. In the context of the calibration we are reporting on the ongoing efforts to separate non-scene and scene signal portions from each other. The non-scene signal portion is contained in the raw image data sets and is usually the dominating signal contribution. The conventional method to measure the non-scene signal contributions using a shutter or spaceview and perform a time-interpolation is compared to an approach using linear pixel-to-pixel relations in which information from the outer regions of the image matrix is used for the estimation of the non-scene signal components of the inner regions where additional scene signal components exist. The results of both methods are discussed in terms of noise or errors of the extracted scene information. The proposed method could be used without further instrument modifications offering a functional redundancy which is important to keep alive the MERTIS operation in the case of a breakdown of the mechanically stressed high-speed shutter device.
MERTIS: system theory and simulation
Carsten Paproth, Thomas Säuberlich, Herbert Jahn, et al.
The deep-space ESA mission BepiColombo to planet Mercury will contain the advanced infrared remote sensing instrument MERTIS (MErcury Radiometer and Thermal infrared Imaging Spectrometer). The mission has the goal to explore the planets inner and surface structure and its environment. With MERTIS investigations of Mercury's surface layer within a spectral range of 7-14μm shall be conducted to specify and map Mercury's mineralogical composition with a spatial resolution of 500m. Due to the limited mass and power budget the used micro-bolometer detector array will only have a temperature-stabilization and will not be cooled. The theoretical description of the instrument is necessary to estimate the performance of the instrument especially the signal to noise ratio. For that purpose theoretical models are derived from system theory. For a better evaluation and understanding of the instrument performance simulations are performed to compute the passage of the radiation of a hypothetical mineralogical surface composition through the optical system, the influence of the inner instrument radiation and the conversion of the overall radiation into a detector voltage and digital output signal. The results of the simulation can support the optimization process of the instrument parameters and could also assist the analysis of gathered scientific data. The simulation tool can be used as well for performance estimations of MERTIS-like systems for future projects.
MERTIS: using diffractive optical elements for geometrical calibration
M. Bauer, D. Griessbach, T. Säuberlich, et al.
Geometrical sensor calibration is essential for space applications based on high accuracy optical measurements, in this case for MERTIS. The goal is the determination of interiour sensor parameters. A conventional method is to measure the line of sight for a subset of pixels by single pixel illumination with collimated light. To adjust angles which define the line of sight of a pixel a manipulator construction is used. A new method for geometrical sensor calibration is presented using Diffractive Optical Elements (DOE) in connection with laser beam equipment. This method is especially used for 2D-sensor array systems but can also be applied to the thermal infrared push-broom imaging spectrometer MERTIS. Diffractive optical elements (DOE) are optical microstructures which are used to split an incoming laser beam with a dedicated wavelength into a number of beams with well-known propagation directions. As the virtual sources of the diffracted beams are points at infinity, the object to be imaged is similar to the starry sky which gives an image invariant against translation. This particular feature allows a complete geometrical sensor calibration with one image avoiding complex adjustment procedures which means a significant reduction of calibration effort.
MERTIS: reflective baffle design and manufacturing
T. Zeh, C. Gal, S. Kaiser, et al.
Optical instruments for remote sensing applications frequently require measures for reducing the amount of external, unwanted stray light in the optical instrument path. The reflective planet baffle design and manufacturing process for the thermal infrared imaging spectrometer MERTIS onboard of ESA's cornerstone mission BepiColombo to Mercury is presented. The baffle has to reflect the unwanted solar flux and scattered IR radiation, and minimize the heat load on the instrument. Based on optical stray light simulations and analyses of different baffle concepts the Stavroudis principle showed the best performance and the smallest number of internal reflections. The setup makes use of the optical properties of specific conic sections of revolution. These are the oblate spheroid, generated by rotating an ellipse about its minor axis, and the hyperboloid of one sheet, obtained by the rotation of a hyperbola around its conjugate axis. Due to the demanding requirements regarding surface quality, low mass and high mechanical stability, electroforming fabrication was selected for the baffle. During manufacturing, a layer of high strength nickel alloy is electrodeposited onto a diamond turned aluminum mandrel. The mandrel is subsequently chemically dissolved. Not only the baffle, but also the baffle support structure and other mating components are electroformed. Finally, the baffle and support structure are assembled and joined by an inert gas soldering process. After the optimum baffle geometry and surface roughness has been realized, the remaining total heat flux on the baffle is only dependent on the selection of the appropriate, high reflective coating.
MERTIS: optics manufacturing and verification
Andreas Gebhardt, Ralf Steinkopf, Sebastian Scheiding, et al.
The MERTIS reflective infrared optics can be beneficial implemented as diamond turned aluminium mirrors coated with a thin gold layer. The cutting processes allow the manufacturing of both, the optical surface and mechanical interfaces, in tight tolerances. This is one of the major advantages of metal optics and was consequently used for the MERTIS sensor head optics. This paper describes the entire process chain of the MERTIS spectrometer optics including the manufacturing methods for the mirrors and for the spherical grating, the coating with sputtered gold for infrared reflectivity as well as the alignment and the verification of the spectrometer optics.
The Way Forward: FIRST to CLARREO
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Technologies supporting radiative science
Robert A. Bauer, George J. Komar, Philip M. Larkin, et al.
Technology investments made over the past decade by the NASA Earth Science Technology Office (ESTO) have enabled the current mission concept of the Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission. Early investments include the Far-Infrared Spectroscopy of the Troposphere (FIRST) instrument, which today is being used as a testbed to demonstrate new detectors under development. Current investments, aimed at the CLARREO goals of high absolute accuracy and onorbit international measurement standards traceability, include a prototype hyperspectral imager, extended blocked impurity band detectors for far-infrared detection, and a high-accuracy blackbody.
Far-IR measurements at Cerro Toco, Chile: FIRST, REFIR, and AERI
Richard P. Cageao, J. Ashley Alford, David G. Johnson, et al.
In mid-2009, the Radiative Heating in the Underexplored Bands Campaign II (RHUBC-II) was conducted from Cerro Toco, Chile, a high, dry, remote mountain plateau, 23°S , 67.8°W at 5.4km, in the Atacama Desert of Northern Chile. From this site, dominant IR water vapor absorption bands and continuum, saturated when viewed from the surface at lower altitudes, or in less dry locales, were investigated in detail, elucidating infrared (IR) absorption and emission in the atmosphere. Three Fourier Transform InfraRed (FTIR) instruments were at the site, the Far-Infrared Spectroscopy of the Troposphere (FIRST), the Radiation Explorer in the Far Infrared (REFIR), and the Atmospheric Emitted Radiance Interferometer (AERI). In a side-by-side comparison, these measured atmospheric downwelling radiation, with overlapping spectral coverage from 5 to 100μm (2000 to 100cm-1), and instrument spectral resolutions from 0.5 to 0.643cm-1, unapodized. In addition to the FTIR and other ground-based IR and microwave instrumentation, pressure/temperature/relative humidity measuring sondes, for atmospheric profiles to 18km, were launched from the site several times a day. The derived water vapor profiles, determined at times matching the FTIR measurement times, were used to model atmospheric radiative transfer. Comparison of instrument data, all at the same spectral resolution, and model calculations, are presented along with a technique for determining adjustments to line-by-line calculation continuum models. This was a major objective of the campaign.
Infrared detectors overview in the short-wave infrared to far-infrared for CLARREO mission
M. Nurul Abedin, Martin G. Mlynczak, Tamer F Refaat
There exists a considerable interest in the broadband detectors for CLARREO Mission, which can be used to detect CO2, O3, H2O, CH4, and other gases. Detection of these species is critical for understanding the Earth's atmosphere, atmospheric chemistry, and systemic force driving climatic changes. Discussions are focused on current and the most recent detectors developed in SWIR-to-Far infrared range for CLARREO space-based instrument to measure the above-mentioned species. These detector components will make instruments designed for these critical detections more efficient while reducing complexity and associated electronics and weight. We will review the on-going detector technology efforts in the SWIR to Far-IR regions at different organizations in this study.
A high-accuracy blackbody for CLARREO
Harri Latvakoski, Mike Watson, Shane Topham, et al.
The NASA climate science mission Climate Absolute Radiance and Refractivity Observatory (CLARREO), which is to measure Earth's emitted spectral radiance from orbit for 5 years, has an absolute accuracy requirement of 0.1 K (3σ) at 220 K over most of the thermal infrared. To meet this requirement, CLARREO needs highly accurate on-board blackbodies which remain accurate over the life of the mission. Space Dynamics Laboratory is developing a prototype blackbody that demonstrates the ability to meet the needs of CLARREO. This prototype is based on a blackbody design currently in use, which is relatively simple to build, was developed for use on the ground or on-orbit, and is readily scalable for aperture size and required performance. We expect the CLARREO prototype to have emissivity of ~0.9999 from 1.5 to 50 μm, temperature uncertainties of ~25 mK (3σ), and radiance uncertainties of ~10 mK due to temperature gradients. The high emissivity and low thermal gradient uncertainties are achieved through cavity design, while the SItraceable temperature uncertainty is attained through the use of phase change materials (mercury, gallium, and water) in the blackbody. Blackbody temperature sensor calibration is maintained over time by comparing sensor readings to the known melt temperatures of these materials, which are observed by heating through their melt points. Since blackbody emissivity can potentially change over time due to changes in surface emissivity (especially for an on-orbit blackbody) an on-board means of detecting emissivity change is desired. The prototype blackbody will include an emissivity monitor based on a quantum cascade laser to demonstrate the concept.
IR Instruments and Missions
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Ordered/disordered broadband antireflective structures for near-infrared detector applications
Young Min Song, Eun Sil Choi, Gyeong Cheol Park, et al.
This study reports broadband antireflective subwavelength structures (SWS) on various semiconductor materials for near-infrared detector applications. Two fabrication methods are proposed, i.e., a lenslike shape transfer and an overall dry etch process of Ag nanoparticles. These methods provide relatively simple, fast, inexpensive process steps, which is applicable for practical device applications. The fabricated SWS showed extremely lower reflectance spectra compared to that of flat surface in the near-IR range, indicating good agreement with the simulation results. We also propose amorphous silicon SWS on InGaAs photodetector to enhance the absorption efficiency.
Measurement of trace gases in East Asia from satellite infrared radiometer
Measurement of trace gases from satellite is useful technique to grasp the atmospheric information on a regional scale. In recent years, exhaust gas emitted by developing country has become a huge social issue. It greatly affects global environmental problems. In this study, we focused on Nitrous Oxide (N2O) in East Asia. N2O has a strong radiative forcing and has gotten a lot of attention as the greenhouse effect and ozone-depleting gases recently. We conducted the sensitivity analysis of N2O using the infrared spectral radiances measured by Tropospheric Emission Spectrometer (TES), which was launched on NASA's EOS Aura satellite in July 2004. Based on these result, we selected retrieval channel and tried to retrieve the troposheric profile of N2O. In this paper, we will present the preliminary result.
Imaging stand-off detection of explosives by quantum cascade laser based backscattering spectroscopy
Frank Fuchs, Stefan Hugger, Michel Kinzer, et al.
In this contribution we present the results of an imaging stand-off detection system based on a mid-IR external-cavity quantum cascade laser (EC-QCL) with a broad tunable range of 200 cm-1. Traces of TNT (trinitrotoluene) and PETN (pentaerythritol tetranitrate) as well as various non-hazardous substances such as flour or skin cream on different substrate-materials were investigated by illuminating them with the EC-QC laser and collecting the diffusely backscattered light. By tuning the EC-QCL across the significant absorption spectra we were able to detect the explosives
The evolution of the performance of the AVHRR, HIRS, and AMSU-A instruments on board MetOp-A after over three years in orbit
It is well known that the varying geometrical relationships between the Sun and the Earth throughout the year affect to some degree the performance of the instruments onboard Earth orbiting satellites. Following the commissioning of MetOp-A, EUMETSAT and NOAA have continued monitoring the long term trends in in-orbit performance of AVHRR, HIRS and AMSU-A. The data acquired since the launch of the satellite has allowed studying how the yearly seasonal variations, as well as aging, have affected the instrument performance. This paper presents the evolution of the performance of the AVHRR, HIRS and AMSU-A for more than three years since the launch of the Metop-A satellite.
1.5 to 5 micron radiometer for spectral contrast of objects in changing backgrounds in real time (Background Discrimination Radiometer or BDR)
A digital FLIR (Forward Looking Infrared camera) in the 1.5 to 5 micron range can measure the contrast of selfemission of objects with respect to their background in real time: however, when such a measurement is carried out in a narrow spectral range through an interference filter the amount of unfiltered stray photons from the environment reaching the detector contributes a significant part of the total signal with respect to the filtered photons from the object of interest. The result is a significant reduction of dynamic range of the measurement and of the ability of the FLIR to measure large variation of signal in real time. A somewhat more advantageous instrument to measure the contrast of an object against its background in real time is proposed here: it is a non-imaging single-detector, 1.5 to 5 micron radiometer (BDR). A classical example of application is measuring the radiant intensity contrast of an airplane or missile in the background of sky during its flight. The instrument is built so that it can measure this contrast in one narrow or wide wavelength range as function of time or in successive wavelength ranges to provide contrast information in absolute units of irradiance (Watts/cm2) in different regions of the spectrum. Several filters can be accommodated in a wheel to provide the spectral capability. The reason for the ability of such configuration to avoid the dynamic range problem of the FLIR is the fact that in this detection method the detector is AC coupled and the electronic amplification acts only on the difference between the source and background signals. We present here the instrument's design and its calibration algorithm1.
Advances in modeling the obstruction in the HIRDLS optical train and resulting data
John Gille, Charles Cavanaugh, Christopher Halvorson, et al.
A piece of plastic film came loose during launch and blocked most of the optical aperture. The largest remaining problem in correcting the measured radiances is the removal of the signals from this blockage. The present method is briefly described, followed by an outline of a new version, called the (ST)3 method. It relies on more understanding of the behavior of the blockage signals acquired in previous work. The method involves Scaling and Time interpolating the signals, Shifting them to align features, and Translating them to recover the scaled value at the reference angle. The residuals are represented by empirical orthogonal functions, coefficients of which may be Substituted from other channels. Finally, allowance for long-term Temporal changes in the blockage signals are being developed. Results for a day in the middle of the mission are presented, as well as their effects on water vapor retrievals.
In-orbit health and performance of operational AVHRR instruments
The Advanced Very High Resolution Radiometer (AVHRR) instruments on board NOAA-18, MetOp-A and NOAA-19 satellites are key components of the current operational NOAA-EUMETSAT Initial Joint Polar System (IJPS) and are routinely monitored. Overall, the results of trending analysis show that the AVHRR instruments on NOAA-18/19 and MetOp-A are functioning well outperforming the channel noise specification limits. The backup NOAA-17 AVHRR functioned well for the on-orbit period prior to the onset of scan motor failure around April 11, 2010. The sun-earthsatellite geometry driven seasonality is exhibited by temperature measurements from thermistors on various instrument housing components including blackbody with the exception of patch temperature which is typically maintained stable. The only electrical measurement which exhibits seasonality is patch power. It is shown that the seasonality has no significant adverse impact on AVHRR radiometric performance. On the other hand the space view is adversely affected by intermittent periodic lunar signals and ubiquitous low frequency variability presumably connected to space clamping mechanism. Based on this it is suggested that the AVHRR channel noise estimation should be based on blackbody view. Finally, the temporal stability of the monitored parameters and the smaller or comparable magnitudes of seasonal variability in most of the instrument housekeeping measurements as compared to their orbital variability confirm the good health of AVHRR instruments on-board NOAA-18/19 and MetOp-A.
The multi-spectral imager on board the EarthCARE spacecraft
Clouds and aerosols are important atmospheric elements that strongly influence the weather and climate on planet Earth. The European Space Agency (ESA) is currently developing, in co-operation with the Japan Aerospace Exploration Agency (JAXA) the EarthCARE satellite mission with the objective of improving the understanding of the cloudaerosols- radiation interactions within the Earth's atmosphere. It is foreseen that the data provided by the EarthCARE satellite will allow the improvement of the currently available numerical prediction models, and therefore the quality of the weather forecast and climate evolution predictions. The payload of the EarthCARE satellite consists of a Cloud Profiling Radar (CPR), a Backscatter Lidar (ATLID), a Broadband Radiometer (BBR), and a Multi-spectral Imager (MSI). The MSI instrument will provide images of the earth in 7 spectral bands in the visible and infrared parts of the spectrum, with a spatial ground resolution of 500 m and an image width on the ground of 150 km. This paper provides a description of the MSI instrument and its expected performance.
A highly integrated micropayload for broadband infrared spectrometry (HIBRIS)
Marco Esposito, Sandro Hannemann, Scott Moon, et al.
We present a highly integrated payload suite which consists of the following instruments: a hyperspectral imager covering the wavelength range from 0.7 μm up to 5μm, and a thermal infrared radiometric imaging spectrometer. The payload design is the result of a design study that was performed in the context of the development of space exploration technologies under ESA contracts. The payload is broadly applicable to environmental research and for a number of remote sensing mission scenarios. All instruments have imaging capability and have been chosen such that they profit from close integration. HIBRIS is a combination of the hyperspectral NIR spectrometer, considered as generic instrument being part of many missions, and the radiometric micro-bolometer in the thermal infrared spectrum. A linear variable filter (LVF) concept is implemented in the NIR range that avoids the use of gratings which are usually limited to one decade of spectral range or less. The thereby rather compact design does allow the integration of multiple instruments within a rather limited volume envelope. The suite also makes use of a microcooler and the most advanced NIR detector technologies. The use of an LVF drives the spectral resolution of the instruments to 1% of the wavelength. The SNR is satisfactory in the most part of the spectrum for LEO EO missions. Current activities at cosine Research have focused on the design and performance of uncooled microbolometers, linear filters, light shielding baffles, beam splitters for shared optical paths, and the thermal design of HIBRIS.
Novel IR Device and Instrument Concepts
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Spaceborne laser transmitters for remote sensing applications
Anthony W. Yu, Steven X Li, Mark A Stephen, et al.
NASA Goddard Space Flight Center (GSFC) has been engaging in Earth and planetary science remote sensing instruments development for many years. The latest instrument was launched in 2008 to the moon providing the most detailed topographic map of the lunar surface to-date. NASA GSFC is preparing for several future missions, which for the first time will perform active spectroscopic measurements from space. In this paper we will review the past, present and future of space-qualified lasers for remote sensing applications at GSFC.
Next generation infrared sensor instrumentation: remote sensing and sensor networks using the openPHOTONS repository
Stephen So, Evan Jeng, Clinton Smith, et al.
We describe our novel instrumentation architectures for infrared laser spectrometers. Compact, power efficient, low noise modules allow for optimized implementation of cell phone sized sensors using VCSELs, diode, and quantum cascade laser sources. These sensors can consume as little as 0.3W with full laser temperature (<0.001K/Hz1/2) and current control (<2ppm/Hz1/2 noise), photodiode preamplification (<2pA/Hz1/2 noise floor, 1MΩ transimpedance), and digital lock-in amplification with 3 independent channels. We have implemented sensors based on laser absorption spectroscopy, photoacoustic spectroscopy, and Faraday rotation spectroscopy using the openPHOTONS systems, with performance rivaling standalone laboratory measurement instrumentation. Additionally, as openPHOTONS is an open source software repository, this instrumentation can be quickly adapted to new optical configurations and applications. Such modules allow the development of flexible sensors, whether implementing closed path spectrometers, open path perimeter monitoring, or remote backscatter based sensors. This work is also the enabling technology for wireless sensor networks (WSN) of precision sensors, a desirable sensing paradigm for long term, wide area, precision, temporally and spatially resolved studies. This approach can complement existing remote sensing and mapping technologies including satellite observations and sparse networks of flux towers.
Applications of quantum cascade lasers in chemical sensing
Sheng Wu, Andrei Deev, Yongchun Tang
We show new results in modulating and modifying Quantum Cascade (QC) lasers to make them more suitable for chemical sensing spectroscopy. Spectroscopy results using QC lasers are demonstrated with whispering gallery mode CaF2 disc/ball, saturated absorption in hollow waveguide and direct chemical analysis in water.
Advanced optoacoustic sensor designs for environmental applications
Cinzia Di Franco, Angela Elia, Vincenzo Spagnolo, et al.
We will report on the design and realization of optoacoustic sensors based on commercial quantum cascade lasers for environmental analysis applications. Different configurations will be described: i) sensors based on resonant photoacoustic cells, a "standard" H cell and an innovative T-cell; ii) sensor based on quartz enhanced photoacoustic spectroscopy. We will analyze the results obtained in the detection of nitric oxide.
Radiometric Calibration and Standards
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Calibration of far-IR and sub-mm detectors traceable to the international system of units
Precision power measurement of electromagnetic radiation is required to establish metrological applications, e.g. remote sensing. The Physikalisch-Technische Bundesanstalt (PTB), as the national metrology institute of Germany, has started to determine the spectral responsivity of detectors for THz radiation. In this work, the THz spectral range denotes the wavelength range from 60 μm to 300 μm, corresponding to 5 THz to 1 THz, which is traditionally the overlap between far-IR and the sub-mm range. Traceability of power measurement to the international system of units (SI) has been missing in the THz region in the past. The PTB establishes this traceability by using two complementary optical approaches, source- and detector-based radiometry. Both methods have been successfully prototyped. These primary investigations led to the design of a new measurement facility for the determination of THz radiant power and the responsivity calibration of THz detectors traceable to the SI.
NPP Visible/Infrared Imaging Radiometer Suite (VIIRS) radiometric calibration emissive bands: tested performance
Eric Johnson, Karen Galang, Courtney Ranshaw, et al.
The Visible/Infrared Imaging Radiometer Suite (VIIRS) collects radiometric and imagery data in 22 spectral bands within the visible and infrared spectrum ranging from 0.4 to 12.5 μm. This paper describes the radiometric uncertainty requirements for the 7 VIIRS thermal emissive bands and the calibration methodology employed to meet these requirements, including the on-board calibration subsystems and the retrieval algorithm for generating calibrated radiance from instrument data. The instrument characteristics contributing to uncertainties in retrieved radiance are presented based on results from the recently completed pre-launch test program. The final roll-up of these uncertainties relative to the absolute radiometric requirements are shown, and compared against the results obtained from the radiance retrieval algorithm exercised during thermal-vacuum testing for a NIST traceable Blackbody Calibration Source.
Pre-launch characterization of the WISE payload
Harri Latvakoski, Joel Cardon, Mark Larsen, et al.
The Wide-field Infrared Survey Explorer (WISE), launched on December 14, 2009, is a NASA-funded Explorer mission that is providing an all-sky survey in the mid-infrared with far greater sensitivity and resolution than any previous IR survey mission. The WISE science payload is a cryogenically cooled infrared telescope with four 1024x1024 infrared focal plane arrays covering from 2.8 to 26 μm, which was designed, fabricated, and characterized by Utah State University's Space Dynamics Laboratory. Pre-launch charaterization included measuring focus, repeatability, response non-linearity, saturation, latency, absolute response, flatfield, point response function, scanner linearity, and relative spectral response. We will provide a brief overview of the payload, discuss the overall characterization approach, review several pre-launch characterization methods in detail, and present selected results from ground characterization and early on-orbit performance.
Poster Session
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Aberrations of a transparent sphere
We present a ray trace through the sphere in support of sub-aperture testing of the shape of a transparent sphere, used as a volume (density) standard. The radius of curvature for a sub-aperture may be determined after finding zero for the defocus aberration, localizing the back focal plane.
Image splitter for mid-infrared bi-spectral analysis of flames
We propose and evaluate an optical "image splitter" by which we can capture two simultaneous infrared images of a single object, using a single detector. With this device, we can perform experiments in which we are interested to observe transitory phenomena in two different spectral bands, without losing the spatial information of the test subject. We also present experimental results of using this array for mid-infrared flame analysis.
Oxygen saturation with simulated breathing
We describe a systematic procedure to arrive at the optimal wavelengths for monitoring oxygen delivery to and its consumption in an organ. On the basis of the signal-to-noise optimization study, we propose several high performance 2-D wavelength intervals within the therapeutic window. Furthermore, we find that at least one of the traditional wavelength choices falls near the interval of decreased performance, providing a possible explanation for the occasional failure of currently used devices.
Tunable filter imager for JWST: etalon opto-mechanical design and test results
The Tunable Filter Imager of the James Webb Space Telescope will be based on blocking filters and a tunable Fabry- Perot etalon with an average resolution of about 100. It will operate in two wavelength bands from 1.6 μm to 2.5 μm and from 3.1 μm to 4.9 μm at a cryogenic temperature of about 35K. It will respectively be used to study the First Light and re-ionization of the universe by surveying Lyman-alpha sources and to provide an in-depth study of proto-planetary systems as well as giant planets of nearby stars. The Tunable Filter Imager (TFI) is designed to image a sky field of view of 2.2' by 2.2' (magnified to 4.6 deg. x 4.6 deg. at the etalon). Its tunable etalon has an aperture of 56 mm. It operates at low orders 1 and 3 for the two wavelength bands which reduces the number of blocking filters to a number of eight. The etalon gap tuning between 2.5 μm and 5.5 μm is provided by piezoelectric actuators and will be servo controlled by using capacitive displacement sensors. In this paper, we present the etalon's opto-mechanical design that allows us to achieve the stringent requirements in terms of resolution over a wide infrared wavelength band, and operation at low gap at cryogenic temperature. Cryogenic test results will be shared as well.
Micro-controller based fall detector to assist recovering patients or senior citizens
Francisco Páez, Lars Asplund
Senior citizens and patients recovering from surgery or using strong medications with severe side effects tend to fall unexpectedly. The consequences of such an uncontrolled fall could be worse than the original malady, especially when there is no communication with the care-takers. We describe a fall-detector device capable of distinguishing falls from normal daily activities. Based on three-axis accelerometer and advanced data processing, the microcontroller emits an alarm requesting help in the case of a physical fall. We design and construct the fall-detector prototype for either inside or outside use. In order to determine the device performance, fifty instances of each fall event have been evaluated; all of them detected as fall event. In the case of daily activities, the only movement that produces an alarm is the transition from standing up to lying in 5% of the occurrences.
The Astro-Comb project
G. Schettino, C. Baffa, E. Giani, et al.
An Optical Frequency Comb-based apparatus, to be used as a calibration system of the IR GIANO astronomical spectrograph, is the aim of the Astro-Comb project. We plan to obtain, starting from a comb repetition rate of 100 MHz, a final calibration spectrum of lines equally spaced by 16 GHz over the spectral range from 1 μm to 2 μm. Such a system is able to overcome some limits of the present day calibrators, allowing to complement a high resolution spectrograph, such as GIANO, for precision measurements like the detection of extra-solar rocky planets.
Simultaneous measurement of multiple parameters using a single fiber Bragg grating
A novel approach for simultaneous measurement of chirp (any parameter that can induce strain gradient on FBG) and temperature using a single FBG is proposed. Change in reflectivity at central wavelength of FBG reflection & Bragg wavelength shifts induced due to temperature were used for chirp & temperature measurements respectively. Theoretical resolution limit for chirp and temperature using an Optical Spectrum Analyzer (OSA) with 1pm wavelength resolution and >58dB dynamic range are 12.8fm and 1/13 oC respectively.