Infrared detector technology based on intersubband absorption in III-V materials has shown remarkable success in advancing low-cost, highly uniform, high-operability, large-format focal plane arrays (FPAs). It also permits vertical integration of detector stacks to create multi-band or tunable FPAs. Each detector stack of multi-quantum well layers absorbs photons within the specified wavelength band, allowing other photons to transmit through permitting multiband detection. The wavelength of the peak response and cutoff can be continuously tailored by varying layer thickness (well width), barrier composition (barrier height), and carrier density (well-doping density). The GaAs/Al_xGa_1-xAs material system allows the quantum well parameters to be varied over a range wide enough to enable light detection at any wavelength range from 6 to 20 μm. By adding a few monolayers of In_yGa_1-yAs during the GaAs quantum well growth, the short wavelength limit can be extended to 3 μm. The spectral bandwidth of these detectors can be tuned from narrow (Δλ/λ ~ 10%) to wide (Δλ/λ ~ 40%), according to application requirements. Multi-band detector technology can be extended to near IR or visible wavelengths by adding detector layers utilizing interband absorption in these materials.

We propose a design of the frequency-selective sub-mm-W detector, which must operate at room temperature. The idea is based on a standing wave enhancement of the detector responsivity. The detector contains a lateral semiconductor superlattice with electrons performing Bloch oscillations as an active medium, a broadband bow-tie terahertz (THz) antenna, a built-in resonator and an external dc circuit. As compared with well-known THz-photon detector based on one-dimensional layered superlattice the switch to the lateral superlattice leads to a necessary change in technology of antenna attachment to the superlattice and allows the additional growth of a resonator. The estimation calculations of the current responsivity of the proposed detector fulfilled by means of an equivalent transmission line model have proved that the detector responsivity can be enhanced in several hundred times near a resonance frequency due to the matching between the incident radiation and the superlattice provided by built-in resonator. The expected rise time of the proposed detector is in order of 10^-11s.

A three color normal incidence quantum dots in a well (DWELL) operating in the mid-wave infrared (MWIR), long wave infrared (LWIR) and very long wave infrared (VLWIR) are reported. The peak operating wavelengths are at ~ 6 mm, ~10.5 mm and ~ 23.2 mm. We believe that the shorter wavelength response (6 mm and 10.5 mm) are due to bound-to-continuum and bound-to-bound transitions between the states in the dot and states in the well, whereas the longer wavelength response (23.2 mm) is due to intersubband transition between dot levels. A bias dependent activation energy ~ 100 meV was extracted from the Arrhenious plots of the dark currents, which is a factor of three larger than that observed in quantum well infrared photodetectors operating at comparable wavelengths.

Inter-subband detectors such as quantum well infrared photodetectors (QWIP) have been widely used in infrared remote sensing. Quantum dot infrared photodetectors (QDIPS) have been predicted to have better performanc than QWIPs due to the novel properties of quantum dots caused by the extra confinement. Here we report our recent results of InAs QDIP grown on InP substrate by low-pressure metalorganic chemical vapor deposition. The device structure consists of multiple stacks of InAs quantum dots with GaAs/AlInAs/InP barrier. 400μx400μm test mesas were fabricated for device characterizations. Photoresponse was observed with a peak wavelength of 6.4 μm and a cutoff wavelength of 6.6 μm at both 77K and 100K. A detectivity of 1.0x10¹⁰ cmHz^1/2/W was obtained at 77K at a bias of -1.1. V. To the best of our knowledge, this is the highest detectivity reported for InAs QDIP grown on InP substrate. At 100K, the detectivity only drops to 2.3x10⁹cmHz^1/2/W.

We present an overview of laser cooling of solids. In this all-solid-state approach to refrigeration, heat is removed radiatively when an engineered material is exposed to high power laser light. We report a record amount of net cooling (88 K below ambient) that has been achieved with a sample made from doped fluoride glass. Issues involved in the design of a practical laser cooler are presented. The possibility of laser cooling of semiconductor sensors is discussed.

An energy-balance equation for excited carriers and phonons is established for studying the laser cooling of wide-bandgap semiconductors using three-photon excitation process. The power-exchange densities of the system are calculated for different strengths of the excitation filed. When the power-exchange density is positive, it implies laser cooling of the lattice. The effects of initial lattice temperature and field-frequency detuning on the laser-cooling phenomenon under the three-photon excitation process is demonstrated. The power-exchange densities are compared for both laser cooling and heating using nonlinear excitation.

Imaging devices working in the near infrared (NIR), especially in the so-called eye-safe range, i.e., around 1.5 mm, have become increasingly important in many military and commercial applications; these include night vision, covert surveillance, range finding and semiconductor wafer inspection. We proposed a new approach in which a wafer-fused optical up-converter, combined with a commercially available charged coupled device (CCD), functions as an infrared camera. The optical up-converter converts incoming infrared light into shorter wavelength radiation that can be efficiently detected by the silicon CCD (cutoff wavelength about 1 mm). An optical up-converter with high efficiency at room-temperature is critical for low cost and large-area infrared imaging applications. A prototype 1.5 mm optical up-converter based on wafer fusion technology has been successfully fabricated. The device consists of an InGaAs/InP pin photodetector and a GaAs/AlGaAs light emitting diode. Experimental results show that the end-to-end up-conversion efficiency is 0.0177 W/W at room-temperature, corresponding to an internal quantum up-conversion efficiency of 76%. In this paper, the design, fabrications and characterization of the optical up-conversion devices is presented. Issues related to device optimization, such as improving internal and external up-conversion efficiency, are addressed. Preliminary results demonstrate the room-temperature up-conversion imaging operation of a pixelated wafer-fused device.

Carbon nanotubes are found to have versatile properties ranging from exceptional mechanical strength to semiconductor behavior with varying band gap, ranging from 0 eV to ~1 eV. In this work, we have explored the applicability of the carbon nanotubes for optical and IR sensing. Our platform is a vertical integration of highly uniform carbon nanotube arrays with silicon, forming a heterojunction structure. The heterojunction structure exhibits very good current rectification, voltage dependent capacitance and photocurrent response, all suggestive of an electronic diode function. However, we found, that the photogeneration in the first generation test devices is so far dominated by the silicon part of the heterojunction. Of the possible reasons for the elusive mid-IR photocurrent expected in the carbon nanotube is the presence of a thin barrier layer at the heterojunction. Further optimization of the devices is possible by modifying the technology to avoid the barrier layer formation and by improving the quality of the aluminum oxide matrix.

At previous SPIE meetings, we reported on an optoelectronic device that measures the complete polarization state of incident infrared light in a single pixel and in a single frame for a narrow wavelength band (δλ<0.05 μm). Using at least four quantum-well stacks and four linear gratings, each stacked alternating above the other, the device uses the interference among light paths to create a distinct pattern of photocurrents at each quantum-well stack coding for a specific polarization. In this paper, we will model the performance of this device, a quantum-well infrared single-pixel polarimeter (QWISPP), in the setting of a Fourier transform infrared (FTIR) imager. We model one column of QWISPP pixels detecting an inferferogram. Using an FTIR with randomly varying QWIsPP pixels to detect the interferogram, we discovered a technique that allows an 100x improvement in measured spectral-polarization uncertainty compared to the use of identical QWISPP pixels in an FTIR or grating spectrometer. The technique also enables a 15x improvement in the uniformity of the error across a sample spectrum. In other words, we turn into an advantage the imperfections in fabricating an FPA of QWISPPs.

Point-diffraction interferometry has found wide applications spanning much of the electromagnetic spectrum, including both near- and far-infrared wavelengths. Any telescopic, spectroscopic or other imaging system that converts an incident plane or spherical wavefront into an accessible point-like image can be tested at an intermediate image plane or at the principal image plane, in situ. Angular field performance can be similarly tested with inclined incident wavefronts. Any spatially coherent source can be used, but because of the available flux, it is most convenient to use a laser source. The simplicity of the test setup can allow testing of even large and complex fully-assembled systems. While purely reflective IR systems can be conveniently tested at visible wavelengths (apart from filters), catadioptric systems could be evaluated using an appropriate source and an IRPDI, with an imaging and recording system. PDI operating principles are briefly reviewed, and some more recent developments and interesting applications briefly discussed. Alternative approaches and recommended procedures for testing IR imaging systems, including the thermal IR, are suggested. An example of applying point-diffraction interferometry to testing a relatively low angular-resolution, optically complex IR telescopic system is presented.

We present the design and fabrication of voltage tunable two-color superlattice infrared photodetectors (SLIPs), where the detection wavelength switches from the long-wavelength infrared (LWIR) range to the mid-wavelength infrared (MWIR) range upon reversing the polarity of applied bias. The photoactive region of these detectors contains multiple periods of two distinct short-period SLs that are designed for MWIR and LWIR detection. The voltage tunable operation is achieved by using two types of thick blocking barriers between adjacent SLs - undoped barriers on one side for low energy electrons and heavily-doped layers on the other side for high energy electrons. We grew two SLIP structures by molecular beam epitaxy. The first one consists of two AlGaAs/GaAs SLs with the detection range switching from the 7-11 μm band to the 4-7 μm range on reversing the bias polarity. The background-limited temperature is 55 and 80 K for LWIR and MWIR detection, respectively. The second structure comprises of strained InGaAs/GaAs/AlGaAs SLs and AlGaAs/GaAs SLs. The detection range of this SLIP changes from the 8-12 μm band to the 3-5 μm band on switching the bias polarity. The background-limited temperature is 70 and 110 K for LWIR and MWIR detection, respectively. This SLIP is the first ever voltage tunable MWIR/LWIR detector with performance comparable to those of one-color quantum-well infrared detectors designed for the respective wavelength ranges. We also demonstrate that the corrugated light coupling scheme, which enables normal-incidence absorption, is suitable for the two-color SLIPs. Since these SLIPs are two-terminal devices, they can be used with the corrugated geometry for the production of low-cost large-area two-color focal plane arrays.

III-V based single photon avalanche diodes (SPADs), avalanche photodiodes (APDs) operated in Geiger-mode, are ideally suited for ultra-weak signal detection in the near infrared for photon counting and photon timing applications. Spaceborne SPADs would provide a rugged, compact alternative to photomultiplier tubes with lower operating voltage requirements, stronger near-IR response, and the possibility for array implementation. Results from a performance characterization of an in-house fabricated In_0.53Ga_0.47As/InP SPAD are presented. Sensitivity (NEP) and timing resolution (δt) were investigated as a function of bias from T = 135 K to 165 K; an NEP ≈ 5 x 10¹⁵W/Hz^1/2 at T = 150 K and δt ≈ 230 ps at T = 165 K were measured for λ = 1.55 μm light.

Though a Phase I and II NASA SBIR initiative Michigan Aerospace Corp. has demonstrated a spaceflight qualified, tunable infrared Fabry Perot etalon. The design included use of single crystal ferroelectric actuators for tuning the etalon gap. The operational wavelength range of this etalon was designed for 10-14μm and utilized Zinc-Selenide for the plate substrate with a plate reflectivity of 0.8. At a temperature of 193 K and 0.4 milli-torr, the etalon achieved a finesse of 11.8, a bandpass of 1.23 nm and had a free-spectral range of 14.2 nm at the test wavelength of 10.013 μm. At this temperature, the etalon was tunable over ~8.5 free-spectral ranges, or 45 μm in gap spacing. Testing concluded that the etalon will retain 57% of its total dynamic range at a temperature of 75 K compared to its dynamic range at room temperature. The design was qualified for a Delta-II launch vehicle vibration specification.

Low temperature refrigeration is an increasingly vital technology for NASA's Space Science program. Ultra-sensitive detectors for x-ray, IR and sub-millimeter missions must be cooled below 0.1 K in order to reach their fundamental limits for energy and spatial resolution. Moreover, the ability to fabricate large arrays of these detectors means the cooler must have relatively large cooling power. Infrared missions also require telescope cooling into the 4 K range. Since the lifetime requirements for these missions go well beyond what is achievable with stored cryogen systems, the low temperature coolers for future missions must be able to use cryocoolers, operating at temperatures in the 4-10 K range, for pre-cooling. There is also a demand for laboratory coolers for developing the detectors and instruments for these missions. To meet these cooling requirements, we have developed several types of adiabatic demagnetization refrigerators (ADRs): a continuous ADR (CADR) that operates continuously at temperatures of 0.035 K and above for detector cooling in space; a CADR version for laboratory use; a quick turn around ADR system for detector development; and a multistage, higher cooling power CADR for cooling telescopes.

There is a branch of radiative transport theory that is customarily expressed with an integrodifferential equation or an integral equation. The new formulation in this article is, without approximation, expressed through partial differential equations in both the frequency and time domains. Its accuracy is demonstrated in the frequency domain by applying it to a problem solved long ago. It was expressed with the conventional integrodifferential equation. Confidence is bolstered in the new method by showing how the new method produces the identical analytical answer. This article also analyses a situation in the time domain in both the appropriate differential and integrodifferential equations and the identical results are again obtained.

In presented paper the analytical method of the complex analysis for PIR fiber-optic depending on number of optical modes was applied with numeral estimations. In this paper the consideration of polycrystalline-fiber materials (ArBrCl) for the wavelengths 4-20mm were performed with real appropriate numeral estimations. The physical nature of imaginary part of refractive indexes was assumed as the total sum of material scattering with material absorption. The simple equations were received and used for calculations of the imaginary parts of these main functions as well as for the set of mode's attenuations (am) from the imaginary parts of propagation constants. Using designed in given paper algorithm, the analysis of the operation of surrounding water was organized for effective desirable absorption of the set of optical cladding's modes.

This paper shows the possibility of separating and classifying remotely-sensed multispectral data from rocks and minerals onto seven geological rock-type groups. These groups are extracted from the general categories of metamorphic, igneous and sedimentary rocks. This study is performed under ideal conditions for which the data is generated according to laboratory hyperspectral data for the members, which are, in turn, passed trough the Multispectral Thermal Imager (MTI) filters yielding 15 bands. The main challenge in separability is the small size of the training data sets, which initially did not permit the reliable estimation of the second-order statistics for every class. To enable Bayesian classification, the original training data is linearly perturbed with the addition of minerals, vegetation, soil, water and other valid impurities. As a result, the size of the training data is significantly increased and estimates of the covariance matrices are obtained. An eigenvalue analysis is used to generate a set of reduced (five) multispectral vectors, viz., feature vectors, providing principal information about the data. In addition, a nonlinear band-selection method is also employed, based on spectral indices, comprising a small subset of all possible ratios between bands. By applying three optimization strategies, optimal combinations of two and three ratios are found that provide reliable separability and classification between all seven groups. To set a benchmark to which the MTI capability in rock classification can be compared, an optimization strategy is performed for the selection of optimal multispectral filters, other than the MTI filters, and an improvement in classification is predicted when these filters are used.

Measurements of spectrally resolved outgoing longwave radiation allows signatures of many aspects of greenhouse warming to be distinguished without the need to amalgamate information from multiple measurements, allowing direct interpretation of the error characteristics. Here, data from three instruments measuring the spectrally resolved outgoing longwave radiation from satellites orbiting in 1970, 1997 and 2003 are compared. The data are calibrated to remove the effects of differing resolutions and fields of view so that a direct comparison can be made. Comparisons are made of the average spectrum of clear sky outgoing longwave radiation over the oceans in the months of April, May and June. Difference spectra are compared to simulations created using the known changes in greenhouse gases such as CH₄, CO₂ and O₃ over the time period. This provides direct evidence for significant changes in the greenhouse gases over the last 34 years, consistent with concerns over the changes in radiative forcing of the climate.

The selection of the Venus Express mission by ESA in 2002 was the occasion to propose the VIRTIS imaging spectrometer for the payload of this mission to Venus. After the discovery of the infrared windows in the near infrared from ground based observations in the 80ies, it was realized that the surface of Venus is accessible to infrared observation on the night side of Venus. Imaging spectroscopy in the visible and near infrared is therefore a powerful tool to study the Venus atmosphere down to its deepest levels. VIRTIS, the imaging spectrometer of the Rosetta mission (Coradini et al, 1998), as the second generation instrument of this kind after the Phobos/ISM (Bibring et al, 1989), Galileo/NIMS (Carlson et al, 1990) Mars Express/OMEGA (Bibring et al, 2004) and Cassini/VIMS (Brown et al, 2000), is perfectly fitted for extensive observations of the infrared and visible spectral images of Venus, with its unique combination of mapping capabilities at low spectral resolution (VIRTIS-M channel) and high spectral resolution slit spectroscopy (VIRTIS-H channel).

Concern about the climatic effects of anthropogenic emissions of carbon dioxide (CO₂) has resulted in a growing need, both scientifically and politically, to monitor atmospheric CO₂. The development of a satellite instrument which could measure the global distribution of atmospheric CO₂ would greatly improve our understanding of the global carbon cycle and provide a means of monitoring regional sources and sinks. In this paper, we propose and analyse the potential of a nadir-viewing, satellite-based remote sensing instrument consisting of a multi-channel Gas-Filter Correlation Radiometer (GFCR) tuned to the 6300 cm^-1 (1.6 μm) and 5000 cm^-1 (2.0 μm) regions to globally measure the atmospheric CO₂ column. Although such an instrument would present some engineering challenges, we find that it could potentially measure the atmospheric CO₂ integrated-column to a precision of 1ppmv of CO₂ or better.

The Infrared Atmospheric Sounding Interferometer (IASI) is a key payload element of the METOP series of European meteorological polar-orbit satellites. IASI will provide very accurate data about the atmosphere, land and oceans for application to weather predictions and climate studies. The IASI measurement technique is based on passive IR remote sensing using an accurately calibrated Fourier Transform Spectrometer operating in the 3.7 - 15.5 μm spectral range and an associated infrared imager operating in the 10.3-12.5 μm spectral range. The optical configuration of the sounder is based on a Michelson interferometer. Interferograms are processed by the on-board digital processing subsystem which performs the inverse Fourier Transform and the radiometric calibration. The integrated infrared imager allows the co registration of the IASI sounder with AVHRR imager on-board METOP. The first model (proto-flight) of IASI has successfully completed a verification program conducted at ALCATEL SPACE premises in Cannes. This paper provides a brief overview of the IASI mission, instrument architecture and key performances results. A companion paper1 by Alcatel provides more information on instrument design and development.

The purpose of this paper is to present the IASI overall architecture and the IASI functional chain including optics and interferometer, analogue to digital acquisition, on board and on ground digital processing. It points out special features of IASI's design and critical technologies. The IASI technical description is followed by a development status including activities on breadboards, engineering models, proto flight and flight models with emphasis put on achieved critical steps. A companion paper by CNES will provide detailed information on the IASI mission and instrument key performance achievement.

GaAs photoconductive detectors offer an extended spectral response in the far-infrared (FIR) compared to presently available stressed Ge photoconductors. Furthermore, responsivity at wavelengths up to 330 microns can be reached without having to apply uniaxial stress close to the breaking limit on each pixel. This would greatly simplify the production of detector arrays and therefore allow much larger numbers of pixels. Such arrays are highly demanded for upcoming far-infrared astronomy missions with space and airborne telescopes. However, bulk GaAs photoconductors have only limited sensitivity, due to low absorption and high dark currents. Considerable improvement of the detector performance can be expected from the development of GaAs blocked impurity band (BIB) devices. Our recent crystal growth experiments show that the liquid phase epitaxial (LPE) technique is capable of producing the required purity for the blocking layer. We have also performed far-infrared absorption measurements of doped GaAs layers which demonstrate the spectral range extension to about 330 microns and the enlarged absorption coefficient for the more highly doped absorption layer. Experimental work is supported by numerical modeling of BIB devices done in our group.

Knowledge of the spatial and temporal distribution of atmospheric species such as CO₂, O₃, H₂O, and CH₄ is important for understanding the chemistry and physical cycles involving Earth's atmosphere. Although several remote sensing techniques are suitable for such measurements they are considered high cost techniques involving complicated instrumentation. Therefore, simultaneous measurement of atmospheric species using a single remote sensing instrument is significant for minimizing cost, size and complexity. While maintaining the instrument sensitivity and range, quality of multicolor detector, in terms of high quantum efficiency and low noise are vital for these missions. As the first step for developing multicolor focal plan array, the structure of a single element multicolor detector is presented in this paper. The detector consists of three p-n junction layers of Si, GaSb and InAs wafer bonded to cover the spectral range UV to 900 nm, 800 nm to 1.7 micron, and 1.5 micron to 3.4 micron, respectively. Modeling of the absorption coefficient for each material was carried out for optimizing the layers thicknesses for maximum absorption. The resulted quantum efficiency of each layer has been determined except InAs layer. The optical and electrical characterization of each layer structure is reported including dark current and spectral response measurements of Si pin structure and of GaSb and InAs p-n junctions. The effect of the material processing is discussed.

Infrared radiometers for irradiance measurement have been developed at the National Institute of Standards and Technology (NIST). These high performance irradiance meters are used to realize and maintain the spectral irradiance responsivity scale between 1000 nm and 5000 nm. They are also working standards that disseminate the infrared irradiance responsivity scale to other institutions and facilities. Both design considerations and responsivity scale transfer to the irradiance meters are discussed. The radiometers were calibrated for spectral irradiance responsivity on the new NIST Infrared Facility for Spectral Irradiance and Radiance Responsivity Calibrations using Uniform Sources (IR-SIRCUS). The spectral irradiance responsivity calibrations described are derived from absolute cryogenic radiometers.

Persistent photoconductivity in a Pb_0.75Sn_0.25Te(In) alloy initiated by monochromatic submillimeter-range radiation at wavelengths of 176 and 241 μm was observed at helium temperatures. This photoconductivity is shown to be associated with optical excitation of metastable impurity states.

The Cross-track Infrared Sounder (CrIS) is one of the mission-critical instruments onboard the National Polar-orbiting Operational Environmental Satellite System (NPOESS). CrIS develops vertical profiles of moisture, temperature, and pressure in the earth's atmosphere by measuring upwelling atmospheric infrared radiation at very high spectral resolution. This paper describes initial test results for the CrIS Engineering Development Unit #3 (EDU3).

Global warming has become a very serious issue for human beings. In 1997, the Kyoto Protocol was adopted at the Third Session of the Conference of the Parties to the United Nations Framework Convention on Climate Change (COP3), making it mandatory for developed nations to reduce carbon dioxide emissions by six (6) to eight (8) per cent of their total emissions in 1990, and to meet this goal sometime between 2008 and 2012. The Greenhouse gases Observing SATellite (GOSAT) is design to monitor the global distribution of carbon dioxide (CO₂) from orbit. GOSAT is a joint project of Japan Aerospace Exploration Agency (JAXA), the Ministry of Environment (MOE), and the National Institute for Environmental Studies (NIES). JAXA is responsible for the satellite and instrument development, MOE is involved in the instrument development, and NIES is responsible for the satellite data retrieval. The satellite is scheduled to be launched in 2008. In order to detect the CO₂ variation of boundary layers, both the technique to measure the column density and the retrieval algorithm to remove cloud and aerosol contamination are investigated. Main mission sensor of the GOSAT is a Fourier Transform Spectrometer with high optical throughput, spectral resolution and wide spectral coverage, and a cloud-aerosol detecting imager attached to the satellite. The paper presents the mission sensor system of the GOSAT together with the results of performance demonstration with proto-type instrument aboard an aircraft.

The Wide Field-of-view Imaging Spectrometer (WFIS), a high-performance pushbroom hyperspectral imager designed for atmospheric chemistry and aerosols measurement from an aircraft or satellite, underwent initial field testing in 2004. The results of initial field tests demonstrate the all-reflective instrument's imaging performance and the capabilities of data processing algorithms to render hyperspectral image cubes from the field scans. Further processing results in spectral and photographic imagery suitable for identification, analysis, and discrimination of subjects in the images. The field tests also reveal that the WFIS instrument is suited for other applications, including in situ imaging and geological remote sensing.

Remote temperature sounding from the vantage point of Earth Orbit improves our weather forecasting, monitoring and analysis capability. Recent advances in the infrared hyperspectral sensor technology promise to improve the spatial and temperature resolution, while offering relatively quick re-look times to witness atmospheric dynamics. One approach takes advantage of a two-dimensional, imaging Fourier transform spectrometer to obtain a data cube with the field of view along one plane and multiple IR spectra (one for every FPA pixel) along the orthogonal axis. Only the pixel pitch in the imaging focal plane and the optics used to collect the data limit the spatial resolution. The maximum optical path difference in the Michelson FTS defines the spectral resolution and dictates the number of path-length interferogram samples (FPA frames required per cube). This paper discusses the unique challenges placed on the focal plane by the Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) approach and how advanced focal plane technology is applied to satisfy these challenges. The instrument requires a midwave spectral band from 4.4 to 6.1m to capture the C02 and H20 absorption bands, and an optional VLWIR spectral band to cover from 8.85-14.6m. The paper presents performance data of Liquid Phase Epitaxy (LPE) fabricated HgCdTe detectors and design details of the advanced readout integrated circuit necessary to meet the demanding requirements of the imaging sensor for the GIFTS instrument. Point defects are removed by using a unique super-pixel approach to improve operability for the VLWIR focal plane. Finally, early focal plane performance measurements are reported, including Noise Equivalent Input, responsivity uniformity, output offset stability and 1/f noise knee.

Accurate temperature and pressure profiles are the key to high quality retrievals from solar occultation measurements. For best results these profiles should be retrieved from measurements that have an identical field-of-view and are simultaneous, with companion measurements. We explore three general methods, corresponding implementation strategies and their major error sources. These methods include: 1) one or more channels sensing CO₂ extinction, 2) a single channel using the oxygen A band, and 3) use of refraction angle measurements to infer temperature from density derivatives (limited to the stratosphere). It is shown that extraordinary results can be achieved if high precision solar tracking, and solar pointing knowledge, are accomplished.

Contemporary and emerging sensor systems typically require in-flight calibration reference sources. These are required to satisfy increasingly stringent specifications for stability, repeatability, dynamic range, absolute irradiance accuracy, and irradiance distribution uniformity, while meeting stray light, weight, and power constraints. While SSG has successfully designed and flight-qualified an internal calibration source for a telescope in a Schmidt configuration, future remote sensing programs are more likely to require telescopes in a 3-mirror off-axis re-imaging configuration. A major advantage to developing an internal calibration reference source for a re-imaging telescope is the availability of an intermediate field stop where the illumination from the calibration source can be inserted into the optical train. SSG's internal source design offers important advantages over existing approaches using in-flight blackbodies, including reduced volume, weight, and power requirements and the ability to generate multiple irradiance levels over a short period of time. The GIFTS (Geosynchronous Imaging Fourier Transform Spectrometer) telescope has been used as a representative platform to demonstrate this new internal calibration source, as it is representative of a design that may be used for future programs including the HES (Hyperspectral Environmental Suite) telescopes.

EBEX is a balloon-borne polarimeter designed to measure the intensity and polarization of the cosmic microwave background radiation. The measurements would probe the inflationary epoch that took place shortly after the big bang and would significantly improve constraints on the values of several cosmological parameters. EBEX is unique in its broad frequency coverage and in its ability to provide critical information about the level of polarized Galactic foregrounds which will be necessary for all future CMB polarization experiments. EBEX consists of a 1.5 m Dragone-type telescope that provides a resolution of less than 8 arcminutes over four focal planes each of 4 degree diffraction limited field of view at frequencies up to 450 GHz. The experiment is designed to accommodate 330 transition edge bolometric detectors per focal plane, for a total of up to 1320 detectors. EBEX will operate with frequency bands centered at 150, 250, 350, and 450 GHz. Polarimetry is achieved with a rotating achromatic half-wave plate. EBEX is currently in the design and construction phase, and first light is scheduled for 2008.

Satellite-based remote sensing of atmospheric CO₂ holds the promise to greatly improve our understanding of the processes which regulate atmospheric CO₂ and the global carbon cycle. However, the required precision and resolution of such measurements needed to characterise sources and sinks of CO₂ on regional scales presents strong instrument design challenges. One type of remote sensing instrument which has been proposed to measure the integrated-column concentration of CO₂ is a Gas-Filter Correlation Radiometer (GFCR). As a technique, a GFCR is a radiometer which uses a sample of the gas of interest as a spectral filter for that gas in the atmosphere. In this paper we present a "strawman" design for a GFCR satellite instrument to remotely sense atmospheric CO₂. This design, which includes multi-pass CO₂ and O₂ gas cells with path lengths of up to 10 metres, demonstrates that such an instrument can be built within the constraints of a satellite environment.

A vectorial shearing interferometer with variable sensitivity based in the rotation of a pair of wedge prisms is discussed. The prism rotations incorporates differential and extended wavefront controlled displacements, combining the advantages of high sensitivity of conventional interferometers and low sensitivity of traditional shearing interferometers. The vectorial shearing interferometer allows the optimization of the measurement parameters for wave reconstruction algorithms. The reliable directional sensitivity of this interferometer has been experimentally demonstrated in spherical and aspherical surfaces. We also show the regularization technique to estimating the wavefront shearing interferometric patterns generated in vectorial shearing interferometry.

High-resolution analytical techniques based on scanned microprobes over surfaces are useful to investigate reactions at different materials in solution, with possibilities for remote sensing. One of these techniques is Scanning Electrochemical and Photoelectrochemical Microscopy (SPECM), which allows to investigate both electrochemical and photoelectrochemical reactions either concurrently or simultaneously over a semiconductor surface. SPECM is based on the use of an optical fiber coated with a noble metal and isolated from its surrounding media with a polymer film. Spatial resolution for this technique strongly depends on the characteristics of the probe, for instance numerical aperture or the characteristics of optical fiber tips. According to this, there is an increasing need for reducing the optical probe sizes, as well as the illumination spot size, in order to improve spatial resolution for this technique. Usually, optical scanning probes are prepared by chemically etching an optical fiber in HF solutions or by heating and stretching an optical fiber locally with an oscillating flame or a CO₂ laser beam. In this work, the goal of this study is to establish the optimal tip diameter and the total length of the taper in order to obtain a good transmission efficiency and thus to improve the sensitivity of the SPECM technique.

The derivative of the detected incidance in a wavelength interval with respect to temperature includes two terms. The first term depends on the change in blackbody emission and the second one on the change of emissivity with temperature. The error of neglecting the second term is analyzed and evaluated for a standard radiation source, a tungsten lamp. In this case, the error changes form a negligible amount of 6% to a significant value of more than 45% in two spectral regions of interest.

A novel concept for an IR-to-visible converter is based on the up-conversion, incorporating a pumping radiation with the wavelength in the near IR. The theoretical heat transfer predictions are followed by the experimental results whereby the fiber is maintained at a series of temperatures. Additionally, an IR camera (2003 CEDIP), sensitive in the spectral range from 8 μm to 12 μm, is being used to ascertain the converter feasibility for room temperature applications under laboratory conditions.

We derive the alignment condition for the detection of binaries with an interferometer. We present 2-D and 3-D simulations containing the phase, Q, and cos(Q) as a function of the misalignment deviations (qx and qy) and position at the aperture. We generate patterns that enable us to determine, qualitatively, the misalignment degree of our optical system.