This PDF file contains the front matter associated with SPIE Proceedings Volume 7082, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

Recent progress made in the structure design, growth and processing of Type-II InAs/GaSb superlattice photo-detectors lifted both the quantum efficiency and the R₀A product of the detectors. Type-II superlattice demonstrated its ability to perform imaging in the Mid-Wave Infrared (MWIR) and Long-Wave Infrared (LWIR) ranges, becoming a potential competitor for technologies such as Quantum Well Infrared Photo-detectors (QWIP) and Mercury Cadmium Telluride (MCT). Using an empirical tight-binding model, we developed superlattices designs that were nearly lattice-matched to the GaSb substrates and presented cutoff wavelengths of 5 and 11 μm. We demonstrated high quality material growth with X-ray FWHM below 30 arcsec and an AFM rms roughness of 1.5 Å over an area of 20x20 μm². The detectors with a 5 μm cutoff, capable of operating at room temperature, showed a R₀A of 1.25 10⁶ Ω.cm² at 77K, and a quantum efficiency of 32%. In the long wavelength infrared, we demonstrated high quantum efficiencies above 50% with high R₀A products of 12 Ω.cm² by increasing the thickness of the active region. Using the novel M-structure superlattice design, more than one order of magnitude improvement has been observed for electrical performance of the devices. Focal plane arrays in the middle and long infrared range, hybridized to an Indigo read out integrated circuit, exhibited high quality imaging.

LWIR and VLWIR type II InAs/GaSb superlattice photodetectors have for long time suffered from a high dark current level and a low dynamic resistance which hampers the its emergence to the infrared detection and imaging industry. However, with the use of M-structure superlattice, a new type II binary InAs/GaSb/AlSb superlattice design, as an effective blocking barrier, the dark current in type II superlattice diode has been significantly reduced. We have obtained comparable differential resistance product to the MCT technology at the cut-off wavelength of 10 and 14μm. Also, this new design is compatible with the optical optimization scheme, leading to high quantum efficiency, high special detectivity devices for photon detectors and focal plane arrays.

We report the fabrication of low strain quantum-dots-in-a-double-well (DDWELL) infrared photodetector where the net strain on the system has been reduced by limiting the total indium content in the system. The detector consists of InAs dots embedded in In_0.15Ga_0.85As and GaAs wells with a Al_0.1Ga_0.9As barrier, as opposed to In_0.15Ga_0.85As wells and a GaAs barrier in standard dots-in-a-well (DWELL) detector. The structure was a result of multilevel optimization involving the dot, well layers above and below the dot for achieving the desired wavelength response and higher absorption, and the thickness of the barriers for reduction in dark current. Detector structures grown using solid source molecular beam epitaxy (MBE) were processed and characterized. The reduction in total strain has enabled the growth of higher number of active region layers resulting in enhanced absorption of light. The detector shows dual color response with peaks in the mid-wave infrared (MWIR) and the long-wave infrared (LWIR) region. A peak detectivity of 6.7×10¹⁰ cm.√ Hz/W was observed at 8.7μm. The detector shows promise in raising the operating temperature of DWELL detectors, thereby enabling cheaper operation.

ARL and L3-CE have been developing corrugated quantum well infrared photodetector (C-QWIP) technology for long wavelength applications. Several large format 1024 × 1024 C-QWIP focal plane arrays (FPAs) have been demonstrated. In this paper, we provide a detailed analysis on the FPA performance in terms of quantum efficiency η and compare it with a detector model. We found excellent agreement between theory and experiment when both the material parameters and the pixel geometry are taken into account. For C-QWIPs with the bound-to-quasi-bound structure, a η of 37% is observed, albeit at a large voltage of -11V. Since this voltage is outside the operating regime of the existing readout electronics, we investigated several more compatible structures and achieved η in the range of 15 - 26%. This range of η, although lower than the original value, is still approximately three times higher than that of the grating coupled QWIPs, and the coupling bandwidth is also three times wider. The C-QWIP approach thus holds significant performance advantages over the grating approach. Combined with its economical processing steps and flexible wavelength coverage, the C-QWIP technology has proven its advantages in infrared detection.

Mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) 1024x1024 pixel InGaAs/GaAs/AlGaAs based quantum well infrared photodetector (QWIP) focal planes and a 320x256 pixel dualband pixel co-registered simultaneous QWIP focal plane array have been demonstrated as pathfinders. In this paper, we discuss the development of 1024x1024 MWIR/LWIR dualband pixel co-registered simultaneous QWIP focal plane array.

Results are presented on three different approaches which show room temperature infrared sensing. The first approach is based on transitions from the light/heavy hole to the split-off band in p-doped GaAs/AlGaAs heterostructure showing a response threshold of 3.4 µm and operating up to a temperature of 330 K. The peak responsivity at 2.5 μm was ~1.5 mA/W with a D* of 2.3×10⁶ Jones at 330 K. The split-off threshold can be extended to longer wavelengths by using different materials. The second approach is based on capacitance variations in a quantum dot (QD) embedded dielectric medium. The incident IR photons induce charge separation inside the QDs and effectively change the dielectric properties varying the capacitance. Initial devices using PbS and ZnO QDs in paraffin have shown detection at 310 K in both the visible-NIR range. Using other materials and sizes of dots the range can be tailored for applications in other ranges including the UV range. The third approach uses tunneling quantum dot infrared photodetector (TQDIP) structures providing multi-color characteristics, and bias dependent wavelength selectivity. Here a tunneling barrier is used to block the dark current while permitting the photocurrent to pass through due to resonance effects. A preliminary TQDIP detector showed room temperature response at 6 and 17 μm with responsivity of 75 mA/W and 150 mA/W, respectively. The peak detectivity of ~10⁷ Jones was reported for both peaks.

Plasmon resonances in the two dimensional electron gas (2-deg) of a high electron mobility transistor (HEMT) can affect transport properties. The resonance frequency depends on the gate-tuned sheet charge density of the 2deg and on the characteristic length of the gate metallization by which free space THz radiation couples to the plasmon. Thus, this type of device can be used as a tunable detector. This work presents an experimental investigation of such a device fabricated from the InGaAs/InP material system. E-beam lithography was used to fabricate a gate in the form of a grating with sub-micron period. Sensitivity of the conductance to incident THz fields is reported. Direct absorption of THz, temperature effects, and the effects of source to drain current on system performance are also investigated. It is expected that this class of device will find use in space-borne remote sensing applications.

Detectors in the far infrared based on HgTe/Hg_1-xCd_xTe superlattices (SL's) are superior to those based on Hg_1-xCd_xTe alloys. This is based on their band structure, however, it was concluded in an investigation of the hydrostatic pressure dependence of photoluminescence (PL) peaks investigation reported in Phys. Rev. B 48, 4460 (1993) that either the band structure model was incorrect or the observed PL peaks were related to impurities. In contrast, in optical absorption experiments, the hydrostatic pressure dependence of intersubband transitions agrees with theory, which corroborates the validity of the band structure model. The first advantage is the required precision of the growth parameters for the desired band gap or cut off wavelength (λ_co). More important is the possibility to significantly reduce leak currents by the appropriate choice of barrier thickness. Furthermore the absorption edge is much steeper and therefore the SL can be much thinner. Due to Auger suppression in these type III SL's, carrier lifetimes are significantly enhanced. Finally the SL is significantly less susceptible to a Burstein-Moss shift of the adsorption edge; at least an order of magnitude greater electron concentration is necessary in order to produce the same Burstein-Moss shift. A method for <i>in situ p</i> type doped quantum wells (QW's) and SL's with nitrogen and arsenic by means of molecular beam epitaxy (MBE) is discussed.

DRS Sensors & Targeting Systems with silicon materials partner Lawrence Semiconductor Research Laboratory and development partner NASA Langley Research Center Earth Science Directorate are developing improved far-infrared detectors for Earth energy balance observations from orbit. Our team has succeeded in demonstrating the feasibility of extending the wavelength range of conventional arsenic-doped-silicon Blocked Impurity Band (BIB) detectors (cut-off ~28 μm) into the far infrared. The new far-IR member of the BIB detector family operates at temperatures accessible to existing space-qualified cryocoolers, while retaining the very high values of sensitivity, stability, linearity, and bandwidth typical of the broader class of silicon BIB detectors. The new detector should merit serious consideration for the Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission defined by the recent National Research Council's Decadal Survey for Earth Science. Proposed further development of this detector technology includes wavelength extension to a goal of at least 100 μm, improvements in detector design, and implementation of light-trapping packaging. These are developments that will enable increased radiometric accuracy, reduced spatial smearing, and simpler calibration approaches for CLARREO.

High-speed, high-sensitivity, avalanche photodiodes operating at 1.55 μm spectral range have been utilized in modern long-haul and high-bit rate optical communication systems. Related research was focused on developing detectors with minimized excess noise and maximized gain-bandwidth product. Recently imaging and critical sensing applications stimulated development of modified avalanche photodiode structures operating in 1.55 μm spectral range. For these devices speed is no more critical. Instead, very low current densities and low multiplication noise are the main requirement. In the present work the performance of uncooled InGaAs/InAlAs/InP avalanche photodiodes operating near 1.5 μm has been studied. Device modeling based on advanced drift and diffusion model have been performed with commercial Crosslight APSYS simulator. Conventional separate absorption, charge and multiplication (SACM) avalanche photodiode as well as devices with a relatively thick undepleted p-type InGaAs absorption region and thin InAlAs multiplication layer have been considered. The latter type of APD structure enables to increase device quantum efficiency, reduce dark current and eliminate impact ionization processes within absorbing layer.

We describe two new optoelectronic mid-IR devices employing narrow gap lead-chalcogenide (IV-VI) layers on Si or BaF₂ substrates: (1) Tunable resonant cavity enhanced detectors (RCED) for the mid-infrared with an epitaxial Bragg mirror and a thin p-n+ heterojunction as detecting layer have been realized for the first time. They are tunable by moving the top micro-electro-mechanical micromirror, thus changing the cavity length. (2) Optically pumped vertical external cavity surface emitting lasers (VECSEL) with an emission wavelength above 5 μm were fabricated, for the first time, too. Presently they operate with an output power of up to 260 mW_p and up to 175 K. With improved appropriate precautions for efficient heat removal, still much higher operation temperatures are expected. Both resonant cavity enhanced devices may be used as miniature infrared spectrometers to cover the spectral range from < 3 μm up to > 20 μm.

Raytheon has been building silicon p-i-n (Si-PIN) detector arrays for the past twenty years for various remote sensing instruments such as MODIS, EO-1, and Landsat now on orbit. See Figure 1. The Si-PIN technology at Raytheon has matured in the past five years with the addition of a dedicated silicon wafer fab, improvements in hybrid technologies, and the enhanced digital functionality of RVS custom read out integrated circuits (ROICs). This paper will discuss the advantages that Raytheon Si-PIN arrays offer over conventional CCDs and monolithic CMOS imagers such as 100% optical fill factor, high QE (visible - near IR), high MTF, and radiation hardness.

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. With this detector the instrument can be operated in the hot environment of Mercury without the need for a cryogenic cooling system. The challenge is the characterization and calibration of the instrument. We are reporting on the ongoing calibration efforts including laboratory measurements of analogue materials, end-to-end simulations and a detailed characterization of all components and discuss each of the three elements. The measurement of planetary analogue materials in grain sizes <25 μm and at temperatures up to 500°C relevant for Mercury's surface provide a realistic input signal for the end-to-end simulation. A radiometric and a spectroscopic breadboard model of MERTIS are used to derive all necessary parameters of the instrument, for example the spectral resolution or the wavelength registration on the detector. This parameters support setting up the end-to-end simulation which can then process the spectra of the planetary analog materials as input signal to create a realistic representation of the MERTIS output signal.

A novel thermal-band imager is proposed for space-based Earth science measurement applications such as rock identification and volcano monitoring. The instrument, MAGI-L (Mineral and Gas Identifier - LEO), would also enable detection of gases from natural and anthropogenic sources. Its higher spectral resolution, compared to ASTER-type sensors, will improve discrimination of rock types, greatly expand the gas-detection capability, and result in more accurate land-surface temperatures. The optical design for MAGI-L will incorporate a novel compact Dyson spectrometer. Data from SEBASS have been used to examine the trade-offs between spectral resolution, spectral range, and instrument sensitivity for the proposed sensor.

We use an IR camera to record and visualize the ignition process in a domestic gas stove during the first second after the electrical spark has initiated the combustion. The measurement and visualization of the flame growth and distribution process resulted in an improved design of thermo-mechanical properties and ventilation characteristics of the ignition chamber. We report recording and the actual visualization of the real-time ignition process, incorporating frame interpolation and other image processing and subtraction schemes to play back the temporal evolution of the fire-propagation process at a rate suitable for human inspection and visual processing at about 30 frames per second.

We evaluate the degree of oxygen saturation for several explicit wavelengths in the spectral interval from 650 to 1050 nm (therapeutic window). We analyze the effect of selecting a particular wavelength pair to calculate oxygen saturation considering the known absorption specific coefficients of oxy- and deoxy-hemoglobin. Also, we design a heart simulator to determine the most useful wavelength couple for oxygen saturation for all wavelengths in the therapeutic window. We present a selection map to facilitate wavelength choice. Furthermore, we examine the random noise sensitivity of the trans-illuminated irradiance. This information will be used to determine accurately the illumination sources for NIR spectroscopy and oximetry.

A cryogenic Fourier transform infrared spectrometer (Cryo-FTS) was developed for the Low Background Infrared (LBIR) facility at the National Institute of Standards and Technology (NIST). This spectrometer was developed for the Missile Defense Agency Transfer Radiometer (MDXR) that will be used to calibrate infrared sources that cannot be transported to NIST for calibration. When used inside the MDXR, the Cryo-FTS provides relative spectral measurements with a repeatability better than 1 % over the spectral range from 3 μm to 15 μm and at a spectral resolution of 0.6 cm^-1. This level of performance is enabled by the use of an advancec real-time resampling method. The compact interferometer uses a compensated Michelson configuration and has an operating temperature range between 10 K and 340 K with very low static beam redirection (< 215 μrad). The interferometer uses flat mirrors and a KBr beamsplitter and compensator. This optics maintains low wavefront distortion for infrared beams of up to 2 cm diameter and 5 mrad divergence. It integrates a digitally servo-controlled porchswing mechanism to provide an accurate and repeatable optical path difference and is supported by a Wavefront Alignment (WA) system to correct for wavefront residual tilt in real time using a fibre optic coupled metrology system. The interferometer provides modulation efficiency of better than 44% with limited power dissipation (< 2.8 W) during operation.

The Dyson spectrometer form is capable of providing high throughput, excellent image quality, low spatial and spectral distortions, and high tolerance to fabrication and alignment errors in a compact format with modest demands for weight, volume, and cooling resources. These characteristics make it attractive for hyperspectral imaging from a space-based platform. After a brief discussion of history and basic principles, we present two examples of Dyson spectrometers being developed for airborne applications. We conclude with a concept for an earth science instrument soon to begin development under the Instrument Incubator Program of NASA's Earth Science Technology Office.

We discuss a scheme for a photon-counting detection system that overcomes the difficulties of photon-counting at high rates at telecom wavelengths. Our method uses an array of N detectors and a 1-by-N optical switch with a control circuit to direct input light to live detectors. We conclude that in addition to detection deadtime reduction, the multiplexed switch also reduces so-called trigger deadtime, common to infrared photon counting detectors. By implementing the new algorithm we obtain an overall deadtime reduction of a factor of 5 when using just N=2 multiplexed detectors. In addition to deadtime reduction, our scheme reduces afterpulsing and background counts (such as dark counts). We present experimental results showing the advantage of our system as compared to passive multi-detector detection systems and our previous active multiplexing system that only reduced detection deadtime.

Infrared imaging has typically relied on quantum well and quantum dot focal plane arrays which inherently have a narrow spectral response. In order to detect 'color' information within the infrared spectrum, several detectors are used with a filtering scheme to sample different wavelengths and the data is post-processed to yield multi-spectral images. Using the 320 x 256 pixel quantum dot-in-a-well (DWELL) infrared focal plane arrays developed by the University of New Mexico's Center for High Technology Materials offers numerous advantages including wide spectral response (1 μm to 30 μm +) and response tunability. The latter of these allows multi-spectral imaging without switchable filters. A simple external bias voltage is applied to tune spectral response on a pixel by pixel basis. This presentation outlines the work to date and future work to be accomplished on this project to implement tunable color imaging capabilities in several wavelengths throughout the infrared spectrum using the DWELL structure. Precision radiometry, similar to astronomical photometry using a charge coupled device, will be realized in addition to color imaging capabilities, requiring a full characterization of noise processes and techniques for noise reduction in this novel device.

Previously, we measured temperature variations employing the spectral power and lifetime of the β-diketonate chelate europium (III) thenoyltrifluoroacetonate (EuTTA). The main goal of our work is to develop a system to convert infrared into visible radiation with EuTTA as the active medium of conversion. Here, we calibrate the fluorescence properties of EuTTA and confirm the reliability of the calibration. We detect black body radiation which serves to change the local temperature of the transducer, with our proposed system. When excited with UV radiation (365 nm), EuTTA fluoresces with its principal emission peak at 615 nm. The changes in spectral power, P₀(T), and mean lifetime, τ(T), of the fluorescence are related with the temperature change induced in the film due to the impinging black body radiation. We present the relative error and temperature differences obtained between the calculated (with calibration) temperature and reference measurements. Furthermore, we demonstrate that incoming radiation, which causes a temperature increase in the transducer (i.e. IR radiation), can be detected through the changes in EuTTA fluorescence parameters.

The pre-launch characterization and calibration of remote sensing instruments should be planned and carried out in conjunction with their design and development to meet the mission requirements. In the case of infrared instruments, the onboard calibrators such as blackbodies and the sensors such as spectral radiometers should be characterized and calibrated using SI traceable standards. In the case of earth remote sensing, this allows intercomparison and intercalibration of different sensors in space to create global time series of climate records of high accuracy where some inevitable data gaps can be easily bridged. In the case of ballistic missile defense, this provides sensor quality assurance based on SI traceable measurements. The recommended best practice for this pre-launch effort is presented based on experience gained at National Institute of Standards and Technology (NIST) working with National Aeronautics and Space Administration (NASA), National Oceanic and Atmospheric Administration (NOAA) and Department of Defense (DoD) programs in the past two decades. Examples of infrared standards and calibration facilities at NIST for serving the remote sensing community will be discussed.

We have developed a goniometric reflectometer using a Fourier-transform infrared (FTIR) spectrometer source for polarized reflectance measurements from 1 μm to 20 μm wavelength at angles of incidence from 10° to 80°, with an incident beam geometry of approximately f/25. Measurements are performed in either absolute mode, or relative to a reference mirror that has been calibrated at near-normal incidence using an integrating sphere-based reflectometer. Uncertainties in the 0.2 % to 0.5 % range are achieved using a photoconductive 77 K InSb detector from 1 μm to 5 μm and a 12 K Si:As BIB detector from 2 μm to 20 μm. The performance of the system has been tested using dielectric materials such as Si as well as high-quality Au mirrors. We describe measurements of SiO_x-coated Ag mirrors to assess their performance for such applications as the half-angle mirror (HAM) in the VIIRS optical scanning system. Various coatings are analyzed to help assess the effect of p-polarized absorption bands at angles of incidence from 10° to 65° and wavelengths between 3 μm and 13 μm.

As part of the optical detector characterization program at the Optical Technology Division at NIST, we have established a capability for the calibration of spectral radiant power responsivity in the infrared from 785 nm to 14 μm. We have used our facilities to characterize two commercial pyroelectric radiometers with KRS5 windows. The calibration methodology consists of the determination of the responsivity at single wavelength tie points together with relative spectral responsivity measurements. Responsivity tie points at 785, 1064, 1320, 1600, 2000 and 10600 nm are obtained against the NIST ACR-L1 absolute cryogenic radiometer as well as a domed pyroelectric transfer standard, using an OPO tunable laser and a stabilized CO₂ laser as sources. The spatial variation of the responsivity of the test radiometers has also been measured. This enables us to minimize the uncertainties due to interference fringes from the KRS5 window. The relative spectral responsivity curves for the two radiometers are obtained indirectly through measurement of the detector absorptance with an FTIR-based integrating sphere reflectometer. In order to obtain the actual absorptance at the detector from the reflectance measurements, an individual KRS5 window and a bare detector were also measured. The results are compared and the uncertainty budgets will be discussed.

SPICA (SPace Infrared telescope for Cosmology and Astrophysics) was selected for study as a mission of opportunity within the science programme Cosmic Vision 2015-2025 of the European Space Agency, with a planned launch in 2017. Observing in the 5 - 210 micron waveband, one of its major goals is the discovery of the origins of planets and galaxies. ESA's contribution is the provision of the SPICA Telescope Assembly (STA) featuring a 3.5 m primary mirror cooled to < 5K, and instrument engineering and management of a nationally funded European FIR instrument (SAFARI) as part of SPICA's payload. SAFARI is an imaging spectrometer operating at 30 - 210 micron, baselined as a Mach-Zehnder (MZ) Fourier Transform Spectrometer (FTS). An internal ESA study has been carried out to address the specific challenges associated in particular with STA and SAFARI, taking into account resource margins and interface specifications driven by the overall spacecraft design. This paper provides a summary of the preliminary results achieved during this study.

We are interested in designing, fabricating and characterizing a Dove prism for interferometric use. In a previous work, we determined the prism tolerance to manufacturing errors. When the manufacturing tolerance of the angles is maintained within ± 0.35 arc sec, the maximum wave-front deviation is better than λ/10 (at 633 nm). Afterward, we studied the optical (angular) and the error-induced misalignments, caused by an interferometric Dove prism. The misalignment analysis showed that to ensure a maximum OPD of λ/10 (at 633 nm) the tolerance to misalignment must be ± 0.33 arc sec. In this work, we analyze the mirror movements in a Rotationally-Shearing Interferometer to reach a performance better than λ/10 (at 633 nm), employing exact ray trace. The compensation study shows the presence of a 0.66 arc sec window needed to ensure such performance. In addition, we demonstrate that it is possible to reduce the wave-front deviation caused by manufacturing errors of the interferometric Dove prism, by implementing fine mirror movements. The analysis illustrates that a piezoelectric might be used to control the mirror mounts, thus ensuring the desired performance.

It is well known that the varying geometrical relationship between the Sun and the Earth within a year as well as the in-orbit ageing, affect in to some degree the performance of the instruments on-board the Earth orbiting satellites. Following the successful launch and commissioning of the Metop-A satellite, the in-orbit performance of the AVHRR, HIRS and AMSU-A instruments have been continuously monitored. The data acquired since the launch of the satellite has been analysed in order to detect any potential ageing or seasonal effects that might affect instrument performance.

The Atmospheric Chemistry Experiment (ACE) is the mission on-board Canadian Space Agency's science satellite, SCISAT-1. ACE consists of a suite of instruments in which the primary element is an infrared Fourier Transform Spectrometer (FTS) coupled with an auxiliary 2-channel visible (525 nm) and near infrared imager (1020 nm). A secondary instrument, a grating spectrometer named MAESTRO, provides spectrographic data from the near ultra-violet to the near infrared, including the visible spectral range. With all instruments combined, the payload covers the spectral range from 0.25 to 13.3 micron. A comprehensive set of simultaneous measurements of trace gases, thin clouds, aerosols and temperature are being made by solar occultation from this satellite in low earth orbit. The ACE mission measures and analyses the chemical and dynamical processes that control the distribution of ozone in the upper troposphere and stratosphere. A high inclination (74°), low earth orbit (650 km) allows coverage of tropical, mid-latitude and polar regions. The ACE/SciSat-1 spacecraft was launched by NASA on August 12th, 2003. This paper presents the status of the ACE-FTS instrument, after nearly five years on-orbit. On-orbit SNR and some telemetry signals are presented. The health status of the instrument is discussed.

Final assembly and integration of the Orbiting Carbon Observatory instrument at the Jet Propulsion Laboratory in Pasadena, California is now complete. The instrument was shipped to Orbital Sciences Corporation in March of this year for integration with the spacecraft. This observatory will measure carbon dioxide and molecular oxygen absorption to retrieve the total column carbon dioxide from a low Earth orbit. An overview of the design-driving science requirements is presented. This paper then reviews some of the key challenges encountered in the development of the sensor. Diffraction grating technology, lens assembly performance assessment, optical bench design for manufacture, optical alignment and other issues specific to scene-coupled high-resolution grating spectrometers for this difficult science retrieval are discussed.

TANSO-FTS (Thermal And Near infrared Sensor for carbon Observation Fourier Transform Spectrometer) and TANSO-CAI (Cloud and Aerosol Imager) are a space-born optical sensor system mainly oriented for observation of greenhouse gases (GHGs). TANSO will be installed on the Greenhouse gases Observing SATellite "GOSAT" and launched in early 2009. The TANSO-FTS is a Fourier transform spectrometer which has 3 SWIR bands (0.76, 1.6 and 2.0 μm) and 1 TIR band (5.5 - 14.3 μm) for observation of scattering light and thermal radiation from the earth, mainly focused on CO₂ absorption spectra. The TANSO-CAI is an imager for detection and correction of clouds and aerosol effects to determine GHGs quantities. The instrument characteristics of TANSO-FTS are high SNR (~300), quick interferogram scan (1.1 ~ 4.0 s) with moderate wave-number resolution (~0.2 cm^-1), and polarization measurement. Now, integration and test of proto-flight model of TANSO have been completed. In this paper, the results of performance test such as SNR, ILS, polarization sensitivity, etc. are described.

The High Resolution Dynamics Limb Sounder (HIRDLS) instrument was launched on the NASA Aura satellite in July 2004. HIRDLS is a joint project between the UK and USA, and is a mid-infrared limb emission sounder designed to measure the concentrations of trace species, cloud and aerosol, and temperature and pressure variations in the Earth's atmosphere from the upper troposphere to the mesosphere. The instrument is intended to make measurements at both high vertical and horizontal spatial resolutions, but validating those measurements is difficult because few other measurements provide that vertical resolution sufficiently closely in time. However, the FORMOSAT-3/COSMIC suite of radio occultation satellites that exploit the U.S. GPS transmitters to obtain high resolution (~1 km) temperature profiles in the stratosphere does provide sufficient profiles nearly coincident with those from HIRDLS. Comparisons show a good degree intercorrelation between COSMIC and HIRDLS down to about 2 km resolution, with similar amplitudes for each, implying that HIRDLS and COSMIC are able to measure the same small scale features. The optical blockage that occurred within HIRDLS during launch does not seem to have affected this capability.

The HIRDLS instrument, like any other remote sensor must be able to maintain a high degree of measurement accuracy through its mission life. There are many factors that influence radiometric stability including direct and indirect thermal effects and other aging processes. Ideally the sensor should be capable of 'self-calibrating' and there must be independent methods to track its long term accuracy. For the HIRDLS instrument, being handicapped with regard to 'self-calibration', the high fidelity data available to the ground data processors provide substantive evidence that it has retained good long term 'accuracy'. Details of the long term performance are presented and discussed, together with reference to some problems and their solutions.

The High Resolution Dynamics Limb Sounder (HIRDLS) instrument suffered a debilitating event during the Aura Satellite launch on July 15, 2004. After the initial instrument activation phase was completed 25 days later, the first atmospheric scan tests revealed a much different radiance field than was expected prior to launch. A subsequent lengthy investigation suggested that the HIRDLS exit aperture was mostly obstructed by sheathing material that lined the inner fore-optics cavity. As part of the radiance correction process workaround, it is necessary to provide radiances to the retrieval algorithm that are equivalently unobstructed (clear view); hence, knowledge on the amount of unobstructed exit-aperture area is needed. This manuscript describes the problem and the modeling method used to estimate the amount of unobstructed area of the HIRDLS exit aperture. Particular emphasis will be given to the type of data required to ascertain this quantity. Lastly, a diagnostic scheme for evaluating the calculated unobstructed open area for each channel will be discussed, along with a look to the future.

The HIRDLS instrument is a limb viewing infra-red radiometer on the NASA Aura spacecraft in a sun synchronous low earth orbit and obtains measurements of the composition of the atmosphere covering the whole Earth each day. The MIPAS instrument is a limb viewing infra-red interferometer on board the European Envisat satellite in a very similar orbit to Aura except that the local solar time is different. The complement of geophysical data products of both instruments is very similar, and because of similar observation strategies their two data sets can be usefully compared. The comparison provides the means to support validation in order to obtain statistics such as systematic differences and variance. This is performed over the full latitude range of HIRDLS and height range of MIPAS and thereby helps to identify sources of errors. The identification of known atmospheric features is a useful diagnostic, and includes such things as regions of upwelling of tracer gases, or the propagation of coherent structures as with mid-latitude waves and we can test whether these structures are consistently represented in both data sets. HIRDLS version 2.04.19 (v004) temperature, ozone and nitric acid show very low systematic 'errors' compared to MIPAS over most of the spatial range. Currently pre-released water vapour, nitrous oxide and F-11 are reasonably similar, CH4 somewhat more restricted, and nitrogen dioxide, N2O5, chlorine nitrate and F-12 as yet susceptible to complications from the obstructed telescope. Further details are discussed in the paper.