This PDF file contains the front matter associated with SPIE Proceedings Volume 6678, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

We have characterized a heterodyne receiver based on an NbN hot electron bolometer integrated with spiral antenna as mixer and an optically pumped FIR ring laser at 4.3 THz as local oscillator (LO). We succeeded in measuring the receiver output power, responding to the hot/cold load, as a function of bias voltage at optimum LO power. From the resulted receiver noise temperature versus the bias voltage, we found a DSB receiver noise temperature of 3500 K at a bath temperature of 4 K, which is a minimum average value. This is the highest sensitivity reported so far at frequencies above 4 THz.

In future space applications, widely distributed sensors, as well as, large deployable structures, such as mirrors and sunshades, will require active thermal control. However, thermal integration by conductive coupling with regenerative cryocoolers is not feasible for such distributed loads, as it requires massive copper straps and provides only limited means of thermal control. To address these issues, we are developing a continuous-flow rectified cooling loop (RCL) for use with pulse tube refrigerators. The RCL consists of a rectifier, integrated into the cold heat exchanger of the pulse tube refrigerator, and a flow loop with a MEMS-based, micro-scale, control valve. The RCL allows simple mechanical integration and has the benefit of load temperature regulation using the actively controlled valve to regulate the gas flow. The MEMS valve may also serve as the basis for a system of distributed Joule-Thomson (JT) coolers. In this paper, we summarize the work that has been done to date by Atlas Scientific, in collaboration with the University of Wisconsin Cryogenic Engineering Group (UWCEG) and the University of Michigan Solid State Electronics Lab (UMSSEL), in developing the RCL and the MEMS-based micro-scale control valve.

Development of two-dimensional cryogenic readouts suitable for far infrared and submillimeter detectors is a key step in fabrication of large format far infrared focal-plane arrays. In collaboration with Raytheon Vision Systems, we have designed and fabricated the first 32x32 readout multiplexer, SB349, capable of operating at cryogenic temperatures as low as 1.7K. This readout is a capacitive-transimpedance amplifier multiplexed to eight outputs and is buttable on two sides to form a 64x64 mosaic array. It features eight selectable gain settings, AC coupling (auto zero) for better input uniformity, sample-and-hold circuitry, and provisions to block the readout glow. A special, 2-micron cryo-CMOS process has been adopted to prevent freeze out and ensure low noise and proper operation at deep cryogenic temperatures. An overview of the design and the results of the initial functionality tests on this device are reported in this paper.

We are developing a kilopixel, filled bolometer array for infrared astronomy. The array consists of three individual components, to be merged into a single, working unit; 1) a transition edge sensor (TES) bolometer array, operating in the milliKelvin regime, 2) quarter-wave resonance backshorts, and 3) superconducting quantum interference device (SQUID) multiplexer readout. The detector array is a filled, square-grid of suspended, silicon membrane bolometers with superconducting thermistors. The spacing of the backshort beneath the detector grid can be set from ~30-300 microns by adjusting two process parameters during fabrication. We have produced prototype, monolithic arrays having 1 mm and 2 mm pitch detectors. The key technologies required for kilopixel arrays of detectors to be hybridized to SQUID multiplexer readout circuits have been demonstrated. Mechanical models of large-format detector grids have been indium bump-bonded to dummy multiplexer readouts to study electrical continuity. A monolithic array of 1 mm pitch detectors has been mated to a backshort grid optimized for a 350 micron resonant wavelength. Through-wafer microvias, for electroplated, low-resistance electrical connection of detector elements, have been prototyped using deep reactive ion etching. The ultimate goal of this work is to develop large-format (thousands of pixels) bolometer array architecture with background-limited sensitivity, suitable for a wide range of long wavelengths and a wide range of astronomical applications such as imaging, spectroscopy, and polarimetry and applicable for ground-based, suborbital, and space-based instruments.

Doping of the lead telluride and related alloys with the group III impurities results in appearance of the unique physical features of a material, such as persistent photoresponse, enhanced responsive quantum efficiency (up to 100 photoelectrons/incident photon), radiation hardness and many others. We present the physical principles of operation of the photodetecting devices based on the group III-doped IV-VI including the possibilities of a fast quenching of the persistent photoresponse, construction of the focal-plane array, new readout technique, and others. The advantages of infrared photodetecting systems based on the group III-doped IV-VI in comparison with the modern photodetectors are summarized. The spectra of the persistent photoresponse have not been measured so far because of the difficulties with screening the background radiation. We report on the observation of strong persistent photoconductivity in Pb_0.75Sn_0.25Te(In) under the action of monochromatic submillimeter radiation at wavelengths of 176 and 241 microns. The sample temperature was 4.2 K, the background radiation was completely screened out. The sample was initially in the semiinsulating state providing dark resistance of more than 100 GOhm. The responsivity of the photodetector is by several orders of magnitude higher than in the state of the art Ge(Ga). The red cut-off wavelength exceeds the upper limit of 220 microns observed so far for the quantum photodetectors in the uniaxially stressed Ge(Ga). It is possible that the photoconductivity spectrum of Pb_1-xSn_xTe(In)covers all the submillimeter wavelength range.

The photoconductors used in the integral field spectrometers of the PACS instrument onboard the Herschel space observatory consist of stressed gallium doped germanium crystals featuring cut-off wavelengths of 127μm and 205μm. The measured transient responses of these Ge:Ga photoconductors to a step change in the incident photon flux level as well as a test setup that allows creation of transients by different methods are presented in this paper. The transient response of extrinsic photoconductors is caused by charge carriers drifting or diffusing to a contact region and recombining. This limits the initial gain of the device. Because of potentially long time constants, the transient behavior presents a serious challenge to high-sensitivity, low-temperature extrinsic semiconductors. In particular at low IR photon fluxes it usually is impossible for the detector to reach steady-state behavior during a reasonable observation time. However, since the time constants depend on the inverse photon flux, theory suggests the transient times for the high thermal background levels anticipated for PACS to be of the order of tens of milliseconds. Experimentally we find the response time to be limited by the transition time between the different infrared fluxes. The experimental studies on the transients are accompanied by numerical calculations. The results support the prediction that transients are not expected to play a major role for the low signal regime in PACS.

DRS Sensors & Targeting Systems, supported by detector materials supplier Lawrence Semiconductor Research Laboratory, is developing far-infrared detectors jointly with NASA Langley under the Far-IR Detector Technology Advancement Partnership (FIDTAP). The detectors are intended for spectral characterization of the Earth's energy budget from space. During the first year of this effort we have designed, fabricated, and evaluated pilot Blocked Impurity Band (BIB) detectors in both silicon and germanium, utilizing pre-existing customized detector materials and photolithographic masks. A second-year effort has prepared improved silicon materials, fabricated custom photolithographic masks for detector process, and begun detector processing. We report the characterization results from the pilot detectors and other progress.

The joint U.S. and German SOFIA project to develop and operate a 2.5-meter infrared airborne telescope in a Boeing 747-SP is now in its final stages of development. Flying in the stratosphere, SOFIA allows observations throughout the infrared and submillimeter region with an average transmission of ≥ 80%. The SOFIA instrument complement includes broadband imagers, moderate resolution spectrographs capable of resolving broad features due to dust and large molecules, and high resolution spectrometers suitable for kinematic studies of molecular and atomic gas lines at km/s resolution. These instruments will enable SOFIA to make unique contributions to a broad array of science topics. First science flights will begin in 2009, and the observatory is expected to operate for more than 20 years. The sensitivity, characteristics, science instrument complement, and examples of first light science are discussed.

Multi-wavelength imaging polarimetry at far-infrared wavelengths has proven to be an excellent tool for studying the physical properties of dust, molecular clouds, and magnetic fields in the interstellar medium. Although these wavelengths are only observable from airborne or space-based platforms, no first-generation instrument for the Stratospheric Observatory for Infrared Astronomy (SOFIA) is presently designed with polarimetric capabilities. We study several options for upgrading the High-resolution Airborne Wideband Camera (HAWC) to a sensitive FIR polarimeter. HAWC is a 12 × 32 pixel bolometer camera designed to cover the 53−215 μm spectral range in 4 colors, all at diffraction-limited resolution (5−21 arcsec). Upgrade options include: (1) an external set of optics which modulates the polarization state of the incoming radiation before entering the cryostat window; (2) internal polarizing optics; and (3) a replacement of the current detector array with two state-of-the-art superconducting bolometer arrays, an upgrade of the HAWC camera as well as polarimeter. We discuss a range of science studies which will be possible with these upgrades including magnetic fields in star-forming regions and galaxies and the wavelength-dependence of polarization.

The THIS instrument (Tuneable Heterodyne Infrared Spectrometer) is a versatile heterodyne receiver with a sensitivity close to theoretical prediction. It uses a Quantum Cascade Laser (QCL) as local oscillator and a HgCdTe photo-voltaic detector as mixer. The IF-spectrum is analyzed by means of a new broadband Acousto-Optical Spectrometer (AOS) with 3 GHz bandwidth and 1 MHz resolution. A dual sideband (DSB) system noise temperature has been measured with 2300 K at 10 μm wavelength, which is only 60% above the quantum limit. The stability of the system has been determined at an Allan variance minimum time of 50 seconds. Below this integration time the performance is purely radiometric. Also, the frequency stability has been measured with 1 MHz rms error within several hours. The quality of the instrument has been demonstrated by a few observing campaigns at the McMath-Pierce observatory on Kitt Peak. Measurements of Winds on Mars and Venus have been carried out and molecular line signals in sunspots have been detected. We propose to develop THIS as a second generation instrument for future astronomical observations on SOFIA.

Mid-infrared polarimetry remains an underexploited technique; where available it is limited in spectral coverage from the ground, and conspicuously absent from both the Spitzer and JWST instrument suites. The unique characteristics of SOFIA affords unprecedented spectral coverage and sensitivity in the mid-infrared waveband, offering new vistas in the exploration of astrophysical objects, including (a) galaxies and AGN, (b) star formation regions and (c) debris disks. Furthering the existing 5-40μm imaging and spectroscopic capabilities of SOFIA, and the University of Florida's mid-IR imagers, spectrometer and polarimeter designs of T-ReCS and CanariCam, we present an overview of science highlights that could be performed from a ~5-40μm imaging- and spectro-polarimeter on SOFIA. A secondary science driver is the inclusion of low- to moderate- resolution (total flux) spectroscopy at these wavelengths. Such an instrument concept would plug an unfilled area of both SOFIA and space-based instrumentation, providing SOFIA with unique and exciting science capabilities.

We present a concept for a far-IR integral field spectrograph for SOFIA, the Cornell Mapping Spectrometer (CMS). CMS takes advantage of the next generation of large bolometer arrays to deliver moderate resolution spectroscopy in the wavelength range between 40 μm and 220 μm over a large field of view. Two separate wavelength channels with each employing six SCUBA-2-like bolometer arrays will provide 64 element spectra over a 10 × 12 spatial pixel footprint. By matching the pixel size to the beam size the field of view obtained is 190" × 160" at the important [CII] line in the long-λ channel and 77" × 64" at the [OI] line in the short-λ channel. The sliced image is fed into an R2 echelle spectrometer of modest resolving power (R ≈ 2000). The grating will operate in 4th order at 158 μm in the long-λ channel and 4th order at 63 μm in the short-λ channel. This results in nearly matching orders for other important fine-structure lines of [NII] and [OIII]. Filterwheels are placed right in front of the detector arrays to separate the orders. By subdividing the detector assemblies and appropriately placing the 3 × 1 detector sub-assemblies it is possible to observe four fine-structure lines simultaneously. CMS combines the advantages of a FIFI-LS design (instantaneous spatial and spectral coverage) with the sensitivity advantage of bolometers over photo-conductors. This will make CMS the instrument of choice for deep spectroscopic integrations of extended regions in galaxies.

The Stratospheric Observatory for Infrared Astronomy (SOFIA) will enable unique astronomical observations from visible to millimeter wavelengths. AIRES, a long-slit spectrograph with a mid-infrared slit viewing camera, would enable spectral imaging of gas-phase spectral features between 17 and 210 μm with resolving powers from ~60,000 to 5000. The Cryogenic Grating Spectrometer (CGS: AIRES' predecessor) which was flown on NASA's Kuiper Airborne Observatory (KAO) for 13 years, demonstrated the importance of this wavelength range. A 1997 proposal to develop AIRES was selected as the highest-ranked of 19 U.S. competitors for first-generation SOFIA science instruments. Funding was terminated in 2001 due to budget problems associated with an original under estimate and the advent of full cost accounting in NASA. Here we summarize AIRES' expected performance, its science potential, its status, and lessons learned. Highlighted are three successfully accomplished major technical developments: the world's largest monolithic cryogenic grating, cryogenic multiplexing amplifiers for far-infrared germanium photoconductor detectors, and an optical/mechanical design in a package suitable for installation on SOFIA. We show that AIRES would fill a unique role among other spectroscopic capabilities foreseen for space-borne missions. AIRES' capabilities remain a high but unfilled priority for SOFIA, and for the science community in general.

GREAT, the German REceiver for Astronomy at Terahertz frequencies, is a first generation SOFIA dual channel heterodyne PI−instrument for high resolution spectroscopy. The system is developed by a consortium of German research institutes. The receiver will allow simultaneous observations in two out of the following three far−infrared frequency bands: * a low−frequency (1.4−1.9 THz) channel for e.g. the fine-structure lines of ionized nitrogen [NII] at 205μm and ionized carbon [CII] at 158μm; * a mid−frequency (2.4−2.7 THz) channel for e.g. the 112μm transition of HD; and * a high−frequency (4.7 THz channel) for the 63 μm fine−structure line of neutral atomic oxygen. Hot electron bolometers (HEB) mixers provide state of the art sensitivity. A spectral resolving power of up to 108 is achieved with chirp transform spectrometers, and a total bandwidth of 4 GHz at 1 MHz resolution is reached with wide band acousto-optical spectrometers. The modular concept of GREAT allows to observe with any combination of two out of the three channels aboard SOFIA. A more complete frequency coverage of the THz regime by adding additional GREAT channels is possible in the future. The adaptation of new LO−, mixer− or backend−techniques is easily possible. We describe details of the receiver and the results of first performance tests of the system at 1.9 THz. As an outlook to future developments we show first results obtained with phase locking a quantum cascade laser, the most promising option for future high power local oscillators in the Terahertz regime.

Objects shielded from direct illumination, or lying in shadows, can be difficult to detect using airborne hyperspectral sensors. Diminished illumination of objects reduces the signal contrast with respect to the background and shade shifts the spectral signature distribution. Supervised detection of shadowed objects is therefore confounded from implementing the simplest approach, namely inserting signatures trained on fully illuminated objects into target searches. Previously developed statistical temporal transformation ("whitening/dewhitening") of target signatures and target covariance matrices has been adapted to convert fully illuminated signatures to the more appropriate shadowed signatures for target detection. The choice of areas to transform the signatures must include dimilar background composition under full illumination and shadow conditions. A new search algorithm, Regularized Maximum Likelihood Clustering (RMLC), uses pixels for the CV computation associated with the object. "Regularizing" the object's covariance matrix avoids non-singularities from the CV computation and mitigates statistical degradation for the covariance matrix calculation due to undersampling of the small number of pixels. To accurately compute the required covariance matrices from imagery of small open and shadowed areas, "regularization" is also applied to the covariance matrices associated with those areas. The searches are applied to visible/near IR data collected from forested areas. Inserting the transformed signatures into RMLC and the adaptive cosine estimator (ACE) achieved higher target detection for fixed alarm rate, relative to the matched filter. The temporal transform of the signatures was compared to a scaling approach using mean signatures from the open and shadowed areas. This study successfully extracted targets from shadows by using a sensitive target search and through transforming signatures collected from fully illuminated conditions into shadowed spectra.

For about 15 years, the Solid-State Electronics Lab at the TU Dresden in co-operation with the DIAS Infrared GmbH has been developing pyroelectric linear arrays on the basis of lithium tantalate. These arrays have up to 256 responsive elements and are responsive in the wavelength range of 0.8 . . . 25 μm. The geometry of the elements can be easily adjusted to the actual application. The available array technology allows the cost-effective production of linear arrays with a high signal-to-noise ratio and an excellent long-term stability. The paper describes the essential properties of the manufactured and newly developed linear arrays and also their applications in contactless temperature measurement, spectrometry and security systems.

Absolute stellar photometry is based on 1970s terrestrial measurements of the star Vega calibrated by using the Planck radiance from a Cu fixed-point blackbody. Significant advances in absolute radiometry have been made in the last 30 years that offer the potential to improve both terrestrial and space-based absolute stellar photometry. These advances include new high-temperature blackbody standards, absolute cryogenic radiometry, solid-state optical radiation sources, improved atmospheric transmittance modeling, and laser-based radiometric calibration. We describe the possible use of these new technologies for ground-based calibration of standard stars and their impact on stellar photometry, including present efforts to achieve highly accurate measurements from the ultraviolet to the near infrared for cosmological applications.

One of the James Webb Space Telescope's (JWST) primary science goals is to characterize the epoch of galaxy formation in the universe and observe the first galaxies and clusters of galaxies. This goal requires multi-band imaging and spectroscopic data in the near infrared portion of the spectrum for large numbers of very faint galaxies. Because such objects are sparse on the sky at the JWST resolution, a multi-object spectrograph is necessary to efficiently carry out the required observations. We have developed a fully programmable array of microshutters that will be used as the field selector for the multi-object Near Infrared Spectrograph (NIRSpec) on JWST. This device allows apertures to be opened at the locations of selected galaxies in the field of view while blocking other unwanted light from the sky background and bright sources. In practice, greater than 100 objects within the field of view can be observed simultaneously. This field selection capability greatly improves the sensitivity and efficiency of NIRSpec. In this paper, we describe the microshutter arrays, their development, characteristics, fabrication, testing, and progress toward delivery of a flight-qualified field selection subsystem to the NIRSpec instrument team.

A mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) 1024x1024 pixel quantum well infrared photodetector (QWIP) focal plane arrays (FPAs) have been demonstrated with excellent imagery. MWIR FPA has given noise equivalent differential temperature (NEΔT) of 19 mK at 95K operating temperature and LWIR FPA has given NEΔT of 13 mK at 70K operating temperature. In addition, epitaxially grown self-assembled InAs/InGaAs/GaAs quantum dots (QDs) are exploited for the development of large-format FPAs. The QD devices were fabricated into the first LWIR 640x512 pixel QDIP FPA, which has produced excellent infrared imagery with NEΔT of 40 mK at 60K operating temperature.

Detection of both UV and IR radiation is useful for numerous applications such as firefighting and military sensing. At present, UV and IR dual wavelength band detection requires separate detector elements. Here results are presented for a GaN/AlGaN single detector element capable of measuring both UV and IR response. The initial detector used to prove the dualband concept consists of an undoped AlGaN barrier layer between two highly doped GaN emitter/contact layers. The UV response is due to interband absorption in the AlGaN barrier region producing electron-hole pairs which are then swept out of the barrier by an applied electric field and collected at the contacts. The IR response is due to free carrier absorption in the emitters and internal photoemission over the work function at the emitter barrier interface, followed by collection at the opposite contact. The UV threshold for the initial detector was 360 nm while the IR response was in the 8-14 micron range. Optimization of the detector to improve response in both spectral ranges will be discussed. Designs capable of distinguishing the simultaneously measured UV and IR by using three contacts and separate IR and UV active regions will be presented. The same approach can be used with other material combinations to cover additional wavelength ranges, e.g. GaAs/AlGaAs NIR-FIR dual band detectors.

In our research group, we develop novel dots-in-a-well (DWELL) photodetectors that are a hybrid of the quantum dot infrared photodetector (QDIP). The DWELL detector consists of an active region composed of InAs quantum dots embedded in InGaAs quantum wells. By adjusting the InGaAs well thickness, our structure allows for the manipulation of the operating wavelength and the nature of the transitions (bound-to-bound, bound-to-quasibound and bound-to-continuum) of the detector. Based on these principles, DWELL samples were grown using molecular beam epitaxy and fabricated into 320 x 256 focal plane arrays (FPAs) with Indium bumps using standard lithography at the University of New Mexico. The FPA evaluated was hybridized to an Indigo 9705 readout integrated circuit (ROIC) in collaboration with QmagiQ LLC and tested with a CamIRa^TM system manufactured by SE-IR Corp. From this evaluation, we report the first two-color, co-located quantum dot based imaging system that can be used to take multicolor images using a single FPA. We demonstrated that we can operate the device at an intermediate bias (V_b=-1.25 V) and obtain two color response from the FPA at 77K. Using filter lenses, both MWIR and LWIR responses were obtained from the array at the same bias voltage. The MWIR and LWIR responses are thought to be from bound states in the dot to higher and lower lying states in the quantum well respectively. Temporal NEDT for the DWELL FPA was measured to be 80mK at 77K.

Plasmons can be generated with photons in the two dimensional electron gas (2-deg) of high electron mobility transistors (HEMTs). Because the plasmon frequency at a given wavevector depends on sheet charge density, a gate bias can tune the plasmon resonance. This effect allows a properly designed HEMT to be used as a voltage-tunable narrow-band detector or filter. This work reports on both the theory and design of such a device in the InP materials system and discusses its potential uses. By using a sub-micron grating to couple incident radiation to a high sheet charge 2-deg, a minimum detectible wavelength of roughly 26 microns is obtained. Fabrication issues, terahertz response, and tunability are discussed. Because of its small size, this novel device could find use in spaceborne remote sensing application.

Focal plane arrays (FPAs), which are two-dimensional array of detectors hybridized to Read Out Integrated Circuits (ROIC), present unique challenges in characterization and functionality tests. Parameters such as temporal and spatial NEΔT, detectivity (D*), quantum efficiency (η), spectral response (R(λ)), etc., are generally the typical figures of merits. However, detailed operational information extractable from the electro-optical properties of the FPAs normally requires very time-consuming data analyses. One major difficulty in analyzing large format FPAs is the volume of data that are present in dealing with individual or group of pixels. Additional complications arise from circuit and subsystems that are an integral part of the FPA operations, and analyzing their effect individually requires detailed knowledge of the ROIC properties and the driving electronics. The noise analyses add another complexity in understanding the characteristics since noises can be generated externally as well as internally. The characterization techniques presented in this paper are performed specifically for very large format 1Kx1K LWIR QWIP FPA but will also be applicable to other types of FPAs.

The Solar Occultation For Ice Experiment (SOFIE) was launched onboard the Aeronomy of Ice in the Mesosphere (AIM) satellite on 25 April 2007, and began science observations on 14 May 2007. SOFIE conducts solar occultation measurements in 16 spectral bands that are used to retrieval vertical profiles of temperature, O₃, H₂O, CO₂, CH₄, NO, and polar mesospheric cloud (PMC) extinction at 11 wavelengths. SOFIE provides 15 sunrise and 15 sunset measurements each day at latitudes from 65°-85°S and 65°-85°N. This work describes the SOFIE experiment and shows preliminary retrieval results based on observations from the initial months on-orbit.

SOFIE (Solar Occultation for Ice Experiment) is a 16-channel radiometer that was launched into a polar orbit on NASA's Aeronomy of Ice in the Mesosphere (AIM) spacecraft on 25 April 2007. An in-depth jitter analysis was performed to verify that the spacecraft could meet the pointing requirements. The analysis was based on an integrated modeling capability which combines structural dynamics with dynamic ray tracing to determine the motion of the boresight on the focal plane array (FPA) in the presence of disturbances. Two approaches were used and compared: a frequency-based analysis and a time-based analysis. For the frequency approach, the spacecraft provider determined the peak amplitude of the disturbance motions within 10% of each SOFIE modal frequency. The transmissibility factor Q between disturbance motion input and boresight motion output was determined for each degree of freedom and modal frequency. The disturbance amplitudes were then multiplied by each Q and summed over all frequencies and degrees of freedom. For the time-based analysis, the disturbance time histories were applied directly to the integrated model to generate the motions of the boresight ray on the FPA. The resulting motions were input to the sun sensor simulation to determine if the sun tracking algorithm could stay in fine track mode, or lose lock and jump to coarse track mode. As expected, the jitter from the frequency-based analysis was worse than the time-based analysis due to the implied assumption that the disturbance frequencies lined up exactly with the modal frequencies. Even so, the worst-case result met the requirement of 35 arcsec peak-peak jitter. The sun sensor simulation showed that the algorithm would still remain in fine-track mode and not lose lock even under the worst-case condition. Actual on-orbit data is presented that verifies the validity of the analysis.

Space Dynamics Laboratory (SDL), in partnership with GATS, Inc., designed and built an instrument to conduct the Solar Occultation for Ice Experiment (SOFIE). SOFIE is an infrared sensor in the NASA Aeronomy of Ice in the Mesosphere (AIM) instrument suite. AIM's mission is to study polar mesospheric clouds (PMCs). SOFIE will make measurements in 16 separate spectral bands, arranged in 8 pairs between 0.29 and 5.3 μm. Each band pair will provide differential absorption limb-path transmission profiles for an atmospheric component of interest, by observing the sun through the limb of the atmsophere during solar occulation as AIM orbits Earth. The AIM mission was launched in April, 2007. SOFIE originally completed calibration and was delivered in March 2006. The design originally included a steering mirror coaligned with the science detectors to track the sun during occultation events. During spacecraft integration, a test anomaly resulted in damage to the steering mirror mechanism, resulting in the removal of this hardware from the instrument. Subsequently, additional ground calibration experiments were performed to validate the sensor performance following the change. Measurements performed in this additional phase of calibration testing included SOFIE end-to-end relative spectral response, nonlinearity, and spatial characterization. SDL's multifunction infrared calibrator #1 (MIC1) was used to present sources to the instrument for calibration. Relative spectral response (RSR) measurements were performed using a step-scan Fourier transform spectrometer (FTS). Out-of-band RSR was measured to approximately 0.01% of in-band peak response using the cascaded filter Fourier transform spectrometer (CFFTS) method. Linearity calibration was performed using a calcium fluoride attenuator in combination with a 3000K blackbody. Spatial characterization was accomplished using a point source and the MIC1 pointing mirror. These techniques are described in detail, and resulting SOFIE performance parameters are presented and compared to original SOFIE calibration results.

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, MAESTRO, provides spectrographic data from the near ultra-violet to the near infrared, including the visible spectral range. In combination, the instrument 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 (74⁰), 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 12^th, 2003. This paper presents the status of the ACE-FTS instrument, after four years on-orbit. On-orbit performance is presented. The health and safety status of the instrument payload is discussed. Optimization of on-orbit performance is presented as well as operational aspects. Aspects related to reliability of FTS are discussed as well as potential future follow-on missions.

Aquarius/SAC-D is a cooperative international mission conducted jointly by the National Aeronautics and Space Administration (NASA) of the United States of America (USA) and the Comisión Nacional de Actividades Espaciales (CONAE) of Argentina. The overall mission targets the understanding of the total Earth system and the consequences of the natural and man-made changes in the environment of the planet. Jointly developed by CONAE and the Canadian Space Agency (CSA), the New IR Sensor Technology (NIRST) instrument will monitor high temperature events on the ground related to fires and volcanic events, and will measure their physical parameters. Furthermore, NIRST will take measurements of sea surface temperatures mainly off the coast of South America as well as other targeted opportunities. NIRST has one band in the mid-wave infrared centered at 3.8 um with a bandwidth of 0.8 um, and two bands in the thermal infrared, centered respectively at 10.85 and 11.85 um with a bandwidth of 0.9 um. The temperature range is from 300 to 600 K with an NEDT < 0.5 K for the mid-infrared band and from 200 to 400 K with an NEDT < 0.4 K for the thermal bands. The baseline design of the NIRST is based on micro-bolometer technology developed jointly by INO and the CSA. Two arrays of 512x3 uncooled bolometric sensors will be used to measure brightness temperatures. The instantaneous field-of-view is 534 microradians corresponding to a ground sampling distance of 350 m at the subsatellite point. A pointing mirror allows a total swath of +/− 500 km. This paper describes the detailed design of the NIRST camera module. Key performance parameters are also presented.

In order to estimate and demonstrate the performance of Thermal And Near infrared Sensor for carbon Observation Fourier-Transform Spectrometer (TANSO-FTS) and Cloud and Aerosol Imager (TANSO-CAI) under the environmental condition on orbit, the Engineering Model (EM) for TANSO-FTS and CAI have been developed and demonstrated. The TANSO-FTS has three narrow bands detectable regions; 0.76, 1.6 and 2micrion (Band1, 2 and 3) with +/⊥2.5cm maximum optical path difference, and a wide band (5.5 − 14.3micron in thermal near infrared region. The TANSO-CAI is a radiometer of ultraviolet (UV), visible, and SWIR, which has 4 spectral band regions with 1 dimensional array CCDs. The initial performance tests have been carried out in the laboratory and the thermal vacuum chamber. The Signal to Noise Ratio (SNR), the polarization sensitivity (PS), Instantaneous Field Of View (IFOV) and response for FTS and CAI, and also the Instrumental Line Shape Function (ILSF) for FTS have been characterized in this test by introducing the light emitted from the black body, halogen lamp and the tunable diode laser. As a results of these experiments, it is appeared that the some modification of system for manufacturing the proto flight model (PFM) is required, and now in progressing. In addition to these characterizations, the newly developed tests, such as the stray light measurement and micro vibration test, are applied on TANSO-FTS to estimate the effect on orbit. These tests methods and results are presented in this paper.

In order to validate and calibrate the GOSAT satellite data, and also to develop the retrieval algorism for deriving the column density of CO₂ and CH₄ from spectra, the airborne SWIR (Short Wave Infrared Region) FTS (Fourier transform spectrometer) has been developed and characterized. This instrument is called as TSUKUBA model. The initial performance test of TSUKUBA model was carried out in our laboratory, and the measured modulation efficiencies are 70% (Band1), 85% (Band2) and 88% (Band3), respectively. The measured values of SNR with the equivalent black body temperature for 30% surface albedo are 190 (13050cm^-1), 148 (6200cm^-1), and 165 (5000cm^-1). The measured values of full width at half maximum (FWHM) of instrumental line shape functions are 0.38cm^-1, 0.26cm^-1, 0.25 cm^-1 for band 1, 2, and 3, respectively. The instrumental design and the results of performance tests are presented.

Greenhouse gases Observing SATellite (GOSAT) is designed to monitor the carbon dioxide (CO₂) and the methane (CH₄) globally from orbit and is scheduled to be launched in 2008. Two instruments are accommodated on GOSAT. Thermal And Near infrared Sensor for carbon Observation Fourier-Transform Spectrometer (TANSO-FTS) detects the Short wave infrared (SWIR) reflected on the earth's surface as well as the thermal infrared (TIR) radiated from the ground and the atmosphere. TANSO-FTS is capable of detecting wide spectral coverage, specifically, three narrow bands (0.76, 1.6, and 2 micron) and a wide band (5.5-14.3 micron) with 0.2 cm^-1 spectral resolution. As the second sensor, TANSO Cloud and Aerosol Imager (TANSO-CAI) is a radiometer of ultraviolet (UV), visible, and SWIR to correct cloud and aerosol interference. Since the contaminant deposition onto these optical sensors significantly affects the sensing capability, the spectroscopic contamination control over wide spectral range is exercised from the initial phase of GOSAT development to on-orbit operation. This paper presents overview of GOSAT contamination control plan and test results from contamination environment monitoring during thermal vacuum test using satellite system Structure and Thermal Model "STM". The result from on-going contamination environment monitoring of clean room at the spacecraft test and assembly building is also presented in launch site.

The Metop series of satellites constitutes the space segment for the EUMETSAT Polar System, the European contribution to the Initial Joint Polar System, being developed in co-operation with the National Oceanic and Atmospheric Administration (NOAA) of the USA, to provide meteorological data from the Polar Orbit. The first Metop satellite was launched on 19 October 2006 on a Soyuz launcher from the Baikonur Cosmodrome in Kazakhstan. Following the in-orbit commissioning of the spacecraft, Metop became the first European polar orbiting operational meteorological satellite. The Advanced Very High Resolution Radiometer (AVHRR), the High-resolution Infrared Radiation Sounder (HIRS) and the Advanced Microwave Sounding Unit-A (AMSU-A) instruments constitute the operational meteorological payload provided by NOAA that, in addition to the EUMETSAT provided Microwave Humidity Sounder (MHS), is flown on both, the NOAA Polar Orbiting Satellites (POES) and the EUMETSAT Metop satellites. Following the launch of Metop-A, an extensive in-orbit verification of the instruments was conducted with the involvement of EUMETSAT and NOAA/NASA as well as European and US Industry. In this paper the performance of the AVHRR, HIRS and AMSU-A instruments attained after the in-orbit verification of the Metop-A satellite is presented.

The Calipso mission aims to provide the geographic location, altitude and optical properties of cloud layers and aerosols to help scientists understand how they shape climate processes. The payload is composed of three instruments, a two-wavelength (532 nm and 1064 nm) polarization-sensitive backscatter Lidar, a Wide Field visible Camera (WFC) and the Imaging Infrared Radiometer (IIR). The satellite was launched on the 28th of April 2006. The IIR is an infrared three channel broadband radiometer which uses an uncooled infrared microbolometer detector. The use of this microbolometer technology allows the design of compact and low-consumption infrared instruments while providing acceptable radiometric performances. The IIR provides calibrated infrared radiances at three wavelengths (B1 : 8.2-9.1 μm - B2 : 10.3-10.9μm - B3 : 11.55- 12.55 μm), which will be combined with daytime and nighttime lidar measurements to retrieve radiative and microphysical parameters of clouds. This paper reminds of the Calipso mission goal, then describes the IIR instrument architecture and highlights its main features. It presents the performances achieved in flight by analysing the data provided by the IIR during checkout phase.

An MWIR TDI (Time Delay and Integration) Imager and Spectrometer (MTIS) instrument for characterizing from orbit the moons of Jupiter and Saturn is proposed. Novel to this instrument is the planned implementation of a digital TDI detector array and an innovative imaging/spectroscopic architecture. Digital TDI enables a higher SNR for high spatial resolution surface mapping of Titan and Enceladus and for improved spectral discrimination and resolution at Europa. The MTIS imaging/spectroscopic architecture combines a high spatial resolution coarse wavelength resolution imaging spectrometer with a hyperspectral sensor to spectrally decompose a portion of the data adjacent to the data sampled in the imaging spectrometer. The MTIS instrument thus maps with high spatial resolution a planetary object while spectrally decomposing enough of the data that identification of the constituent materials is highly likely. Additionally, digital TDI systems have the ability to enable the rejection of radiation induced spikes in high radiation environments (Europa) and the ability to image in low light levels (Titan and Enceladus). The ability to image moving objects that might be missed utilizing a conventional TDI system is an added advantage and is particularly important for characterizing atmospheric effects and separating atmospheric and surface components. This can be accomplished with on-orbit processing or collecting and returning individual non co-added frames.

Incontrovertible evidence of climate change and the underlying causes is necessary to inform public debate and to guide policy and economic decisions. To affect key societal decisions, this evidence must be obtained from measurements that are irrefutably tied to recognized international measurement standards. The International System of Units (SI) provides the appropriate measurement foundation for this application. The feasibility of achieving this objective and the resulting benefits to long-term climate forecasting are presented. The significant differences between realizing SI-traceability for space-based measurements and for laboratory measurements are detailed. An overview is presented of technological innovations in calibration standards and evolution in measurement approaches that define these new infrared standards. These include calibration blackbodies with built-in temperature standards and redundant sensors that admit new diagnostic tests of measurement uncertainty. An approach to rapid deployment is discussed, along with its resulting data product and benefits for long-term climate forecasting.

The calibration of infrared (IR) radiometers, thermal imagers and electro-optical systems relies on use of extended area blackbodies (BB) operating in the ambient environment. "Flat plate" designs, typically using a thermoelectric heat pump backed with an air- or liquid-cooled radiator, allow one to adequately meet the requirements of geometrical size and temperature span. The tradeoff comes in the form of limited temperature uniformity and lower emissivity that such an approach can provide given the limitations in achievable thermal conductivity of the plate and reflectance of the black paint, respectively. The availability of spectrally resolved radiance temperature data for infrared calibrators has become especially vital in the last few years with the widespread use of multi- and hyper-spectral electro-optical systems that enable better detection and identification of targets. In an effort to increase the measurement accuracy of IR spectral radiance of near-ambient BB calibrators, NIST has recently built a dedicated capability which is a part of its new AIRI (Advanced Infrared Radiometry and Imaging) facility. The Tunable Filter Comparator (TFC) is a key new element in this setup, allowing us to perform a precise comparison of the unit under test (UUT) with two reference blackbodies of known temperatures and emissivity. The report describes the major design features of the TFC comparator, the algorithm used for signal processing, and results of a performance evaluation of the TFC. The TFC development has enabled us to achieve BB radiance temperature comparisons with a standard deviation of 5 to 15 mK at temperatures of 15-150 C across the 3 to 5 µm and 8 to 12 µm atmospheric band ranges with a relative spectral resolution of 2 to 3%.

The ISI (Infrared Stellar Interferometer), an interferometer operating at mid-infrared wavelengths will be discussed, including both the instrumentation and results of stellar measurements. The ISI operates in the 10 micron wavelength region using three movable telescopes and heterodyne detection with CO₂ laser local oscillators. Phase closure allows rather complete imaging of stars and their dust shells, including measurement of asymmetries. Measurements have been conducted of the emission of material from stars, some ejected at very high velocity, the size and change of size of some stars, stellar ellipticity, and stellar asymmetry. Material blown off from stars is often emitted in periodic shells, and frequently asymmetric.

In order to best detect real changes in the Earth's climate system, it is estimated that in space based instrumentation measuring the Earth Radiation Budget (ERB) must remain calibrated with a stability of 0.3Wm⁻² per decade and reach an absolute accuracy of 1Wm⁻². Such stability is beyond that specified by existing ERB programs such as the Clouds and the Earth's Radiant Energy System (CERES, using three broadband radiometric scanning channels: the shortwave (SW 0.3−5um), Total (0.3− > 100um), and window (8−12um)). The CERES measurement of daytime outgoing longwave radiance (OLR) is obtained using subtraction of the SW channel signal from that of the co-aligned Total channel telescope. This requires precise balancing of the estimated response of the Total channel optics with those of the SW only channel when viewing daytime Earth scenes. Any post ground calibration contamination of Total channel optics that reduces its response to SW radiance can therefore upset this balancing process, introducing biases and trends in measurements of daytime LW radiance. This paper presents a new methodology used for balancing Total and SW channel spectral responses for all daytime Earth scenes using a model of contaminant spectral darkening. The results of the technique when applied to both CERES units on Terra are shown to remove significant trends and biases in measurements of daytime LW radiance.

The CERES Flight Model-1 and -2 instruments flew aboard the Terra into orbit in December 1999 and the FM-3 and -4 instruments flew on the Aqua spacecraft in May 2002. To date these instruments have provided seven years of measurements on Terra and five years on Aqua. The accuracy requirement for CERES is 0.5% for longwave radiances and 1.0% for shortwave. Achieving this objective is possible by using experience from the ERBE instrument to evolve the CERES design and the methods for analyzing the data. In order to achieve and maintain this accuracy, an internal calibration system and an attenuated view of the Sun are used. Subsequently, to validate that this accuracy has been achieved, a number of techniques have been developed which cover a range of temporal and spatial scales. This ensemble of methods provides a protocol which assures that the CERES measurements are of climate quality. In addition to retrieving fluxes at the top of the atmosphere, the CERES program uses data from other instruments aboard the spacecraft to compute the radiation balance at the surface and at levels through the atmosphere. Finally, the CERES data products are upgraded as higher-level data products show the need for revisions. The calibration stability is better than 0.2% and traceability from ground to in-flight calibration is 0.25%

We study the feasibility of using the fluorescence properties of the β-diketonate chelate europium (III) thenoyltrifluoroacetonate (EuTTA) in order to achieve IR-to-visible conversion. Previously, we studied the dependence of fluorescence power with temperature and suggested to use fluorescence properties of EuTTA in formation of thermal images. Here we propose to employ the correlation between two fluorescence parameters and the impinging IR radiation, in order to assess temperature distributions. We are developing a self-referenced system to convert infrared into visible radiation, employing EuTTA as the active medium of conversion. The operational principle of the proposed device is based on the variation of EuTTA fluorescence spectral power and lifetime with temperature. In this work, we perform a feasibility evaluation of the system, obtaining figures of merit of the proposed device, including sensitivity, noise, and thermal resolution.

We are interested in detecting planets around nearby stars by direct methods. Previously, we developed the radiometric and imaging conditions for detection of extra-solar planets. With star to planet irradiance factor of 10⁵, it appears that the interferometric method is the most likely to produce adequate signal. A rotational shearing interferometer (RSI) may be used to cancel the infrared radiation of the host star, allowing the detection of the planet. We have established the conditions for star-radiation cancellation with an RSI. Among these conditions, we have that the star must be on the optical axis, and that the phase difference between the interferometer arms must be π. Nevertheless, the ideal conditions are almost impossible to achieve. Therefore, we have analyzed the caused effect when we consider that the star is not on the optical axis, and an arbitrary phase difference is included. In this work, we extend the study considering the interferometer misalignments.

We are 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. We evaluated the change in the image quality introduced by this performance deterioration. In this work, we study the optical (angular) and the error-induced misalignments, caused by a real Dove prism, using exact ray trace. A Dove prism is aligned when the interferometer optical axis and the prism axis are collinear. We determine the tolerance to misalignment of the Dove prism for its incorporation in a Rotationally-Shearing Interferometer (RSI). We show that it is possible to reduce the wave-front deviation caused by base-angle errors with a specific optical misalignment. The misalignment analysis of a Dove prism, with an index of refraction of 1.515, shows that to ensure a maximum OPD of λ/10 (at 633 nm) the tolerance to misalignment must be ± 0.33 arc sec.

We have been working on improving several specific areas to make optical coherence tomography more efficient. First, we are using simultaneously a number of apertures in order to accelerate scanning over the object surface. Second, to increase the depth of use of the technique we devised ways of lengthening compensating path in one interferometer arm. In this work, we describe both of these techniques and their overall contribution to the performance improvements.

Oximetry is a technique to detect differential changes of oxygenation in hemoglobin. In previous work, we extended the classical mathematical model of oxygen saturation to reduce noise, to consider amplification parameters and detector's responsivity. We proposed a new expression for oxygen saturation in blood. This expression is less sensitive to noise, isolates the attenuation coefficients, is independent of multiplicative noise, and increases modulation. In the present work, we evaluate the feasibility of this new expression in thick tissue.

We examine the viability of implementing the Vectorial Shearing Interferometer (VSI) in order to determine the sphericity of a glass standard patron. We use the patron sphere as an optical component to collimate the expanded wave front of a laser. The collimated wave front impinges on the VSI. The resulting fringe pattern carries the phase gradient information of the original wave front, in the sheared direction. We estimate qualitatively the asphericity of the element under test, comparing the phase gradients in different sections of the sphere. When the gradients of two or more directions are identical, we consider that the standard patron has uniform sphericity. Here, we report on the experimental setup to test the asphericity, the experimental results, and perform comparison with theoretical calculations.

We study the viability of using scaled bodies to predict the heat distribution in tooth that are exposed to pulsed heat sources. We develop the scaling model with four scaling parameters. We used this model to simulate dental tissue ablation with Er:YAG laser. Good agreement between the simulated predictions and the published experimental results is found for low values of fluence, less than 100 J/cm².

We introduce the concept of tuning in the low-coherence trans-illumination interferometer to enhance its overall applicability (i.e., to enable selective diagnosis from different tissue regions). Modulation artifacts of the tuned interferometer are restricted to the reference arm. Displacements in this system, for pass-through photon-based modality, must be inverted. Tuning of specific radiation depends on modulation parameters and coherence-time gate. We propose to use Recurrence Plots and Recurrence Quantification Analysis (RQA) as a robust platform to identify different tuning states in the trans-illumination experiment. To the best of our knowledge, this is the first time that recurrence analyses are employed in trans-illumination studies. We suggest the quantitative metric of Determinism as a reference to assess the degree of tuning of the instrument. Theoretical results confirm that RQA may be useful for discriminating between different tuning states, including photon isolation for pass-through photon-based biomedical trans-illumination.

The sensitivity of a sensor system and its optical aperture size are two key parameters commonly used to characterize the performance of a remote sensing or space-borne surveillance system. In this work, a sensitivity model for space-borne staring IR sensor systems which are mainly used for point-source detection and identification is developed. Different noise components, including the photon noise from background radiation and near-field thermal radiation of optics, the electronic noise of sensors, as well as the nonuniformity noise of an infrared focal plane array (FPA), are considered. Based on the published parameters of the Multispectral Thermal Imager (MTI) electro-optic sensor system, the feasibility and validity of the model are demonstrated, with emphasis on the prediction of the cryogenic temperature impact on the sensor sensitivity and the optical aperture size requirement in a space-borne multispectral infrared (IR) system.