The Cross-track Infrared Sounder (CrIS) is one of the mission-critical instruments onboard the National Polar-orbiting Operational Environmental Satellite System (NPOESS). CrIS develops vertical profiles of moisture, temperature, and pressure in the earth’s atmosphere by measuring upwelling atmospheric infrared radiation at very high spectral resolution. This paper presents the current design status and performance projections of the CrIS instrument, which is approaching a Critical Design Review. Preliminary results from tests of an Engineering Development Unit will also be presented.

For the proper radiometric calibration of the CrIS sensor it is imperative to provide high quality characterizations of the ILS and the spatial response of the sensor. The methodology for determining the self-apodized ILS using both a laser and gas cell measurements is discussed with emphasis on the updates to the gas cell methodology. These methods for characterizing the self-apodized ILS have recently been exercised using the CrIS Engineering Development Unit. A description of the test configuration, data collection and data analysis is presented. Finally, the results are presented for the ILS determination are presented.

EarthCARE(Earth Clouds, Aerosols and Radiation Explorer) project is a candidate of the ESA (European Space Agency) Earth Explorer Core Missions. EarthCARE is the joint proposal between ESA, National Space Development Agency of JAPAN (NASDA) and Communications Research Laboratory (CRL). THe Phase-A study is started in NOvember 2001. The EarthCARE satellite has five sensors, CLoud Profiling Radar (CPR), ATmospheric LIDar (ATLID), Multi-Spectral Imager (MSI), Broad Band Radiometer (BBR) and Fourier Transform Spectromter (FTS). Main objective of EarthCARE FTS is to provide spectrally resolved outgoing radiance. Another objecitve of EarthCARE FTS is to retrieve temperature and water vapor profiles in clear air and above the clouds. NASDA is carrying out the Phase A study of EarthCARE. Preliminary Concept Review (PCR) was held at March 2003. We describe the objectives and instrument design concept of EarthCARE FTS in this paper.

An Internal Calibration Unit (ICU) has been designed, built, and tested to meet a stringent set of quantitative performance requirements for an infrared sensor in a Schmidt telescope configuration. The design concept is readily applicable to re-imaging telescopes. The design optimizes optics, source design, and power supply electronics for irradiance accuracy, repeatability, and uniformity, as well as power and weight.

The Wide Field-of View Imaging Spectrometer (WFIS) is a patented optical design allowing horizon to horizon imaging of the earth and earth’s atmosphere in the pushbroom-imaging mode from an aircraft or space platform. The design couples a fast, F/2.8, unobstructed all reflective telescope to an all-reflective three element imaging spectrometer using a unique field coupling mirror arrangement. Early laboratory demonstrations of the technology covered fields of view exceeding 70 degrees. The latest instrument, the incubator WFIS, demonstrate the field of view can be extended to 120 degrees. This paper summarizes the current ongoing work with the engineering model WFIS covering this field of view and a spectral range from 360 nm to 1000 nm. Also presented are the results of the latest laboratory and field demonstrations. The paper also identifies specific applications the technology is now addressing.

This paper presents the recent advance of our activity in the field of frequency selective surfaces (FSSs) for microwave and millimeter-wave applications. Both metal plates perforated periodically with holes (inductive FSSs) and periodic arrays of metal patches patterned on a dielectric substrate (capacitive FSSs) are presented. The analysis approach based on the MoM/BI-RME method is outlined, and some relevant structures are reported, for applications which span from large antennas for radio-astronomy to sub-millimeter wave scientific purposes.

Moving spot illuminated semiconductor panels are used as millimeter-wave image converters. To determine the performance of this system, it is required to know the response of illuminated semiconductor panels as a function of scanning velocity, width of the strip, time and so forth, is studied.

Developments in the area of signature suppression make it progressively more difficult to recognize targets. Due to the high resolution of modern sensors it is necessary to focus on a wide range of target and partial target sizes, i.e. small structures as well as the whole target. Measures of the difference between targets and background are crucial when assessing signature reduction efforts. These measures should to some extent be associated with the process of detection of targets in background. Two approaches are feasible, trying to simulate human performance or using an autonomous sensor. In both cases we have to rely on a set of features discriminating targets from the background. In the spatial domain we need filters on different scales. The smallest filter will not be able to catch statistical features but has to be based on the use of small image parts like blobs and lines. Larger filter will give statistically relevant feature values. In addition, spectral properties can be used in a multi-dimensional approach investigating targets on different scales, i.e. from very low-resolution to well-resolved objects. Experiments with a new set of features and the use of linear discriminant analysis to get overall signature assessment values are described.

Many studies, based mostly on ultra-sensitive length measurements, have revealed dimensional micro-instabilities in various optical materials. In some components, probe arrays and interferometric methods have also revealed changes in surface figure over time. Both types of measurements have shown that creep can be observed over periods of days, to months, and years. The typical asymptotic form of the aging curve points to the relaxation of structural or embedded stress. However, details of the mechanisms involved are not well understood. Additionally, the results of an interferometric study of an optical flat over a period of several years have provided some specific indicators for further studies in this area. For example, the extremely small change in shape of the surface was found to be rotationally symmetric, and hence apparently unrelated to the large amount of internal strain non-uniformly distributed throughout the flat substrate. This change in shape approached a limiting value after a period of eight years. The form of this curve suggests that the activation of the change was initiated at the time of the component fabrication, and not at the time of material manufacture. Some scenarios for possible sources of the observed change are discussed and some critical tests are suggested with the aim of clarifying the role of possible mechanisms responsible for long-term changes. Finally, a practical method for using an oil film as a reference standard of flatness in a Fizeau-type interferometer is presented.

Space-based experiments have contributed much to our knowledge of the stratosphere in recent years. These observations have been characterized by large horizontal or vertical scales, leaving a range of unobserved phenomena at smaller scales. This is especially true at the tropopause, the boundary between the troposphere and stratosphere, where rapid changes in the vertical in temperature and composition have been unobserved on a global basis. The HIRDLS instrument has been designed to address these issues. HIRDLS is a 21 channel limb scanning infrared radiometer designed to make global measurements at smaller vertical and horizontal scales than have been previously observed, from pole to pole, at altitudes of 8-80 km. This paper will present an overview of the HIRDLS science and instrument, as well as the data retrieval process. It will serve as an introduction to the series of subsequent papers dealing with the calibration and other aspects of the experiment.

The High Resolution Dynamics Limb Sounder (HIRDLS) instrument is scheduled for launch on the NASA AURA satellite in January 2004; it is a joint project between the UK and USA. HIRDLS is a mid-infrared limb emission sounder which will measure the concentration of trace species and aerosol, and temperature and pressure variations in the Earth's atmosphere between about 8 and 100 km altitude on a finer spatial scale than has been achieved before. This will depend upon both a high quality of instrument build, and very precise pre-launch calibration. Proto Flight Model calibration was performed in a purpose-built laboratory at Oxford University during an 13-week period in 2002. The tests were made in vacuum under cryogenic conditions close to the space environment. The measurements were divided into spectral, spatial and radiometric, with the HIRDLS pointing capability being used to control which item of test equipment was viewed. A large degree of automation was achieved, and this combined with 24-hour/7-day working enabled a large quantity of information to be obtained.

A state-of-the-art calibration facility was designed and built for the calibration of the HIRDLS instrument at the University of Oxford, England. This paper describes the main features of the facility, the driving requirements and a summary of the performance that was achieved during the calibration. Specific technical requirements and a summary of the performance that was achieved during the calibration. Specific technical requirements and other constaints determined the design solutions that were adopted and the implementation methodology. The main features of the facility included a high performance clean room, vacuum chamber with thermal environmental control as well as the calibration sources. Particular attention was paid to maintenance of cleanliness (molecular and particulate), ESD control, mechanical isolation and high reliability. Schedule constraints required that all the calibration sources were integrated into the facility so that the number of re-press and warm up cycles was minimized and so that all the equipment could be operated at the same time.

The techniques used to calibrate the field of view of the High Resolution Dynamics Limb Sounder (HIRDLS) instrument and the results of the calibration are presented. HIRDLS will be flown on the NASA EOS Aura platform. Both in-field and out-of-field calibrations were performed. The calibration results are compared to the requirements and, in the case of out-of-field, mechanisms explaining the results are discussed.

A specially designed and built monochromator was developed for the spectral calibration of the HIRDLS instrument. The High Resolution Dynamics Limb Sounder (HIRDLS) is a precision infra-red remote sensing instrument with very tight requirements on the knowledge of the response to received radiation. A high performance, vacuum compatible monochromator, was developed with a wavelength range from 4 to 20 microns to encompass that of the HIRDLS instrument. The monochromator is integrated into a collimating system which is shared with a set of tiny broad band sources used for independent spatial response measurements (reported elsewhere). This paper describes the design and implementation of the monochromator and the performance obtained during the period of calibration of the HIRDLS instrument at Oxford University in 2002.

Results from a pre-launch in-band spectral characterization of the 21-channel HIRDLS flight instrument will be presented. These data were obtained during a pre-launch calibration of HIRDLS at Oxford University (Fall 2002). A monochromator, equipped with a controllable diffraction grating, was used to produce monochromatic light for these tests. The monochromator was enclosed, with HIRDLS, in a large vacuum chamber. The monochromator was also equipped with a polarizer, which allowed for data to be procured at known orthogonal polarizations for each channel. A calibration detector, with a flat spectral response, was used to monitor the output from the monochromaotr. This report will consist of a description of the analyiss methodlogy, leading to an unpolarized instrument spectral response function for each channel.

The pre-launch calibration of the HIRDLS instrument took place in a dedicated facility at the University of Oxford. One aspect of this calibration was the determination of the response of the instrument to black body radiation. This was achieved with the use of purpose built full aperture black body targets which were mounted in the vacuum chamber together with all of the calibration equipment. Special attention was placed on the absolute knowledge of the emission from these targets. This was done through a combination of thermometric sensor calibration traceable to the International Temperature Standard (ITS-90), surface emission measurements, cavity design and modeling and controlling the stray light sources in the vacuum chamber. This paper describes the design requirements, implementation and performance achieved.

Results from a pre-launch radiometric calibration of the 21-channel HIRDLS instrument will be presented. These data were obtained during a pre-launch calibration of HIRDLS at Oxford University (Fall 2002). Two external blackbody cavities were used to generate temperatures between ~90 K to ~320 K. These blackbodies were located, along with HIRDLS, inside a large vacuum chamber. Data were taken at three different focal-plane temperatures (61 K, 66 K, and 71 K). This paper will cover a variety of details; such as, data--taking procedures, analysis methodology, and the resulting linearity analyses.

The High Resolution Dynamics Limb Sounder (HIRDLS) instrument is scheduled for launch on the NASA AURA satellite in January 2004; it is a joint project between the UK and USA. HIRDLS is a mid-infrared limb emission sounder which will measure the concentration of trace species and aerosol, and temperature and pressure variations in the Earth's atmosphere between about 8 and 100 km altitude on a finer spatial scale than been achieved before. HIRDLS has particularly stringent radiometric calibration accuracy requirements. A warm (280-300K) 'In-Flight Calibrator' (IFC) black cavity within the instrument plus a view to cold space are used to perform radiometric calibration. The cavity has an entrance aperture which is much smaller than the full beam size, and it is viewed through a focusing mirror. The cavity and focusing mirror are ideally maintained at the same temperature but differences of up to 1 C may exist, in which case a correction utilising the mirror emissivity can usefully be made. That emissivity has been measured at instrument level during pre-launch calibration by viewing an external target at the same temperature as the IFC while varying the calibration mirror temperature.

Requirements, performance and life-test results are presented for the optical chopper installed in the High-Resolution Dynamics Limb Sounder (HIRDLS) to be flown on the AURA mission of the NASA Earth Observing System (EOS). Optical chopping is essential in order to achieve the required sensitivity and accuracy in measurement of infrared emission from various chemical species in the earth's atmosphere. Chopping of the optical input as far forward in the telescope as practical minimizes calibration errors arising from variations in emission from warm optics and due to electronic drifts in the infrared detecting system. At 500 Hz, a reflective chopper blade is used to alternate the instrument view between the atmospheric limb and cold space. The HIRDLS chopper is a six-toothed, mirrored wheel driven by a brushless DC motor. Chopper design was driven by requirements of 1) continuous operation at 5000 RPM for 50,000 hours in space vacuum, 2) chopping amplitude stability of one part in 100,000, 3) lubricant loss control for both bearing reliability and prevention of optics contamination, 4) compact size to fit in the folded telescope, and 5) survival in the launch environment.

In the development and test of the High-Resolution Dynamics Limb Sounder (HIRDLS) instrument, it was necessary to create automated test and operational procedures in several different System Test and Operational Languages (STOLs). The methodology selected utilized different conversion programs to generate automated test scripts in each STOL. This resulted in working scripts with minimal manual revision necessary.

The Mid-Infrared Instrument (MIRI) and the Near-Infrared Spectrograph (NIRSpec) of the JWST require various mechanisms for positioning optical elements in cryo-vacuum environment (7K resp. 35K): Wheels for exchanging filters, gratings and prisms, a flip mirror for switching between the sky and internal calibration sources and a linear actuator for refocusing purposes will have to be developed. In order to fulfill the stringent requirements of the mission, comprising to survive a warm ARIANE 5 launch, to guarantee high accuracy positioning in the cryovacuum with minimal power dissipation, to be operational with high reliability during 10 years of lifetime and to be testable under various environmental conditions, we propose a low cost and low schedule risk approach, based on the successful flight experience and qualification heritage from ESA’s infrared missions ISO and HERSCHEL.

The Cologne spectrometer THIS (Tuneable Heterodyne Infrared Spectrometer) opens the mid-infrared wavelength region from 5 to 17 µm for ultra-high-resolution spectroscopy. With a current bandwidth of 14 km/sec and a frequency resolution of R=2*10⁷ it is the only widely tuneable and transportable infrared heterodyne receiver. A Quantum-Cascade laser is used as local oscillator (LO). To provide optimum beam combination a Fabry-Perot ringresonator is used to superimpose the LO and the radiation. Frequency mixing is done by a Mercury-Cadmium-Telluride photomixer and spectral analysis is performed by an Acousto-Optical spectrometer. The system noise temperature is about three times the quantum limit giving THIS a sensitivity equivalent to CO₂-laser based heterodyne systems. Various measurements at different ground based telescopes including the analysis of trace gases in Earth's atmosphere, observations of molecular features in sunspots, and detection of non-LTE CO2 emission from the atmosphere of Venus' have been performed and demonstrate the instrument's capabilities for astronomical observations at ground based telescopes and the stratospheric observatory SOFIA in the near future. Possible targets for future observations with THIS will be discussed.

We have developed a theoretical model which allows us to retrieve the temperature of burning areas employing the thermal infrared spectral-radiance data gathered by the used sensor. The algorithm performs the temperature-emissivity separation by coupling together radiance data from a pair of neighbouring similar image pixels, which are assumed to have the same emissivity spectrum and independent temperatures. The characteristic uncertainty in the basic thermal infrared equations is thus resolved using a double number of spectral measurements (radiance samples) for the temperature estimation. Results produced by this model have been compared with fire-front temperatures assessed utilising spectral data collected at short-wave infrared wavelengths between 1.99 μm and 2.48 μm. Moreover, we have also applied the GBE-method for retrieving the pixel temperature and spectral emissivity utilising thermal infrared spectral data. In order to test the three considered methods, we have utilised a rare example of airborne hyperspectral image acquired over a natural active fire. This image was collected by the MIVIS operated on board of a Casa 212 airplane over the Alps (Italy). The paper shows the image acquired by the MIVIS sensor, the related processing and is completed with a theoretical discussion of the involved topics.

The first Meteosat Second Generation (MSG) satellite was launched in August 2002. This EUMETSAT satellite carries 2 new instruments on the geostationary orbit: the Spinning Enhanced Visible and InfraRed Imager, SEVIRI, and the Geostationary Earth Radiation Budget, GERB. The unique feature of GERB in comparison with previous measurement missions of the Earth's radiation budget (e.g. ERBE, ScaRab and CERES experiments) is the high temporal sampling afforded by the geostationary orbit, albeit for a limited region of the globe. The GERB instrument provides accurate broadband measurements of the radiant energy originating in the reflection of the incoming solar energy by the Earth-atmosphere system and in the thermal emission within this system. The synergetic use of the SEVIRI data is needed to convert these directional measurements (radiances) into radiative fluxes at the top-of-atmosphere. Additionally, the SEVIRI data allows the enhancement of the spatial resolution of the GERB measurement. This paper describes the near real-time GERB processing system that has been set up at the Royal Meteorological Institute of Belgium (RMIB). This includes the unfiltering of the instrument data, the radiance-to-flux conversions and the enhancement of the instrument spatial resolution. An early validation of the instrument data by comparison with CERES data is presented. Finally, the different data formats, the way to access them and their expected accuracy are presented.

The Stratospheric Observatory for Infrared Astronomy (SOFIA) will carry a 2.5 meter effective aperture telescope onboard a Boeing 747SP aircraft to altitudes of 41,000 to 45,000 ft, above most of the atmosphere's IR-absorbing water vapor. SOFIA will start its astrophysical observations in early 2005, flying from Moffett Field, California with a suite of specialized cameras and spectrometers covering wavelengths between 0.3 and 600 m. A high-speed visible range CCD camera will use the airborne observatory to chase the shadows of celestial bodies during occultations. The SOFIA telescope was designed and built in Germany and has been delivered to the U.S. in September 2002. Its integration into the B747SP is well advanced so flight-testing will start in mid of 2004. After an initial test phase dedicated to the re-certification of the modified aircraft, functional and performance tests of the telescope and other scientific systems will commence. At NASA's Ames Research Center the ground support facilities for the observatory are being prepared.

We present imagery taken with a quantum well infrared photodetector (QWIP) dual-band infrared (IR) focal plane array (FPA) of the inaugural launch of the Atlas 5 launch vehicle. The FPA was developed under the Army Research Laboratory's Advanced Sensors Federated Laboratory program and used a read-out integrated circuit produced under the Air Force Research Laboratory's Advanced Multi-Quantum Well Technology program. The detectors are able to sense light in both the 3-5 micron (MWIR) and 8-12 micron (LWIR) atmospheric transmission windows such that the resulting LWIR and MIWR images are pixel registered and simultaneous. The FPA was installed in a camera system that used a closed-cycle cooler to operate at 60 K. The camera was placed at the prime focus of an all-reflective telescope on a computer-controlled tracking mount at the Innovative Sensor Technology Evaluation Facility (ISTEF) at the Kennedy Space Center. The launch was observed from ISTEF at a distance of 15 km from the pad. Before and after the launch, The FPA/camera system was calibrated using standard blackbody sources. The launch vehicle was observed from about 30 s after launch until approximately 4 minutes after launch. This corresponded to ranges between 15 km and more than 300 km and altitudes from just over 1 km to more than 100 km. Several interesting differences in the structure of the plume were observed. In addition, the hardbody of the rocket was seen in the LWIR imagery but was undetectable in the MWIR imagery. The imagery was unsaturated in both bands allowing us to obtain good measurements of the radiance of the plume in both the MWIR and LWIR bands.

Short wavelength infrared (SWIR) photovoltaic diode structures made of InGaAs material were grown on GaAs by means of molecular beam epitaxy. Growth quality and composition of the layers are determined by HRXRD. The electrical characterization is performed by Current-Bias characterization (proposal) and spectral resolved measurements to determine the resistance area product (R0A) and the spectral responsivity (R) of diodes. The processing is performed with standard photolithography and micro-structuring techniques aiming at the production of 1D and 2D infrared camera arrays. The diced IR sensor is flip chip assembled on a Silicon read out integrated circuit (ROIC). Linear arrays of 256 pixels with 25 μm pitch were fabricated as well as focal plane arrays (FPA) of 256 × 320 pixel with 30 μm pitch. Measures of electrical interconnection yield will be shown. Functionality is proven for different applications up to 2.5 μm wavelength.

A 640×512 pixel, long-wavelength cutoff, narrow-band (Δλ/λ~10%) quantum well infrared photodetector (QWIP) focal plane array (FPA), a four-band QWIP FPA in the 4-15 μm spectral region, and a broad-band (Δλ/λ~42%) QWIP FPA having a 15.4 μm cutoff have been demonstrated. In this paper, we discuss the electrical and optical characterization of these FPAs, and their performance. In addition, we discuss the development of a very sensitive (NEDT~~10.6 mK) 640×512 pixel thermal imaging camera having a 9 μm cutoff.

A major concern today is to accurately measure CO₂, O₃, H₂O, and CH₄ in the atmosphere for the prediction of climate and weather. These measurements are critical for understanding the Earth's atmosphere, atmospheric chemistry, and systemic forcing driving climactic changes. For these measurements, detectors with high quantum efficiency and near background limited performance detectivity over a wide wavelength range are necessary. In this article, we will review the state-of-the-art single and multicolor detector technologies in a wide spectral-range, for use in space-based and airborne remote sensing applications. Simultaneous detection in multi-wavelength bands with a single focal plane array (FPA) will result in reduction or elimination of heavy and complex optical components now required for wavelength differentiation in atmospheric remote sensors leading to smaller, lighter, simpler instruments with higher performance. Discussions are focused on current and the most recently developed FPA in addition to emphasizing future development in UV-to-Far infrared multicolor FPA detectors for next generation space-based instruments to measure water vapor and greenhouse gases. This novel detector component will make instruments designed for these critical measurements more efficient while reducing complexity and associated electronics and weight. Finally, we will discuss the on-going detector technology efforts at NASA Langley Research Center (LaRC), Jet Propulsion Laboratory (JPL), and Rensselaer Polytechnic Institute (RPI).

We have observed, for the first time, microwave-assisted photoconductivity in high purity GaAs. The enhancement of response appears to be dictated by two distinct mechanisms. First, a broadband enhancement which is believed to be due to detrapping of the free carriers and, therefore, increased photoconductive gain. Secondly, microwave-ionization of the excited states. We expect that both of these mechanisms contribute very little, if any, to the detector noise and, therefore, improve the detector's NEP. In this paper, we report the results of our preliminary tests showing broadband enhancement in response and an indication of enhancement of the excited-state response. Further investigation is currently underway.

FireMapper^®2.0 is a second-generation airborne system developed specifically for wildfire mapping and remote sensing. Its design is based on lessons learned from two years of flight-testing of a research FireMapper^® system by the Pacific uthwest Research Station of the USDA Forest Service. The new, operational design features greater coverage and improved performance with a rugged sensor that is less than one third the size and weight of the original research sensor. The sensor obtains thermal infrared images in two narrow spectral bands and one wide spectral band with the use of a single uncooled microbolometer detector array. The dynamic range of the sensor is designed to accurately measure scene temperatures from normal backgrounds, for remote sensing and disaster management applications, up to flaming fronts without saturating. All three channels are extremely linear and are calibrated in-flight with a highly accurate absolute calibration system. Airborne testing of the research system has led to improved displays and simplified operator interfaces. These features facilitate the operational use of the FireMapper^®2.0 system on both fixed wing aircraft and helicopters with minimal operator inputs. The operating system features custom software to display and zoom in on the images in realtime as they are obtained. Selected images can also be saved and recalled for detailed study. All images are tagged with GPS date, time, latitude, longitude, altitude, and heading and can be recorded on a portable USB hard drive upon operator command. The operating system can also be used to replay previously recorded image sequences. The FireMapper^® 2.0 was designed and fabricated by Space Instruments, Inc. as part of a Research Joint Venture with the USDA Forest Service.

In the Advanced Detectors Research Group within the Space-Based Optical Sensing Center of Excellence in the Spacecraft Technology Division of the Air Force Research Laboratory’s Space Vehicles Directorate, we look to enhance existing detector technologies and develop new detector capabilities for future space-based surveillance missions. To that end, we present some ideas for tuning the wavelength response of detectors throughout the IR (using applied electric or magnetic fields or via a lateral biasing technique). We also present a concept for detecting the full polarization vector of a signal within a single pixel of a quantum well detector.

We study the feasibility of using decay-time measurements in order to develop a temperature sensor superior to the intensity-based one. We measured the fluorescence output of erbium-doped silica fiber segment upon pumping with 980-nm radiation. For low pumping powers (from 4 mW to 10 mW, in our case), the fluorescence power increases rapidly with pumping power. At an intermediate pumping power that depends on fiber dopant concentration and fiber geometry, the fluorescence power starts to saturate, approaching asymptotically the saturation value. We also report that the time constant of transition from excited level 4I13/2 to ground level 4I15/2 depends on the pumping power.

We use the modulation transfer function (MTF) to evaluate the performance of several multi-aperture interferometric configurations for the detection of a faint planet in the vicinity of its bright star. We design non-redundant interferometric layouts that provide satisfactory coverage of the spatial frequencies of interest. We propose a design incorporating a rotating, rotationally shearing interferometer in a gravity-free environment. The side peak of its MTF may be centered on the spatial frequency associated with likely planet coordinates, resulting in the planet signal enhancement and isolation.

A compact, aberration-selective, reversal interferometer with variable rotational shearing of wave front is described. It is constructed with only two beam-splitter cubes, each one with one face aluminized, cemented together, and mounted in a rotary holder. This interferometer is quite insensitive to vibrations, because the wave fronts pass only through the cemented cubes to generate the interference pattern. All the rotationally symmetric aberrations are removed and the asymmetrical ones can be selectively isolated with an appropriate rotation of the cubes. The variable shearing angle is shown to control the sensitivity for detection of rotationally asymmetric aberrations like coma and tilt.

We describe the rotationally shearing interferometer (RSI) employing modified Dove prisms, designed with a widened aperture to increase throughput and with larger base angles to minimize the wave-front tilt introduced due to manufacturing errors. Experimental results obtained with the RSI ascertain the feasibility of the design. This work demonstrates that the rotationally shearing interferometry may be used to perform some functions of the traditional astronomical instruments.

Fourier transform spectrometer (FTS) has fast optics, and it can realize high resolution within the range from visible light to thermal infrared radiation. FTS intrinsically has the problem that it takes long time to obtain spectrum, because it needs mechanical scanning. But we developed spaceborne FTS system which has the ability of high speed scanning and data handling. By high speed scanning, FTS makes it possible to have high altitude resolution in occultation, and imaging in nadir observation.

We describe experimental results demonstrating the performance of the erbium-doped silica fiber as a remote temperature sensor in the temperature interval [21 C - 96 C]. We present the measured fluorescence spectrum corresponding to the energy levels ²H_11/2 and ⁴S_3/2. This sensor incorporates simple signal detection in a band and data analysis system, incorporating a power ratio to reduce noise effects. We find the channel responsivity, the power ratio, and the sensitivity for a number of possible filters. The best responsivity is above 0.2μW/C, and its sensitivity is 0.0065 C^-1 with the filters transmitting in the [527 nm - 537 nm] and [545 nm - 555 nm] spectral bands. With a custom-made filter, centered on 545 nm, even higher sensitivity is predicted.

We present a design concept for a new state-of-the-art balloon borne atmospheric monitor that will allow enhanced limb sounding of the Earth's atmosphere within the submillimeter and far-infrared wavelength spectral range: TELIS, TErahertz and submm LImb Sounder. The instrument is being developed by a consortium of major European institutes that includes the Space Research Organization of the Netherlands (SRON), the Rutherford Appleton Laboratory (RAL) will utilize state-of-the-art superconducting heterodyne technology and is designed to be a compact, lightweight instrument cpaable of providing broad spectral coverage, high spectral resolution and long flight duration (~24 hours duration during a single flight campaign). The combination of high sensitivity and extensive flight duration will allow evaluation of the diurnal variation of key atmospheric constitutenets sucyh as OH, HO2, ClO, BrO togehter will onger lived constituents such as O₃, HCL and N₂O. Furthermore, TELIS will share a common balloon platform to that of the MIPAS-B Fourier Transform Spectrometer, developed by the Institute of Meteorology and Climate research of the over an extended spectral range. The combination of the TELIS and MIPAS instruments will provide atmospheric scientists with a very powerful observational tool. TELIS will serve as a testbed for new cryogenic heterodyne detection techniques, and as such it will act as a prelude to future spaceborne instruments planned by the European Space Agency (ESA).

A segmented or diluted aperture optical system will undergo phase errors due to errors in the positing of the segments. The errors associated with a segmented primary mirror limit the image quality obtainable with the synthetic aperture telescopes. Here, we study the effects of segmentation errors on image quality considering both the phase angle and amplitude of the OTF. We show that, in these kind telescopes, the phasing and alignment errors among segments reduce the amplitude and distort the phase angle of the OTF.

We study the feasibility of using decay-time measurements in order to develop a temperature sensor superior to the intensity-based one. We measured the fluorescence output of erbium-doped silica fiber segment upon pumping with 980-nm radiation. For low pumping powers (from 4 mW to 10 mW, in our case), the fluorescence power increases rapidly with pumping power. At an intermediate pumping power that depends on fiber dopant concentration and fiber geometry, the fluorescence power starts to saturate, approaching asymptotically the saturation value. We also report that the time constant of transition from excited level ⁴I_13/2 to ground level ⁴I_15/2 depends on the pumping power.