Japanese remote sensor ASTER was successfully launched on the NASA's Satellite Terra on December 18, 1999 by the cooperation between METI and NASA HQ, and ASTER is working without any major problems and continues to provide ASTER data. This is a result of the cooperation between US and Japan, especially ASTER Science Team, NASA GSFC, JPL, JAROS and ERSDAC. After the period of the Initial Checkout, ASTER GDS started ASTER data distribution to the public, and ASTER data is currently available without any restriction. In this paper, activities of ASTER operation and some scientific results are provided.

The author proposes a method to estimate two dimensional spatial distribution of volcanic SO₂ using a multispectral scanner in thermal infrared region. Volcanic SO₂ flux can be estimated from the spatial distribution of SO₂ and the plume flow velocity. As ASETR has both Thermal Infrared Radiometer (TIR) and nadir-backward stereoscopic viewing function, we can estimate volcanic SO₂ flux by ASTER data alone. These methods are applied to the Oyama volcano in Miyakejima, Japan. SO₂ flux derived from ASTER is 3 - X 104⁴, which is slightly larger than one derived from COSPEC.

Land Surface Emissivity product is one of standard products generated from Advanced Space borne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite launched in December 1999. This product is important for detailed lithologic mapping and precise land surface temperature determination. The accuracy of ASTER-derived emissivity is a function of various factors such as radiometric calibration of the instrument, assumptions used in a temperature-emissivity separation algorithm, and spatial temperature/material mixture in a pixel. In this study, the effects of spatial material mixture on ASTER-derived emissivity are investigated as one of the validation activities of this product. First, the mixture effects on ASTER-derived emissivity are evaluated through numerical simulations under various land surface material and temperature conditions. Also, at several sites including Cuprite, Nevada, ASTER-derived emissivity and airborne sensor-derived emissivity are compared. Applications of ASTER emissivity products to environmental and geologic studies will be also presented.

The ASTER SWIR radiation characteristics are evaluated when it decreases with increasing a distance from the edge. This phenomena is known as cross-talk due to a structure of the ASTER SWIR sensor. Similar characteristics is known as an adjacency effect due to atmosphere surface. In this paper, a possible contribution of adjacency effect is discussed at SWIR channels in conjunction with cross-talk phenomena. ASTER and MISR on Terra satellite adopted the dust-like aerosol model. Therefore, the aerosol model is in accordance to this model. The radiation characteristics at bands, 4(1.65 micrometers ), 5(2.165 micrometers ) and 9(2.395 micrometers ) on the sample data over Cape Atsumi peninsula near Nagoya indicates cross talk phenomena due to a structure of the ASTER SWIR sensor. It would not be due to the adjacent effect. A further sample data analysis is required.

The mechanism of the crosstalk phenomena in the ASTER/SWIR subsystem, which has six bands in the wavelength of 1.6 - 2.43 micrometers region, is investigated. It is found that the incident light to a detector array of the band 4 of the SWIR subsystem is reflected at an electrical wiring at the focal plane. It is transported to detectors of other bands by multiple reflections through the bandpass filter in front of detectors. By analyzing SWIR images around islands and peninsulas, crosstalk components in images are estimated. For this purpose, the crosstalk correction software is developed. Parameters of the crosstalk phenomena, i.e., the amount of stray light and the influential area of stray light, are determined by image analysis. It is found that the spectral separation performance of the SWIR subsystem is enhanced using the correction software in this study, which leads to more accurate spectral studies of SWIR images and is promising in exploiting natural resources.

The standard atmospheric correction algorithm for five thermal infrared (TIR) bands of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is currently based on radiative transfer computations with global assimilation data on a pixel-by-pixel basis. In the present paper, we verify this algorithm using 100 ASTER scenes globally acquired during the early mission period. In this verification, the max-min difference (MMD) of the water surface emissivity retrieved from each scene is used as an atmospheric correction error index, since the water surface emissivity is well known; if the MMD retrieved is large, an atmospheric correction error also will be possibly large. As the results, the error of the MMD retrieved by the standard atmospheric correction algorithm and a typical temperature/emissivity separation algorithm is shown to be remarkably related with precipitable water vapor, latitude, elevation, and surface temperature. It is also mentioned that the expected error on the MMD retrieved is 0.05 for the precipitable water vapor of 3 cm.

A brief introduction to SOFIA will be given with an outline of its planned investigator program, followed with a summary of the expected performance capabilities of SOFIA at first light. The remainder of the paper will then give examples of SOFIA science to be expected from science instruments to be commissioned on the observatory within the first year os operation.

The SOFIA is a major milestone in the prospering wavelength range of the IR. As a successor of the tremendously successful Kuiper Airborne Observatory it will be the biggest astronomical airborne observatory ever hilt, comprising a 3m-class telescope onboard a Boeing 747SP. Presented in an overview on the telescope as the heart of SOFIA, and discussion of some of the requirements; description of the optical and mechanical design and give an update on the current status of construction.

The SOFIA Airborne Observatory will operate a 2.5 m aperture telescope with the goal of obtaining over 960 successful science hours per year at a nominal altitude of 12.5 km and covering a wavelength range from 0.3 mm to 1.6 mm. The observatory platform is comprised of a Boeing 747SP with numerous significant modifications. The ground and flight mission operations architectures and plans are tailored to keep the telescope emissivity low and achieve high observing efficiency.

The Stratospheric Observatory for Infrared Astronomy (SOFIA) will operate from NASA's Ames Research Center in Moffett Field, CA. To insure that the observatory's objective of conducting at least 960 successful science flight hours per year will be met, a ground support facility called SOFIA Science and Missions Operation Center (SSMOC) is being developed. This new science institute will be located in an aircraft hangar housing the Boeing 747SP, laboratories supporting the aircraft and its scientific payload, and office space for 80 scientists, engineers, technical support personnel, and the flight crews. The SSMOC will include a mirror coating facility, a pre-flight integration facility for the pre-alignment of science instruments, a system integration laboratory supporting the observatory's software, communications and data acquisition systems, a science data center, and facilities for SOFIA's education and public outreach program. SOFIA and the SSMOC will be jointly operated by the U. S. and German project partners.

In May 2001 was planned to launch the small satellite BIRD, but the launch was shifted to August/September 2001. The main payload is dedicated to the observation of high temperature events and consists mainly of a Bi-Spectral IR Push Broom Scanner and a Push Broom Imager in the Visible. Solid state detector arrays with adaptive high dynamic front end electronics and advanced digital signal processing capabilities are the key element of IR imaging devices. With respect to the main mission objectives besides the high radiometric requirements to the detectors their mutual geometrical alignment is essential. The main problem of the radiometric calibration is the required high dynamic range which makes necessary to consider the non linear characteristic of the detector elements. On the other hand the application of special bi-spectral methods requests a carefully geometrical calibration. Besides the alignment of the different spectral channels the knowledge of the PSF is necessary. The laboratory radiometric and geometrical calibration procedures are described in this paper.

The AIRS is a grating spectrometer deisgne4d to obtain high- resolution absorption spectra form the atmosphere. The AIRS instrument is scheduled for launch in late 2001 or early 2002 on the Earth Observing System Aqua platform. The primary scientific objectives of AIRS are to investigate the dynamics of the atmosphere, to look for climatological changes, and to improve weather prediction. These investigations will be carried out on a global scale. The instrument acquires data in the spectral range of 3.5 micrometers to 15.4 micrometers using 2378 IR spectral channels. In addition four medium to broad band visible and near-IR channels are primarily used for diagnostics involving the presence and extent of clouds.

The CRyogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) instrument measured atmospheric trace gas emissions in the infrared using the limb scanning technique. For the first time three viewing directions were used by a satellite instrument in near-earth orbit (300 km) to obtain an unprecedented spatial density of the daily global measurement net. The high measurement speed needed for an enhanced horizontal resolution was achieved by cooling the instrument with supercritical and subcooled helium and by using Si:Ga bulk or Si:As blocked impurity band (BIB) detectors for the wavelength range 4-17 micrometers and Ge:Ga bulk detectors for longer wavelengths. The detectors were operated at temperatures between 2.5 and 13 Kelvin. Under these conditions the signal of the detectors shows non-stationary effects (relaxation effects) degrading measured spectra to some extent.These effects are difficult to account for as they can only be described by using at least 6 parameters depending on signal height and illumination history. In this paper an empirical model to correct the non-stationary effects of the Si:Ga detectors is presented. The model is based on measured signal responses after step-like illumination changes. Several tests using different data sets show that the model works well under various conditions.

The Measurements Of Pollution In The Troposphere (MOPITT) instrument is one of five instruments flying on NASA's Terra (formerly EOS-AM1) spacecraft that was launched in December 1999. This paper describes the MOPITT instrument mechanical configuration and how it was derived based on system considerations and spacecraft interfaces. These system level considerations include contamination control, EMC/EMI, thermal, optical and structural behavior. The key spacecraft interfaces include mechanical mounting, optical field-of-view (FOV), and thermal transfer. In addition, a detailed discussion is provided for the cryogenic region of the instrument that contains detectors, cold optics, warm optics, and active coolers. Special test fixtures were designed and incorporated in this region of the instrument to permit cooling of the detectors during ambient atmospheric conditions. Some of these test fixtures were designed to fly due to the difficulty in removing them. This utility of operating the instrument's cryogenic detectors within the laboratory environment was extremely beneficial during the instrument optical alignment, EMC testing, and special optical system tests. Final configuring (or closeout) of the instrument's cryogenic region for flight was performed to balance contamination and EMC risks. On-orbit data about the effectiveness of this closeout is provided.

The MOPITT instrument operates on the principle of correlation spectroscopy where the incoming signal is modulated by gas filter and chopper mechanisms and synchronously demodulated within the signal processing system. The performance and flexibility required by the MOPITT instrument resulted in the development of a novel timing control and signal processing design. This design synchronizes modulation and demodulation from a central programmable timing control unit. The data collection system performs a highly linear sigma-delta analog-to-digital conversion prior to signal demodulation. The demodulation operation includes data averaging which reduces the sampled signal bandwidth and extends the signal to noise ratio of the data to in excess of the analog-to-digital converter's rated 16-bit dynamic range.

Large, greater than about 1 Ghz, bandwidth acousto-optical spectrometers are based on Bragg cells made by LiNbO₃ working in birefringent regime. It is well known that the frequency response of this kind of cells is nonlinear. The purpose of this paper is the study of possible solutions for the correction of this nonlinearity. We studied several different optical design. We analyzed 3, 4 and 5 lenses optical design with particular care to distortions and quality of the reimaging. About distortion we designed some lenses slightly off-axis in order to achieve a partial compensation of the asymmetric distortion in the spectra introduced by the non-linear frequency response of the Bragg cell. A solution involving all cylindrical lenses is also briefly shown along with some practical drawback leading to the rejection of such an option. Finally a trade-off is performed in order to balance difficulty and cost of realization, the optical quality, and the true residual distortion. For multichannel Bragg cells the differential distortion between the various channels is also analyzed.

We present the newly developed transportable setup of the Cologne Tuneable Heterodyne Infrared Spectrometer (THIS) designed for astronomical observations aboard the Stratospheric Observatory For Infrared Astronomy (SOFIA). With THIS a competitive tuneable heterodyne spectrometer for the mid-infrared is available that will allow measurements in a wide field of astronomical applications. Frequency tuneability over a wide range provided by the use of semiconductor lasers as local oscillators (LO) allows a variety of molecules in the mid infrared to be observed under very high frequency resolution. With the use of newly developed quantum-cascade lasers (QCL) a sensitivity close to the quantum limit will be in reach.

We report on growth, fabrication, and performance of Sb- doped Ge Blocked Impurity Band (BIB) detectors. Sb-doped Ge epilayers that exhibit impurity banding were grown on pure Ge wafers by Liquid Phase Epitaxy (LPE) from a Pb solution. A heavily doped surface region was observed using spreading resistance measurements. For proper BIB operation this layer must be removed by polishing. The diffusion of Sb into the blocking layer during growth has been studied as it affects the electric field distribution in a BIB detector. Secondary Ion Mass Spectroscopy analysis of an LPE layer grown at a starting temperature of 650 degrees C had a sharp interface. The growth of pure blocking layer material by LPE has been limited by the lack of availability of sufficiently pure commercial Pb, which we have found to contain phosphorus. Unintentionally doped layers grown from Pb solution were n- type approximately 10¹⁵ cm^-3 with compensating acceptors approximately 10¹² cm^-3. This is too high for the blocking layer, but sufficient for the doped layer of an n-type BIB. We have studied Pb purification by distillation and evaporation and have reached a lower limit of 10¹⁴ cm^-3. Ge:Sb BIB detectors have been fabricated by growing a doped IR active layer, typically 45 micrometers thick, and thinning the pure wafer to 10 micrometers to form the blocking layer. We demonstrate a working BIB device showing blocking behavior and a spectral response extending to 50 cm^-1.

IR calibration sources have been built using a 'reverse bolometer' approach. A NiCr thin film is deposited on a thin sapphire chip, forming a robust, resistive heater with high emissivity. The heater is suspended within a metal ring using nylon fibers, and electrically connected with low thermal conductivity wires. Finished devices may be mounted directly ona cryostat work surface and provide a wide range of greybody output with minimal power dissipation to the cold bath. Under typical operating conditions, a 40K equivalent blackbody output can be obtained with 1 to 2 mW electrical input power. The time constant varies according to type of device and specified temperature, but ranges from 100 ms to seconds. Accelerated lifetime test show output repeatability to within +/- 0.8 percent throughout 94,000 cycles from 4.2 K to 60K. The devices have survived shake testing at cryogenic temperatures and will be used for in- flight array calibration in the Multiband Imaging Photometer for SIRTF instrument, a part of the SIRTF.

A sensor's Modulation Transfer Function (MTF) characteristics determine the upper limits of the image quality, i.e. the image resolution or sharpness. The MTF describes the image quality in terms of contrast as a function of spatial frequency, normalized to unity at zero spatial frequency. Unfortunately, characterization of the MTF of semiconductor-based focal plane arrays (FPAs) has typically been one of the more difficult and error-prone performance testing procedures. Discussed in this paper are several commonly used techniques for measuring the MTF in the visible and IR wavelength regions. A brief description of the physical nature of FPAs is presented. This description will show that, because the MTF varies as a function of illumination wavelength and can vary as a function of illumination intensity, the conditions and techniques used for MTF measurement should be chosen based on the ultimate application of the FPA. Trade-offs between complexities in measurement and complexities in analysis as applied to an MTF characterization will be discussed as well as the importance of proper sensor calibration and the measurement of the optical test system's MTF. A discussion of analysis validation, including the effects of noise, using simulated image data is given. Following this, a sample comparison of a sensor's MTF curves as measured by a variety of techniques is presented. Opto-mechanical issues that can significantly influence the quality of an MTF measurement are also discussed.

An optical processing technique is introduced. This technique can improve the resolution of any scanning imaging system, that extract information by using the electronic behavior of materials. In this optical processing technique proper transparency, and adjusting the scanning light intensity are used. This technique can improve the performance of digital image enhancer. We implement our idea on a familiar millimeter image converter.

Advanced panchromatic, multispectral, and hyperspectral imaging applications from the visible through the longwave IR, are pushing image sensor to higher line and frame rates, wider fields-of-view, and high spatial and spectral resolution. When implemented with realistic focal plane architectures, the resulting multiple parallel output video streams must operate at high pixel data rates and with excellent amplitude resolution. The video signal chains necessary to process and digitally encode the raw pixel video must operate at very high speed, with low noise and wide pixel dynamic range. We discuss issues and constraints associated with advanced video signal chain circuit board design, including methods to improve settling times, electrical crosstalk, and the implementation of grounding approaches needed to ensure low noise. We describe the design and fabrication of a one-channel prototype signal chain board designed to operate at 14-bits and 20 MHz. In addition, we discuss video signal chain testing and verification constraints and report on noise, step response and differential nonlinearity measurements made on our prototype signal chain board.

Panchromatic, multispectral, and hyperspectral image sensors spanning the visible to longwave IR (LWIR) regions of the electromagnetic spectrum are finding increased application in advanced DOD, civil, scientific, and commercial space- based programs. Research and development advancing the state-of-the-art in visible to LWIR focal plane technology requires a careful understanding of system level requirements and a methodology for the translation of these requirements to focal pane specifications. At the focal plane level, signal-to-noise based performance is generally defined in terms of wavelength dependent noise equivalent irradiance and dynamic range specifications under conditions dictated by the system application. In this paper we illustrate a process that starts with system level performance requirements and results in focal plane performance requirements. The input spectral radiances were determined with the MODTRAN atmospheric code coupled with simple sensor and focal pane signal and noise models. The process is illustrated with two different space-based sensor examples, resulting in very different focal plane designs, configurations, and physical operating conditions. Finally, these characteristics were translated to focal pane electro- optical, thermal and electronic design parameters such as: spectral quantum efficiency, integration capacitance values and areas, and likely pixel unit-cell circuit selections.

We present a new point of view for investigation radiative transfer problems by showing it involves the scattering of traveling evanescent waves. Its accuracy is demonstrated by applying it to a solved problem whose solution was published by Chandrasekhar. He determined it with a conventional method and we bolster confidence in our method by showing how the new method produces the same analytical answer. The new technique converts the 95-year-old, usually difficult to solve, integro-differential equation formulation of radiative transfer into a less formidable 'pure' differential equation formulation, consisting here in a mixture of ordinary and partial derivatives, and solves that. This paper focuses on a single class of cases. It also demonstrates surprising success at solving a narrowly defined class of nonlinear radiative transfer problems initially expressed as a nonlinear integro-differential equation formulation of the radiative transport problem.

An FTS instrument is proposed for a part of active and passive sensor combination of the EarthCARE mission, jointly proposed to the 2nd ESA earth explorer selection. The FTS will be a compact 4-ports dual pendulum design with 0.5 cm^-1 spectral resolution to cover 400-2000 cm^-1 region. The IFOV is 10 by 10 km square to coincide with other passive instruments, and the observation is contiguous which is required for the EarthCARE.

The interferometric Monitor for Greenhouse gases (IMG) measured the high-resolution infrared spectra emitted from Earth from October 1996 to June 1997. It is a Fourier Transform Spectrometer based on the Michelson interferometer achieving 0.05 cm-1 wavenumber resolution and covers between 660 cm^-1 and 3030 cm^-1 with three infrared detectors. Since detectors are large and are not located in the center of the field of view (FOV), the instrument line shape (ILS) is shifted and widened. In this paper, we describe the ILS theoretical model and evaluate it by comparing the synthesized spectrum with the IMG observed spectrum. We checked the improvement of ILS by the FOV geometry. The retrieval accuracy will be improved by using this ILS model in the retrieval program.

Following the successful mission of the Global Ozone Monitoring Experiment (GOME) on-board the European Space Agency (ESA) ERS-2 satellite, the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT) and ESA have decided to embark on-board the Metop satellites an improved version of the GOME spectrometer. The new generation of GOME instruments will provide data for the ozone product chain of the EUMETSAT Polar System, in charge not only of the daily production of ozone data but also of the long term ozone monitoring. This imposes strong accuracy and stability requirements to the instrument, the calibration activities and the ground processing.

Satellite instruments detected two intense decreases of the ozone column values over Europe in November 1996 and November 1999. These low ozone events have been studied using atmospheric data and air parcel trajectory analyses. It was found that both ozone events were accompanied by rapid temperature decreases in the lower stratosphere. The anti-correlation found between total ozone and air parcel height along the air parcels trajectories suggested that the vertical displacement of air contributed significantly to the total ozone and temperature decreases observed. The Azores high-pressure cell over the mid Atlantic region, perturbed the flow in the lower stratosphere, forcing the vertical displacement of air parcels and causing the temperature and total ozone minima observed.

The Solar Occultation FTS for Inclined-orbit Satellite (SOFIS) is a solar occultation Fourier transform spectrometer (FTS), developed by the Ministry of the Environment (MOE) of Japan, that will be onboard the Global Change Observation Mission-A1 satellite. We describe the performance test results of the laboratory model and present the instrument and engineering model test results.

Solar occultation measurements from satellite have been very successful at sounding the upper atmosphere from cloud-top to well into the mesosphere (e.g. HALOE, ATMOS, SAGE, POAM). The HALOE instrument achieves transmission precision of 4 X10^-6 at 2 arcminute resolution (1.6 Km at the Earth limb) with the differential gas correlation technique. With modern detectors, high precision tracking, better throughput and differential broadband radiometry, achievable precision should approach 10-7 (~10-9 km-1 extinction) or better. We show that this will allow accurate sounding of CO2, O3, H2O and NO mixing ratios simultaneously with temperature and pressure well into the lower thermosphere. In addition, such precision could provide the first mapping of the Earth's cosmic dust layer.

The 1990s saw the rapid evolution of staring IR focal plane arrays (FPAs), with array formats progressing from 128 by 128 arrays at the beginning of the decade, to 1K by 1K arrays in low-rate production at the end of the decade. The maturation of large-format staring FPAs has given astronomers new capabilities for wide-field, high-resolution imaging and spectroscopy. The trends that emerged in the 1990s are continuing with larger format FPAs currently under development.

A digital readout for a 128 by 128 MWIR focal plane using InSb detectors was developed for imaging spectrometry. There are a total of 16,384 oversample A/D converters on the chi p that provide a 14 bit linear data output at a nominal frame rate of 4,000 samples per second. An early prototype design was completed and tested without detectors and found to meet all requirements. A second iteration is in final hybrid assembly for demonstration where it will be mounted in a dewar with optics. The device is designed to work with a 3.3 volt power supply with on chip A/D power consumption of under 50 milliwatts. This technology was developed under a SBIR program sponsored by US Air Force, Arnold Air Force Base.

The Atmospheric Chemistry Experiment (ACE) is the mission selected by the Canadian Space Agency for its new science satellite, SCISAT-1. Dr. Peter Bernath of the University of Waterloo is the ACE Mission Scientist, and ABB Bomem is the industrial contractor for the development of the ACE primary instrument. The principal goal of the ACE mission is to measure and to understand the chemical and dynamical processes that control the distribution of ozone in the upper troposphere and stratosphere. A comprehensive set of simultaneous measurements of trace gases, thin clouds, aerosols and temperature will be made by solar occultation from a satellite in a low earth orbit. A high inclination, low earth orbit will allow coverage of tropical, mid-latitude and polar regions. The ACE primary instrument is an infrared Fourier Transform Spectrometer (FTS) coupled with an auxiliary 2-channel visible and near infrared imager. The FTS, operating from 2.4 to 13.3 microns, will measure at high resolution (0.02 cm-1) the infrared absorption signals that contain information on different atmospheric layers to provide vertical profiles of atmospheric constituents. Its highly folded design results in a very high performance instrument with a compact size. The imager will monitor aerosols based on the extinction of solar radiation using two filtered detectors at 1.02 and 0.525 microns. The instrument also includes a suntracker, which provides the sun radiance to both the FTS and the imager during solar occultation of the earth's atmosphere. This paper will describe the recent developments on the ACE instrument. Results obtained with the engineering model will be given and the latest status of the flight model will be presented.

This paper presents the status of the ongoing development of the laboratory Wide Field-of-view Imaging Spectrometer (WFIS) and the new engineering model WFIS. The design is shown to provide a unique solution to wide field hyperspectral imaging with several advantages over traditional scanning systems. Tests of the engineering model, funded under NASA's Instrument Incubator program, take the WFIS to the next level of technology readiness. The WFIS is based on a patented optical design intended for optical remote sensing of the earth and the earth's atmosphere in the hyperspectral-imaging mode. The design of the laboratory spectrometer and the initial test results obtained with it were presented at the 1999 SPIE Annual Meeting in Denver, Colorado (3759-32). Since that time, the laboratory unit has undergone several upgrades in the optical path and continues to be a pathfinder for the new engineering model instrument. The WFIS engineering model incorporates several improvements to provide increased wavelength coverage from the UV to the NIR and an increase in the field-of-view coverage to 120 degrees. It differs most significantly from the laboratory unit in that it is designed for flight. The status of the hardware, software, and the assembly of the engineering WFIS is discussed as well as an overview of the planned demonstration tests.

The crosstrack IR Sounder (CrIS) is one of the key sensors now under development for the National Polar-orbiting Operational Environmental Satellite System program, which is the follow-on to the current DMSP and POES meteorological satellite systems. CrIS is a interferometric sounding sensor which accurately measures upwelling earth radiances at very high spectral resolution, and uses this data to construct vertical profiles of atmospheric temperature, moisture and pressure. These profiles are also called Environmental Data Records, or EDRs. The purpose of this paper is to describe the top level trade studies that led to the selection of the overall CrIS sensor design. Most of these trade studies involved a tradeoff between system performance and relative system cost. This paper discusses how EDR performance was determined for different trade study options, and review the key design and cost tradeoffs that led to the selection of the CrIS design.

For a complex remote sensor like the NPOESS Crosstrack Infrared Sounder (CrIS), the process of requirements flowdown is extremely important to the success of the project. When there is both an algorithm and a sensor, the task of allocating requirements between the sensor and the algorithm becomes a challenge. This is where the use of system models and simulations has been an invaluable tool. Complex requirements such as radiometric uncertainty and Instrument Line Shape (ILS) uncertainty have utilized system models and simulations for the allocation of requirements. For radiometric uncertainty the sensor model in conjunction with the algorithm which handles the calibration of the sensor was used to assess the contribution of parameters such as component and detector temperature stability on radiometric uncertainty. Variation of the parameter values within the sensor model allowed us to compute the impact on radiometric uncertainty and allocate requirements appropriately. Examples of how the model and simulations were used to develop requirements for the CrIS radiometric uncertainty will be presented. For the assessment of ILS uncertainty a model for predicting the ILS of a Michelson interferometer was employed. The model calculates the ILS and associated spectral shift based upon a set of input parameters. By varying the input parameters the sensitivity of the ILS to the specific parameters could be determined and used to allocate the requirements from a top level down to the module level. A description of the model, the input parameters and results for the CrIS requirements development will be presented.

The CrIS (Cross-track Infrared Sounder) instrument collects IR spectral radiance data to calculate calibrated atmospheric temperature, pressure, and moisture profiles for the NPOESS (National Polar-orbiting Operational Environmental Satellite System) program. CrIS features a Michelson Interferometer with three spectral bands (SWIR to LWIR), each with a 3 by 3 array of circular sensing apertures at the focal plane. The optical design includes a folded Gregorian telescope after the interferometer, a field stop to define the sensing aperture array, and collecting optics to place the interferogram energy onto the photovoltaic HgCd detectors. Many trade studies and analyses were performed to determine the design of the optical system, including telescope configuration, pupil locations, elimination of channelled spectra, polarization sensitivity, stray energy rejection, and compact packaging. This paper will describe the trade studies and analysis performed during the design of the CrIS instrument optics.

The mechanical design characteristics of the CrIS sensor module is presented. Several structural and thermal challenges are addressed. An 8-cm optical system, which includes a scanner, interferometer, 25-cm focal length telescope, aft optics, and cooler, efficiently use the available volume (0.158 m3). The sensor manages 90 Watts of electronic dissipation while maintaining a stable radiometric environment. It uses multi-stage passive cooling to provide 81 K focal plane and 220 K aft optics temperatures for low-earth orbits at up to 90-degree orbit normal-to-sun angles. Structurally, the interferometer scanning mirror maintains pointing accuracy of less than 20 microradians in the presence of self-induced and external disturbances.

It is important in any remote sensing radiometer to identify and characterize the noise and error sources of the radiometer. At ITT, we have produced a number models to characterize noise and its impacts. The latest noise model is for the Cross-track Infrared Sounder (CrIS) instrument which is part the National Polar-orbiting Operational Satellite System (NPOESS). The required accuracy of the instrument demands identifying and characterizing the noise and random error sources to lower the risk of poor instrument performance. This paper lists the sources of noises and random errors identified in the CrIS sensor and compares model predictions to measurements from the first CrIS Engineering Development Unit (EDU).

The Crosstrack Infrared Sounder (CrIS) is one of the sensors now under development for the National Polar-orbiting Operational Environmental Satellite System (NPOESS) program. In order to reduce program risk and verify instrument performance on the CrIS Program, various independent research projects were integrated into a prototype instrument. This was a rapid prototype built in 6 months that was similar to flight in the significant risk areas. This prototype instrument is referred to as the EDU1 (Engineering Development Unit). The coordination between the various, previously disjointed research tasks was a critical part of the effort. A layout of the flight CrIS instrument was the departure point for this effort. This layout was used to establish interfaces between the various modules. A set of clear cardinal requirements was established. The layout and the cardinal requirements therefore provided a conceptual overview and a basis for deriving lower level requirements. These requirements remained basically unchanged throughout the effort. The purpose of this paper is to describe the CrIS EDU1 system design and build, and summarize the key performance capabilities of the EDU1.

Space based optical instruments are evolving toward large apertures and requiring high sensitivity at longer wavelengths. Instruments that collect light at wavelengths longer than about 15 microns often use Potassium Bromide (KBr) as part of the optical system. Since KBr has rather poor mechanical properties, many engineers have been hesitant to design instruments with KBr optics larger than a few centimeters. This problem is made more difficult by the fact that sensors in these longer wavelengths are often operated at cryogenic temperatures to minimize self- emission. The overall objective of this effort was to examine methods of mounting KBr optics to improve their vibrational, optical, and thermal characteristics. A legacy KBr mount is examined and revised to increase its robustness and scalability. Using finite element models and dynamic testing, the limits of the current design was explored. An alternative design using a bonded support was investigated. A new thermally engineered composite material (TECMat) was developed that appears to match the thermal expansion of KBr over a wide temperature range. TECMat's general properties and possible methods of implementing it in optical mount are described.

Gallium arsenide extrinsic photoconductive detectors offer an extended spectral response in the far infrared (FIR) compared to presently available photodetectors, with the possibility of wavelength coverage from 60 to 300 mm. They can also be made in large planar structures, making them attractive for various far-infrared astronomical applications. In the past, continuous progress in material research has led to the production of pure, lightly and heavily doped n-type GaAs layers using liquid phase epitaxy (LPE). Sample detectors demonstrated the expected infrared characteristics of bulk type devices. Considerable improvement of detector performance could be expected from development of blocked impurity band (BIB) devices. These multi-structured detector types provide enhanced IR absorption and sensitivity due to the attainable higher doping of the infrared sensitive layer. However, the dark current in BIB detectors is determined by the level of unintentional majority doping for the relatively thin blocking layer, thus requiring ultra-high purity GaAs. With a new technique, using centrifugal forces for the LPE material growth, we intend to achieve this goal. Recently, such a growth facility has become operational at UC Berkeley. Outside contamination during the LPE growth process is largely reduced by a suspension of the crucible on active magnetic bearings in a completely closed environment. A sequential combination of centrifugal and gravitational forces provides the proper transport of the Ga solution in the growth crucible. Technical details of this unique equipment and first results of the initial growth runs will be reported.

This project seeks to assess plant productivity and health in time and space by measuring spectral reflectance from soybean canopies using remote sensing images that do not require ground assessment. Aerial images and reflectance measurements from a multi-spectral radiometer were obtained simultaneously from a soybean field located in Story County, Iowa. The multi-spectral radiometer has eight wavelength bands, ranging from 460-nm to 810-nm and was used as a ground reference for the data analysis. Aerial images were obtained from altitudes ranging from 152 to 427 meters from the ground during summer 2000. Aerial images were analyzed using Matlab, ArcView and Imagine. Difficulties in image analysis and interpretation may occur as the sensing equipment increases in altitude because atmospheric influences become more pronounced. Scattering and absorption of electromagnetic waves in the atmosphere change the spectrum of the reflected wave emitting from the plants as it propagates from the plants to the sensors. Color calibration procedures were used with red, green and blue ground cloths to correct aerial images in the respective red, blue and green bands. Regression analysis was carried out to quantify the relationships between multi-spectral radiometer data and aerial image data.

Short term as well as long term water stress has the same effects on plant physiology and canopy architecture. Changes in water status of a canopy can have indirect effects on remotely sensed optical reflectance. This study consists of two inter-related experiments on small canopy under laboratory conditions. The main aim of this study was to study spectral reflectance of water stressed canopies and to implement radiative transfer models to simulate the spectral reflectance of water stressed vegetation. Measurements were taken in the laboratory, which include spectral data and biophysical variables. Results from this research indicated that the pattern of change in both measured and modeled spectral canopy reflectance was similar, but there was a poor fit of the model to the measured canopy reflectance. Overall, this work investigated the relationship between vegetation variables and reflectance of water stressed vegetation and showed that biophysical variables that affect canopy reflectance should be considered carefully in any attempt to implement remote sensing techniques.

We develop an analytical estimate for the error that arises when approximating the generalized Planck's equation with a truncated series of N-terms. We present an analytical expression to evaluate the number of terms required to achieve specific accuracy. The results are applied to evaluation of the integral of the generalized Planck's equation over a wavelength interval.

A pair of thin prisms may be used to deviate the light beam without changing the image orientation in a vectorial shearing interferometer. The prism rotations determine the position of the wave front and the amount of its tilt. The separation between the prisms and their orientation determine the direction and the magnitude of the beam displacement. We designed a high precision mechanism with a fine resolution to rotate and displace each of two thin prisms. The device incorporates a two-axis calibration system. The angular resolution is 18 arc sec, with a periodic error of 3 arc sec, and a cumulative error of 10 arc sec is predicted.

We present experimental results demonstrating the performance of the erbium-doped silica fiber as a remote temperature sensor in the temperature interval [26 C - 60 C]. It uses the fluorescence intensity-ratio with energy levels 2H11/2 and 4S3/2. With the measured fluorescence data and incorporating a fiber optic link, its measured responsivity is 0.3 nW/C, its temperature resolution is better than 0.06 C, and the sensitivity is 0.06/C.

Recently, we developed a new type of a shearing interferometer, based on the Mach-Zehnder configuration, except that a beam director is incorporated in one arm of the interferometer and a compensator in the other one. The wave-front displacement is accomplished upon the angle setting between two Risley prisms. With the control of this angle, wave-front displacements are effectuated such that large and small aberrations may be measured with the same instrument. The vectorial shearing interferometer allows the optimization of the measurement parameters tailored to the specific application and the possible absence of available references. We present several applications of the vectorial shearing interferometer to the optical testing and the alignment of the optical systems.

We analyze the detection and interpretation of high fringe-density interferograms with CCD cameras. The high spatial frequencies beyond the Nyquist frequency of the CCD elements are shown in the recorded interferogram as fringes of lesser density and reduced contrast. This is due to the large sampling interval and intensity averaging over the pixel. We develop an analytic expression for the detected modulation intensity. It is seen to contain the phase information in its partial derivatives. We perform a simulation with a set of phase-shifted interferograms detected with finite pixel size to recover the detected modulation intensity. The phase is compared with the analytic expression resulting in the maximum error of less than 0.02 percent demonstrating the feasibility of the proposed model.

We analyze the feasibility of replacing hexagonal mirror segments with the circular ones in the very large telescopes, requiring the approximately same performance in the spatial frequency domain. The potential advantage of circular segments is their easier fabrication and a decreased amount of stray light contribution from the edges.

The incidence from a gray-body source detected in a wavelength interval is determined for a quantum and thermal detectors, for the ideal and non-ideal behavior. The results are applied to a common spectrometric reference source, a tungsten lamp, with measured, published emissivity values.