This paper presents a simulated architecture of an envisioned future intelligent Earth observing satellite system (FIEOS). The proposed system is a space-based architecture for dynamic and comprehensive on-board integration of Earth observing sensors, data processors and communication systems. It is intended to enable simultaneous, global measurements and timely analyses of Earth's environment for a variety of users. This paper also reports our progress of initial research in on-board image database management, including data structure, data model, and query. The intelligence of EO satellite system lies in that common users would access data directly, and in a manner similar to selecting a TV channel. The imagery viewed would most likely be obtained directly from the satellite system. The future of this system is promising for Earth observation. Real-time information systems are key to solving the challenges associated with this innovative architecture. Realization of such a technologically complex system will require contributions of scientists and engineers from many disciplines. Hopefully, this revolutionary concept will impact dramatically how future Earth observing satellite's development in the next few decades.

The Landsat Data Continuity Mission (LDCM) is next in the series of Landsat Earth remote sensing missions. At this writing, both the Thematic Mapper on the Landsat 5 spacecraft and the Enhanced Thematic Mapper Plus on the Landsat 7 spacecraft are producing routine Earth images, as part of a data set extending over three decades. The LDCM is required to continue this series of measurements. The LDCM Project has developed requirements for the data set to be produced by the LDCM sensor based on previous Landsat data, the proven technology from the Advanced Land Imager instrument flown on the EO-1 technology demonstration spacecraft, and on trade-offs made during the LDCM Formulation Phase. The unique nature of the LDCM government-commercial industry cooperative effort has resulted in a set of calibration and validation requirements intended to guarantee that the data from the commercially-owned LDCM sensor maintains the legacy of highly calibrated Landsat data.

Observations of coastal waters require high spectral and radiometric resolution, as compared to land, and high spatial resolution, as compared to the open ocean. An imaging instrument in geostationary orbit with a nominal aperture diameter of one meter in the spectral region from 400 - 1000 nm, ould meet these requirements on demand, over a large area of the Earth's surface. Observations made during daylight hours using filter wheel technology and large 2-D silicon focal plane arrays can achieve these objectives at reasonable coverage rates. Polarization-sensitive measurements would allow this instrument to optimize its observations of water-leaving radiance and to better compensate for atmospheric background. This instrument can be fabricated with existing technology.

In order to measure cloud top radiances from Unmanned Aerial Vehicles (UAVs) or other light aircraft, two small calibrated fisheye imaging systems have recently been developed. One of these systems uses a visible-wavelength CCD and is optically filtered to measure cloud top and ground radiances near 645 nm. The other uses an InGaAs detector and is optically filtered to measure radiances near 1610 nm. These sensors are specifically designed for use with DOE's Atmospheric Radiation Measurement (ARM) Program UAV Project, and it is anticipated that they will be used for comparison with a variety of satellite-borne radiance measurements. Radiometric calibration of solid-state imagers is never trivial, as the effects of exposure time, system non-linearities, temperature, gain and other system characteristics must be adequately measured and characterized. Much experience has been gained with the ground-based Day/Night Whole Sky Imagers and the Daylight Visible/NIR Whole Sky Imagers developed and used by the group for many years. New techniques for the radiometric calibration of the two new airborne systems are being developed based on this experience and the characteristics of the sensors involved. In addition, new techniques for a more accurate angular calibration have been developed.

Synthetic Aperture Ladar (SAL) could provide high resolution optical/infrared imaging of planetary surfaces from airborne or spaceborne platforms, using only modest-sized optics feasible for high-altitude flight or orbital missions. We discuss the characteristics of a planetary observing SAL (range and azimuth resolutions, field of regard, imaging swath size, altitude, aperture size, laser power, wavelength, etc.) and model the imaging performance of a SAL. Required laser power grows exponentially with range from the sensor platform ground track, due to atmospheric extinction, and also depends on wavelength as λ^-1 for a shot-noise-limited receiver. Planetary observing by SAL from space may be feasible in the terahertz band (~ 100 μm) with ~10 W of laser power. A planetary-observing SAL at shorter wavelengths (e.g. 1-2 μm) would require correspondingly higher laser power and would be much more challenging. SAL imaging may be attractive from low orbit around other planets, in particular those with little or no atmosphere (e.g Mars, Mercury, the Moon and many other planetary satellites). Beam stabilization, motion compensation and autofocus are among the most challenging aspects of a SAL mission.

An overview of silicon carbide (SiC) materials is provided, focusing on the optical properties required for space-based earth observing applications. NASA’s SiC Advanced Land Imager (ALI), produced by SSGPO and flown under the New Millennium Program, is described in order to illustrate the suitability of SiC to provide high-quality optics for these critical applications. The manufacturing processes used to produce SiC optics are described and recent improvements in the surface figure, surface finish, and stray light performance associated with SiC optics are reported. The two critical optical properties associated with the ALI instrument are surface figure and Bi-directional Reflectance Distribution Function (BRDF). In the results reported here, we demonstrate the ability to exceed these requirements by an order of magnitude using mature and repeatable processes.

This paper describes work towards building an integrated Earth sensing capability, in particular the demonstration of a prototype in-situ sensorweb in autonomous remote operation in the context of soil moisture monitoring. A five-node prototype sensorweb was deployed and tested at Bratt's Lake Station in Saskatchewan. The sensorweb operated autonomously and standard meterological parameters and soil moisture measurements were accessed remotely via satellite from the Integrated Earth Sensing Workstation (IESW) at the Canada Centre for Remote Sensing in Ottawa. The paper reports on the prototype sensorweb deployment in general and on soil moisture measurements in particular.

The invariant signatures of a polarimetric radar are considered. It is established theoretically that the polarimetric characteristics of the backscattered radar signals depend on the shape and the electrophysical parameters of the sensed objects. This statement is confirmed by the experimental data. The presented polarimetric diagrams of the backscattered signals of the vertical and horizontal polarizations reflected from different sensed objects show the difference in the polarimetric invariant signatures. The presented radar images illustrate that the polarimetric characteristics of the backscattered radar signals depend on the shape and the electrophysical parameters of the RS objects. These correlations create the preconditions for the development of the highly efficient radar systems for the detection, selection, recognition and cartography on the base of the use of the invariant polarimetric signal parameters.

The SeaWinds instrument on the QuikSCAT satellite was designed to measure near surface winds over the ocean; however, this remarkable remote sensing instrument has proven very useful in polar ice studies. Unlike previous radar scatterometers which were limited to 2 or 3 azimuth angles, the Ku-band SeaWinds instrument uses a circular scanning pencil beam, allowing it to make radar backscatter measurements from all azimuth angles. This geometry makes it an ideal candidate for studies of azimuth modulation of the normalized radar cross section of natural surfaces. Previous studies have observed a second order azimuth modulation of radar backscatter on the Antartic ice sheet, which has been related to wind-generated sastrugi (snow dunes) on the surface. In this paper we use SeaWinds data to make more detailed studies of the azimuth modulation in both Antarctica and Greenland where little has been done. Using the higher azimuth resolution possible with SeaWinds, we find that the azimuth variation of the backscatter is better described using a fourth order model in areas with the highest modulation. The orientation of these fourth order terms appears to be highly correlated to the katabatic wind direction. Azimuth modulation is as observed over Greenland, but it is much smaller than over Antarctica. Comparing SeaWinds and ERS-1/2 satterometer mode data we examine the frequency dependence, finding the modulation larger at C-band than Ku-band. The largest azimuth modulation in Greenland is observed in the transition region between dry snow and percolation zones.

Formation structure and relative spacecraft velocities for a multiple baseline single pass IFSAR system are investigated to optimize a composite interferometric observation over several subapertures. Two major system models are developed: (1) relative spacecraft motion, and (2) pixel height measurement variance. Analysis demonstrates that a generalized Keplerian trajectory model with an equal gravity gradient assumption provides sufficient accuracy over typical IFSAR flyby aperture lengths. A pixel height variance model is developed to address issues unique to single pass multiple baseline space-based systems. A bistatic spotlight mode IFSAR system is assumed. Bistatic operation is not necessary, but the reduced future costs of deploying high performance sensor arrays of smaller receiver spacecraft drive the development of this important technology. Modeled noises for the multiple baseline system include internal sensor noise, spatial decorrelation noise, non-parallel ground track (grid rotation) decorrelation noise, and system parameter uncertainties. With expected observation ranges in excess of 500 kilometers, large baselines are required to maximize IFSAR height sensitivity. An analysis of optimal correlation is presented that extends the work of Rodriguez & Martin (1992) to include model uncertainties. Four IFSAR formation scenarios have been investigated. The system trajectory mimics the planned flyby of the Kilauea volcano by the Air Force TechSat 21 multiple spacecraft demonstration. Supposed formations include (1) a free-fall cluster formation, (2) an optimal formation assuming adequate thrust, and (3) a free-fall flyby after optimal initial formation. Results demonstrate pixel height errors at the spotlight aim point to range from 1 to 4 meters over the several 1-second subaperture lengths, and 0.2 to 0.5 meters over the 47-second full aperture length. A fourth scenario investigates performance over a hyperbolic flyby trajectory.

The Rapid Terrain Visualization interferometric synthetic aperture radar was designed and built at Sandia National Laboratories as part of an Advanced Concept Technology Demonstration (ACTD) to “demonstrate the technologies and infrastructure to meet the Army requirement for rapid generation of digital topographic data to support emerging crisis or contingencies.” This sensor is currently being operated by Sandia National Laboratories for the Joint Precision Strike Demonstration (JPSD) Project Office to provide highly accurate digital elevation models (DEMs) for military and civilian customers, both inside and outside of the United States. The sensor achieves better than DTED Level IV position accuracy in near real-time. The system is being flown on a deHavilland DHC-7 Army aircraft. This paper outlines some of the technologies used in the design of the system, discusses the performance, and will discuss operational issues. In addition, we will show results from recent flight tests, including high accuracy maps taken of the San Diego area.

Data collection for interferometric synthetic aperture radar (IFSAR) mapping systems currently utilize two operation modes. A single-antenna, dual-pass IFSAR operation mode is the first mode in which a platform carrying a single antenna traverses a flight path by the scene of interest twice collecting data. A dual-antenna, single-pass IFSAR operation mode is the second mode where a platform possessing two antennas flies past the scene of interest collecting data. There are advantages and disadvantages associated with both of these data collection modes. The single-antenna, dual-pass IFSAR operation mode possesses an imprecise knowledge of the antenna baseline length but allows for large antenna baseline lengths. This imprecise antenna baseline length knowledge lends itself to inaccurate target height scaling. The dual-antenna, one-pass IFSAR operation mode allows for a precise knowledge of the limited antenna baseline length but this limited baseline length leads to increased target height noise. This paper presents a new, innovative dual-antenna, dual-pass IFSAR operation mode which overcomes the disadvantages of the two current IFSAR operation modes. Improved target height information is now obtained with this new mode by accurately estimating the antenna baseline length between the dual flight passes using the data itself. Consequently, this new IFSAR operation mode possesses the target height scaling accuracies of the dual-antenna, one-pass operation mode and the height-noise performance of the one-antenna, dual-pass operation mode.

In this paper, the microwave radiometer with computer controlled automatic gain compensation is briefly introduced. By using this method, a four-frequency-band (1.4GHz, 3.0GHz, 5.4GHz, 10.0GHz) compact microwave radiometer machine is designed and developed. After showing the methods of selecting some parameters of the system, the paper gives out the system calibration equation, sensitivity and linear correlative coefficients. Finally, it presents the system test results of the long-term stability, the ability of gain compensation, and also the test results of some crops: wheat, corn, and bean.

SciSat-1, otherwise known as the Atmospheric Chemistry Experiment (ACE), is a satellite mission designed for remote sensing of the Earth’s atmosphere using occultation spectroscopy. It has been developed under the auspices of the Canadian Space Agency and is scheduled for launch in August 2003. The suite of instruments on the satellite consists of a high-resolution (25 cm maximum path difference) Fourier Transform Spectrometer (FTS) operating in the infrared (2.4 to 13.3 microns), a UV/Visible Spectrometer operating between 0.285 and 1.03 microns with a resolution of 1 to 2 nm, and a pair of filtered imagers operating at 1.02 and 0.525 microns. The primary science goal of the ACE mission is to investigate the chemical and dynamical processes that govern ozone distribution in the stratosphere and upper troposphere. To this end, vertical profiles for trace gases, aerosols, temperature and pressure will be deduced from analysis of the solar occultation spectra. In particular, the role of heterogeneous reactions on ozone loss will be investigated, with a focus on the Arctic winter stratosphere.

The Atmospheric Chemistry Experiment (ACE) is the mission selected by the Canadian Space Agency for its next 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 will be made by solar occultation from a satellite in low earth orbit. The ACE mission will measure and analyse the chemical and dynamical processes that control the distribution of ozone in the upper troposphere and stratosphere. A high inclination (74 degrees), low earth orbit (650 km) allows coverage of tropical, mid-latitude and polar regions. This paper presents the instrument-related activities in preparation for launch. In particular, activities related to the integration of instrument to spacecraft are presented as well as tests of the instrument on-board the SciSat-1 bus. Environmental qualification activities at spacecraft-level are described. An overview of the characterization and calibration campaign is presented. Activities for integration and verification at launch site are also covered. The latest status of the spacecraft is also presented.

The Atmospheric Chemistry Experiment (ACE) is the mission selected by the Canadian Space Agency (CSA) for its next 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 will be made by solar occultation from a satellite in low earth orbit. The ACE mission will measure and analyze the chemical and dynamical processes that control the distribution of ozone in the upper troposphere and stratosphere. A high inclination (74 degrees), low earth orbit (650 km) allows coverage of tropical, mid-latitude and polar regions. This paper describes the results of the environmental qualification campaign of the ACE-FTS instrument flight model. Performance test results during thermal-vacuum (TVAC) testing are presented. Stability of the instrument at various temperatures under thermal and vacuum environment are discussed. Qualification of the ACE-FTS under vibrations at instrument and spacecraft levels are covered.

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 is the industrial contractor for the development of the ACE primary instrument. 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 an unapodised resolution of 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. In order to meet all science objectives, the instrument line width of the ACE-FTS has to be smaller than 0.028 cm-1. There are however different instrument function contributors affecting the width and the symmetry of spectral lines. These contributors are related to effects inherent to the instrument. This paper will describe these different effects and their impacts on the instrument line shape (ILS). Results obtained during the ILS characterisation of the flight model will be presented. A short description of a correction algorithm is also discussed.

The SCISAT-1 mission, also known as the Atmospheric Chemistry Experiment (ACE), is a Canadian satellite mission to investigate the chemical and dynamical processes that control the distribution of ozone in the stratosphere and upper troposphere. The satellite is scheduled to launch in August 2003, carrying two main instruments: a high-resolution infrared Fourier transform spectrometer (ACE-FTS) and a dual grating UV-Vis-NIR spectrometer known as MAESTRO (Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation) both operating primarily in solar occultation mode. Aspects of the mission pertaining to work done by ACE science team members from the University of Waterloo will be described, such as: the ACE-FTS forward model for retrieval of temperature, pressure and VMR profiles; ACE-FTS instrument testing and results; and the ACE Database along with data storage and processing hardware.

A novel and simple technique is described for the calibration of satellite instruments for the measurement of atmospheric ozone. Ozone is generated in a gas cell and spectral measurements of the ozone absorption are measured with a standard Fourier-transform spectrometer (FTS) in order to determine the amount of ozone in the cell. The satellite instrument then views the cell using an appropriate illumination source. In this presentation the preliminary results from the ozone calibration procedure are presented for the ACE FTS and MAESTRO instruments to show how consistently both instruments measure ozone. The thermal infrared band of ozone at 4.7 microns was used to provide the calibration of the ACE interferometer, whereas the Chappuis band at 600 nm was used to characterize the response of the MAESTRO instrument. The ozone transmission spectra that were derived from the ACE FTS and MAESTRO spectrograph measurements were found to be in good agreement with the simulated spectra of known amounts of ozone from a radiative transfer model. All of the results yielded column ozone amounts that were within 10% of each other. These calibration measurements were taken at the University of Toronto in March 2003, before the expected launch date of the SciSat-1 satellite in August 2003.

The SciSat-1 satellite will primarily function in occultation mode; however, during the dark portion of the orbit the Earth will pass between the sun and the satellite. This configuration will give rise to the opportunity of acquiring some nadir-view FTIR spectra of the Earth. Since the ACE FTS was designed to view a hot source (i.e., the Sun) at high resolution using a single scan, it is necessary to determine if the FTS will provide nadir spectra of the relatively cold atmosphere and surface with a sufficient signal-to-noise ratio. Hence, preliminary tests were performed on the ACE FTS instrument using a background source that provided a radiative contrast of about 100 K with the gas in a cell, thereby approximately simulating the atmospheric temperature conditions of the Earth. Methane, ozone and carbon monoxide gases were used in the cell for the purpose of determining the measurement characteristics of the ACE FTS instrument with respect to the nadir radiation emanating from the planet’s surface and atmosphere over most of the thermal infrared region. The signal-to-noise ratio from the laboratory test measurements is used to estimate the error on column measurements of carbon monoxide and other gases.

The Atmospheric Infrared Sounder (AIRS), Advanced Microwave Sounding Unit (AMSU), and Humidity Sounder from Brazil (HSB) are three instruments onboard the Earth Observing System (EOS) Aqua Spacecraft. Together, they form the Aqua Infrared and Microwave Sounding Suite (AIMSS). This paper discusses the science objectives and the status of the instruments and their data products one year after launch. All instruments went through a successful activation and calibration and have produced exceptional, calibrated, Level 1B data products. The Level 1B Product Generation Executables (PGEs) have been given to NOAA and the GSFC DAAC for production and distribution of data products. After nine months of operations, the HSB instrument experienced an electrical failure of the scanner. Despite the loss of HSB, early validation results have shown the AIRS and AMSU are producing very good temperature profiles.

We describe preliminary comparisons of AIRS/AMU/HSB retrieved geophysical products with correlative data sets to constrain retrieval uncertainties. The results are relevant to the 70% of oceanic retrieval footprints within the latitude range from 40S to 40N where infrared retrievals are completed. Comparisons are further limited to those retrievals whose sea surface temperatures (SST) agree with forecast model SST to within ±3 K. We present here comparisons with forecast model assimilations and dedicated radiosondes. Retrieved cloud cleared radiances and those calculated from weather forecast model output agree within 0.5 to 3 K, depending on cloud amount. Retrieved sea surface temperatures at night are compared against model output, with a resulting difference of 0.94 ± 0.95 K (a result skewed by the ±3 K selection criterion). Retrieved temperature profiles are compared with model output, and with dedicated radiosondes. Temperature profile uncertainties vary from about 1.3 K just above the surface to less than 1 K in the troposphere. Total water vapor is compared against dedicated radiosondes. Under dry conditions retrieved total water vapor agrees with radiosonde total water to within 10%, with small biases. The current retrieval algorithm generates temperature profiles meeting the 1 K per km requirement of the AIRS system.

The Atmospheric Infrared Sounder (AIRS) is one instrument in a suite of six instruments currently flying onboard NASA’s Earth Observing System (EOS) Aqua spacecraft. NASA’s Aqua spacecraft was launched successfully on May 4, 2002 from Vandenberg Air Force Base in California. AIRS is a cryogenic instrument developed under a Jet Propulsion Laboratory contract by BAe Systems formely Lockheed Martin Infrared Imaging Systems, for NASA. AIRS will provide new and more accurate data about the atmosphere, land and oceans, which provides a powerful new tool for climate studies and enables the advancement of weather prediction models. AIRS observations permit the measurement of the atmospheric temperature with an accuracy of 1 K in 1 km thick-layers in the troposphere and surface temperatures with an accuracy of 0.5 K. The Aqua spacecraft was placed in a sun-synchronous near-circular polar orbit with an inclination of 98.2 degrees, mean altitude of 705 km, 98.72 minute orbit period and 1:30 pm ascending node. The nominal on-orbit mission lifetime for the instrument is 6 years. AIRS measurements are based on passive infrared remote sensing using a precisely calibrated, high spectral resolution grating spectrometer with an infrared coverage from 3.7 to 15.4 μm. To achieve this high performance over this broad wavelength range, the spectrometer is cooled to 155 K and the Mercury Cadmium Telluride (HgCdTe) focal plane is cooled to 58 K. The detectors are cooled by a pair of long-life, low vibration, pulse tube mechanical coolers to 58 K, and a two-stage passive cooler with a deployable Earth shield provides cooling for the spectrometer to achieve a stable temperature near 155 K. This paper provides a general overview of the cryogenic system design and presents its on-orbit performance for the first year of operation.

The current performance of AIRS radiometric, spectral, and spatial calibration algorithms are described. Radiometric accuracy is validated to tenths of a kelvin. Spectral stability is better than 0.5% of the spectral response function FWHM. Geolocation accuracy is accurate to approximately 2 km at nadir. An algorithm has been implemented to correct for space views contaminated by the moon. Planned algorithm improvements include correcting the 2 km bias in geolocation.

AIRS was launched on EOS Aqua on May 5 2002, together with AMSU A and HSB, to form a next generation polar orbiting infrared and microwave atmospheric sounding system. The primary products of AIRS/AMSU/HSB are twice daily global fields of atmospheric temperature-humidity profiles, ozone profiles, sea/land surface skin temperature, and cloud related parameters including OLR. The sounding goals of AIRS are to produce 1 km tropospheric layer mean temperatures with an rms error of 1K, and layer precipitable water with an rms error of 20%, in cases with up to 80% effective cloud cover. Pre-launch simulation studies indicated that these results should be achievable. Minor modifications have been made to the pre-launch retrieval algorithm as described in this paper. Sample fields of parameters retrieved from AIRS/AMSU/HSB data are presented and validated as a function of retrieved fractional cloud cover. As in simulation, the degradation of retrieval accuracy with increasing cloud cover is small. Select fields are also compared to those contained in the ECMWF analysis, done without the benefit of AIRS data, to demonstrate information that AIRS can add to that already contained in the ECMWF analysis.

The comparison of global sea surface skin temperatures derived from cloud-free AIRS super window channel at 2616 cm-1 (sst2616) with the Real-Time Global Sea Surface Temperature (RTG.SST) for September 2002 shows a surprisingly small standard deviation of 0.44 K; however, sst2616 is colder than the RTG.SST by 0.67 K. About 0.35 K of the cold bias is due the expected bulk-skin gradient and the effect of using the day/night average RTG.SST for a nighttime comparison. The other 0.32 K is due to an absorbing layer in the atmosphere. There are large areas of the oceans where this absorbing layer is absent, and other areas where it is as large at 1.5 K. The layers persist regionally on a months timescale and might be related to some form of aerosol or marine haze. A correlation with major weather events, like the Monsoon season in the Indian ocean and, possibly, El Nino events is suspected, but has not been demonstrated. AIRS was lauched into polar orbit on the EOS Aqua spacecraft on May 4, 2002.

The AIRS instrument has a large number (2378) of potential channels. For use for observing meteorological parameters, several methods have been proposed and/or used. These include selecting a subset of channels, using eigenvectors, and using "super channels", which are averages of channels which view similar atmospheric features. The channels are selected using a constraint on the wavelength range to be covered, then selecting all the channels that have similar transmittances to be combined in one "super channel". Super channels have a number of features that make them attractive. They use all the information to reduce the noise and are efficient to use since both rapid transmittance models and equivalent Planck functions can be generated. This means that it requires the same effort to calculate the radiance for one super channel as for a single AIRS channel. Super channels and Planck function have been calculated for AIRS instrument and a rapid transmittance model is being used to generate coefficients to allow a rapid calculation of the corresponding transmittances. Results using the super channels compared to measures of the truth from forecast models and radiosondes will be shown.

The AIRS Science Data Processing System, responsible for processing data from the 4-instrument AIRS suite, includes 14 separate executable programs and produces dozens of products. These executable programs and products conform to ECS standards for processing and archival at Goddard Earth Sciences DAAC. These standards include format and metadata constraints, and the PGE paradigm. Before launch the AIRS team defined and implemented all PGEs, created simulated test data, verified PGE performance with simulated and ground test data, and verified PGE integration within the GES DAAC processing and archiving systems. To support validation and continued software development, Jet Propulsion Laboratory (JPL) developed a limited shadow production system, and received all instrument data after launch. This in-house system was not designed to process and serve all data, but rather to run experimental versions of our software and to run additional non-deliverable programs in support of validation. These pre-flight preparations paid off, and the first year after launch has been very active for the AIRS science data processing group. Still, lessons can be learned from our experiences during our first year of data processing and post-launch software development. These experiences and observations may be useful to science seams developing future Earth observing instruments.

The CERES Flight Models 1 through 4 instruments were launched aboard NASA’s Earth Observing System (EOS) Terra and Aqua Spacecraft into 705 Km sun-synchronous orbits with 10:30 a.m. and 1:30 p.m. equatorial crossing times. These instruments supplement measurements made by the CERES Proto Flight Model (PFM) instrument launched aboard NASA’s Tropical Rainfall Measuring Mission (TRMM) spacecraft on November 27, 1997 into a 350 Km, 38-degree mid-inclined orbit. An important aspect of the EOS program is the rapid archival and dissemination of datasets measured by EOS instruments to the scientific community. Six months after the commencement of science measurements, CERES is committed to archiving the Edition 1 Level 1 instrument, and Level 2 ERBE-Like data products. These products consist of geolocated and calibrated instantaneous filtered and unfiltered radiances through temporally and spatially averaged TOA fluxes. CERES filtered radiance measurements cover three spectral bands including shortwave (0.3 to 5 μm), total (0.3 to <100 μm) and an atmospheric window channel (8 to 12 μm). The current work summarizes both the philosophy and results of a validation protocol designed to rigorously quantify the quality of the data products as well as the level of agreement between the TRMM, Terra and Aqua datasets.

The Clouds and the Earth's Radiant Energy System (CERES) spacecraft scanning thermistor bolometers were used to measure earth-reflected solar and earth-emitted longwave radiances, at satellite altitude. The bolometers measured the earth radiances in the broadband shortwave solar (0.3 - 5.0 micrometers) and total (0.3->100 micrometers) spectral bands as well as in the (8 - 12 micrometers) water vapor window spectral band over geographical footprints as small as 10 kilometers at nadir. In May 2002, the fourth and fifth sets of CERES bolometers were launched aboard the Aqua spacecraft. Ground vacuum calibrations defined the initial count conversion coefficients that were used to convert the bolometer output voltages into filtered earth radiances. The mirror attenuator mosaic (MAM), a solar diffuser plate, was built into the CERES instrument package calibration system in order to define in-orbit shifts or drifts in the sensor responses. The shortwave and total sensors are calibrated using the solar radiances reflected from the MAM's. Each MAM consists of baffle-solar diffuser plate systems, which guide incoming solar radiances into the instrument fields-of-view of the shortwave and total sensor units. The MAM diffuser reflecting type surface consists of an array of spherical aluminum mirror segments, which are separated by a Merck Black A absorbing surface, overcoated with silicon dioxide. Temperature sensors are located in each MAM plate and baffle. The CERES MAM is designed to yield calibration precisions approaching .5 percent for the total and shortwave detectors. In this paper, the MAM solar calibration procedures are presented along with on-orbit results. Comparisons are also made between the Aqua, Terra and the Tropical Rainfall Measurement Mission (TRMM) CERES MAM solar calibrations.

Clouds and the Earth's Radiant Energy System (CERES) instruments are currently flying on two satellite platforms, Terra, launched 18 December 1999 and Aqua, launched 04 May 2002. Both satellites are at a 705-km altitude, in high inclination, polar orbits. Terra crosses the equator at local morning, while Aqua crosses at local afternoon. Each platform carries two CERES instruments. Each CERES instrument contains three scanning radiation-detecting bolometers. The three detectors measure reflected solar and Earth emitted radiation in three bandwidths: shortwave (0.3-5 μm), window (8-12 μm), and total (0.3 to >100 μm). Earth views of each instrument are geolocated to the Earth fixed coordinate system using satellite attitude, ephemeris, and instrument pointing data. An analysis has been developed which uses radiation gradients at ocean-land boundaries measured by the CERES instrument as an aid to validate the computed geolocation. The detected coastlines are compared to known map coordinates and an error analysis is performed after a best fit is made in the coastline comparison. Spatial differences are mapped from latitude, longitude to absolute distance in along-track (ground path) and cross-track (perpendicular to ground path) of the satellite. Results of the Terra CERES instruments have shown maximum errors to be within 10% of the nadir footprint size. A description of the coastline detection and error analysis will be presented along with results for the Terra CERES instruments. Initial results from the coastline detection and error analysis for the Aqua instruments will be presented also.

Clouds and the Earth's Radiant Energy System (CERES) is an investigation into the role of clouds and radiation in the Earth's climate system. Four CERES scanning thermistor bolometer instruments are currently operational. Flight model 1 (FM1) and 2 (FM2) are aboard the Earth Observing System (EOS) Terra satellite and FM3 and FM4 are aboard the EOS Aqua satellite. Terra was launched in December 1999 and Aqua in May 2002. Each CERES instrument measures in three broadband radiometric regions: the shortwave (0.3 - 5.0 μm), total (0.3 ->100 μm), and window (8 - 12 μm). Several vicarious analyses have been developed to aid in monitoring the health and stability of the instruments' radiometric measurements. One analysis is a three-channel inter-comparison of the radiometric channel measurements for each instrument. A second analysis compares temporally synchronized nadir measurements for each sensor of two instruments on the same platform. These analyses along with onboard calibrations have been used to monitor the drifts in the shortwave measurements and have provided information used to remove the drift using ground software. Previously documented, these analyses will be reviewed and further results for the Terra CERES instruments will be presented along with initial findings for the CERES instruments on Aqua.

Studies were conducted to define lunar radiances on an absolute radiometric scale tied to the International Temperature Scale of 1990 (ITS-90). The Clouds and the Earth's Radiant Energy System (CERES) thermistor bolometer sensor instruments were used to measure lunar radiances from the NASA Tropical Rainfall Measuring Mission (TRMM), Terra, and Aqua spacecraft platforms. Each CERES instrument package consisted of three different sensors: (1) broadband shortwave [0.3 to 5 micrometers]; (2) broadband total [0.3 to >100 micrometers]; and (3) narrowband, water vapor window [8 to 12 micrometers]. Moon-reflected solar radiances were measured with the shortwave sensor while both moon-reflected solar and moon-emitted longwave radiances were measured using the total sensor. The differences between the total and shortwave sensor measurements were used to determine the broadband longwave, moon-emitted radiances. The narrowband, water vapor window sensor measured only the longwave, moon-emitted radiances. The radiances were obtained as a function of phase angle (formed at the moon between directions to the sun and the spacecraft). The resulting filtered radiances were normalized to the mean sun-moon distance, one astronomical unit (AU), and to the mean earth-moon distance of 0.0026 AU (384,400 kilometers). 1998, 2000, and 2001, CERES lunar filtered measurements are presented, compared, and analyzed. Additional measurements are presented from the January 9, 2001, and May 16, 2003, total lunar eclipse events. Analyses of the Clouds and the Earth's Radiant Energy System (CERES) thermistor bolometer sensor observations of lunar radiances indicated that broadband shortwave and longwave lunar filtered radiances can be linked to a radiometric scale based upon an International Temperature Scale of 1990 (ITS-90) at absolute levels approaching ± 0.2 Wm^-2sr^-1. For a lunar image diameter of 31 minutes of arc, an emitting lunar disc temperature of approximately 400 Kelvin was estimated from the longwave radiances near 7-degree phase angle. The integration of the CERES unfiltered radiances over all reflection angles can be used to define the moon radiation budget (MRB).

The MODerate-resolution Imaging Spectroradiometer (MODIS) is the keystone instrument for the NASA’s Earth Observing System (EOS). Currently two nearly identical MODIS instruments are operating on-board the EOS Terra spacecraft (launched in December 1999) and the EOS Aqua spacecraft (launched in May 2002), providing global coverage of the Earth’s land, oceans, and atmosphere with both morning and afternoon observations. This paper reviews the EOS MODIS development history, its design concepts, system implementation and calibration, current status and the follow-on Visible/Infrared Imaging Radiometer Suite (VIIRS) under development for the National Polar Orbiting Environmental Satellite System (NPOESS).

The MODerate Resolution Imaging Spectroradiometer (MODIS) is one of the key instruments for the NASA’s Earth Observing System (EOS). The MODIS ProtoFlight Model (PFM) was launched on-board the EOS Terra spacecraft on December 18, 1999. The science data acquisition started on February 24, 2000. Since then it has been providing the science community and public users unprecedented amount of data sets for the global monitoring of the Earth’s land, oceans, and atmosphere. MODIS has 36 spectral bands with wavelengths ranging from 0.41 micrometer to 14.5 micrometers. Its 16 thermal emissive bands (TEB) range from 3.7 to 14.2 micrometers and have a total of 160 individual detectors (10 detectors per band). The thermal emissive bands are calibrated on-orbit by an on-board calibrator blackbody (OBC BB) on a scan by scan basis. The detectors responses to the BB source track their operational stability and therefore their noise characteristics as well. In this paper, we provide a brief review of the MODIS TEB on-orbit calibration algorithm with a focus on detector stability using over three years of on-orbit calibration data sets. The on-orbit changes in detectors responses from one operational configuration to another, the changes within the same operational condition, and the impact of these changes on the calibration and on the Earth scene observations are carefully examined. Except for a few detectors that were identified from pre-launch or became noisy on-orbit, the overall performance of MODIS TEB detectors is very satisfactory according to the design specifications.

During the Terra-Aqua experiment -- 2002 (TX-2002), a NASA ER-2 was used to underfly the EOS Aqua satellite over the Gulf of Mexico for the purpose of gaining insight on the accuracy of MODIS and AIRS thermal infrared (TIR) band radiances. The ER-2 payload included the MODIS Airborne Simulator (MAS) and the Scanning High resolution Interferometer Sounder (SHIS); these instruments have flown previously on the ER-2 for assessing Terra MODIS TIR band radiances. On November 21, 2002, the ER-2 flew directly under the Aqua satellite, with MODIS and AIRS, as it swept over a clear sky region of the Gulf of Mexico. The MAS and SHIS observations were used to simulate the MODIS thermal IR band radiances for the warm (~ 295 K) Gulf of Mexico scene. The results of comparing the simulated MODIS radiances with the MODIS observations show Aqua MODIS TIR bands are performing well. The residuals (MAS - MODIS) in most bands are within or very near specification. The split window 11 and 12 μm band residuals are small and very close to one another at -0.15°C and -0.13°C, respectively. The comparisons suggest that MODIS LWIR CO₂ sensitive bands 35 (13.9 μm) and 36 (14.2μm) may be calibrated slightly warm by about 1°C. Early direct comparisons between MODIS and AIRS on Aqua also suggest that the MODIS bands 35 and 36 may be calibrated slightly warm.

The MODIS Protoflight Model (PFM), launched onboard the NASA s Earth Observing System (EOS) Terra spacecraft, has been in operation for more than three years. In addition to constant radiometric calibration activities, the sensor s on-orbit spectral bandpasses of the reflective solar bands (RSBs) with wavelengths from 0.41 to 2.2 micrometers have been measured (every three months) using the on-board Spectral Radiometric Calibration Assembly (SRCA). The spectral characteristics of the SRCA were calibrated pre-launch using the Spectral Measurement Assembly (SpMA). The MODIS on-orbit spectral characterization using the SRCA has been performing as designed and the key spectral parameters, with few exceptions, are well within the specification limits. This paper provides a brief review of the MODIS prelaunch spectral characterization. It focuses on the Terra MODIS instrument s on-orbit spectral characterization activities, trending results, and comparisons with pre-launch characterizations and the specifications.

The MODerate Resolution Imaging Spectroradiometer (MODIS) uses an on-board solar diffuser (SD) panel made of Spectralon for the radiometric calibration of its 20 reflective solar bands (RSB). The spectral wavelengths of the RSB range from 0.41 to 2.1 micrometers. The on-orbit calibration coefficients are determined from the sensor s responses to the diffusely reflected solar illumination from the SD. This method requires an accurate pre-launch characterization of solar diffuser s bi-directional reflectance factors (BRF) that should cover the sensor s spectral range and illumination/viewing angles and accurate on-orbit monitoring of SD degradation over time. The MODIS SD panel s bi-directional reflectance factors were characterized prior to the sensor s final system integration (pre-launch by the instrument vendor using reference samples traceable to the NIST reflectance standards at a number of wavelengths and carefully selected combinations of the illumination/viewing angles. The measured BRF values were fitted into smooth surfaces and then interpolated for each of the MODIS reflective solar bands. In this paper, we describe an approach designed for the MODIS on-orbit characterization and validation of its SD BRF using multiple SD solar observations at several spacecraft yaw angels. This approach has been successfully applied to both the Terra and Aqua MODIS. This paper presents the algorithm used to derive the SD s relative BRF from observations during spacecraft yaws and compares the on-orbit results with corresponding pre-launch values.

Nearly identical copies of the MODerate Resolution Imaging Spectroradiometer (MODIS) are currently operating onboard the NASA s Earth Observing System (EOS) Terra and Aqua satellites launched on December 18, 1999 and on May 04, 2002 respectively. MODIS has 36 spectral bands with wavelengths from 0.41 to 14.5 μm. Bands 1 - 19 and 26 are the reflective solar bands (RSB) with spectral wavelengths from 0.41 to 2.2 μm and bands 20 - 25 and 27 - 36 are the thermal emissive bands (TEB) with spectral wavelengths above 3.5 μm. The two latest Advanced Very High Resolution Radiometer (AVHRR) instruments were launched onboard the NOAA-16 and NOAA-17 on September 21, 2000 and on June 24, 2002 respectively. The new AVHRR/3 instrument (onboard NOAA-15 to -17) is a six-channel imaging radiometer in the visible and infrared spectral region. There have been many important parameters and science products derived from observations made by both MODIS (more data products) and AVHRR (longer data record). In this paper, we present an inter-comparison of the 11 μm and 12 μm bands of the Terra and Aqua MODIS (bands 31 and 32) using the NOAA-17 AVHRR (channels 4 and 5). The AVHRR is served as an intermediate transfer vehicle. The intercomparison data sets from the MODIS and AVHRR are selected from nearly simultaneous observations (within 30 seconds) over relatively uniform scenes near the instrument nadir view with pixel-by-pixel matches in the Polar region. Preliminary results show that the measured temperature differences between the Terra and Aqua MODIS at 11 μm and 12 μm are about 0.25 K and 0.35 K at a brightness temperature of about 250 K, indicating consistent and reliable on-board calibration and characterization for the MODIS instruments. Using the same approach this paper also presents the results from comparing the NOAA-16 and 17 AVHRR 11 μm and 12 μm channels. At a brightness temperature range from 240 to 270 K, the observations show that the NOAA-17 AVHRR is about 0.45 K cooler than the NOAA-16 AVHRR for its 11 μm and 12 μm channels.

The Moderate Resolution Imaging Spectroradiometer (MODIS) is onboard both the Terra and Aqua platforms. An important aspect of the use of MODIS, and other Earth Science Enterprise sensors, has been the characterization and calibration of the sensors and validation of their data products. The Remote Sensing Group at the University of Arizona has been active in this area through the use of ground- based test sites. This paper presents the results from the reflectance-base approach using the Railroad Valley Playa test site in Nevada for both Aqua and Terra MODIS. The key to the approach is the measurement of surface reflectance over a 1-km² area of the playa and results from this method shows agreement with both MODIS sensors to better than 5%. Early results indicate that while the two sensors both agree with the ground-based measurements to within the uncertainties of the reflectance-based approach, there were significant differences between the Aqua and Terra MODIS for data prior to September 2002. Recent results indicate that this bias, if any, is now within the uncertainties of the reflectance-based method of calibration.

Besides pre-launch and on-board calibration, the method of vicariously calibrating space sensors became a reliable tool for space sensor calibration. One possibility of vicarious calibration is to inter-calibrate sensors aboard different satellite platforms directly. This leads to a better understanding of differences in global data sets produced these sensors. Recently, ADEOS-2 was launched (14 Dec 2002) successfully and the optical sensor GLI onboard the ADEOS-2 satellite became operational from April 2003. In a first calibration check-up, the radiometric performance of GLI was compared relatively to that of other sensors on different satellites with different calibration backgrounds. As calibration site a large snowfield near Barrow (Alaska, USA) was used, where space sensors in polar orbits view the same ground target on the same day with small differences in the local crossing times. This is why GLI, MODIS (terra, aqua), SeaWiFS, AHVRR (N16, N17) and MERIS data sets were selected for the following clear-sky condition days: April 14th and 26th 2003. At the same time ground-truth experiments, e.g., measurements of ground reflectance, BRDF, aerosol optical thickness (AOT), were carried out. Thereinafter, top-of-atmosphere (TOA) radiance/reflectance was forward calculated by means of radiative transfer code (RTC) for each sensor, each band and each day. Finally, the vicariously retrieved TOA reflectance was compared to TOA sensor L1B data. As a result GLI’s performance is encouraging at this early time of the mission. GLI and the other 6 sensors deliver similar sensor output in the range of about 5-7% around the expected vicariously calculated TOA signal.

The whiskbroom scanner Global Imager (GLI) was launched in December 2002 on the Advanced Earth Observation Satellite 2 (ADEOS-2). The sensor provides remotely sensed data from the Earth surface in the visible to the thermal infrared part of the spectrum. Since the Earth observation data require careful post-launch calibration, different on-board calibration tools have been integrated in the GLI hardware design. For the VIS-SWIR spectral range a special calibration device allows solar and lamp calibration. In this paper we describe first results on solar calibration of GLI.

Due to optical misalignment, visible and infrared channels of the Geostationary Operational Environmental Satellite (GOES) I-M Imager may not be properly registered. This “co-registration” error is currently estimated by comparing groups of visible and infrared observation residuals from the GOES Orbit and Attitude Tracking System (OATS). To make the channel-to-channel comparison more direct, it was proposed to compare individual observations rather than groups of observations. This has already been done for landmarks but not for stars. Stars would help determine nighttime co-registration when visible landmarks are not available. Although most stars in the GOES catalog are not detectable in the shortwave infrared channel, many are. Because stars drift west-to-east across the detectors and because of their high observation frequency, stars provide good east-west co-registration information. Due to the large detector fields-of-view, stars do not provide much information about north-south co-registration.

The in-orbit calibration of the Modular Optoelectronic Scanner MOS on the Indian Remote Sensing Satellite IRS-P3 has delivered the actual radiometric recalibration coefficients with sufficient accuracy for most of the 18 spectral channels in the VIS/NIR spectral range during the 7 years mission time. This has been the basis for the thematic interpretation of the MOS data. The three different and independent in-orbit calibration methods: lamp calibration, sun calibration and ground target based (vicarious) calibration as well as different possibilities of dark signal determination and the extensive knowledge of instrument performance data and instrument characteristics from the lab measurements have enabled us to overcome all failures and difficulties of the instrument which occurred in orbit. The failure of the lamp and sun calibration equipment in September 2000 has been overcome by using the vicarious calibration and dark signal measurements at the earth night side at new moon. The failure of the thermo-electric cooling of the detectors in November 2002 could be overcome only by the knowledge of the temperature dependence of the spectral responsivity of the different spectral channels and its dark signals. Thus we are able to continue the determination of the time trend of the recalibration coefficients in spite of these problems. In the paper we will give a resume of the most important events concerning the in-orbit calibration during the mission time, try to find explanations for some effects and present the results of determining the recalibration coefficients and the accuracy reached under the concrete environmental and instrumental conditions in orbit.

Organic materials in the oceans have spectral signatures based on their light-scattering properties. These optical properties are related to bio-physical and bio-chemical data products such as the concentration of phytoplankton chlorophyll-α through bio-optical algorithms. A primary quantity of interest in ocean color research is the water-leaving spectral radiance L_w(λ), often normalized by the incident solar flux. For quantitative studies of the ocean, derivation of the relationship between the optical properties and physically meaningful data products is critical. There have been a number of recent advances in radiometry at the National Institute of Standards and Technology that directly impact the uncertainties achievable in ocean-color research. These advances include a new U.S. national irradiance scale; a new laser-based facility for irradiance and radiance responsivity calibrations; and a novel tunable, solid-state source for calibration and bio-optical algorithm validation. These advances, their relevance to measurements of ocean color, and their effects on radiometrically derived ocean-color data products such as chlorophyll-α are discussed.

Exo-atmospheric solar irradiance measurements made by the solar irradiance community over the past 25 years incorporated limiting apertures measured by a number of metrology laboratories using a variety of techniques. Knowledge of the aperture area is a critical component in the conversion of radiant flux measurements to solar irradiance. An Earth Observing System (EOS)-sponsored international comparison of aperture area measurements of limiting apertures provided by solar irradiance researchers is under way, the effort being executed by the National Institute of Standards and Technology (NIST) in coordination with the EOS Project Science Office. Apertures that have institutional heritage with historical solar irradiance measurements are measured using the absolute aperture measurement facility at NIST. The measurement technique employs non-contact video microscopy using a high-precision stage. The aperture area comparison aims to quantify the relative differences between the participating institutions' aperture area measurements. Preliminary results of the comparison will be reported.

The RObotic Lunar Observatory (ROLO) project has developed radiometric models of the Moon for disk-integrated irradiance and spatially resolved radiance. Although the brightness of the Moon varies spatially and with complex dependencies upon illumination and viewing geometry, the surface photometric properties are extremely stable, and therefore potentially knowable to high accuracy. The ROLO project has acquired 5+ years of spatially resolved lunar images in 23 VNIR and 9 SWIR filter bands at phase angles up to 90°. These images are calibrated to exoatmospheric radiance using nightly stellar observations in a band-coupled extinction algorithm and a radiometric scale based upon observations of the star Vega. An effort is currently underway to establish an absolute scale with direct traceability to NIST radiometric standards. The ROLO radiance model performs linear fitting of the spatially resolved lunar image data on an individual pixel basis. The results are radiance images directly comparable to spacecraft observations of the Moon. Model-generated radiance images have been produced for the ASTER lunar view conducted on 14 April 2003. The radiance model is still experimental -- simplified photometric functions have been used, and initial results show evidence of computational instabilities, particularly at the lunar poles. The ROLO lunar image dataset is unique and extensive and presents opportunities for development of novel approaches to lunar photometric modeling.

We describe the development of a mechanically simple, radiometrically stable transfer radiometer designed for both radiance and irradiance measurements. The filter radiometer consists of a six-element Si trap detector, a temperature stabilized filter wheel with up to 5 filters, and two precision apertures in a Gershun tube arrangement. With the Gershun tube installed, the instrument operates in radiance mode; with the front aperture removed, in irradiance mode. Two trap detector filter radiometers have been designed and built by the National Institute of Standards and Technology (NIST) for use in remote sensing applications. The filter radiometers have been characterized for optical and electrical performance, and have been calibrated for responsivity using both narrow-band, tunable-laser-illuminated and broad-band, lamp-illuminated integrating sphere sources. This paper describes the filter radiometer design, characterization, and deployments for two remote sensing projects.

Hyperspectral systems are increasingly being mated with on-board target detection algorithms. However the only way to test these algorithms is with field testing which are expensive and inherently unrepeatable. This paper will describe a Hyperspectral Scene Generator that can display hundreds of programmable high resolution spectra simultaneously. This allows a target to be inserted into a previously measured field for testing of a hyperspectral sensor and target detection algorithms in the lab. The design of the Hyperspectral Scene Generator is presently applied to the Visible and Near InfraRed (VNIR) and Short Wave InfraRed (SWIR) but may also be applied to the MidWave InfraRed (MWIR) and Long Wave InfraRed (LWIR) spectral region. Funding for this study is provided from Office of the Secretary of Defense and Director, Operational Test and Evaluation (DOT&E) to investigate the development of a hyperspectral scene generator that will have broad application to many hyperspectral systems.

Next-generation polar and geostationary systems, such as the National Polar-orbiting Operational Environmental Satellite System (NPOESS) and the Geostationary Operational Environmental Satellite (GOES)-R, will deploy new generations of electro-optical reflective and emissive capabilities. These will include low-radiometric-noise, improved spatial resolution multi-spectral and hyperspectral imagers and sounders. To achieve specified performances (e.g., measurement accuracy, precision, uncertainty, and stability), and best utilize the advanced space-borne sensing capabilities, a new generation of retrieval algorithms will be implemented. In most cases, these advanced algorithms benefit from ongoing testing and validation using heritage research mission algorithms and data [e.g., the Earth Observing System (EOS)] Moderate-resolution Imaging Spectroradiometer (MODIS) and Shuttle Ozone Limb Scattering Experiment (SOLSE)/Limb Ozone Retreival Experiment (LORE). In these instances, an algorithm's theoretical basis is not static, but rather improves with time. Once frozen, an operational algorithm can “lose ground” relative to research analogs. Cost/benefit analyses provide a basis for change management. The challenge is in reconciling and balancing the stability, and “comfort,” that today’s generation of operational platforms provide (well-characterized, known, sensors and algorithms) with the greatly improved quality, opportunities, and risks, that the next generation of operational sensors and algorithms offer. By using the best practices and lessons learned from heritage/groundbreaking activities, it is possible to implement an agile process that enables change, while managing change. This approach combines a “known-risk” frozen baseline with preset completion schedules with insertion opportunities for algorithm advances as ongoing validation activities identify and repair areas of weak performance. This paper describes an objective, adaptive implementation roadmap that takes into account the specific maturities of each system’s (sensor and algorithm) technology to provide for a program that contains continuous improvement while retaining its manageability.

We describe a new method for the quantitative characterization of condensed phases in the atmosphere. It uses broad band IR extinction spectra to obtain the density, size distribution, phase and the approximate composition of aerosols within a single retrieval process. The method is based on a linear least squares fitting procedure with physically-based constraints. In this report, the method is applied to the analysis of spectra measured by the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument. The volume density, size distribution and composition of the stratospheric sulfate aerosols observed in several ATMOS missions are reported. The values of these properties for aerosols observed shortly after the eruption of Mount Pinatubo in 1992 are compared with those of aerosols present at much lower levels in 1993 and 1994.

Reflectance-based vicarious calibration of satellite sensors is a method by which in-situ radiometric measurements of a surface target and the atmosphere are used to constrain a radiative transfer model for estimating a top-of-atmosphere (TOA) radiance. The procedure provides an at-sensor radiance, independent of the on-board calibrator, that can be used to maintain knowledge of the in-flight calibration performance of the remote sensing system. However, an estimate of the TOA radiance is incomplete unless accompanied with an uncertainty that quantifies the random and systematic errors associated with that estimate. Presented in this paper is a methodology for predicting a TOA radiance with an absolute accuracy estimate derived using an error propagation analysis based principally on validation data recorded by calibrated ground-based radiometer measurements. A vicarious calibration data collect for the airborne sensor ATLAS and the IKONOS satellite on June 30, 2000 at Brookings, South Dakota provides a test case for this technique in the solar reflective spectrum. The results show that using a natural grass covered target under moderate aerosol loading, absolute accuracies between 3% and 5% are achieved for band integrated TOA radiances between 0.4 and 1.6 microns.

This paper describes the use of photogrammetric principles to georeference imagery collected by the Multispectral Thermal Imager (MTI) satellite. The photogrammetric image registration (PIR) method consists of two main parts. The first part estimates a trajectory (exterior orientation as a function of time) for the sensor based on a photogrammetric bundle adjustment governed by user defined ground control points. The ground control points are defined by manual identification of conjugate points between the LEVEL1B_U imagery and reference data (an orthoimage and a digital elevation model derived from aerial photography). The second part uses this trajectory as input to a direct georeferencing method to determine the location of each pixel in the imagery. The PIR method uses mathematical models of the sensor, its trajectory, timing, and the terrain to mimic the actual image acquisition event. It was found that accurate calculation of the exterior orientation parameters was not a requirement to obtain accurately georeferenced imagery. This is particularly intriguing, and deserves more in-depth study, because the values of the exterior orientation parameters solved for through photogrammetric bundle adjustment are known to be in disagreement with the actual motion of the satellite platform. The individual steps of the PIR method, the mathematical models used, and the results of georeferencing MTI imagery through the use of this approach are described.

A very useful Real-Time Ocean Surveying System (RTOSS) has been developing. Because of the real-time transmission and the huge synthesize aperture radar (SAR) imagery data and video imagery data and because of the restricted communication channel and the limited transmitting power condition the image data compression methods have to be developed. The compressed SAR imagery data and video imagery data have to satisfy two conditions: One is the excellent quality reconstruction; another is that the system can work on the real-time operating condition. It is contradictory for the excellent quality reconstruction with the real time system operation. In order to satisfy the real-time operating condition, the wavelet-based SAR imagery and improved H.263-based video imagery compression algorithms have been developed, which is of a high compression multiples and tiny compression distortion. In this paper, several typical SAR imagery compression algorithms are introduced and their performances and practical feasibility are compared. Secondly, the developed compression software that adopts improved H.263-based video imagery methods will be introduced. Finally, some experiment results will be given.

CNES has launched in May 2002 a new high resolution (2.5m) and large swath (2 x 60km) optical remote sensing satellite: SPOT5. To achieve a high image acquisition capacity with this system, a large on-board mass memory (100 Gbits) together with a 3:1 real-time compression are being used. The quasi-lossless and fixed output rate requirements put on the on-board image compression resulted in the development of a custom algorithm. This algorithm is based on: a DCT decorrelator, a scalar quantizer, an entropy coder and a rate regulator. It has been extensively tested before launch both in terms of quantitative performances and in terms of visual performances. The objectives of the on-orbit validation of the SPOT5 image compression function were the following: (1) Perform an image quality assessment in worst case conditions for the compression. In particular, the THR mode (2.5 m resolution) is potentially sensitive to compression noise and was therefore thoroughly checked for any compression artefacts. Compression noise characteristics were taken into account in the denoising stage of the ground processing for improved performances; (2) Verify the adequacy of the compression parameters with regard to the in-flight characteristics of the instruments (MTF, radiometric spreading, ...); (3) Technological checkout of the compression unit on board the satellite. This paper will present an overview of SPOT5 mission, the methods used for on-orbit validation of the compression and, finally, all the validation results together with the lessons learned throughout this development. On-board image compression for future CNES remote sensing missions will be addressed as a conclusion.

The Moderate Resolution Imaging Spectroradiometer (MODIS) is an Earth-viewing sensor that is currently operating on the EOS-Terra and EOS-Aqua satellites. Each MODIS instrument has 36 bands. Data are received from 490 detectors in these reflective Solar and infrared emissive bands. Calibration of the 490 channels on each MODIS instrument is performed by the MODIS Characterization Support Team (MCST), which works closely with the members of the MODIS Science Team to provide a calibration product that is useful for their geophysical products. The MODIS Level 1B (L1B) algorithm performs radiometric calibration for the duration of each mission. The L1B input files, output data products, and the emissive and reflective calibration algorithms are described. The Look-up Tables (LUTs) that provide the instrument characterization needed to run the L1B software are also described. We briefly present the L1B code standards, properties, and enhancement process. Lastly, "lessons learned" are discussed.

The High Resolution Dynamics Limb Sounder (HIRDLS) Science Investigator-led Processing System (SIPS) is a software framework designed for operational, event-driven, instrument data processing. At its foundation are multiple open-source components that are assembled into a distributed architecture. The framework allows creation and modification of a wide array of processor and product scenarios. Java is used as the primary software language though processors can be implemented with any technology supported on the target platform. The software development approach, design and implementation technology are described along with several features and benefits of the system.

The Advanced Land Imager (ALI) is a VNIR/SWIR, pushbroom instrument that is flying aboard the Earth Observing-1 (EO-1) spacecraft. Launched on November 21, 2000, the objective of the ALI is to flight validate emerging technologies that can be infused into future land imaging sensors. During the first two and one-half years on-orbit, the performance of the ALI has been evaluated using on-board calibrators and vicarious observations. The results of this evaluation are presented here. The spatial performance of the instrument, derived using stellar, lunar, and bridge observations, is summarized. The radiometric stability of the focal plane and telescope, established using solar, lunar, ground truth, and on-board sources, is also provided.

The DLR small satellite BIRD (Bi- spectral Infrared Detection) is successfully operating in space since October 2001. The main payload is dedicated to the observation of high temperature events and consists mainly of a Bi-Spectral Infrared Push Broom Scanner (3.4-4.2μm and 8.5-9.3μm), a Push Broom Imager for the Visible and Near Infrared and a neural network classification signal processor. The BIRD mission answers topical technological and scientific questions related to the operation of a compact infra-red push-broom sensor on board of a micro satellite. A powerful Payload Data Handling System (PDH) is responsible for all payload real time operation, control and on-board science data handling. The IR cameras are equipped with an advanced real time data processing allowing an autonomously adaptation of the dynamic range to different scenarios. The BIRD mission control, the data reception and the data processing is conducted by the DLR ground stations in Weilheim and Neustrelitz (Germany) and is experimentally performed by a low cost ground station implemented at DLR Berlin-Adlershof. The BIRD on ground data processing chain delivers radiometric and geometric corrected data products, which will be also described in this paper. The BIRD mission is an exemplary demonstrator for small satellite projects dedicated to the hazard detection and monitoring.

Meteosat Second Generation (MSG) is a series of 3 (possibly 4) geostationary satellites developed and procured by the European Space Agency (ESA) on behalf of the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT). The first satellite (MSG-1) was launched on 29th August, 2002 by an Ariane 5 rocket. After the LEOP and the drift to the commissioning longitude, the satellite was positioned above the Atlantic Ocean at 10.5° W (longitude) with a 1.9° orbital inclination. The prime contractor of MSG satellite series is Alcatel Space Industries (France) and the Imaging Radiometer SEVIRI is procured under the responsibility of Astrium SAS (France). The MSG-1 satellite commissioning is performed by EUMETSAT with the support of ESA and industry. MSG-1 commissioning started on 25th September 2002. This paper addresses the results of the SEVIRI functionality tests performed as part of the MSG-1 commissioning and describes the radiometric and imaging performances of the main optical payload SEVIRI, including the image quality after its rectification and calibration. The performance results presented here are based on an offline analysis of a limited subset of the large amount of SEVIRI data obtained during the MSG-1 commissioning tests.

Ozone Monitoring Instrument (OMI) is a Dutch-Finnish ozone monitoring imaging spectrometer that is designed to provide accurate measurements of total column ozone, ozone profile, surface UV irradiance, aerosols and cloud characteristics, and the column amounts of trace gases SO₂, NO₂, HCHO, BrO, and OClO at high spatial resolution. The OMI along with the three other instruments, the Microwave Limb Sounder (MLS), the High Resolution Dynamics Limb Sounder (HIRDLS), and the Tropospheric Emission Spectrometer (TES), will be flown on the NASA’s Aura mission in early 2004. The standard atmospheric chemistry and dynamics products derived from OMI, MLS, and HIRDLS will be archived at the NASA's GES DAAC (TES data products will be archived at NASA Langley Research Center DAAC) and will be freely available to the public. Highlights of OMI data products, as well as their availability, distribution and data support are discussed in this paper.

Designed to retrieve near-surface winds over the ocean, the SeaWinds scatterometer makes 13.4 GHz Ku-band measurements of the normalized radar backscatter of the Earth's surface. SeaWinds backscatter measurements are being used in a wide variety of studies, including ocean wind retrieval, sea-ice mapping and classification, iceberg tracking, vegetation, soil moisture, and snow accumulation. Two SeaWinds instruments are currently flying in orbit. Due to the high spatial sampling density, SeaWinds data is ideally suited for the application of reconstruction and resolution enhancement algorithms. Such algorithms require accurate knowledge of the spatial response function of the individual measurements, "slices" and "eggs." Standard SeaWinds data products from JPL include the locations of the measurements, but not the response functions. In this paper we derive the spatial response function for both egg and slices. The response functions vary with antenna azimuth and orbit location. Because computation of the response function is laborious, methods of tabularizing and interpolating the response function have been developed. These are described in this paper. We provide code and the tables to enable computation the response function using information from standard JPL data products. We hope these will further the development of resolution-enhanced SeaWinds data. Examples of resulting enhanced resolution images are included.