The Global Earth Observation System of Systems (GEOSS) will provide long-term data
for a wide variety of communities. . To be meaningful and useful in the societal benefit
applications, the global satellite observations need continuous and consistent measurements,
which require improved cross instrument calibration and product validation. Cross-sensor
calibration/validation is necessary for achieving data continuity and consistency.
Several institutes and laboratories have been trying to plan and initiate the appropriate
processes to accomplish the calibration/validation indicated for the various measurements and
disciplines that will most likely be involved. EastFIRE Laboratory at George Mason University
(GMU) in the United States has been working on a cross-sensor calibration/validation system
during the past seven years, and has demonstrated the capability and performance of the system
for NPP/NPOESS prelaunch testing support. The EastFIRE cross-sensor calibration and
validation system can be further extended to include more sensors and measurements to support
the GEOSS communities in data consistency control and construction of long-term consistent
Climate Data Records (CDRs). The primary objectives of the present system expansion and
integration are:
1) to support satellite observation research and operations; 2) to support multiple sensor
cross-calibration and product cross-validation; 3) to support prelaunch testing and post-launch
validation of the next generation earth observation missions; and 4) to build global FCDRs
(Fundamental Climate Data Records) for the GEOSS communities using Sensor Data Records
(SDRs) from multiple sensors.
Satellite infrared hyperspectral instruments provide atmospheric soundings with high spatial resolution. Already
implemented aboard polar orbiting satellites, these instruments have provided data that are proving to improve greatly
global Numerical Weather Prediction (NWP). When implemented aboard geostationary satellites as imaging
spectrometers, even greater impacts on global NWP are expected from their capability to observe vertically resolved
cloud and water vapor tracer winds. Possibly most important, geostationary imaging spectrometry will enable much
improved mesoscale severe weather prediction because of the ability to observe atmospheric dynamics through nearcontinuous
observation of the three dimensional water vapor and temperature distribution of the atmosphere.
Furthermore, hyperspectral measurements of greenhouse and pollutant gas fluxes from geostationary orbit are expected
to be an important ingredient for understanding climate change and producing timely air quality forecasts.
In this paper, the Global Earth Observation System of Systems (GEOSS), recent improvements in the satellite observing
system, and the importance and expected benefits of geostationary satellite imaging spectrometry for the GEOSS are
discussed. Demonstration of a few of the expected measurement capabilities of these systems is provided from
experimental aircraft and satellite measurements. Finally, the status of the development of the geostationary satellite
imaging spectrometer is provided.
During the GEOSS era, a Doppler wind lidar (DWL) described in this paper will be able to measure
directly the 3-dimensional wind field. These observations can be used synergistically with traditional
imagers, passive radiometers and active scatterometers to improve significantly the weather and climate
missions.
Synergisms being explored include laser height assignment and layer wind calibration for Cloud Motion
Vectors (CMVs) and Water Vapor Motion Vectors (WVMVs), and the adjudication of directional
ambiguities in Ocean Vector Winds (OVW) retrievals. These synergistic links will be incorporated into
adaptive targeting schemes being evaluated within Observing System Simulation Experiments designed
to explore ways to optimize the utility of the DWL observations.
Atmospheric thermodynamic parameters and surface properties are basic meteorological variables for weather
forecasting. A physical geophysical parameter retrieval scheme dealing with cloudy and cloud-free radiances observed
with satellite ultraspectral infrared sounders has been developed and applied to data from the Infrared Atmospheric
Sounding Interferometer (IASI) and the Atmospheric InfraRed Sounder (AIRS). The retrieved parameters presented
herein are from radiance data gathered during the Joint Airborne IASI Validation Experiment (JAIVEx). JAIVEx
provided intensive aircraft observations obtained from airborne Fourier Transform Spectrometer (FTS) systems, in-situ
measurements, and dedicated dropsonde and radiosonde measurements for the validation of the IASI products. Here,
IASI atmospheric profile retrievals are compared with those obtained from dedicated dropsondes, radiosondes, and the
airborne FTS system. The IASI examples presented here demonstrate the ability to retrieve fine-scale horizontal features
with high vertical resolution from satellite ultraspectral sounder radiance spectra.
Absolute sensor calibration is the basis on which measured radiance from multiple sensors can be
compared with each other or with time. Despite the increasing sophistication and reliability of on-board
satellite sensor calibration systems, vicarious (or ground-look) calibration methods remain an important
component of calibration validation. These methods, particularly the surface reflectance method, typically
involve intensive measurements, at the time of satellite over-flight, of the surface and atmospheric
properties (such as, surface reflectance and temperature, atmospheric pressure, water vapor and temperature
profiles, and aerosol optical properties) that are ideally uniform, stable, and well defined. Such conditions
are found, for example, in the desert southwest of the United States or in the atmosphere above high
altitude lakes. A key measurement that has been often neglected and one that is becoming increasingly
important due to rapid industrialization of developing countries, is the single scattering albedo of aerosols--a measure of the fraction of light that is scattered from the total amount extinguished from the direct beam;
typical values range from close to 1 to 0.8 or lower for highly absorbing aerosols. It is obtained from a
measurement of aerosol absorption for which many techniques are available. The error in the measurement
of absorptance disproportionately impacts the error in the scattered radiance as seen by the remote sensor.
Here we describe the sensitivity of sensor calibration to aerosol absorption and illustrate why it should be
an important measurement in the field calibration campaigns, including those planned for the next
generation satellites of the US National Polar-Orbiting Operational Environmental Satellite System.
Atmospheric and surface thermodynamic parameters retrieved with advanced hyperspectral remote sensors of Earth observing satellites are critical for weather prediction and scientific research. The retrieval algorithms and retrieved parameters from satellite sounders must be validated to demonstrate the capability and accuracy of both observation and data processing systems. The European AQUA Thermodynamic Experiment (EAQUATE) was conducted mainly for validation of the Atmospheric InfraRed Sounder (AIRS) on the AQUA satellite, but also for assessment of validation systems of both ground-based and aircraft-based instruments which will be used for other satellite systems such as the Infrared Atmospheric Sounding Interferometer (IASI) on the European MetOp satellite, the Cross-track Infrared Sounder (CrIS) from the NPOESS Preparatory Project and the following NPOESS series of satellites. Detailed inter-comparisons were conducted and presented using different retrieval methodologies: measurements from airborne ultraspectral Fourier transform spectrometers, aircraft in-situ instruments, dedicated dropsondes and radiosondes, and ground based Raman Lidar, as well as from the European Center for Medium range Weather Forecasting (ECMWF) modeled thermal structures. The results of this study not only illustrate the quality of the measurements and retrieval products but also demonstrate the capability of these validation systems which are put in place to validate current and future hyperspectral sounding instruments and their scientific products.
A linear mathematical error model for the assessment of validation activity of atmospheric retrievals is presented. The purpose of the validation activity is to assess the actual performance of the remote sensing validated system while in orbit by comparing its measurements to some relevant-validating-data sets. The validating system samples volumes of the atmosphere at times and locations that are different from the ones when and where the validated system makes its own observations. The location of the validating system can be either stationary, e.g. a ground ARM site, or movable, e.g. an aircraft or some other satellites. The true states may be correlated or not. The sampled volumes differ from each other by their location, timing, and size. The validated and validating systems have different vertical resolution and grid, absolute accuracy, and noise level. All the above factors cause apparent differences between the data to be compared. The validation assessment model makes the comparison accurate by allowing for the differences. The model can be used for assessment and interpretation of the validation results when the above mentioned sources of discrepancies are significant, as well as for evaluation of a particular validating data source.
The overall objective of the NPOESS Preparatory Project (NPP)/National Polar-Orbiting Operational Environmental Satellite System (NPOESS) Joint Government Shared System Performance Responsibility (SSPR) Contractor Calibration Validation (CalVal) Program is to ensure the environmental data products meet the system specification, and satisfy the users and scientific community. Work spans all program phases, from pre-launch sensor characterization and data prduct verification to on-orbit calibration verification/data product validation and long-term data product quality monitoring/maintenance. A cooperative approach is in place to leverage expertisxe throughout the program-developer, government-customer and users, and scientific community. Draft Calibration and Validation Plans are in development and NPP pre-launch activities are under way. This paper provides an NPP/NPOESS Cal Val Program system perspective, describes the cooperative strategy, and summarizes progress and planned activities to ensure a successful NPP mission.
The Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) is the first hyper-spectral remote sounding system to be orbited aboard a geosynchronous satellite. The GIFTS is designed to obtain revolutionary observations of the four dimensional atmospheric temperature, moisture, and wind structure as well as the distribution of the atmospheric trace gases, CO and O3. Although GIFTS will not be orbited until 2006-2008, a glimpse at the its measurement capabilities has been obtained by analyzing data from the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Airborne Sounder Test-bed- Interferometer (NAST-I) and Aqua satellite Atmospheric Infrared Sounder (AIRS). In this paper we review the GIFTS experiment and empirically assess measurement expectations based on meteorological profiles retrieved from the NAST aircraft and Aqua satellite AIRS spectral radiances.
The Integrated Program Office (IPO) developed and supports high-altitude aircraft flights of the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Airborne Sounding Testbed (NAST) as part of risk mitigation activities for future NPOESS sensors. The NAST-Interferometer (NAST-I) is a high spectral and spatial resolution (0.25 cm-1 and 0.13 km nadir footprint per km of aircraft altitude, respectively) cross-track scanning (2 km swath width per km of altitude) Fourier Transform Spectrometer (FTS) observing within the 3.7 - 15.5 micron spectral range. NAST-I infrared spectral radiances are used to characterize atmospheric thermal and moisture structure and provide information on radiatively active trace gases (e.g. O3 & CO) observed during flights. These direct and derived NAST-I data products greatly contribute toward instrument and forward model pre-launch specification optimization and will enhance post-launch calibration/validation activities for the Cross-track Infrared Sounder, CrIS, to fly on NPP and NPOESS (as well as for other advanced atmospheric spaceborne sensors). In this paper we address some of the challenges associated with validating infrared spectral radiances obtained from such high spectral resolution remote sensing systems. This will include comparison of NAST-I infrared spectral radiances measured during recent field experiment campaigns with other radiance measurements as well as radiance calculations performed using Line-by-Line (LBL) forward radiative transfer model based on independent, nearly-coincident observations of atmospheric state.
The Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) is the first hyper-spectral remote sounding system to be orbited aboard a geosynchronous satellite. The GIFTS is designed to obtain revolutionary observations of the four dimensional atmospheric temperature, moisture, and wind structure as well as the distribution of the atmospheric trace gases, CO and O3. Although GIFTS will not be orbited until 2005, a glimpse at its measurement capabilities has been obtained by analyzing data from a series of aircraft flights of the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Airborne Sounder Test-bed- Interferometer (NAST-I). In this paper we review the GIFTS experiment and empirically assess measurement expectations based on meteorological profiles retrieved from the aircraft data.
This paper presents the strategy designed by the government team, IPO and NASA, for the NPOESS Preparatory Project (NPP) instrument characterization and calibration, and product validation, in preparation for the NPOESS operational system. NPP is a risk reduction mission for NPOESS, managed by the IPO and NASA. NPP will carry three (3) instruments, VIIRS, CrIS and ATMS, and an Instrument of Opportunity to be announced soon. Responsibilities will be
shared between government and industry participants to ensure high performance at all system levels. This will include provision of the sensor pre-launch characterization and post-launch calibration procedures, definition of validation approaches for all NPP products, and identification of the resources and assets required to achieve these activities. This calibration and validation plan will benefit greatly from the validation efforts and infrastructure of several existing programs at the national and international scale. The synergy between the SSPR system integrator and the government
team, IPO and NASA, will build the foundation for interactions that will lead to better sensors, better algorithms, and better ground data systems.
A new era in atmospheric remote sensing will begin with the launch of the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project (NPP) spacecraft in 2006, and the multiple operational NPOESS launches in sun-synchronous orbital planes (nominally 13:30, 17:30, or 21:30 local equatorial crossing times) starting in 2009. Cloud and atmosphere polar-orbiting environmental satellite data will be profoundly improved in radiometric quality, spectral coverage, and spatial resolution relative to current operational civilian and military polar-orbiting systems. The NPOESS Visible Infrared Imaging Radiometer Suite (VIIRS) will provide Environmental Data Records (EDRs) for day and night atmosphere and cloud operational requirements, as well as sea surface temperature (SST) and many important land EDRs by ground processing of raw data records (RDRs) from the VIIRS sensor. VIIRS will replace three currently operating sensors: the Defense Meteorological Satellite Program (DMSP) Operational Line-scanning System (OLS), the NOAA Polar-orbiting Operational Environmental Satellite (POES) Advanced Very High Resolution Radiometer (AVHRR), and the NASA Earth Observing System (EOS Terra and Aqua) MODerate-resolution Imaging Spectroradiometer (MODIS). This paper describes the VIIRS all-reflective 22-band single-sensor design, following the Critical Design Review (CDR) in Spring 2002. VIIRS provides low noise (driven by ocean color for the reflective visible and near-IR spectral bands and by SST for the emissive mid and long-wave IR spectral bands), excellent calibration and stability (driven by atmospheric aerosol and cloud EDRs, as well as SST), broad spectral coverage, and fine spatial resolution driven by the cloud imagery EDR. In addition to improved radiometric, spectral, and spatial performance, VIIRS features DMSP OLS-like near-constant resolution, global twice-daily coverage in each orbit plane, and direct heritage to proven design innovations from the successful Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and Earth Observing System (Terra and Aqua) MODIS.
A new high spectral resolution (0.25 cm-1) and high spatial resolution (2.6 km) scanning (46 km swath width) Fourier Transform Spectrometer (FTS) has been built for flight on NASA high altitude (approximately 20 km) aircraft. The instrument, called the NPOESS Aircraft Sounding Testbed- Interferometer (NAST-I), has been flown during several field campaigns to provide experimental observations needed to finalize specifications and to test proposed designs for future satellite instruments; specifically, the Cross-track Infrared Sounder (CrIS) to fly on the National Polar-orbiting Operational Environmental Satellite System (NPOESS). NAST-I provides new and exciting observations of mesoscale structure of the atmosphere, including the fine scale thermodynamic characteristics of hurricanes. The NAST-I instrument is described, its excellent spectral and radiometric performance is demonstrated, and surface and atmospheric remote sensing results obtained during airborne measurement campaigns are presented.
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