Polar-orbiting Operational Environmental Satellite Research Articles

Cirrus cloud top temperatures retrieved from radiances in the National Polar-Orbiting Operational Environmental Satellite System--Visible Infrared Imager Radiometer Suite 855 and 120 μm bandpasses

We describe what is believed to be a new approach developed for the National Polar-Orbiting Operational Environmental Satellite System (NPOESS) to retrieve pixel-level, cirrus cloud top temperatures (CTTs) from radiances observed in the 8.55 and 12.0 microm bandpasses. The methodology solves numerically a set of nonlinear algebraic equations derived from the theory of radiative transfer based upon the correlation between emissivities in these two bandpasses. This new approach has been demonstrated using NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) as a proxy to Visible Infrared Imager Radiometer Suite (VIIRS) data. Many scenes have been analyzed covering a wide range of geophysical conditions, including single-layered and multilayered cirrus cloud situations along with diverse backgrounds and seasons. For single-layer clouds, the new approach compares very favorably with the MODIS 5 km resolution cloud products; the mean CTT for both methods are very close, while the standard deviation for the new approach is smaller. However, in multilayered cloud situations, the mean CTTs for the new approach appear to be colder than the CTTs from MODIS cloud products, which are acknowledged to be too warm. Finally, partly because the new approach is applied at the pixel level, CTTs do not increase toward cloud edges as is seen in the MODIS products. Based upon these initial results, the new approach to retrieve improved VIIRS cloud top properties has been incorporated into the ground-based data processing segment of the NPOESS system where prelaunch testing of all VIIRS algorithms continues.

SeaWiFS long-term solar diffuser reflectance and sensor noise analyses

The NASA Ocean Biology Processing Group's Calibration and Validation (Cal/Val) team has undertaken an analysis of the mission-long Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) solar calibration time series to assess the long-term degradation of the solar diffuser reflectance over 9 years on orbit. The SeaWiFS diffuser is an aluminum plate coated with YB71 paint. The bidirectional reflectance distribution function of the diffuser was not fully characterized before launch, so the Cal/Val team has implemented a regression of the solar incidence angles and the drift in the node of the satellite's orbit against the diffuser time series to correct for solar incidence angle effects. An exponential function with a time constant of 200 days yields the best fit to the diffuser time series. The decrease in diffuser reflectance over the mission is wavelength dependent, ranging from 9% in the blue (412 nm) to 5% in the red and near infrared (670-865 nm). The Cal/Val team has developed a methodology for computing the signal-to-noise ratio (SNR) for SeaWiFS on orbit from the diffuser time series corrected for both the varying solar incidence angles and the diffuser reflectance degradation. A sensor noise model is used to compare on-orbit SNRs computed for radiances reflected from the diffuser with prelaunch SNRs measured at typical radiances specified for the instrument. To within the uncertainties in the measurements, the SNRs for SeaWiFS have not changed over the mission. The on-orbit performance of the SeaWiFS solar diffuser should offer insight into the long-term on-orbit performance of solar diffusers on other instruments, such as the Moderate-Resolution Imaging Spectrometer [currently flying on the Earth Observing System (EOS) Terra and Aqua satellites], the Visible and Infrared Radiometer Suite [scheduled to fly on the NASA National Polar-orbiting Operational Environmental Satellite System (NPOESS) and NPOESS Preparatory Project (NPP) satellites] and the Advanced Baseline Imager [scheduled to fly on the National Oceanic and Atmospheric Administration Geostationary Environmental Operational Satellite Series R (GOES-R) satellites].

History of the NOAA satellite program

For more than 46 years, NOAA's environmental satellites have been an integral key to life-saving weather and climate forecasts for the United States. NOAA, the National Oceanic and Atmospheric Administration, has a rich history of successfully operating geostationary operational environmental satellites (GOES) and polar-orbiting environmental satellites (POES) that have helped take some of the mystery out of atmospheric phenomenon. Through the years, NOAA, with cooperation with NASA, has developed increasingly advanced satellites that have provided higher spatial and temporal resolution images, operational soundings, atmospheric temperature and moisture data in all weather situations. During those 46 years, NOAA has also built strong partnerships within the U.S. and throughout the world, leading to satellite-data sharing agreements that will strengthen the scientific community's understanding of the world's changing climate.The article, History of the NOAA Satellite Program, traces the development of the U.S. weather satellite system from an early commitment in 1953 by the Eisenhower administration to hoist an Earth satellite in orbit in 1958, to the next generation polar-orbiting system, the National Polar-orbiting Operational Environmental Satellite System, or NPOESS.

Panel considers future of U.S. land imaging

A U.S. government interagency working group charged with developing a strategy for the future of U.S. land imaging began eliciting comments from the users of Landsat data at a public workshop held on 26 July in Washington, D.C.The U.S. Office of Science and Technology Policy, in December 2005, announced that it would acquire the Landsat Data Continuity Mission (LDCM), which for a time had been planned to be part of the National Polarorbiting Operational Environmental Satellite System. In addition, the National Science and Technology Council (NSTC) and other government agencies would develop a plan for what to do after Landsat and the LDCM to acquire moderate‐resolution land images.

NASA MODIS Previews NPOESS VIIRS Capabilities

Abstract The Visible/Infrared Imager Radiometer Suite (VIIRS), scheduled to fly on the satellites of the National Polar-orbiting Operational Environmental Satellite System, will combine the missions of the Advanced Very High Resolution Radiometer (AVHRR), which flies on current National Oceanic and Atmospheric Administration satellites, and the Operational Linescan System aboard the Defense Meteorological Satellite Program satellites. VIIRS will offer a number of improvements to weather forecasters. First, because of a sophisticated downlink and relay system, VIIRS latencies will be 30 min or less around the globe, improving the timeliness and therefore the operational usefulness of the images. Second, with 22 channels, VIIRS will offer many more products than its predecessors. As an example, a true-color simulation is shown using data from the Earth Observing System’s Moderate Resolution Imaging Spectroradiometer (MODIS), an application current geostationary imagers cannot produce because of a missing “green” wavelength channel. Third, VIIRS images will have improved quality. Through a unique pixel aggregation strategy, VIIRS pixels will not expand rapidly toward the edge of a scan like those of MODIS or AVHRR. Data will retain nearly the same resolution at the edge of the swath as at nadir. Graphs and image simulations depict the improvement in output image quality. Last, the NexSat Web site, which provides near-real-time simulations of VIIRS products, is introduced.

Polar Satellites Pared

The U.S. Department of Defense has dropped a number of climate sensors from a satellite program as part of a restructuring of the National Polar-Orbiting Operational Environmental Satellite System (NPOESS) ( Science , 2 June, p. [1296][1]). Along with scaling the program back from six satellites to

Future of Environmental Satellite Program uncertain

The National Polar‐orbiting Environmental Satellite System (NPOESS), over budget and behind schedule, is undergoing a mandatory review process that could leave the program cut back or canceled. However, the outcome of the review will not be known until June, witnesses testified at a 30 March hearing before the U.S. Senate Commerce, Science, and Transportation Subcommittee on Disaster Prevention and Prediction.NPOESS is a set of six satellites that are intended to replace the U.S. National Oceanic and Atmospheric Administration's (NOAA) Polar‐orbiting Operational Environmental Satellite (POES) program and the U.S. Department of Defense (DOD) Defense Meteorological Satellite Program, which collects weather data for the military. POES supports many of NOAA's environmental monitoring programs.

NexSat: Previewing NPOESS/VIIRS Imagery Capabilities

Under the auspices of the National Polar-orbiting Operational Environmental Satellite System's (NPOESS) Integrated Program Office (IPO), the Naval Research Laboratory (NRL) has developed “NexSat” (www.nrlmry.navy.mil/nexsat_pages/nexsat_home.html)—a public-access online demonstration over the continental United States (CONUS) of near-real-time environmental products highlighting future applications from the Visible/Infrared Imager/Radiometer Suite (VIIRS). Based on a collection of operational and research-grade satellite observing systems, NexSat products include the detection, enhancement, and where applicable, physical retrieval of deep convection, low clouds, light sources at night, rainfall, snow cover, aircraft contrails, thin cirrus layers, dust storms, and cloud/aerosol properties, all presented in the context of value-added imagery. The purpose of NexSat is threefold: 1) to communicate the advanced capabilities anticipated from VIIRS, 2) to present this information in near–real time for use by for...

The NPOESS VIIRS Day/Night Visible Sensor

The National Polar-orbiting Operational Environmental Satellite System (NPOESS) will feature the Visible-Infrared Imager-Radiometer Suite (VIIRS), a 22-channel imager that will contribute to nearly half of the NPOESS environmental data records. Included on VIIRS will be the Day/Night band (DNB), a visible channel designed to image the Earth and its atmosphere in all conditions ranging from bright solar illumination, to nocturnal lunar illumination, and negligible external illumination. Drawing heritage from the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) instruments orbiting since the late 1960s, the DNB will be used to detect clouds at night, understand patterns of urban development based on the emissions of cities, monitor fires, and image scenes of snow and ice at the surface of the Earth. Thanks to significant engineering improvements, the DNB will produce superior capabilities to the OLS for a number of new applications.

Thermal performance of the CrIS passive cryocooler

The configuration, performance, and test validation of a passive radiant cooler for the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Crosstrack Infrared Sounder (CrIS) Instrument are presented. The cooler is required to provide cryogenic operation of IR focal planes. The 11 kg device, based on prior ITT Industries Space Systems Division coolers, requires virtually no power. It uses multiple thermally isolated cooling stages, each with an independent cryoradiator, operating at successively colder temperatures. The coldest stage, with a controlled set point at 81 K, cools a longwave IR (LWIR) focal plane. An intermediate stage, with a 98 K control point, cools detectors operating in MWIR and SWIR spectral regions. The warmest stage includes a fixed, integral earth shield that limits the thermal load from the earth in the NPOESS Operational Low-earth Orbiting (LEO) orbit. A study of the thermal balance and loads analysis used to evaluate the predicted cooler performance is discussed. High performance margins have been retained throughout the cooler development, fabrication and test phases of the program. The achievable in-orbit temperatures for this cooler are anticipated to be 73 K for the LWIR cooling stage and 91 K for the midwave IR (MWIR)/shortwave IR (SWIR) stage. Test results from two iterations of thermal vacuum verification testing are presented. Lessons learned from the first test, which failed to produce the predicted performance are included. The thermal model of the cooler and test configuration was used to identify deficiencies in the test targets resulting in unexpected heat loads. Corrective action was implemented to remove the heat leaks and a second test verified both the cooler performance and the correlation of the detailed thermal model.

A Statistical Approach to WindSat Ocean Surface Wind Vector Retrieval

WindSat is the first space-based polarimetric microwave radiometer. It is designed to evaluate the capability of polarimetric microwave radiometry to measure ocean surface wind vectors from space. The sensor provides risk reduction for the National Polar-orbiting Operational Environmental Satellite System Conical Scanning Microwave Imager/Sounder, which is planned to provide wind vector data operationally starting in 2010. The channel set also enables retrieval of sea surface temperature, and columnar water vapor and cloud liquid water over the oceans. We describe statistical algorithms for retrieval of these parameters, and a combined statistical/maximum-likelihood estimator algorithm for retrieval of wind vectors. We present a quantitative analysis of the initial wind vector retrievals relative to QuikSCAT wind vectors.

Weather Satellite Gap Looms

The United States could suffer a several-year hiatus in civilian weather data-gathering due to the slow development of an ambitious satellite. The National Polar-orbiting Operational Environmental Satellite System was supposed to be an economical replacement for two National Oceanic and Atmospheric

Comparison of the University of California at Los Angeles Line-by-Line Equivalent Radiative Transfer Model and the Moderate-Resolution Transmission Model for accuracy assessment of the National Polar-Orbiting Operational Environmental Satellite System’s Visible–Infrared Imager–Radiometer Suite cloud algorithms

To support the verification and implementation of the National Polar-Orbiting Operational Environmental Satellite System's Visible-Infrared Imaging-Radiometric Suite (VIIRS) algorithms used for inferring cloud environmental data records, an intercomparison effort has been carried out to assess the consistency between the simulated cloudy radiances-reflectances from the University of California at Los Angeles Line-by-Line Equivalent Radiative Transfer Model and those from the Moderate-Resolution Transmission Model (MODTRAN) with the 16 stream Discrete Ordinate Radiative Transfer Model (DISORT) incorporated. For typical ice and water cloud optical depths and particle sizes, we found discrepancies in the visible and near-infrared reflectances from the two models, which presumably are due to the difference in phase function (nonspherical versus Henyey-Greenstein), different numbers of phase function expansion terms (16 versus 200 terms), and different treatment of forward peak truncation in each model. Using the MODTRAN4, we also found substantial differences in the infrared radiances for optically thick clouds. These differences led to the discovery by MODTRAN4 developers of an inconsistency in the MODTRAN4-DISORT interface. MODTRAN4 developers corrected the inconsistency, which provided dramatic reductions in the differences between the two radiative transfer models. The comparison not only affects the prospective test plan for the VIIRS cloud algorithms but also should lead to improvements in future MODTRAN releases.

Satellite Instrument Calibration for Measuring Global Climate Change: Report of a Workshop

Measuring the small changes associated with long-term global climate change from space is a daunting task. The satellite instruments must be capable of observing atmospheric and surface temperature trends as small as 0.1°C decade−1, ozone changes as little as 1% decade−1, and variations in the sun's output as tiny as 0.1% decade−1. To address these problems and recommend directions for improvements in satellite instrument calibration, the National Institute of Standards and Technology (NIST), National Polar-orbiting Operational Environmental Satellite System–Integrated Program Office (NPOESS-IPO), National Oceanic and Atmospheric Administration (NOAA), and National Aeronautics and Space Administration (NASA) organized a workshop at the University of Maryland Inn and Conference Center, College Park, Maryland, 12–14 November 2002. Some 75 scientists participated including researchers who develop and analyze long-term datasets from satellites, experts in the field of satellite instrument calibration, and phy...

Effects of air-sea interaction parameters on ocean surface microwave emission at 10 and 37 GHz

WindSat, the first polarimetric radiometer on orbit, launched in January 2003, provides the promise of passive ocean wind vector retrievals on a continuous basis, simultaneous with the retrieval of many other geophysical variables such as sea surface temperature, atmospheric water vapor, cloud liquid water, and sea ice extent and concentration. WindSat also serves as risk reduction for the upcoming National Polar-orbiting Operational Environmental Satellite System (NPOESS) Conical Scanning Microwave Imager/Sounder (CMIS). Since the dependence of microwave brightness temperatures on wind direction is small relative to that of other parameters such as wind speed, wind direction retrieval relies on increasingly accurate knowledge of the ocean surface microwave emission, which depends upon surface properties such as roughness and foam due to wave breaking. Coordinated near-surface measurements of ocean surface microwave emission and air-sea interaction parameters are needed to quantify the effects of the processes mentioned above in surface emission models to improve the accuracy of wind vector retrievals. Such coordinated observations were performed during the Fluxes, Air-Sea Interaction, and Remote Sensing (FAIRS) experiment conducted on the R/P Floating Instrument Platform (FLIP) in the northeastern Pacific Ocean during the Fall of 2000. X- and Ka-band partially polarimetric radiometers were mounted at the end of the port boom of R/P FLIP to measure ocean surface emission at incidence angles of 45/spl deg/, 53/spl deg/, and 65/spl deg/. A bore-sighted video camera recorded the fractional area of foam in the field of view of the radiometers. Air-sea interaction parameters that were measured concurrently include wind speed, friction velocity, heat fluxes, and significant wave height. The measured dependence of ocean surface emissivity on wind speed and friction velocity is in good agreement with, and extends, earlier observations and empirical models based on satellite data. Concurrent radiometric measurements and fractional area foam coverage data strengthen the possibility of retrieval of sea surface foam coverage using airborne or spaceborne radiometry. The dependence of emissivity on atmospheric stability is shown to be much smaller than the dependence of emissivity on wind speed. Analysis of emissivity dependence on atmospheric stability alone was inconclusive, due to the variation in atmospheric stability with wind speed. The effect of long-wave incidence angle modulation on sea surface emissivity for near-surface measurements was found to be negligible when emissivity measurements were averaged over tens to hundreds of long waves.

Daytime Global Cloud Typing from AVHRR and VIIRS: Algorithm Description, Validation, and Comparisons

Abstract Three multispectral algorithms for determining the cloud type of previously identified cloudy pixels during the daytime, using satellite imager data, are presented. Two algorithms were developed for use with 0.65-, 1.6-/3.75-, 10.8-, and 12.0-μm data from the Advanced Very High Resolution Radiometer (AVHRR) on board the National Oceanic and Atmospheric Administration (NOAA) operational polar-orbiting satellites. The AVHRR algorithms are identical except for the near-infrared data that are used. One algorithm uses AVHRR channel 3a (1.6 μm) reflectances, and the other uses AVHRR channel 3b (3.75 μm) reflectance estimates. Both of these algorithms are necessary because the AVHRRs on NOAA-15 through NOAA-17 have the capability to transmit either channel 3a or 3b data during the day, whereas all of the other AVHRRs on NOAA-7 through NOAA-14 can only transmit channel 3b data. The two AVHRR cloud-typing schemes are used operationally in NOAA’s extended Clouds from AVHRR (CLAVR)-x processing system. The third algorithm utilizes additional spectral bands in the 1.38- and 8.5-μm regions of the spectrum that are available on the Moderate Resolution Imaging Spectroradiometer (MODIS) and will be available on the Visible–Infrared Imaging Radiometer Suite (VIIRS). The VIIRS will eventually replace the AVHRR on board the National Polar-Orbiting Operational Environmental Satellite System (NPOESS), which is currently scheduled to be launched in 2009. Five cloud-type categories are employed: warm liquid water, supercooled water–mixed phase, opaque ice, nonopaque high ice (cirrus), and cloud overlap (multiple cloud layers). Each algorithm was qualitatively evaluated through scene analysis and then validated against inferences of cloud type that were derived from ground-based observations of clouds at the three primary Atmospheric Radiation Measurement (ARM) Program sites to help to assess the potential continuity of a combined AVHRR channel 3a–AVHRR channel 3b–VIIRS cloud-type climatology. In this paper, “validation” is strictly defined as comparisons with ground-based estimates that are completely independent of the satellite retrievals. It was determined that the two AVHRR algorithms produce nearly identical results except for certain thin clouds and cloud edges. The AVHRR 3a algorithm tends to incorrectly classify the thin edges of some low- and midlevel clouds as cirrus and opaque ice more often than the AVHRR 3b algorithm. The additional techniques implemented in the VIIRS algorithm result in a significant improvement in the identification of cirrus clouds, cloud overlap, and overall phase identification of thin clouds, as compared with the capabilities of the AVHRR algorithms presented in this paper.

Correlation between visual defects and increased dark current in large-area Hg1−xCdxTe photodiodes

The Cross-Track Infrared Sounder (CrIS) program [an instrument on the National Polar-Orbiting Operational Environmental Satellite System (NPOESS)] requires photodiodes with spectral cutoffs denoted by short-wavelength infrared [γc(98 K) ∼5.1 µm], midwavelength infrared [γc(98 K) ∼9.1 µm], and long-wavelength infrared (LWIR) [γc(81 K) ∼15.5 µm]. The CrIS instrument also requires large-area (850-µm-diameter) photodiodes with state-of-art performance. Molecular beam epitaxy (MBE) is used to grow n-type short-wavelength infrared, midwavelength infrared, or LWIR Hg1−xCdxTe on latticematched CdZnTe. Detectors with p-type implants 7 µm in diameter are used to constitute the 850-µm-diameter lateral collection diodes (LCDs). The photodiode architecture is the double-layer planar heterostructure architecture.

Tropospheric CO observed with the NAST-I retrieval methodology, analyses, and first results

High-resolution infrared spectra from aircraft and space-based observations contain information about tropospheric carbon monoxide (CO) as well as other trace species. A methodology for retrieving tropospheric CO from such remotely sensed spectral data has been developed for the National Polar-Orbiting Operational Environmental Satellite System's Airborne Sounder Testbed-Interferometer (NAST-I). CO profiles of the troposphere, together with its thermodynamic properties, are determined by use of a three-stage retrieval approach that combines the algorithms of physically based statistical eigenvector regression, simultaneous and iterative matrix inversion, and single-variable error-minimization CO profile matrix inverse retrieval. The NAST-I is collecting data while it is aboard high-altitude aircraft throughout many field campaigns. Detailed retrieval analyses based on the NAST-I instrument system along with retrieval results from several recent field campaigns are presented to demonstrate NAST-I CO retrieval capability.

A Four-Season Impact Study of Rawinsonde, GOES, and POES Data in the Eta Data Assimilation System. Part II: Contribution of the Components

Abstract The impact of in situ rawinsonde observations (raob), remotely sensed Geostationary Operational Environmental Satellite (GOES), and Polar-Orbiting Operational Environmental Satellite (POES) observations routinely used in NCEP’s Eta Data Assimilation/Forecast System (EDAS) is studied for extended-length time periods during four seasons. This work examines the contribution of nine individual components of the total observing system. The nine data types examined include rawinsonde mass and wind observations, GOES mass and wind observations, POES observations from the Microwave Sounding Unit (MSU), the Advanced Microwave Sounding Unit (AMSU-A and AMSU-B), the High Resolution Infrared Radiation Sounder (HIRS), and column total precipitable water and low-level wind observations from the Special Sensor Microwave Imager (SSM/I). The results are relevant for users of the Eta Model trying to compare/contrast the overall forecast impact of traditional, largely land-based rawinsonde observations against remotely sensed satellite observations, which are available domainwide. The case studies chosen consist of 15-day periods during fall 2001, winter 2001/02, spring 2002, and summer 2002. Throughout these periods, a November 2001 32-km version of the EDAS is run 10 times at both 0000 and 1200 UTC. The 10 runs include a control run, which utilizes all data types routinely used in the EDAS, and 9 experimental runs in which one of the component data types noted above is denied. Differences between the experimental and control runs are then accumulated over the 15-day periods and analyzed to demonstrate the 00-h sensitivity and 24-h forecast impact of these individual data types in the EDAS. The diagnostics are computed over the entire horizontal model domain and a subsection covering the continental United States (CONUS) and adjacent coastal waters on isobaric surfaces extending into the lower stratosphere. The 24-h forecast impact results show that a positive forecast impact is achieved from most of the nine component data sources during all four time periods. HIRS, MSU, and SSM/I wind observations yield only a slight positive forecast impact to all fields. Rawinsonde and GOES wind observations have the largest positive forecast impact for temperature over both the entire model domain and the extended CONUS. The same data types also provide the largest forecast impact to the u component of the wind, while GOES wind observations provide the largest forecast impact to moisture.

The NPOESS Airborne Sounding Testbed Interferometer—Remotely Sensed Surface and Atmospheric Conditions during CLAMS

Abstract During the Chesapeake Lighthouse and Aircraft Measurements for Satellites (CLAMS), the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Airborne Sounder Testbed-Interferometer (NAST-I), flying aboard the high-altitude Proteus aircraft, observed the spatial distribution of infrared radiance across the 650–2700 cm−1 (3.7–15.4 μm) spectral region with a spectral resolution of 0.25 cm−1. NAST-I scans cross track with a moderate spatial resolution (a linear ground resolution equal to 13% of the aircraft altitude at nadir). The broad spectral coverage and high spectral resolution of this instrument provides abundant information about the surface and three-dimensional state of the atmosphere. In this paper, the NAST-I measurements and geophysical product retrieval methodology employed for CLAMS are described. Example results of surface properties and atmospheric temperature, water vapor, ozone, and carbon monoxide distributions are provided. The CLAMS NAST-I geophysical dataset is available for use by the scientific community.