Szewczyk, Z. Peter; Smith, G. Louis; Daniels, Janet L.; Priestley, Kory J.Szewczyk, Z. P., G. L. Smith, J. L. Daniels, K. J. Priestley, 2023: Comparison of unfiltered CERES shortwave radiances measured in the minor plane over snow/ice of Greenland during summer solstices. Remote Sensing of Clouds and the Atmosphere XXVIII, 12730, 83-93. doi: 10.1117/12.2678565. A purpose of this paper is to present comparison of unfiltered radiances measured by CERES scanners when their scanning is aligned in the plane orthogonal to the solar plane and targeting Greenland around the time of summer solstice. Since the summer solstice in 2002, FM1 on Terra and FM4/FM3 on Aqua have been scanning in the minor plane for the month of June to collect comparison data. Measurements of FM5 on S-NPP and FM6 on NOAA20 have been added to this dataset starting in 2012 and 2018, respectively, with the data collection extended from May to July due to orbit characteristics. This unique dataset presents one-of-a-kind opportunity to compare radiances measured from four different platforms to assess CERES calibrations, particularly the consistency of their shortwave channel, as the solar zenith angles are the smallest for high latitudes producing relatively strong SW signal over ice/snow/clouds of Greenland. Results of comparison reported in this paper will be used in work to release new and updated versions, Edition 5, of ERBE-like (ES8) data products, for Terra and Aqua scanners.
Priestley, Kory J.; Thomas, Susan; Smith, Nathaniel; Daniels, Janet; Wilson, Robert; Walikainen, Dale; Ashraf, AnumPriestley, K. J., S. Thomas, N. Smith, J. Daniels, R. Wilson, D. Walikainen, A. Ashraf, 2018: Ensuring continuity of earth radiation budget observations initial results of CERES FM-6 on NOAA-20 (Conference Presentation). Earth Observing Systems XXIII, 10764, 107640Q. doi: 10.1117/12.2321645. The Clouds and Earth Radiant Energy System (CERES) program has the objective of producing a multi-decadal Climate Data Record (CDR) of Earth Radiation Budget (ERB) measurements. CERES Flight Model 6 was placed in orbit in November 2017 aboard the NOAA-20 spacecraft. FM-6 joined the FM-1 and FM-2 aboard the Terra, FM-3 and -4 aboard the Aqua, and FM-5 aboard the S-NPP spacecraft to seamlessly continue the Earth radiation budget CDR. FM-6 is the most highly calibrated CERES instrument due to improvements in the extensive pre-launch ground calibration campaign. Operations in orbit began with functional check-outs followed immediately by a period of intensive calibrations and validation checks and then transition to the long-term Cal/Val protocol. Initial results demonstrate agreement with ground calibrations within 0.5%. Operations to inter-calibrate with other CERES instruments will commence in the Spring of 2018. The current effort will document the results of the intensive post launch cal/val campaign completed in early 2018 as well as continued radiometric performance and including intercomparisons with other CERES instruments already on orbit.
Smith, N.; Wilson, R.; Szewczyk, Z.; Thomas, S.; Priestley, K.Smith, N., R. Wilson, Z. Szewczyk, S. Thomas, K. Priestley, 2018: Early trends on the Clouds and the Earth's Radiant Energy System (CERES) Flight Model 6 (FM6) instrument's performance. doi: 10.1117/12.2322712.
Smith, Natividad; Thomas, Susan; Shankar, Mohan; Priestley, Kory; Loeb, Norman; Walikainen, DaleSmith, N., S. Thomas, M. Shankar, K. Priestley, N. Loeb, D. Walikainen, 2018: Assessment of on-orbit variations of the Clouds and the Earth's Radiant Energy System (CERES) FM5 instrument. Earth Observing Missions and Sensors: Development, Implementation, and Characterization V, 10781, 1078119. doi: 10.1117/12.2324739. The Clouds and the Earth’s Radiant Energy System (CERES) mission is instrumental in monitoring changes in the Earth’s radiant energy and cloud systems. The CERES project is critical in guaranteeing the continuation of highly accurate Earth radiation budget Climate Data Records (CDRs). The CERES Flight Model-5 (FM-5) instrument, integrated onto the Suomi-National Polar-Orbiting Partnership (NPP) spacecraft, joined a suite of four CERES instruments deployed aboard NASA’s Earth Observing System (EOS) satellites Terra and Aqua. Each CERES instrument consists of scanning thermistor bolometer sensors that measure broadband radiances in the shortwave (0.3 to 5μm), total (0.3 to < 200 μm) and water vapor window (8 to 12 μm) regions. In order to ensure the consistency and accuracy of instrument radiances, needed for generating higher-level climate data products, the CERES project implements rigorous and comprehensive radiometric calibration and validation procedures. This paper briefly describes the trends observed in Edition-1 FM5 flux data products that are corrected for inflight gain changes derived from on-board calibration sources. The strategy to detect artifacts and correct for any sensor spectral response changes is discussed. Improvements and validation results of preliminary FM5 Edition-2 products will be compared with Terra and Aqua data products.
Szewczyk, Z.; Thomas, Susan; Priestley, Kory J.Szewczyk, Z., S. Thomas, K. J. Priestley, 2018: Strategies for shortwave radiances comparison of CERES instruments aboard the JPSS1 and Terra/Aqua satellites. doi: 10.1117/12.2323131.
Thomas, S.; Priestley, K. J.; Smith, N. P.; Wilson, R. S.; Walikainen, D. R.; Smith, N. M.Thomas, S., K. J. Priestley, N. P. Smith, R. S. Wilson, D. R. Walikainen, N. M. Smith, 2018: Performance Stability Evaluation of Clouds and the Earth'S Radiant Energy System (CERES) Flight Model S(FMS) Instrument on S-NPP. IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium, 3292-3295. doi: 10.1109/IGARSS.2018.8518588. Clouds and the Earth's Radiant Energy System (CERES) Flight Model 5 (FM5) instrument is designed to continue the long-term monitoring of the Earth's radiation budget. Flight Model 5, the sixth of the CERES instrument was launched aboard the NPP spacecraft on October 2011 and it has started the Earth-viewing measurements on January 26, 2012. The CERES instrument with the three scanning sensors measure radiances in 0.3 to 5.0 micron region with Shortwave sensor, 0.3 to > 100 microns with Total sensor and 8 to 12 micron region with Window sensor. The prelaunch accuracy goal for the CERES instrument measurements is to have the emitted longwave radiances within 0.5% and the shortwave radiances within 1.0%. An accurate determination of the radiometric gains and spectral responsivity of CERES FM5 sensors was accomplished through rigorous calibrations using the primary sources. Post-launch evaluation of the sensor performance consists of sensor calibrations with the on-board sources and the solar diffuser called Mirror Attenuator Mosaic (MAM). Several validation studies utilising targets such as tropical ocean and deep convective clouds are performed as part of the CallVal protocol. This paper covers the overall performance of the CERES-FM5 instrument. The post-launch calibration and the validation results from the instrument are presented. calibration; clouds; Earth; atmospheric radiation; atmospheric techniques; CERES; Instruments; atmospheric measuring apparatus; radiometry; Sea measurements; Temperature measurement; Sensors; Market research; remote sensing; Radiometry; Calibration; CERES FM5 sensors; CERES instrument measurements; CERES-FM5 instrument; deep convective clouds; Earth radiation Budget; Earth-viewing measurements; Earth's Radiant Energy System; Earth's radiation budget; emitted longwave radiances; Flight Model 5; long-term monitoring; Mirror Attenuator Mosaic; NPP spacecraft; performance stability evaluation; post-launch calibration; post-launch evaluation; S-NPP; scanning sensors measure radiances; sensor calibrations; sensor performance; shortwave radiances; Shortwave sensor; solar diffuser; Total sensor; wavelength 0.3 micron to 5.0 micron; wavelength 8.0 micron to 12.0 micron; Window sensor
Smith, Nathaniel P.; Szewczyk, Z. Peter; Hess, Phillip C.; Priestley, Kory J.Smith, N. P., Z. P. Szewczyk, P. C. Hess, K. J. Priestley, 2017: A strategy to assess the pointing accuracy of the CERES FM1-FM5 scanners. doi: 10.1117/12.2271644. The Clouds and the Earth’s Radiant Energy System (CERES) scanning radiometer is designed to measure the solar radiation reflected by the Earth and thermal radiation emitted by the Earth. Five CERES instruments are currently in service; two aboard the Terra spacecraft, launched in 1999; two aboard the Aqua spacecraft, launched in 2002; and one instrument about the NPP spacecraft, launched in 2011. Verifying the pointing accuracy of the CERES instruments is required to assure that all earth viewing data is correctly geolocated. The CERES team has developed an on-orbit technique for assessing the pointing accuracy of the CERES sensors that relies on a rapid gradient change of measurements taken over a well-defined and known Earth target, such as a coastline, where a strong contrast in brightness and temperature exists. The computed coastline is then compared with World Bank II map to verify the accuracy of the measurement location. This paper briefly restates the algorithm used in the study, describes collection of coastline data, and summarizes the results of the study the CERES FM1, FM2, FM3, and FM5 instruments.
Szewczyk, Z. Peter; Walikainen, Dale R.; Smith, Nitchie; Thomas, Susan; Priestley, Kory J.Szewczyk, Z. P., D. R. Walikainen, N. Smith, S. Thomas, K. J. Priestley, 2017: Improving consistency of the ERB record measured by CERES scanners aboard Terra/Aqua/S-NPP satellites. doi: 10.1117/12.2278457. A purpose of this paper is to present verification of the consistency of unfiltered radiances measured by CERES instruments over their mission 2000-2016. The FM1 scanner on Terra, designated as the climate instrument, is used as a benchmark. The degradation modeling while the instruments on Terra and Aqua were operating in the RAPS mode is being revised, and the rate of the monthly degradation is shown to be 0.03%. The focus of this paper is on consistency between Terra CERES scanners, and it is a part of a broader investigation. Results of comparing FM2 and FM1 are reported for all-sky condition and selected scene types for shortwave and long-wave radiances based on Edition 4 ERBE-like (ES8) data product. Some scene type based results are also verified using an SSF product that contains imager (MODIS) information.
Daniels, J. L.; Smith, G. L.; Priestley, K. J.; Thomas, S.Daniels, J. L., G. L. Smith, K. J. Priestley, S. Thomas, 2016: Using Lunar Observations to Validate Clouds and the Earth's Radiant Energy System Pointing Accuracy. IEEE Transactions on Geoscience and Remote Sensing, 54(1), 65-73. doi: 10.1109/TGRS.2015.2450182. To make measurements of the Earth's radiation budget, a pair of Clouds and the Earth's Radiant Energy System (CERES) instruments, i.e., Flight Models (FM) 1 and 2, have flown on the Terra spacecraft since December 1999, and a pair, i.e., FM-3 and FM-4, have flown on the Aqua spacecraft since June 2002. To produce accurate radiation fluxes at the top of the atmosphere and at various levels within the atmosphere and at the surface, CERES data are combined with higher resolution imager data. Validation is necessary to ensure that the accuracy with which the CERES footprints are located on the Earth will be adequate to use the imager data. The Moon provides a useful target for determining the pointing accuracy of the three channels of CERES. Near full moon, the CERES instruments can be turned to look at the Moon as the host spacecraft passes near the pole. The instrument scans the Moon in a raster-like pattern for a few minutes during the orbit when the Moon is in position. A technique has been developed by which these data can be used to compute accurately the direction in which the instrument is pointed in terms of azimuth and elevation angles when it views the Moon. The difference between this direction and the computed direction of the Moon is taken to be the pointing error of the instrument. The technique has been applied to each of the three channels of all four CERES instruments using lunar observation data from 2006 to present. The maximum error was found to be 0.05° in azimuth and 0.03° in elevation angle. This corresponds to an error in geolocation of 0.37 km near nadir. These results agree with those from the coastline detection method within one standard deviation for all but one case, where the difference was one-and-a-half standard deviations. The lunar and coastline techniques supplement each other for computing pixel location errors away from nadir. The alignment of the three channels in each instrument is evaluated as the differences of- azimuth and elevation angles of the shortwave and window channels from those of the total channel. The alignment was within 0.1° for all cases and within 0.02° for most cases. earth radiation budget; Remote sensing; atmospheric radiation; atmospheric techniques; Instruments; Space vehicles; Detectors; validation; Aqua; Terra; oceanographic techniques; CERES data; Clouds and the Earth's Radiant Energy System (CERES); Aqua spacecraft; Orbits; Terra spacecraft; Moon; accuracy; CERES instruments; Clouds and the Earth Radiant Energy System; lunar observations; AD 1999 12; AD 2002 06; Alignment; Azimuth; CERES footprints; coastline detection method; computing pixel location errors; elevation angle; one-and-a-half standard deviations; pointing accuracy; radiation fluxes; raster-like pattern; top-of-the-atmosphere; window channels
Smith, G. Louis; Daniels, Janet; Priestley, Kory; Thomas, Susan; Lee, Robert B.Smith, G. L., J. Daniels, K. Priestley, S. Thomas, R. B. Lee, 2016: Measurement of the Point Response Functions of CERES Scanning Radiometers. IEEE Transactions on Geoscience and Remote Sensing, 54(3), 1260-1266. doi: 10.1109/TGRS.2015.2476759.
Smith, G. Louis; Thomas, Susan; Priestley, Kory J.; Walikainen, DaleSmith, G. L., S. Thomas, K. J. Priestley, D. Walikainen, 2016: Tropical Mean Fluxes: A Tool for Calibration and Validation of CERES Radiometers. IEEE Transactions on Geoscience and Remote Sensing, 54(9), 5135-5142. doi: 10.1109/TGRS.2016.2556581.
Daniels, J.L.; Smith, G.L.; Priestley, K.J.; Thomas, S.Daniels, J., G. Smith, K. Priestley, S. Thomas, 2015: Using Lunar Observations to Validate In-Flight Calibrations of Clouds and the Earth's Radiant Energy System Instruments. IEEE Transactions on Geoscience and Remote Sensing, 53(9), 5110-5116. doi: 10.1109/TGRS.2015.2417314. The validation of in-orbit instrument performance requires both stability in calibration source and also calibration corrections to compensate for instrument changes. Unlike internal calibrations, the Moon offers an external source whose signal variance is predictable and nondegrading. This paper describes a method of validation using lunar observations scanning near full moon by the Clouds and the Earth's Radiant Energy System (CERES) Flight Model (FM)-1 and FM-2 aboard the Terra satellite, FM-3 and FM-4 aboard the Aqua satellite, and, as of 2012, FM-5 aboard Suomi National Polar-orbiting Partnership. Given the stability of the source, adjustments within the data set are based entirely on removing orbital effects. Lunar observations were found to require a consistent data set spanning at least two to three years in length to examine instrument stability due to the final step when lunar libration effects are addressed. Initial results show a 20% annual variability in the data set. Using this method, however, results show trends per data channel of 1.0% per decade or less for FM-1 through FM-4. Results for FM-5 are not included in this paper because a sufficient data record has not yet been collected. calibration; clouds; Earth; earth radiation budget; Remote sensing; Satellites; atmospheric radiation; atmospheric techniques; Earth Observing System; Instruments; atmospheric measuring apparatus; radiometry; Detectors; validation; Aqua; Terra; Clouds and the Earth's Radiant Energy System (CERES); Orbits; Moon; Aqua satellite; CERES flight model; CERES instruments; AD 2012; calibration source; Clouds and the Earth Energy System; FM-1 satellite; FM-2 satellite; FM-3 satellite; FM-4 satellite; in-flight calibration; in-orbit instrument performance; in-orbit instrument performance validation; lunar libration; lunar measurements; lunar observations; signal variance; Suomi National Polar-orbiting Partnership; telescope
Shankar, Mohan; Priestley, Kory; Smith, Nathaniel; Smith, Nitchie; Thomas, Susan; Walikainen, DaleShankar, M., K. Priestley, N. Smith, N. Smith, S. Thomas, D. Walikainen, 2015: Radiometric calibration and performance trends of the Clouds and Earth’s Radiant Energy System (CERES) instruments onboard the Terra and Aqua spacecraft. Proc. SPIE 9639, Sensors, Systems, and Next-Generation Satellites XIX, 9639, 963915-963915-13. doi: 10.1117/12.2194468. The Clouds and Earth’s Radiant Energy System (CERES) instruments help to study the impact of clouds on the earth's radiation budget. There are currently five instruments- two each on board Aqua and Terra spacecraft and one on the Suomi NPP spacecraft to measure the earth’s reflected shortwave and emitted longwave energy, which represent two components of the earth’s radiation energy budget. Flight Models (FM) 1 and 2 are on Terra, FM 3 and 4 are on Aqua, and FM5 is on Suomi NPP. The measurements are made by three sensors on each instrument: a shortwave sensor that measures the 0.3-5 microns wavelength band, a window sensor that measures the water vapor window between 8-12 microns, and a total sensor that measures all incident energy (0.3- >100 microns). The required accuracy of CERES measurements of 0.5% in the longwave and 1% in the shortwave is achieved through an extensive pre-launch ground calibration campaign as well as on-orbit calibration and validation activities. Onorbit calibration is carried out using the Internal Calibration Module (ICM) that consists of a tungsten lamp, blackbodies, and a solar diffuser known as the Mirror Attenuator Mosaic (MAM). The ICM calibration provides information about the stability of the sensors’ broadband radiometric gains on-orbit. Several validation studies are conducted in order to monitor the behavior of the instruments in various spectral bands. The CERES Edition-4 data products for the FM1-FM4 instruments incorporate the latest calibration methodologies to improve on the Edition-3 data products. In this paper, we discuss the updated calibration methodology and present some validation studies to demonstrate the improvement in the trends using the CERES Edition-4 data products for all four instruments.
Smith, Nathaniel P.; Thomas, Susan; Shankar, Mohan; Hess, Phillip C.; Smith, Natividad M.; Walikainen, Dale R.; Wilson, Robert S.; Priestley, Kory J.Smith, N. P., S. Thomas, M. Shankar, P. C. Hess, N. M. Smith, D. R. Walikainen, R. S. Wilson, K. J. Priestley, 2015: Assessment of the clouds and the Earth’s Radiant Energy System (CERES) instrument performance and stability on the Aqua, Terra, and S-NPP spacecraft. SPIE 9607, Earth Observing Systems XX, 9607, 96070T-96070T-10. doi: 10.1117/12.2190110. The Clouds and the Earth’s Radiant Energy System (CERES) scanning radiometer is designed to measure reflected solar radiation and thermal radiation emitted by the Earth. Five CERES instruments are currently taking active measurements in-orbit with two aboard the Terra spacecraft (FM1 and FM2), two aboard the Aqua spacecraft (FM3 and FM4), and one aboard the S-NPP spacecraft (FM5). The CERES instrument uses three scanning thermistor bolometers to make broadband radiance measurements in the shortwave (0.3 – 5.0 micrometers), total (0.3 - >100 micrometers) and water vapor window (8 – 12 micrometer) regions. An internal calibration module (ICM) used for in-flight calibration is built into the CERES instrument package consisting of an anodized aluminum blackbody source for calibrating the total and window sensors, and a shortwave internal calibration source (SWICS) for the shortwave sensor. The ICM sources, along with a solar diffusor called the Mirror Attenuator Mosaic (MAM), are used to define shifts or drifts in the sensor response over the life of the mission. In addition, validation studies are conducted to understand any spectral changes that may occur with the sensors and assess the pointing accuracy of the instrument, allowing for corrections to be made to the radiance calculations in CERES data products. This paper covers the observed trends in the internal and solar calibration data, discusses the latest techniques used to correct for sensor response, and explains the validation studies used to assess the performance and stability of the instrument.
Szewczyk, Z. P.; Smith, G. L.; Priestley, Kory J.Szewczyk, Z. P., G. L. Smith, K. J. Priestley, 2015: Comparison of unfiltered CERES radiances measured from the S-NPP and Aqua satellites over matched sites. doi: 10.1117/12.2191506. The focus of this paper is to introduce a novel strategy for comparison of unfiltered radiances in remote sensing devised for CERES scanners. The strategy is referred to as “matched sites targeting”, in which CERES instruments scan at nadir along their respective collocated ground-tracks. This strategy is enabled by similarities in the Suomi-NPP (FM5) and Aqua (FM3) satellite orbits, and a special scan profile available for the CERES scanners. Comparison of collected data in this strategy is done at a footprint level for a more stringent test of the consistency between the two instruments (FM5 and FM3) for specific scene types, as averages of 330 collocated nadir samples are compared. A comparison of comprehensive “all-sky” measurements is also included as a reference. Results of the unfiltered radiance comparison are based on ES8 or ERBE-like data product using Edition-1 for FM5, and Edition-4 for FM3; cloud coverage is verified using MODIS data available in a SSF product.
Smith, G. Louis, G.; Daniels, Janet L.; Priestley, Kory J.; Thomas, SusanSmith, G. L., J. L. Daniels, K. J. Priestley, S. Thomas, 2014: Point response function of the Clouds and Earth Radiant Energy System scanning radiometer. Journal of Applied Remote Sensing, 8(1), 084991-084991. doi: 10.1117/1.JRS.8.084991. Abstract. An overview of work related to the point response function (PRF) of the Clouds and Earth Radiant Energy System (CERES) scanning radiometer is presented. The aspects of the CERES design that affect the PRF are described, and then the design of the PRF is explained. The PRF was designed by shaping the field of view so as to minimize the blur plus alias errors of the radiance field reconstructed from the CERES measurements. The design is conducted in the Fourier domain. The PRF can then be computed by transforming the resulting transfer function to the physical domain. Alternatively, the PRF can be computed in the physical plane. The PRF of each model of the CERES instrument has been tested in the Radiation Calibration Facility by use of a PRF source and compared well with prediction. CERES instruments are aboard the Terra, Aqua, and Suomi-NPP spacecraft. In orbit, lunar observations are used to validate the PRF. These results showed nominal performance except for the longwave window channel of flight model 2, for which a region of anomalously high sensitivity was found.
Smith, G.L.; Priestley, K.J.; Loeb, N.G.Smith, G., K. Priestley, N. Loeb, 2014: Clouds and Earth Radiant Energy System: From Design to Data. IEEE Transactions on Geoscience and Remote Sensing, 52(3), 1729-1738. doi: 10.1109/TGRS.2013.2253782. The Clouds and the Earth's Radiant Energy System (CERES) project has instruments aboard the Terra and Aqua spacecraft that have provided a decade of radiation budget data. In October 2011, the CERES flight model 5 was placed in orbit on the NPOESS Preparatory Project spacecraft. Data from these instruments are being used to investigate the radiation balance of the Earth at various time and space scales and the role of clouds in this balance. The design and calibration, both on the ground and in-orbit, and operation of the instrument are discussed. calibration; clouds; Earth; earth radiation budget; Extraterrestrial measurements; Remote sensing; atmospheric radiation; Earth Observing System; Instruments; Space vehicles; atmospheric measuring apparatus; Aqua; Terra; Clouds and the Earth's Radiant Energy System (CERES); AD 2011 10; Aqua spacecraft; CERES flight model 5; CERES project instrument data; cloud and earth radiant energy system; cloud balance role; data design; Earth radiation balance; ground calibration; ground design; in-orbit calibration; in-orbit design; instrument operation; NPOESS Preparatory Project (NPP); NPOESS preparatory project spacecraft; Orbits; radiation budget data; Temperature measurement; Terra spacecraft; time-space scales
Priestley, Kory J.; Smith, G. Louis; Thomas, Susan; Cooper, Denise; Lee, Robert B.; Walikainen, Dale; Hess, Phillip; Szewczyk, Z. Peter; Wilson, RobertPriestley, K. J., G. L. Smith, S. Thomas, D. Cooper, R. B. Lee, D. Walikainen, P. Hess, Z. P. Szewczyk, R. Wilson, 2011: Radiometric Performance of the CERES Earth Radiation Budget Climate Record Sensors on the EOS Aqua and Terra Spacecraft through April 2007. J. Atmos. Oceanic Technol., 28(1), 3-21. doi: 10.1175/2010JTECHA1521.1. Abstract The Clouds and the Earth’s Radiant Energy System (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 p.m. and 1:30 a.m. local time equatorial crossing times. With these instruments CERES provides state-of-the-art observations and products related to the earth’s radiation budget at the top of the atmosphere (TOA). The archived CERES science data products consist of geolocated and calibrated instantaneous filtered and unfiltered radiances through temporally and spatially averaged TOA, surface, and atmospheric fluxes. CERES-filtered radiance measurements cover three spectral bands: shortwave (0.3–5 μm), total (0.3>100 μm), and an atmospheric window channel (8–12 μm). CERES climate data products realize a factor of 2–4 improvement in calibration accuracy and stability over the previotus Earth Radiation Budget Experiment (ERBE) products. To achieve this improvement there are three editions of data products. Edition 1 generates data products using gain coefficients derived from ground calibrations. After a minimum of four months, the calibration data are examined to remove drifts in the calibration. The data are then reprocessed to produce the edition 2 data products. These products are available for science investigations for which an accuracy of 2% is sufficient. Also, a validation protocol is applied to these products to find problems and develop solutions, after which edition 3 data products will be computed, for which the objectives are calibration stability of better than 0.2% and calibration traceability from ground to flight of 0.25%. This paper reports the status of the radiometric accuracy and stability of the CERES edition 2 instrument data products through April 2007. Radiation budgets; satellite observations; Instrumentation/sensors; Climate records
Smith, G. L.; Priestley, K. J.; Loeb, N. G.; Wielicki, B. A.; Charlock, T. P.; Minnis, P.; Doelling, D. R.; Rutan, D. A.Smith, G. L., K. J. Priestley, N. G. Loeb, B. A. Wielicki, T. P. Charlock, P. Minnis, D. R. Doelling, D. A. Rutan, 2011: Clouds and Earth Radiant Energy System (CERES), a review: Past, present and future. Advances in Space Research, 48(2), 254-263. doi: 10.1016/j.asr.2011.03.009. The Clouds and Earth Radiant Energy System (CERES) project’s objectives are to measure the reflected solar radiance (shortwave) and Earth-emitted (longwave) radiances and from these measurements to compute the shortwave and longwave radiation fluxes at the top of the atmosphere (TOA) and the surface and radiation divergence within the atmosphere. The fluxes at TOA are to be retrieved to an accuracy of 2%. Improved bidirectional reflectance distribution functions (BRDFs) have been developed to compute the fluxes at TOA from the measured radiances with errors reduced from ERBE by a factor of two or more. Instruments aboard the Terra and Aqua spacecraft provide sampling at four local times. In order to further reduce temporal sampling errors, data are used from the geostationary meteorological satellites to account for changes of scenes between observations by the CERES radiometers. A validation protocol including in-flight calibrations and comparisons of measurements has reduced the instrument errors to less than 1%. The data are processed through three editions. The first edition provides a timely flow of data to investigators and the third edition provides data products as accurate as possible with resources available. A suite of cloud properties retrieved from the MODerate-resolution Imaging Spectroradiometer (MODIS) by the CERES team is used to identify the cloud properties for each pixel in order to select the BRDF for each pixel so as to compute radiation fluxes from radiances. Also, the cloud information is used to compute radiation at the surface and through the atmosphere and to facilitate study of the relationship between clouds and the radiation budget. The data products from CERES include, in addition to the reflected solar radiation and Earth emitted radiation fluxes at TOA, the upward and downward shortwave and longwave radiation fluxes at the surface and at various levels in the atmosphere. Also at the surface the photosynthetically active radiation and ultraviolet radiation (total, UVA and UVB) are computed. The CERES instruments aboard the Terra and Aqua spacecraft have served well past their design life times. A CERES instrument has been integrated onto the NPP platform and is ready for launch in 2011. Another CERES instrument is being built for launch in 2014, and plans are being made for a series of follow-on missions. earth radiation budget; radiometry
Szewczyk, Z. Peter; Priestley, Kory J.; Walikainen, Dale R.; Loeb, Norman G.; Smith, G. LouisSzewczyk, Z. P., K. J. Priestley, D. R. Walikainen, N. G. Loeb, G. L. Smith, 2011: Putting all CERES instruments (Terra/Aqua) on the same radiometric scale. Proc. SPIE, 8177, 817704-817704-11. doi: 10.1117/12.896897. Clouds and the Earth's Radiant Energy System (CERES) instruments are scanning radiometers on board the Terra and Aqua satellites since March of 2000 and June of 2002, respectively; hence, their continuous Earth's radiation budget dataset is more than a decade long. Since there are four CERES scanners in operation, it is important that their measurements are consistent. A focus of this paper is on placing two Aqua CERES sensors on the same radiometric scale as FM1 on Terra. The paper contains a description of radiation budget experiments that are used in this task, and a complete set of results. It is shown that one-time adjustments to gains and spectral response functions are sufficient in putting FM3 and FM4 on the same radiometric scale as FM1 at the beginning of their mission. The Edition 3 of ERBE-like data products use derived corrections for Aqua CERES sensors.
Priestley, Kory J.; Thomas, Susan; Smith, G. LouisPriestley, K. J., S. Thomas, G. L. Smith, 2010: Validation of Point Spread Functions of CERES Radiometers by the Use of Lunar Observations. J. Atmos. Oceanic Technol., 27(6), 1005-1011. doi: 10.1175/2010JTECHA1322.1. Abstract The Clouds and the Earth’s Radiant Energy System (CERES) scanning radiometers have been operating to make raster scans of the moon on a quarterly basis to validate the point response function for the three channels of flight models 1–4 aboard the Terra and Aqua spacecraft. Instrument pointing accuracy was verified by this method to 0.2° for the total channel of FM-3. The point response functions were computed from the lunar observations and were found to be nominal with the exception of the FM-2 window channel, which was found to have a region of high sensitivity. This anomaly is attributed to a delamination of the detector flake from the heat sink in that region. The influence of this anomaly is accounted for by the in-flight calibration and has no adverse effect on the application of the data. satellite observations; Radiances
Smith, G. Louis; Priestley, Kory J.; Hess, Phillip C.; Currey, Chris; Spence, PeterSmith, G. L., K. J. Priestley, P. C. Hess, C. Currey, P. Spence, 2009: Validation of Geolocation of Measurements of the Clouds and the Earth’s Radiant Energy System (CERES) Scanning Radiometers aboard Three Spacecraft. J. Atmos. Oceanic Technol., 26(11), 2379-2391. doi: 10.1175/2009JTECHA1207.1. Abstract The Clouds and the Earth’s Radiant Energy System (CERES) instrument is a scanning radiometer for measuring Earth-emitted and -reflected solar radiation to understand Earth’s energy balance. One CERES instrument was placed into orbit aboard the Tropical Rainfall Measuring Mission (TRMM) in 1997; two were aboard the Terra spacecraft, launched in 1999; and two were aboard the Aqua spacecraft, launched in 2002. These measurements are used together with data from higher-resolution instruments to generate a number of data products. The nominal footprint size of the pixel at Earth’s surface is 16 km in the cross-scan direction and 23 km in the scan direction for the TRMM platform and 36 km in the cross-scan direction and 46 km in the scan direction for the Terra and Aqua platforms. It is required that the location on Earth of each pixel be known to 1–2 km to use the CERES data with the higher-resolution instruments on a pixel basis. A technique has been developed to validate the computed geolocation of the measurements by use of coastlines. Scenes are chosen in which the reflected solar radiation changes abruptly from the land surface to the darker ocean surface and the Earth-emitted radiation changes from the warm land to the cool ocean, or vice versa, so that scenes can be detected both day and night. The computed coastline location is then compared with the World Bank II map. The method has been applied to data from the three spacecraft and shows that the pixel geolocations are accurate to within 10% of the pixel size and that the geolocation is adequate for current scientific investigations. Remote sensing; Energy budget/balance; satellite observations; Radiances; radiation budget
Loeb, Norman G.; Wielicki, Bruce A.; Su, Wenying; Loukachine, Konstantin; Sun, Wenbo; Wong, Takmeng; Priestley, Kory J.; Matthews, Grant; Miller, Walter F.; Davies, R.Loeb, N. G., B. A. Wielicki, W. Su, K. Loukachine, W. Sun, T. Wong, K. J. Priestley, G. Matthews, W. F. Miller, R. Davies, 2007: Multi-Instrument Comparison of Top-of-Atmosphere Reflected Solar Radiation. J. Climate, 20(3), 575-591. doi: 10.1175/JCLI4018.1. Abstract Observations from the Clouds and the Earth’s Radiant Energy System (CERES), Moderate Resolution Imaging Spectroradiometer (MODIS), Multiangle Imaging Spectroradiometer (MISR), and Sea-Viewing Wide-Field-of-View Sensor (SeaWiFS) between 2000 and 2005 are analyzed in order to determine if these data are meeting climate accuracy goals recently established by the climate community. The focus is primarily on top-of-atmosphere (TOA) reflected solar radiances and radiative fluxes. Direct comparisons of nadir radiances from CERES, MODIS, and MISR aboard the Terra satellite reveal that the measurements from these instruments exhibit a year-to-year relative stability of better than 1%, with no systematic change with time. By comparison, the climate requirement for the stability of visible radiometer measurements is 1% decade−1. When tropical ocean monthly anomalies in shortwave (SW) TOA radiative fluxes from CERES on Terra are compared with anomalies in Photosynthetically Active Radiation (PAR) from SeaWiFS—an instrument whose radiance stability is better than 0.07% during its first six years in orbit—the two are strongly anticorrelated. After scaling the SeaWiFS anomalies by a constant factor given by the slope of the regression line fit between CERES and SeaWiFS anomalies, the standard deviation in the difference between monthly anomalies from the two records is only 0.2 W m−2, and the difference in their trend lines is only 0.02 ± 0.3 W m−2 decade−1, approximately within the 0.3 W m−2 decade−1 stability requirement for climate accuracy. For both the Tropics and globe, CERES Terra SW TOA fluxes show no trend between March 2000 and June 2005. Significant differences are found between SW TOA flux trends from CERES Terra and CERES Aqua between August 2002 and March 2005. This discrepancy is due to uncertainties in the adjustment factors used to account for degradation of the CERES Aqua optics during hemispheric scan mode operations. Comparisons of SW TOA flux between CERES Terra and the International Satellite Cloud Climatology Project (ISCCP) radiative flux profile dataset (FD) RadFlux product show good agreement in monthly anomalies between January 2002 and December 2004, and poor agreement prior to this period. Commonly used statistical tools applied to the CERES Terra data reveal that in order to detect a statistically significant trend of magnitude 0.3 W m−2 decade−1 in global SW TOA flux, approximately 10 to 15 yr of data are needed. This assumes that CERES Terra instrument calibration remains highly stable, long-term climate variability remains constant, and the Terra spacecraft has enough fuel to last 15 yr. satellite observations; radiative forcing; Shortwave radiation
Matthews, Grant; Priestley, Kory; Thomas, SusanMatthews, G., K. Priestley, S. Thomas, 2007: Spectral balancing of a broadband Earth observing radiometer with co-aligned Short Wave channel to ensure accuracy and stability of broadband daytime Outgoing Long-Wave Radiance measurements: Application to CERES. Optical Engineering+ Applications, 6678, 66781H-66781H-10. doi: 10.1117/12.734492. In order to best detect real changes in the Earth's climate system, it is estimated that in space based instrumentation measuring the Earth Radiation Budget (ERB) must remain calibrated with a stability of 0.3Wm −2 per decade and reach an absolute accuracy of 1Wm −2. Such stability is beyond that specified by existing ERB programs such as the Clouds and the Earth's Radiant Energy System (CERES, using three broadband radiometric scanning channels: the shortwave (SW 0.3−5um), Total (0.3− > 100um), and window (8−12um)). The CERES measurement of daytime outgoing longwave radiance (OLR) is obtained using subtraction of the SW channel signal from that of the co-aligned Total channel telescope. This requires precise balancing of the estimated response of the Total channel optics with those of the SW only channel when viewing daytime Earth scenes. Any post ground calibration contamination of Total channel optics that reduces its response to SW radiance can therefore upset this balancing process, introducing biases and trends in measurements of daytime LW radiance. This paper presents a new methodology used for balancing Total and SW channel spectral responses for all daytime Earth scenes using a model of contaminant spectral darkening. The results of the technique when applied to both CERES units on Terra are shown to remove significant trends and biases in measurements of daytime LW radiance.
Matthews, Grant; Priestley, Kory; Thomas, SusanMatthews, G., K. Priestley, S. Thomas, 2007: Transfer of radiometric standards between multiple low earth orbit climate observing broadband radiometers: application to CERES. Optical Engineering+ Applications, 6677, 66770I-66770I-10. doi: 10.1117/12.734478. The Clouds and the Earth's Radiant Energy System (CERES) is the only project currently measuring the global Earth Radiation Budget (ERB) from space. Two CERES instruments are located on the EOS Terra platform and two more are placed on the EOS Aqua satellite. One more CERES unit provided 8 months of ERB data in 1998 from the TRMM platform. Each of the CERES devices uses three broadband radiometric scanning telescopes: the shortwave (SW 0.3 → 5μm), Total (0.3 → 100μm), and window (8 → 12μm) channels. Rigorous pre-launch ground calibration is performed on each CERES unit to achieve an accuracy goal of 1% for Short Wave (SW) and 0.5% for outgoing Long Wave (LW) radiance. Any ground to flight or in-flight changes in radiometer response is monitored using onboard calibration sources. For the total and window channels these take the form of concentric groove blackbodies, while the SW channels use stable tungsten lamps. Recent studies have shown that the SW response of space based broadband radiometers can change dramatically due to optical contamination. With these changes having most impact on optical response to blue-UV radiance, where tungsten lamps are largely devoid of output, such changes are hard to monitor accurately using existing on-board sources. This study details an attempt to use the vicarious stability metric of deep convective clouds (DCC), nighttime LW scenes and a newly developed SW optical darkening model to place all CERES instrument measurements on the same radiometric scale. The results show that scene dependant dispersion in nadir comparisons between instruments on the same satellite are significantly reduced. Also the suggestion is that the pre-flight contamination of the CERES instruments may require an increase in Terra and Aqua measured SW flux. A larger necessary increase in Aqua SW flux is believed to be due to greater pre-flight contamination of the CERES Aqua optics.
Priestley, Kory J.; Smith, G. Louis; Thomas, Susan; Matthews, GrantPriestley, K. J., G. L. Smith, S. Thomas, G. Matthews, 2007: Validation protocol for climate quality CERES measurements. Optical Engineering+ Applications, 6678, 66781I-66781I-12. doi: 10.1117/12.735312. The CERES Flight Model-1 and -2 instruments flew aboard the Terra into orbit in December 1999 and the FM-3 and -4 instruments flew on the Aqua spacecraft in May 2002. To date these instruments have provided seven years of measurements on Terra and five years on Aqua. The accuracy requirement for CERES is 0.5% for longwave radiances and 1.0% for shortwave. Achieving this objective is possible by using experience from the ERBE instrument to evolve the CERES design and the methods for analyzing the data. In order to achieve and maintain this accuracy, an internal calibration system and an attenuated view of the Sun are used. Subsequently, to validate that this accuracy has been achieved, a number of techniques have been developed which cover a range of temporal and spatial scales. This ensemble of methods provides a protocol which assures that the CERES measurements are of climate quality. In addition to retrieving fluxes at the top of the atmosphere, the CERES program uses data from other instruments aboard the spacecraft to compute the radiation balance at the surface and at levels through the atmosphere. Finally, the CERES data products are upgraded as higher-level data products show the need for revisions. The calibration stability is better than 0.2% and traceability from ground to in-flight calibration is 0.25%
Priestley, Kory J; Smith, G Louis; Thomas, Susan; Cooper, Denise; Lee III, Robert B; Walikainen, Dale; Hess, Phil; Szewczyk, Z Peter; Wilson, RobertPriestley, K. J., G. L. Smith, S. Thomas, D. Cooper, R. B. Lee III, D. Walikainen, P. Hess, Z. P. Szewczyk, R. Wilson, 2007: Radiometric performance of the CERES Earth Radiation Budget climate record sensors on the EOS Aqua and Terra Spacecraft. Optical Engineering+ Applications, 66770H–66770H. doi: http://dx.doi.org/10.1117/12.735294. 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. The archived CERES Science data products consist of geolocated and calibrated instantaneous filtered and unfiltered radiances through temporally and spatially averaged TOA, Surface, and Atmospheric fluxes. CERES filtered radiance measurements cover three spectral bands including shortwave (0.3 to 5 micron), total (0.3 to
Thomas, Susan; Priestley, K. J.; Matthews, G. M.Thomas, S., K. J. Priestley, G. M. Matthews, 2007: Analysis of clouds and the Earth's radiant energy system (CERES) lunar measurements. doi: 10.1117/12.735839. Clouds and the Earth's Radiant Energy System (CERES) instruments were designed to measure the reflected shortwave and emitted longwave radiances of the Earth's radiation budget and to investigate the cloud interactions with global radiances for the long-term monitoring of Earth's climate. The CERES instrument with the three scanning thermistor bolometers measure broadband radiances in the shortwave (0.3 to 5.0 micrometer), total (0.3 to >100 micrometer) and 8 - 12 micrometer water vapor window regions. The four CERES instruments (Flight Models 1 through 4) aboard Earth Observing System (EOS) Terra and Aqua platforms were instrumental in conducting lunar radiance measurement on a regular basis. 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 CERES sensors performed lunar measurements at various phase angles ranging from four to ten degrees before and after each full moon phase. Additional measurements were also conducted during the lunar eclipse events. The resulting filtered radiances were normalized to the mean sun-moon distance and the mean earth-moon distance. The lunar radiances measured by the sensors from all CERES instruments for a period of January 2001 to June 2007 were analyzed and compared. The CERES total sensor results showed a variation of about +/- 0.5 percent, while a +/- 2.0 percent variation was seen in shortwave sensor results.
Szewczyk, Z. Peter; Smith, G. Louis; Priestley, Kory J.Szewczyk, Z. P., G. L. Smith, K. J. Priestley, 2005: Validation of Clouds and Earth Radiant Energy System instruments aboard the Terra and Aqua satellites. Journal of Geophysical Research: Atmospheres, 110(D2), D02103. doi: 10.1029/2004JD004776. A comparison of unfiltered radiances measured by Clouds and Earth Radiant Energy System (CERES) instruments (FM1 and FM4) operating on two different platforms, Terra and Aqua satellites, is presented. Data for the comparison were collected at orbital crossings in July and August 2002 and June 2003. Using a special scanning mode, viewing geometries of the instruments were matched to provide a large data set for comparing all three channels. In addition, the data collected over Greenland were used for a more stringent test of the consistency of the shortwave radiances. Statistics are computed for different scene types, and a confidence test is applied to compiled averages to show the consistency of 1% between measurements taken from the two different platforms. Results of the unfiltered radiance comparison are based on Edition2 of the FM1 and FM4 ES8 (Earth Radiation Budget Experiment–like) data product. 1640 Remote sensing; 1694 Instruments and techniques; 3359 Radiative processes; Aqua; Terra; CERES validation
Wielicki, Bruce A.; Wong, Takmeng; Loeb, Norman; Minnis, Patrick; Priestley, Kory; Kandel, RobertWielicki, B. A., T. Wong, N. Loeb, P. Minnis, K. Priestley, R. Kandel, 2005: Changes in Earth's Albedo Measured by Satellite. Science, 308(5723), 825-825. doi: 10.1126/science.1106484. NASA global satellite data provide observations of Earth's albedo, i.e., the fraction of incident solar radiation that is reflected back to space. The satellite data show that the last four years are within natural variability and fail to confirm the 6% relative increase in albedo inferred from observations of earthshine from the moon. Longer global satellite records will be required to discern climate trends in Earth's albedo.
Smith, G. Louis; Wielicki, Bruce A.; Barkstrom, Bruce R.; Lee, Robert B.; Priestley, Kory J.; Charlock, Thomas P.; Minnis, Patrick; Kratz, David P.; Loeb, Norman; Young, David F.Smith, G. L., B. A. Wielicki, B. R. Barkstrom, R. B. Lee, K. J. Priestley, T. P. Charlock, P. Minnis, D. P. Kratz, N. Loeb, D. F. Young, 2004: Clouds and Earth radiant energy system: an overview. Advances in Space Research, 33(7), 1125-1131. doi: 10.1016/S0273-1177(03)00739-7. The Clouds and Earth radiant energy system (CERES) instrument was first flown aboard the TRMM spacecraft whose 35° inclination orbit allowed for the collection of radiation budget data over all local times, i.e. all solar zenith angles for the latitude range. Moreover, this instrument has gathered the only bidirectional radiance data covering all local times. An additional quartet of CERES instruments are now operating in pairs on both the TERRA and AQUA spacecrafts. Thus far, these instruments have collected several years of Earth radiation budget observations and continue to operate. For each of the TERRA and AQUA spacecrafts, one CERES instrument operates in a cross-track scan mode for the purpose of mapping the Earth’s outgoing longwave radiation and reflected solar radiation. The other operates in an azimuthal rotation while scanning also in zenith angle for the purpose of gathering measurements for the angular distribution of radiance from various scene types, to improve the computation of fluxes from radiance measurements. The CERES instruments carry in-flight calibration systems to maintain the measurement accuracy of 1% for measured radiances. In addition to retrieving fluxes at the top of the atmosphere, the CERES program uses data from other instruments aboard the spacecraft to compute the radiation balance at the surface and at levels through the atmosphere. CERES; radiation budget; Aqua; Earth observation system; Terra
Kratz, David P.; Priestley, Kory J.; Green, Richard N.Kratz, D. P., K. J. Priestley, R. N. Green, 2002: Establishing the relationship between the CERES window and total channel measured radiances for conditions involving deep convective clouds at night. Journal of Geophysical Research: Atmospheres, 107(D15), ACL 5-1. doi: 10.1029/2001JD001170. Characterizing the stability of the Clouds and the Earth's Radiant Energy System (CERES) instrument is critical to obtaining accurate measurements of the radiative energy budget of the Earth's atmosphere-surface system. Composed of three broadband radiometers, the CERES instrument measures radiances in the shortwave (>2000 cm−1), infrared window (835–1250 cm−1), and total regions of the spectrum. Such a choice of radiometers does not allow for a straightforward three channel intercomparison of the CERES measurements. We observed, however, the outgoing infrared spectra of high, cold, optically thick clouds were fairly representative of blackbody emission. This observation suggested a potential relationship between the infrared window radiometer and longwave portion of the total radiometer. Using nighttime measurements made by the CERES instrument aboard the Tropical Rainfall Measuring Mission (TRMM) spacecraft during the first eight months of 1998, we were able to determine a highly correlated relationship between the infrared window and total channel radiances for conditions corresponding to high, cold, optically thick clouds. Comparisons were then made between the measurements and reference line-by-line calculations. From these comparisons, a quantified relationship was derived between the total and window channel radiances which could accurately reproduce one set of results from the other. Such a relationship has allowed for the establishment of a three channel intercomparison for the CERES instrument with an accuracy of ∼1% for the case of high, cold, optically thick clouds. An independent relationship based upon the tropical mean is shown to produce results which support the three channel analysis for the deep convective cloud systems. 0360 Radiation: transmission and scattering; 1640 Remote sensing; 0394 Instruments and techniques; 1694 Instruments and techniques; CERES; TRMM; 0325 Evolution of the atmosphere; deep-convective-clouds; infrared-window; radiometer; three-channel-intercomparison
Priestley, K. J; Wielicki, B. A; Green, R. N; Haeffelin, M. P. A; Lee, R. B; Loeb, N. GPriestley, K. J., B. A. Wielicki, R. N. Green, M. P. A. Haeffelin, R. B. Lee, N. G. Loeb, 2002: Early radiometric validation results of the CERES Flight Model 1 and 2 instruments onboard NASA's Terra Spacecraft. Advances in Space Research, 30(11), 2371-2376. doi: 10.1016/S0273-1177(02)80278-2. The CERES Flight Model 1 and 2 instruments were launched aboard NASA's Earth Observing System (EOS) Terra Spacecraft on December 18, 1999 into a 705 Km sun-synchronous orbit with a 10:30 a.m. equatorial crossing time. 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. On September 22, 2000 the CERES Science Team voted to archive the Edition 1 CERES/Terra Level 1b and Level 2 and 3 ERBE-Like data products. These products consist of 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 validation efforts undertaken to quantify the quality of the Terra data products as well as the level of agreement between the Terra and TRMM datasets.
Smith, G. Louis; Pandey, D. K.; Lee, Robert B.; Barkstrom, Bruce R.; Priestley, Kory J.Smith, G. L., D. K. Pandey, R. B. Lee, B. R. Barkstrom, K. J. Priestley, 2002: Numerical Filtering of Spurious Transients in a Satellite Scanning Radiometer: Application to CERES. J. Atmos. Oceanic Technol., 19(2), 172-182. doi: 10.1175/1520-0426(2002)019<0172:NFOSTI>2.0.CO;2. Abstract The Clouds and Earth Radiant Energy System (CERES) scanning radiometer was designed to provide high accuracy measurements of the radiances from the earth. Calibration testing of the instruments showed the presence of an undesired slow transient in the measurements of all channels at 1% to 2% of the signal. Analysis of the data showed that the transient consists of a single linear mode. The characteristic time of this mode is 0.3 to 0.4 s and is much greater than that the 8–10-ms response time of the detector, so that it is well separated from the detector response. A numerical filter was designed for the removal of this transient from the measurements. Results show no trace remaining of the transient after application of the numerical filter. The characterization of the slow mode on the basis of ground calibration data is discussed and flight results are shown for the CERES instruments aboard the Tropical Rainfall Measurement Mission and Terra spacecraft. The primary influence of the slow mode is in the calibration of the instrument and the in-flight validation of the calibration. This method may be applicable to other radiometers that are striving for high accuracy and encounter a slow spurious mode, regardless of the underlying physics.
Haeffelin, Martial; Wielicki, Bruce; Duvel, Jean Philippe; Priestley, Kory; Viollier, MichelHaeffelin, M., B. Wielicki, J. P. Duvel, K. Priestley, M. Viollier, 2001: Inter-calibration of CERES and ScaRaB Earth Radiation Budget datasets using temporally and spatially collocated radiance measurements. Geophysical Research Letters, 28(1), 167-170. doi: 10.1029/2000GL012233. Comparisons of radiance measurements from overlapping independent Earth and cloud radiation budget (ERB) missions are an important contribution to the validation process of these missions and are essential to the construction of a consistent long-term record of ERB observations. Measurements from two scanning radiometers of different design and calibration, the Clouds and the Earth's Radiant Energy System (CERES) and the Scanner for Radiation Budget (ScaRaB), are compared during simultaneous operation in January and March 1999. The instruments are found to be consistent to within 0.5% and 1.5% in the longwave and shortwave spectral domains, respectively. 1694 Global Change: Instruments and techniques
Loeb, Norman G.; Priestley, Kory J.; Kratz, David P.; Geier, Erika B.; Green, Richard N.; Wielicki, Bruce A.; Hinton, Patricia O’Rawe; Nolan, Sandra K.Loeb, N. G., K. J. Priestley, D. P. Kratz, E. B. Geier, R. N. Green, B. A. Wielicki, P. O. Hinton, S. K. Nolan, 2001: Determination of Unfiltered Radiances from the Clouds and the Earth’s Radiant Energy System Instrument. Journal of Applied Meteorology, 40(4), 822-835. doi: 10.1175/1520-0450(2001)040<0822:DOURFT>2.0.CO;2. Abstract A new method for determining unfiltered shortwave (SW), longwave (LW), and window radiances from filtered radiances measured by the Clouds and the Earth’s Radiant Energy System (CERES) satellite instrument is presented. The method uses theoretically derived regression coefficients between filtered and unfiltered radiances that are a function of viewing geometry, geotype, and whether cloud is present. Relative errors in instantaneous unfiltered radiances from this method are generally well below 1% for SW radiances (std dev ≈0.4% or ≈1 W m−2 equivalent flux), less than 0.2% for LW radiances (std dev ≈0.1% or ≈0.3 W m−2 equivalent flux), and less than 0.2% (std dev ≈0.1%) for window channel radiances. When three months (June, July, and August of 1998) of CERES Earth Radiation Budget Experiment (ERBE)-like unfiltered radiances from the Tropical Rainfall Measuring Mission satellite between 20°S and 20°N are compared with archived Earth Radiation Budget Satellite (ERBS) scanner measurements for the same months over a 5-yr period (1985–89), significant scene-type dependent differences are observed in the SW channel. Full-resolution CERES SW unfiltered radiances are ≈7.5% (≈3 W m−2 equivalent diurnal average flux) lower than ERBS over clear ocean, as compared with ≈1.7% (≈4 W m−2 equivalent diurnal average flux) for deep convective clouds and ≈6% (≈4–6 W m−2 equivalent diurnal average flux) for clear land and desert. This dependence on scene type is shown to be partly caused by differences in spatial resolution between CERES and ERBS and by errors in the unfiltering method used in ERBS. When the CERES measurements are spatially averaged to match the ERBS spatial resolution and the unfiltering scheme proposed in this study is applied to both CERES and ERBS, the ERBS all-sky SW radiances increase by ≈1.7%, and the CERES radiances are now consistently ≈3.5%–5% lower than the modified ERBS values for all scene types. Further study is needed to determine the cause for this remaining difference, and even calibration errors cannot be ruled out. CERES LW radiances are closer to ERBS values for individual scene types—CERES radiances are within ≈0.1% (≈0.3 W m−2) of ERBS over clear ocean and ≈0.5% (≈1.5 W m−2) over clear land and desert.
Ramanathan, V.; Crutzen, P. J.; Lelieveld, J.; Mitra, A. P.; Althausen, D.; Anderson, J.; Andreae, M. O.; Cantrell, W.; Cass, G. R.; Chung, C. E.; Clarke, A. D.; Coakley, J. A.; Collins, W. D.; Conant, W. C.; Dulac, F.; Heintzenberg, J.; Heymsfield, A. J.; Holben, B.; Howell, S.; Hudson, J.; Jayaraman, A.; Kiehl, J. T.; Krishnamurti, T. N.; Lubin, D.; McFarquhar, G.; Novakov, T.; Ogren, J. A.; Podgorny, I. A.; Prather, K.; Priestley, K.; Prospero, J. M.; Quinn, P. K.; Rajeev, K.; Rasch, P.; Rupert, S.; Sadourny, R.; Satheesh, S. K.; Shaw, G. E.; Sheridan, P.; Valero, F. P. J.Ramanathan, V., P. J. Crutzen, J. Lelieveld, A. P. Mitra, D. Althausen, J. Anderson, M. O. Andreae, W. Cantrell, G. R. Cass, C. E. Chung, A. D. Clarke, J. A. Coakley, W. D. Collins, W. C. Conant, F. Dulac, J. Heintzenberg, A. J. Heymsfield, B. Holben, S. Howell, J. Hudson, A. Jayaraman, J. T. Kiehl, T. N. Krishnamurti, D. Lubin, G. McFarquhar, T. Novakov, J. A. Ogren, I. A. Podgorny, K. Prather, K. Priestley, J. M. Prospero, P. K. Quinn, K. Rajeev, P. Rasch, S. Rupert, R. Sadourny, S. K. Satheesh, G. E. Shaw, P. Sheridan, F. P. J. Valero, 2001: Indian Ocean Experiment: An integrated analysis of the climate forcing and effects of the great Indo-Asian haze. Journal of Geophysical Research: Atmospheres, 106(D22), 28371-28398. doi: 10.1029/2001JD900133. Every year, from December to April, anthropogenic haze spreads over most of the North Indian Ocean, and South and Southeast Asia. The Indian Ocean Experiment (INDOEX) documented this Indo-Asian haze at scales ranging from individual particles to its contribution to the regional climate forcing. This study integrates the multiplatform observations (satellites, aircraft, ships, surface stations, and balloons) with one- and four-dimensional models to derive the regional aerosol forcing resulting from the direct, the semidirect and the two indirect effects. The haze particles consisted of several inorganic and carbonaceous species, including absorbing black carbon clusters, fly ash, and mineral dust. The most striking result was the large loading of aerosols over most of the South Asian region and the North Indian Ocean. The January to March 1999 visible optical depths were about 0.5 over most of the continent and reached values as large as 0.2 over the equatorial Indian ocean due to long-range transport. The aerosol layer extended as high as 3 km. Black carbon contributed about 14% to the fine particle mass and 11% to the visible optical depth. The single-scattering albedo estimated by several independent methods was consistently around 0.9 both inland and over the open ocean. Anthropogenic sources contributed as much as 80% (±10%) to the aerosol loading and the optical depth. The in situ data, which clearly support the existence of the first indirect effect (increased aerosol concentration producing more cloud drops with smaller effective radii), are used to develop a composite indirect effect scheme. The Indo-Asian aerosols impact the radiative forcing through a complex set of heating (positive forcing) and cooling (negative forcing) processes. Clouds and black carbon emerge as the major players. The dominant factor, however, is the large negative forcing (-20±4 W m−2) at the surface and the comparably large atmospheric heating. Regionally, the absorbing haze decreased the surface solar radiation by an amount comparable to 50% of the total ocean heat flux and nearly doubled the lower tropospheric solar heating. We demonstrate with a general circulation model how this additional heating significantly perturbs the tropical rainfall patterns and the hydrological cycle with implications to global climate. 3359 Meteorology and Atmospheric Dynamics: Radiative processes; 1610 Atmosphere; 0305 Aerosols and particles; 1620 Climate dynamics
Priestley, Kory J.; Barkstrom, Bruce R.; Lee, Robert B.; Green, Richard N.; Thomas, Susan; Wilson, Robert S.; Spence, Peter L.; Paden, Jack; Pandey, D. K.; Al-Hajjah, AimanPriestley, K. J., B. R. Barkstrom, R. B. Lee, R. N. Green, S. Thomas, R. S. Wilson, P. L. Spence, J. Paden, D. K. Pandey, A. Al-Hajjah, 2000: Postlaunch Radiometric Validation of the Clouds and the Earth’s Radiant Energy System (CERES) Proto-Flight Model on the Tropical Rainfall Measuring Mission (TRMM) Spacecraft through 1999. Journal of Applied Meteorology, 39(12), 2249-2258. doi: 10.1175/1520-0450(2001)040<2249:PRVOTC>2.0.CO;2. Abstract Each Clouds and the Earth’s Radiant Energy System (CERES) instrument contains three scanning thermistor bolometer radiometric channels. These channels measure broadband radiances in the shortwave (0.3–5.0 μm), total (0.3–>100 μm), and water vapor window regions (8–12 μm). Ground-based radiometric calibrations of the CERES flight models were conducted by TRW Inc.’s Space and Electronics Group of Redondo Beach, California. On-orbit calibration and vicarious validation studies have demonstrated radiometric stability, defined as long-term repeatability when measuring a constant source, at better than 0.2% for the first 18 months of science data collection. This level exceeds by 2.5 to 5 times the prelaunch radiometric performance goals that were set at the 0.5% level for terrestrial energy flows and 1.0% for solar energy flows by the CERES Science Team. The current effort describes the radiometric performance of the CERES Proto-Flight Model on the Tropical Rainfall Measuring Mission spacecraft over the first 19 months of scientific data collection.
Lee, R.B.; Barkstrom, B.R.; Bitting, H.C.; Crommelynck, D.A.H.; Paden, J.; Pandey, D.K.; Priestley, K.J.; Smith, G.L.; Thomas, S.; Thornhill, K.L.; Wilson, R.S.Lee, R., B. Barkstrom, H. Bitting, D. Crommelynck, J. Paden, D. Pandey, K. Priestley, G. Smith, S. Thomas, K. Thornhill, R. Wilson, 1998: Prelaunch calibrations of the Clouds and the Earth's Radiant Energy System (CERES) Tropical Rainfall Measuring Mission and Earth Observing System morning (EOS-AM1) spacecraft thermistor bolometer sensors. IEEE Transactions on Geoscience and Remote Sensing, 36(4), 1173-1185. doi: 10.1109/36.701024. The Clouds and the Earth's Radiant Energy System (CERES) spacecraft scanning thermistor bolometer sensors measure Earth radiances in the broadband shortwave solar (0.3-5.0 μm) and total (0.3->100 μm) spectral bands as well as in the 8-12-μm water vapor window spectral band. On November 27, 1997, the launch of the Tropical Rainfall Measuring Mission (TRMM) spacecraft placed the first set of CERES sensors into orbit, and 30 days later, the sensors initiated operational measurements of the Earth radiance fields. In 1998, the Earth Observing System morning (EOS-AM1) spacecraft will place the second and third sensor sets into orbit. The prelaunch CERES sensors' count conversion coefficients (gains and zero-radiance offsets) were determined in vacuum ground facilities. The gains were tied radiometrically to the International Temperature Scale of 1990 (ITS-90). The gain determinations included the spectral properties (reflectance, transmittance, emittance, etc.) of both the sources and sensors as well as the in-field-of-view (FOV) and out-of-FOV sensor responses. The resulting prelaunch coefficients for the TRMM and EOS-AM1 sensors are presented. Inflight calibration systems and on-orbit calibration approaches are described, which are being used to determine the temporal stabilities of the sensors' gains and offsets from prelaunch calibrations through on-orbit measurements. Analyses of the TRMM prelaunch and on-orbit calibration results indicate that the sensors have retained their ties to ITS-90 at accuracy levels better than ±0.3% between the 1995 prelaunch and 1997 on-orbit calibrations atmosphere; calibration; clouds; Earth; Extraterrestrial measurements; infrared imaging; Remote sensing; atmospheric techniques; CERES; Clouds and the Earth's Radiant Energy System; measurement technique; Meteorology; radiometers; satellite remote sensing; Space vehicles; 0.3 to 100 mum; atmospheric measuring apparatus; Bolometers; Earth Observing System morning spacecraft; Energy measurement; EOS-AM1; IR radiometry; meteorological instruments; prelaunch calibration; radiometry; rain; rainfall; Sensor systems; Thermal sensors; thermistor bolometer sensor; Thermistors; TRMM; Tropical Rainfall Measuring Mission; visible region
Haeffelin, Martial P. A.; Mahan, J. Robert; Priestley, Kory J.Haeffelin, M. P. A., J. R. Mahan, K. J. Priestley, 1997: Predicted dynamic electrothermal performance of thermistor bolometer radiometers for Earth radiation budget applications. Applied Optics, 36(28), 7129-7142. doi: 10.1364/AO.36.007129. The Earth Radiation Budget Experiment (ERBE) and the Clouds and the Earth’s Radiant Energy System (CERES) rely on scanning thermistor bolometer radiometers of a similar design for accomplishing their mission. High-level dynamic electrothermal models of these instruments have been developed on the basis of the Monte Carlo ray-trace, finite-difference, and finite-element methods. The models are capable of simulating the end-to-end response of the ERBE and the CERES instruments to simulated sequences of Earth scenes. Such models will prove useful in the design of future generations of similar instruments, in defining ground-based and in-flight calibration and data-reduction strategies, in the interpretation of flight data, and in understanding data anomalies that might arise after the instruments have been placed in orbit. Two modules that make up the end-to-end model are presented: the optical–thermal radiative module and the thermistor bolometer dynamic electrothermal module. The optics module is used to determine the point-spread function of the optics, which establishes that the instrument has sharply defined footprints on the Earth. Results obtained with the thermistor bolometer dynamic electrothermal module provide valuable insights into the details of channel operation and establish its high level of equivalence. The combination of the two modules allows the point-spread function of the instrument to be determined and reveals the potential of this tool for scanning realistic Earth scenes.
