Journal Of Geophysical Research: Atmospheres, Mar 3, 2017
A novel analytical model of the calibration error impact on the Earth radiance measurement from t... more A novel analytical model of the calibration error impact on the Earth radiance measurement from thermal emissive bands of sensors is developed. The goal is to assess the impact of calibration errors, to evaluate those errors and to perform correction. This model is applied in the correction of bias in Advanced Very High Resolution Radiometer (AVHRR) channels 4 and 5 observed from the intercomparison with Infrared Atmospheric Sounding Interferometer measurements. A two-step regression is used to separate the effects of calibration radiance errors from calibration coefficient errors. In the first step, the calibration radiance error, primarily due to internal calibration target (ICT) imperfections and temperature measurement error, is evaluated using the bias from selected Earth scenes with brightness temperatures close to the ICT temperature. The effects from the ICT imperfections and temperature measurement errors are analyzed collectively. The resulting estimation of the calibration radiance error is 0.30% for channel 4 and 0.33% for channel 5. After correcting the Earth scene radiance for these effects, the errors in the offset and nonlinear coefficient of instrument response are evaluated through the second step of the regression. A weighting function is used to account for the nonuniformity in the data distribution over the Earth radiance range. After the evaluation of the errors, removal of their effects can be achieved either through corrections of the calibration coefficients or correction of the measured radiance. The results are useful for the improvement of the AVHRR IR channel calibration algorithm. This model and two-step regression approach can also be applied to other similar broadband thermal infrared radiometric sensors. The infrared (IR) channels on AVHRR are calibrated using an onboard blackbody (BB) with reference to cold space, while the nonlinearity in instrument response was characterized at prelaunch using Thermal Vacuum (TV) test data. The imperfection in the BB emissivity, BB temperature measurement error, and errors in the calibration coefficients impact Earth scene radiance measurement. Assessing the impact of these errors on the retrieved radiance and correcting the resulting bias are essential to enhance product accuracy. This paper focuses on modeling the impact of these errors on Earth scene radiance measurements for the AVHRR IR channels and correcting the calibration coefficients.
GEO-LEO reflective band intercomparison with bidirectional reflectance distribution function and atmospheric scattering corrections
Journal of Applied Remote Sensing, Feb 23, 2018
Abstract. The intercomparison of the reflective solar bands (RSB) between the instruments onboard... more Abstract. The intercomparison of the reflective solar bands (RSB) between the instruments onboard a geostationary orbit satellite and a low Earth orbit satellite is very helpful in assessing their calibration consistency. Himawari-8 was launched on October 7, 2014, and Geostationary Operational Environmental Satellite (GOES)-R was launched on November 19, 2016. Unlike previous GOES instruments, the Advanced Himawari Imager (AHI) on Himawari-8 and the Advanced Baseline Imager (ABI) on GOES-R have onboard calibrators for the RSB. Independent assessment of calibration is nonetheless important to enhance their product quality. MODIS and visible infrared imager radiometer suite (VIIRS) can provide good references for sensor calibration. The intercomparison between AHI and VIIRS is performed over a pseudoinvariant target. The use of stable and uniform calibration sites provides comparison with accurate adjustment for band spectral difference, reduction of impact from pixel mismatching, and consistency of BRDF and atmospheric correction. The site used is the Strzelecki Desert in Australia. Due to the difference in solar and view angles, two corrections must be applied to compare the measurements. The first is the atmospheric scattering correction applied to the top of atmosphere reflectance measurements. The second correction is applied to correct the BRDF effect. The atmospheric correction is performed using a vector version of the Second Simulation of a Satellite Signal in the Solar Spectrum (6SV) model and the BRDF correction is performed using a semiempirical model. Our results show that AHI band 1 (0.47 μm) has a good agreement with VIIRS band M3 within 0.15%. AHI band 5 (1.61 μm) shows the largest difference (5.09%) with VIIRS band M10, whereas AHI band 5 shows the least difference (1.87%) in comparison with VIIRS band I3. The methods developed in this work can also be directly applied to assess GOES-16/ABI calibration consistency, a topic we will address in the future.
OMPS Nadir early on-orbit performance evaluation and calibration
Proceedings of SPIE, Nov 9, 2012
ABSTRACT OMPS is the latest advanced hyperspectral sensor suite flying onboard the Suomi National... more ABSTRACT OMPS is the latest advanced hyperspectral sensor suite flying onboard the Suomi National Polar-Orbiting Partnership (Suomi NPP) spacecraft. It measures ozone depletion in total column and vertical profile ozone abundances. OMPS on-orbit calibration is conducted through dark, lamp and solar measurements. Launched on October 28, 2011, OMPS Nadir has successfully undergone a thorough early orbit check (EOC) and is currently in the intensive calibration and validation (ICV) phase. The calibration data gathered during the on-orbit calibration and validation activities allows us to evaluate the sensor's early orbit performance and establish on-orbit calibration baseline. In this paper, we provide details of the sensor major on-orbit calibrations activities and present sensor level performance and calibration results from OMPS early orbit image data. These results have demonstrated that the OMPS has made a smooth transition from ground to orbit, and its early on-orbit performance meets or exceeds sensor level requirements and agrees with the predicted values determined during the prelaunch calibration and characterization. Examples of Nadir CCD orbital performance monitoring are provided.
GEO-LEO reflectance band inter-comparison with BRDF and atmospheric scattering corrections
Earth Observing Systems XXII
The inter-comparison of the reflective solar bands between the instruments onboard a geostationar... more The inter-comparison of the reflective solar bands between the instruments onboard a geostationary orbit satellite and onboard a low Earth orbit satellite is very helpful to assess their calibration consistency. GOES-R was launched on November 19, 2016 and Himawari 8 was launched October 7, 2014. Unlike the previous GOES instruments, the Advanced Baseline Imager on GOES-16 (GOES-R became GOES-16 after November 29 when it reached orbit) and the Advanced Himawari Imager (AHI) on Himawari 8 have onboard calibrators for the reflective solar bands. The assessment of calibration is important for their product quality enhancement. MODIS and VIIRS, with their stringent calibration requirements and excellent on-orbit calibration performance, provide good references. The simultaneous nadir overpass (SNO) and ray-matching are widely used inter-comparison methods for reflective solar bands. In this work, the inter-comparisons are performed over a pseudo-invariant target. The use of stable and uniform calibration sites provides comparison with appropriate reflectance level, accurate adjustment for band spectral coverage difference, reduction of impact from pixel mismatching, and consistency of BRDF and atmospheric correction. The site in this work is a desert site in Australia (latitude -29.0 South; longitude 139.8 East). Due to the difference in solar and view angles, two corrections are applied to have comparable measurements. The first is the atmospheric scattering correction. The satellite sensor measurements are top of atmosphere reflectance. The scattering, especially Rayleigh scattering, should be removed allowing the ground reflectance to be derived. Secondly, the angle differences magnify the BRDF effect. The ground reflectance should be corrected to have comparable measurements. The atmospheric correction is performed using a vector version of the Second Simulation of a Satellite Signal in the Solar Spectrum modeling and BRDF correction is performed using a semi-empirical model. AHI band 1 (0.47μm) shows good matching with VIIRS band M3 with difference of 0.15%. AHI band 5 (1.69μm) shows largest difference in comparison with VIIRS M10.
OMPS early orbit dark and bias evaluation and calibration
2012 IEEE International Geoscience and Remote Sensing Symposium, 2012
ABSTRACT The dark signal on an Ozone Mapper Profiler Suite (OMPS) charge-coupled device (CCD) res... more ABSTRACT The dark signal on an Ozone Mapper Profiler Suite (OMPS) charge-coupled device (CCD) results when electrons are thermally emitted into the conduction band of pixels in the active and storage regions. It effectively adds offsets to the photon-generated pixel counts and therefore impacts the Sensor Data Record (SDR) performance. This paper presents OMPS on-orbit results from dark current and electrical bias characterization and calibration on the system level. In particular, data from nominal and diagnostic activities has been collected and analyzed to extract general trends and features about the in-flight detector behaviors. The in-flight dark and bias signals are then compared with the prelaunch on-ground performance for each channel. The South Atlantic Anomaly (SAA) impact and temperature dependency are also addressed. The analysis results have demonstrated that the OMPS CCD performance successfully transferred from ground to orbit; the in-flight timing pattern of the nominal dark measurements are well suited to determine general dark currents of the individual pixels, and data collected during the early orbit calibration are sufficient to perform internal consistency checks of sensor dark and bias parameters and instrument behavior. Results also suggest that to minimize the influence of hot pixels and other effects of CCD lattice damage due to energetic particle hits, the dark current shall be updated on a daily basis rather than the weekly basis as planned.
Initial results from the Ozone Mapper Profiler Suite on the Suomi National Polar-Orbiting Partnership
2012 IEEE International Geoscience and Remote Sensing Symposium, 2012
ABSTRACT The Ozone Mapper Profiler Suite (OMPS)1 is a new generation system designed to measure t... more ABSTRACT The Ozone Mapper Profiler Suite (OMPS)1 is a new generation system designed to measure the global distribution of atmospheric Ozone on a daily basis by using scattered solar irradiance. The suite consists of three separate sensors that have been integrated and are now flying on the Suomi National Polar-orbiting Partnership (NPP), which was successfully launched in October 2011. The OMPS instrument suite began operating in January 2012. This paper summarizes the initial OMPS nadir sensors on-orbit calibration, data analysis and characterization as well as the transition of sensor and Ozone retrievals performance from ground to real flight conditions.
The inter-comparison of the reflective solar bands (RSB) between the instruments onboard a geosta... more The inter-comparison of the reflective solar bands (RSB) between the instruments onboard a geostationary orbit satellite and a low Earth orbit satellite is very helpful in assessing their calibration consistency. Himawari-8 was launched 7 October 2014 and GOES-R was launched on 19 November 2016. Unlike previous GOES instruments, the Advanced Himawari Imager (AHI) on Himawari-8 and the Advanced Baseline Imager (ABI) on GOES-R have onboard calibrators for the RSB. Independent assessment of calibration is nonetheless important to enhance their product quality. MODIS and VIIRS can provide good references for sensor calibration. In this work, the inter-comparison between AHI and VIIRS is performed over a pseudo-invariant target. The use of stable and uniform calibration sites provides comparison with accurate adjustment for band spectral difference, reduction of impact from pixel mismatching, and consistency of BRDF and atmospheric correction. The site used is the Strzelecki Desert in Australia. Due to the difference in solar and view angles, two corrections must be applied in order to compare the measurements. The first is the atmospheric scattering correction applied to the top of atmosphere reflectance measurements. The second correction is applied to correct the BRDF effect. The atmospheric correction is performed using a vector version of the Second Simulation of a Satellite Signal in the Solar Spectrum (6SV) model and the BRDF correction is performed using a semi-empirical model. Our results show that AHI band 1(0.47 µm) has a good agreement with VIIRS band M3 within 0.15%. AHI band 5 (1.61 µm) shows the largest difference (5.09%) with VIIRS band M10, while AHI band 5 shows the least difference (1.87%) in comparison with VIIRS band I3. The methods developed in this work can also be directly applied to assess GOES-16/ABI calibration consistency, a topic we will address in the future.
Radiometric quality assessment of GOES-16 ABI L1b images
Earth Observing Systems XXIII
The Advanced Baseline Imager (ABI) onboard NOAA’s GOES-16 satellite has been operational as GOES-... more The Advanced Baseline Imager (ABI) onboard NOAA’s GOES-16 satellite has been operational as GOES-East since December 18th, 2017. It is a multi-channel passive imaging radiometer with 16 spectral bands covering the visible, near infrared and infrared (IR) spectra, to captured variable area imagery and radiometric information of the Earth’s surface, atmosphere and cloud cover. The Level 1B (L1b) radiance images of these channels are geometrically and radiometrically corrected to provide high quality input data to the user communities. Three series of tests are undertaken to validate the product maturity levels: Post-launch Test (PLT), Post-launch Product Test (PLPT) and Extended Validation (EV). Engineering-focused metrics reflecting the radiometric quality of ABI L1b radiance image are assessed in these tests, such as signal-to-noise ratio (SNR)/noise-equivalent-differential temperature (NEdT), background coherent noise pattern, detector dynamic range, detector linearity, etc. Direct Earth view image analysis using image processing tool such as Fourier transform can also reveal information about its quality. In this presentation, initial results of selected PLPTs undertaken by GOES-R Calibration Working Group (CWG) are provided with the focus for IR bands. The results show that the general criterion for product maturity have been largely met. Occasional artifacts still existing at smaller scale are reported. There has been continuous effort to monitor, analyze and resolve these artifacts to further improve the L1b image quality.
On September 23 rd , 2012, the Geostationary Operational Environmental Satellite (GOES)-13 Imager... more On September 23 rd , 2012, the Geostationary Operational Environmental Satellite (GOES)-13 Imager and Sounder were placed in standby in response to a scan motor overload in each instrument. Several days prior to this event, GOES-13 Imager Channel 3 imagery exhibited oscillatory noise. In response, a Fourier coherent noise analysis tool with the ability to measure small signals was created and applied to GOES-13 Imager space data. The analysis confirmed a noise frequency calculation by the National Oceanic and Atmospheric Administration (NOAA) Office of Satellite and Product Operations (OSPO) and showed that the GOES-13 Imager Channel 1 was also exhibiting oscillatory noise. After the instruments' return to service, the coherent noise persisted but with a significantly reduced amplitude. Using historical data, the Fourier analysis tool also showed that the GOES-13 Imager coherent noise originated on July 13 th , 2012. To provide potential warnings of future anomalies, daily GOES-EAST and GOES-WEST Imager coherent noise measurements are provided on the GOES Imager Data Quality Monitoring website.
Validation of early GOES-16 ABI on-orbit geometrical calibration accuracy using SNO method
The Advanced Baseline Imager (ABI) onboard the GOES-16 satellite, which was launched on 19 Novemb... more The Advanced Baseline Imager (ABI) onboard the GOES-16 satellite, which was launched on 19 November 2016, is the first next-generation geostationary weather instrument in the west hemisphere. It has 16 spectral solar reflective and emissive bands located in three focal plane modules (FPM): one visible and near infrared (VNIR) FPM, one midwave infrared (MWIR), and one longwave infrared (LWIR) FPM. All the ABI bands are geometeorically calibrated with new techniques of Kalman filtering and Global Positioning System (GPS) to determine the accurate spacecraft attitude and orbit configuration to meet the challenging image navigation and registration (INR) requirements of ABI data. This study is to validate the ABI navigation and band-to-band registration (BBR) accuracies using the spectrally matched pixels of the Suomi National Polar-orbiting Partnership (SNPP) Visible Infrared Imaging Radiometer Suite (VIIRS) M-band data and the ABI images from the Simultaneous Nadir Observation (SNO) images. The preliminary results showed that during the ABI post-launch product test (PLPT) period, the ABI BBR errors at the y-direction (along the VIIRS track direction) is smaller than at the x-direction (along the VIIRS scan direction). Variations in the ABI BBR calibration residuals and navigation difference to VIIRS can be observed. Note that ABI is not operational yet and the data is experimental and still under testing. Effort is still ongoing to improve the ABI data quality.
Global high-resolution (3-hourly, 0.1°Â 0.1°longitude-latitude) water vapor (6.7 mm) and window (... more Global high-resolution (3-hourly, 0.1°Â 0.1°longitude-latitude) water vapor (6.7 mm) and window (11 mm) radiances from multiple geostationary satellites are used to document the diurnal cycle of upper tropospheric relative humidity (UTH) and its relationship to deep convection and high clouds in the whole tropics and to evaluate the ability of the new Geophysical Fluid Dynamics Laboratory (GFDL) global atmosphere and land model (AM2/LM2) to simulate these diurnal variations. Similar to the diurnal cycle of deep convection and high clouds, coherent diurnal variations in UTH are also observed over the deep convective regions, where the daily mean UTH is high. In addition, the diurnal cycle in UTH also features a land-sea contrast: stronger over land but weaker over ocean. UTH tends to peak around midnight over ocean in contrast to 0300 LST over land. Furthermore, UTH is observed to lag high cloud cover by $6 hours, and the latter further lags deep convection, implying that deep convection serves to moisten the upper troposphere through the evaporation of the cirrus anvil clouds generated by deep convection. Compared to the satellite observations, AM2/LM2 can roughly capture the diurnal phases of deep convection, high cloud cover, and UTH over land; however, the magnitudes are noticeably weaker in the model. Over the oceans the AM2/LM2 has difficulty in simulating both the diurnal phase and amplitude of these quantities. These results reveal some important deficiencies in the model's convection and cloud parameterization schemes and suggest the lack of a diurnal cycle in SST may be a shortcoming in the boundary forcing for atmospheric models.
Validation of geostationary operational environmental satellite-16 advanced baseline imager radiometric calibration with airborne field campaign data and reanalysis of north-south scan data
Assessing the GOES-16 ABI solar channels calibration using deep convective clouds
Tropical deep convective clouds (DCCs) are thick, bright, cold, and their reflectance is consider... more Tropical deep convective clouds (DCCs) are thick, bright, cold, and their reflectance is considered stable. Thus, DCCs can be used to calibrate visible/near infrared (VNIR) channels of satellite instruments. Previous studies report how DCCs are identified by providing specific brightness temperature thresholds and are used for calibration purpose as an invariant target for solar channels. On 19 November 2016, the Geostationary Operational Environment Satellite-R Series (GOES-R) was successfully launched and became GOES-16 after it reached the geostationary orbit on 29 November 2016. The Advanced Baseline Imager (ABI) instrument on-board GOES-16 has 16 multi-spectral bands (0.47 - 13.3 μm) which have more accurate and frequent radiometric calibration information than previous GOES satellite series. Assessment and monitoring of the GOES-16 ABI VNIR channels calibration using DCC method is a main objective of this study. The target region is a 20°N-20°S and 119.5°W-59.5°W centered on the GOES-16 ABI check-out spatial domain (at 0.0°N, 89.5°W). This work is expected to provide useful information regarding the ABI radiometric calibration stability and such calibration stability of the ABI VNIR channels will be compared the results with other methods (e.g., ray-matching and desert) in the near future.
In-orbit response versus scan-angle (RVS) validation for the GOES-16 ABI solar reflective bands
Earth Observing Systems XXIII, 2018
The weather instrument of Advanced Baseline Imager (ABI) is the mission critical instrument on-bo... more The weather instrument of Advanced Baseline Imager (ABI) is the mission critical instrument on-board the GOES-16 satellite. Compared to the predecessor GOES Imager, GOES-16 ABI has many new advanced technical devices and algorithms to improve the data quality, including the double scan-mirror system. To validate the in-orbit response versus scan-angle (RVS), the Moon is used as a reference target for this purpose. During the post-launch test (PLT) and post-launch product test (PLPT) period, a series of special scans were conducted to chase and collect the lunar images at optimal phase angle range when it transited across the space within the ABI Field of Regard (FOR) from West to East. Analyses of the chasing events above and below the Earth indicated that the RVS variations at the East-West (EW) direction are generally less than 1% for all the six solar reflective bands. Same method is being applied to validate the GOES-17 ABI spatial uniformity for the visible and near-infrared (VNIR) bands.
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