GOES-16, the first new generation of NOAA’s geostationary satellite, was launched on November 19, 2016. The Advanced Baseline Imager (ABI) is the key payload of the mission. The instrument performance and satellite intercalibration results show that infrared (IR) radiances are well calibrated and very stable. Yet during its early post-launch tests (PLT) and post-launch product tests (PLPT) period, several calibration anomalies were identified with the IR bands: 1) the IR measurements of the Continental United States (CONUS) and mesoscale (MESO) images demonstrated an artificial periodicity of 15 minutes - Periodic Infrared Calibration Anomaly (PICA), in line with the Mode-3 timeline; and 2) the calibration coefficients displayed small discontinuities twice a day around satellite noon and midnight, which resulted in slight detectable diurnal calibration variations. This work is to report our investigation to the root causes of these anomalies, validation of the anomaly corrections, and assessment of the impacts of the corrections on the radiance quality. By examining the radiometrically calibrated space-swath radiance collected from the moon chasing events, it was found that these anomalies were attributed to the residuals of the spatial uniformity corrections for the scan mirrors. A new set of scan mirror emissivity correction Look-Up Tables (LUTs) were later delivered by the Vendor and implemented operationally. Further analyses showed that the new emissivity LUTs significantly reduced the periodic radiometric variation and diurnal variations. The same method will be applied to validate the IR spatial uniformity for the future GOES-R series ABI instruments.
A new generation of imaging instruments, the Advanced Baseline Imager (ABI), was launched on November 19, 2016 aboard the first satellite of the Geostationary Operational Environmental Satellite - R Series (GOES-R). This premier satellite became GOES-16 shortly after launch, and replaced GOES-13 as NOAA’s operational GOES-East satellite on December 18, 2017. ABI has 16 bands covering the spectrum between 0.47μm and 13.3 μm to provide continuous data stream for weather forecasting and disaster monitoring. After launch, it is critical to monitor and evaluate the instrument calibration performance in a timely manner using data processed by the GOES-16 Ground Segment, starting at Post-Launch Tests (PLT) and continuing throughout mission life. For this purpose, the GOES- 16 Calibration Working Group (CWG) has developed an Instrument Performance Monitor (IPM) system that includes metrics for GOES-16 ABI striping identification and characterization. In particular, it includes individual band striping identification, flagging, frequency, and image quality provided at minute to mission-life time scales, and sample and pixel level. Using this tool, severe striping in several ABI bands - e.g., band01-03, band05, and band14-16 were characterized. The root cause of striping has been found to predominately arise from calibration algorithm deficiencies and artifacts. Identification and characterization of such striping thus motivates root-cause study and calibration improvement activities. Working as part of the CWG IPM system, the striping identification and characterization metrics help to make the user well informed of Ground Segment implemented calibration improvements and updates for GOES-16 ABI, but also provides clues for resolving anomalies.
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.
The Advanced Baseline Imager (ABI) is a critical instrument onboard GOES-16 which provides high quality Reflective Solar Bands (RSB) data though radiometric calibration using onboard solar diffuser. Intensive field campaign for post-launch validation of the ABI L1B spectral radiance observations was carried out during March-May, 2017 to ensure the SI traceability of ABI. In this paper, radiometric calibrations of the five RSBs of ABI are evaluated with the measurements by Airborne Visible/Infrared Imaging Spectrometer (AVIRIS-NG) onboard the high-altitude aircraft ER2. The ABI MESO data processed by the vendor with ray-matching to AVIRIS-NG during the field campaign was compared with the AVIRIS-NG measurements for radiometric bias evaluation. Furthermore, there were several implementations and updates in the solar calibration of ABI RSBs which resulted in different versions of detector gains and nonlinear calibration factors. These calibrations included the calibration by the operational ground processing system, by vendor and the calibration with updated nonlinear calibration factor table for striping mitigation and accounting for the integration time difference between solar calibration and Earth view. The North-South Scan (NSS) field campaign data of ABI were re-processed with these calibration coefficients to quantitatively evaluate the detector uniformity change. The detector uniformity difference are traced back to the difference in the implementation of the solar calibration.
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.
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.
GOES-16, which was launched on 19 November 2017, is the first of the next generation of geostationary weather satellites of NOAA. The Advanced Baseline Imager (ABI) is the primary instrument and mission critical payload onboard imaging the Earth with 16 different spectral bands covering 6 visible/near-infrared (VNIR) bands and 10 infrared (IR) bands. Although the GOES-16 ABI data are currently experimental and undergoing testing, in this study we focus on reporting some preliminary assessment results of the ABI radiometric calibration performance during the post-launch test (PLT) and post-launch product tests (PLPT) period. Our results show that the ABI IR full-disk (FD) images mean brightness temperature (Tb) bias with respect to S-NPP/CrIS and Metop-B/IASI of less than 0.3K. Diurnal variation is very small with a jump of less than 0.15K occurring twice a day around satellite local noon and midnight. The ABI VNIR radiometric calibration has a mean reflectance difference to SNPP/VIIRS of less than 5% for all the 6 VNIR bands except for B02 (0.64µm), which was about 8% brighter than corresponding VIIRS data during the PLT period. It may be noted that calibration of the VNIR bands experienced instabilities associated with ground system (GS) software patch testing and data receiving site failover testing, which can be reflected with the time-series monitoring from different earth and space-based invariant targets. Validations and investigations are still ongoing to improve the ABI imagery and data quality.
The Global Space-based Inter-Calibration System (GSICS) geostationary (GEO) vs. low earth orbit (LEO)
inter-calibration correction products have been routinely generated for years at NOAA to improve and harmonize the
data quality of the operational GOES satellite for a better global weather monitoring, prediction and climate change
studies. In this study, the collocated GOES-13 and GOES-15 Imager infrared (IR) data are used to validate the GSICS
GEO-LEO Imager inter-calibration correction products. To compensate the impact of difference in the spectral
response function (SRF) on the GSICS corrected GEO radiance, two radiative transfer models (RTM) with different
atmospheric profiles are used to simulate the relations between the two GEO radiance values. The results of GEO-GEO
inter-calibration shows that the mean Tb difference between GOES-13 and GOES-15 is less than 0.2K(Ch2),
0.65K(Ch3), 0.08K(Ch4) and 0.35K(Ch6). The two RTM models with different atmospheric profiles have significantly
different impacts on the Tb difference at the two absorptive channels, Ch3 and Ch6, indicating that the impact of
different optical path is not well addressed in this study. Future study should apply the double difference using the RTM
as transfer to compensate for the SRF and viewing/optical path difference at each collocated pixel.