The NOAA-21 ATMS, launched in November 2022, collected two-dimensional lunar scan data on March 10, 2023, during its commissioning phase at a Moon phase angle of 34°. The raw data were calibrated using MiCalPS, a microwave calibration and geolocation tool developed at the University of Maryland. Analysis showed that NOAA-21’s lunar antenna gain is generally lower than NOAA-20’s due to sampling rate differences. After correcting for beam pointing errors, disk-averaged lunar brightness temperatures (TDISKB,Moon) were derived for 23–183 GHz. These were compared to NOAA-20 data at 0° phase angle and predictions from the microwave lunar radiative transfer model (ML-RTM). The observed model differences were: −3.3 K (K band), 0.01 K (V), 2.0 K (W), −2.3 K (low-G), and 1.6 K (high-G), consistent with predicted phase delay trends. Further observations at varying Moon phases are recommended to enhance MLRTM validation.

Space-borne microwave sounding instruments have become vital data sources for weather prediction and climate change studies. Among the various radiometer configurations, the total power microwave radiometer is particularly appealing for current and future operational satellites due to its superior sensitivity and simple design. However, its performance is vulnerable to degradation caused by receiver gain fluctuations, electronic 1/f noise, and other time varying receiver characteristics. For Numerical Weather Prediction (NWP) users, 1/f noise introduces inter-channel correlations, complicating the assimilation of affected observations and reducing their accuracy. Addressing this noise issue in ground data processing system is essential to enhance the utility of microwave sounding data. This paper focuses on the characterization and mitigation of noise in current and future microwave sounding instruments, with particular emphasis on the impact of 1/f noise. Various methods are applied to quantitatively characterize noise features in both frequency and time domains. Additionally, the influence of calibration parameters on 1/f noise are analyzed. Based on these findings, we propose a mitigation algorithm for reducing noise during the on-orbit calibration of microwave sounding instruments, aiming to improve the quality of retrieved data for operational use.

The Advanced Technology Microwave Sounder (ATMS) sensor data records (SDRs) product are assimilated for weather forecasts and used to derive environment data records (EDRs) products. Meanwhile, ATMS imagery, derived from SDR product, offers snapshots of weather events, like the warm core of a hurricane. However, its coarse resolution and angular dependence have long been a challenge for improving image visualization. Given these challenges, we have proposed a method which combined limb-correction algorithm and AI resolution enhancement to improve ATMS imagery visualization for bands 16, 18 and 19 [1]. This study further optimized the method and aimed to apply it to most of ATMS bands.

Over ten-years, the Integrated Calibration and Validation System (ICVS) Long-Term Monitoring (LTM) System has provided near-real time (NRT) monitoring for Joint Polar Satellite System (JPSS) spacecraft and instruments including their on-orbit status and performance and science data product quality [1] - [4]. The ICVS also harnesses JPSS Sensor Data Record (SDR) data to rapidly (with little latency) visualize radiometric features of severe weather events such as hurricanes and volcanos [5] [6]. This study presents two case studies, one depicting the 3-dimensional (3D) atmospheric warm core structure inside Hurricane Ian from the 2022 North Atlantic Hurricane Season and another showing the 3D temperature structures present during the 2021 Heat Dome event by using JPSS ATMS (and VIIRS for hurricane events) SDR and TDR data. More details and images/animations for hurricane events can be found at https://www.star.nesdis.noaa.gov/smcd/sew/index.php.

Since early 2012, the cross-track infrared sounder (CrIS) on board the Suomi National Polar-orbiting Partnership (S-NPP) satellite has continually provided the hyperspectral infrared observations for profiling atmospheric temperature, moisture, and greenhouse gases. In this study, the CrIS sensor data record (SDR) data are improved for climate applications with its fine-tuning of calibration coefficients in an NOAA reprocessing project. A specific software system was developed to reprocess the CrIS SDR. This software system was updated with a new calibration algorithm, nonlinearity, and geolocation to improve the SDR data quality and long-term consistency. The calibration coefficients are refined with the latest updates, which were used to calibrate the latest operational SDR products and replace those in the engineering packet (EP) in the raw data record (RDR) data stream. The resampling wavelength was updated based on the metrology laser wavelength and resulted in zero sampling error in the spectral calibration. All the historical SDRs (from February 2012 to March 2017) were generated with the same calibration coefficients and same version of the processing software system, resulting in improved accuracy and stability in terms of spectral and radiometric calibration during the CrIS lifetime mission. The quality of the reprocessed CrIS SDR data at nominal spectral resolution (NSR) is assessed in terms of its radiometric and spectral calibration. Comparisons against the operational SDR data are carried out to demonstrate the improved long-term stability of the reprocessed CrIS SDR data. Overall radiometric biases are found to be small and highly stable over the instrument mission, the FOV-to-FOV differences are less than ~10 mK, and much better than that from the operational SDR data. It is shown that the CrIS metrology laser wavelength varies within 4 ppm as measured by the neon calibration system. The reprocessed SDR data have spectral errors less than 0.5 ppm, which is much better than the operational SDR data with about 4 ppm. This baseline version of the reprocessed SNPP CrIS SDR data is suitable for long-term climate monitoring and model assessments and can provide an infrared reference observation to assess other narrow- or broadband infrared instruments’ calibration accuracy.

Passive microwave sounders provide the highest-impact observations ingested by major numerical weather prediction (NWP) forecast models. The Advanced Technology Microwave Sounder (ATMS), built by Northrop Grumman, Azusa, CA, USA, is the latest operational microwave sounder series being launched by the United States to provide both temperature and water vapor soundings of the atmosphere. The first ATMS was launched on the Suomi National Polar-orbiting Partnership (SNPP) satellite in 2011. This article focuses on the details of the on-orbit performance characterization of the second ATMS, which launched on November 18, 2017, on the Joint Polar Satellite System-1 (JPSS-1) satellite. After successful commissioning, JPSS-1 was renamed National Oceanic and Atmospheric Administration (NOAA)-20 (N-20). We present performance characterizations from prelaunch and postlaunch tests, including the thermal vacuum (TVAC) campaign, and postlaunch activities that contribute to the radiance data products. Significant improvements were found for reflector emissivity,$1/f$noise performance, antenna beam efficiency, interchannel noise correlation, and scan drive bearing design. New geolocation and pointing algorithms were evaluated. The N-20 ATMS has the same channel set, polarizations, scan geometry, and calibration approach as the SNPP ATMS. The N-20 ATMS meets all performance requirements with margin.

The Advanced Technology Microwave Sounder (ATMS) is a passive microwave radiometer for the current generation of polar-orbiting meteorological satellites operated by the National Oceanic and Atmospheric Administration (NOAA). The first two ATMS instruments are manifested onboard the Suomi National Polar-orbiting Partnership (S-NPP) and NOAA-20 satellites. Several critical changes have been made to ATMS operational calibration algorithm since March 2017. The calibration processing has been revised from a Rayleigh–Jeans approximated algorithm to a full radiance algorithm in order to reduce the error introduced by the approximation over cold radiances in the higher frequency channels. In addition, based on the lessons learned from S-NPP and NOAA-20 postlaunch calibration/validation tests, some major improvements have been made in the updated operational algorithm. These include reflector emission and antenna pattern corrections. Details of the radiance-based ATMS on-orbit calibration are documented in this report, and results of prelaunch calibration error budget analysis and postlaunch calibration accuracy evaluation are also presented for reference.

Reported here are disk-integrated Moon surface microwave brightness temperature ($Tb$) retrievals covering the frequency range of 23–183 GHz. Full Moon observations obtained from the advanced technology microwave sounder (ATMS) onboard the NOAA-20 satellite during a special spacecraft pitch–maneuver operation forms the basis of the retrievals. Instrument nonlinearity, Earth sidelobe contamination, cosmic background radiation, and reflector thermal emission corrections are applied to the observations to obtain accurate values of the Moon’s$Tb$at all frequencies. The measured full Moon$Tb$ranges from ~240 to 293 K with frequency increases from 23 to 183 GHz. A clear frequency trend is detected when the brightness temperature increases.

To provide near-real time monitoring of Suomi-National Polar-orbiting Partnership (S-NPP) and NOAA-20 data inter-sensor biases, this study extends the Geosynchronous Equatorial Orbit - Low-Earth Orbit (GEO-LEO) intercalibration method established in [1] to the Visible Infrared Imaging Radiometer Suite (VIIRS) Sensor Data Record (SDR) data at six reflective solar bands (RSBs) and three thermal emissive bands (TEBs) bands via the STAR Integrated Calibration and Validation System (ICVS) framework. The Geostationary Operational Environmental Satellite (GOES) Advanced Baseline Imager (ABI) is used as a transfer to calculate double difference (DD) of VIIRS-ABI Simultaneous Nadir Overpass (SNO) pairs for the S-NPP and NOAA-20 VIIRS SDR cross-calibration biases. A series of sensitivity analyses on the dependence of the results to view geometries, spectral difference corrections, latitudinal variation, and cloud screening are conducted for more accurate bias estimations. The findings are further verified by the other independent approaches, namely the 32-day average difference method (32Day-AD) [2] and DD with radiative transfer model as a transfer (RTM-DD) method.

The Advanced Technology Microwave Sounder (ATMS) is a satellite-based microwave radiometer that provides temperature and humidity sounding observations from low Earth orbit. The instrument utilizes 22 channels that cover a frequency range of 23 to 183 GHz. The first ATMS instrument was launched in 2011 on the Suomi National Polar-orbiting Partnership (S-NPP) satellite and the second ATMS was launched in 2017 on the Joint Polar Satellite System-1 (JPSS-1) satellite (now NOAA-20); both on-orbit ATMS instruments are currently operational. This paper will describe the pre-launch performance of the third ATMS instrument, designated for the JPSS-2 satellite, during ground testing and calibration.

The Nadir Mapper (NM) is one of two nadir sensors of the Ozone Mapping and Profiler Suite (OMPS) that are designed to measure the ultraviolet radiance backscattered by the Earth's atmosphere and surface as well as solar irradiance. This study assesses the lifetime performance of Suomi National Polar-orbiting Partnership (SNPP) satellite NM reflectance data since its launch by using Simultaneous Nadir Overpass (SNO) collocated observations with Global Ozone Monitoring Experiment-2 (GOME-2) spectrometer onboard Meteorological Operational-B (Metop-B) satellite. The study also analyzes the consistency of the NM data quality between SNPP and NOAA-20 satellite using GOME-2 as a transfer.

For the on-orbit calibration of passive microwave radiometers, instrument non-linearity is a major error source, causing a scene-temperature-dependent error if not being properly corrected. non-linearity results from the intrinsic feature of the square-law detector and amplifiers used in total-power microwave radiometers, and can only be accurately characterized through the ground-based Thermal Vacuum Test (TVAC). The ground-based non-linearity characterization is then used in the calibration algorithm to attempt to remove this error source. Evaluation results for current operational microwave-sounding instruments show that the magnitude of the non-linearity error varies from channel to channel and from instrument to instrument, with maximum changes of several tenths of kelvins to several kelvins. While the different responses of the detector and amplifier may explain the non-linearity differences in different instruments, errors in TVAC tests could also increase the uncertainty in the non-linearity assessment. Therefore, accurate knowledge of error sources in the TVAC test and their corrections are important for a reliable and accurate non-linearity measurement. In this paper, major error sources in the TVAC test are studied and identified for the NOAA-20 Advanced Technology Microwave Sounder. Correction methods are developed by combining the pre-launch TVAC test and post-launch deep-space-scan test data sets. An on-orbit evaluation method is also proposed to validate the ground-measured instrument non-linearity.

The second Advanced Technology Microwave Sounder (ATMS) recently launched November 2017 on the Joint Polar Satellite System-l satellite (JPSS-l), now re-named NOAA-20. It joins the first ATMS flight unit aboard the Suomi NPP (S-NPP) satellite, as well as older sounders-the Advanced Microwave Sounding Units A & B (AMSU-A/B) and Microwave Humidity Sounder (MHS)-on polar-orbiting operational weather satellites. Together, these sounders provide critical all-weather temperature and humidity profile information for Numerical Weather Prediction (NWP) models. This paper presents results from a number of special post-launch tests used to characterize the instrument and provide unique calibration information. These special tests-long stares, alternate techniques for lunar intrusion mitigation and geolocation, spacecraft maneuvers, special scan modes, comparisons with NWP models-require nonstandard modes of operation or data analysis, and can only be conducted during commissioning, prior to the start of regular forecast observations.

The Joint Polar Satellite System (JPSS)-1 satellite, also known as National Oceanic and Atmospheric Administration (NOAA)-20, was successfully launched onto a sun-synchronous orbit on November 18, 2017. One of the instruments carried on NOAA-20 is the Advanced Technology Microwave Sounder (ATMS). The first set of ATMS observation data was sent back to Earth on November 29, 2017. Using the first month of the observed data, the instrument biases are estimated based on the differences between observed and simulated antenna temperatures. Model simulations are generated by using the Global Positioning System (GPS) radio occultation (RO) temperature and water vapor profiles from COSMIC, KOMPSAT, MetOp-A/-B GRAS as input to the Community Radiative Transfer Model (CRTM). The same procedure is also carried out to ATMS observations from the Suomi National Polar-orbiting Partnership (S-NPP) satellite during the same one-month time period. It is shown that ATMS channels 7–9, for which the GPS RO data are most accurate, from NOAA-20 are more negatively biased than the corresponding channels of S-NPP. Further investigations will be carried out as more NOAA-20 observations become available.

Accurate global observations from space are critical for global climate change study. However, atmospheric temperature trend derived from spaceborne microwave instruments remains a subject of debate, due mainly to the uncertainty in characterizing the long-term drift of instrument calibration. Thus, a highly stable target with a well-known microwave radiation is required to evaluate the long-term calibration stability. This paper develops a new model to simulate the lunar emission at microwave frequencies, and the model is then used for monitoring the stability of the Advanced Technology Microwave Sounder (ATMS) onboard Suomi NPP satellite. It is shown that the ATMS cold space view of lunar radiation agrees well with the model simulation during the past five years and this instrument is capable of serving the reference instrument for atmospheric temperature trending studies, and connecting the previous generation of microwave sounders from NOAA-15 to the future Joint Polar Satellite System Microwave Sounder onboard NOAA-20 satellite.

The key calibration parameters important to instrument health and safety of Ozone Mapping Profiler Suite (OMPS) Nadir Sensors on board Suomi NPP (Suomi National Polar-orbiting Partnership) are being monitored since November 2011 at NOAA/STAR by the Intensive Calibration and Validation System (ICVA). OMPS has two instrument modules: a combined Nadir Mapper (NM) and Nadir Profiler (NP), and a separate Limb Profiler (LP). Both nadir sensors are designed to make measurements of the ultraviolet radiance backscattered by the Earth's atmosphere and surface and of the extra-terrestrial solar irradiance. In this paper, the trending of the OMPS key calibration parameters in the past four years is shown. The impacts of these parameters on OMPS earth view radiance and albedo for nadir sensors are analyzed.

The Advanced Technology Microwave Sounder (ATMS) onboard the Suomi National Polar-orbiting Partnership (NPP) satellite is a total power radiometer and scans across the track within a range of ±52.77° from nadir. It has 22 channels and measures the microwave radiation at either quasi-vertical or quasi-horizontal polarization from the Earth's atmosphere. From the ATMS pitch-over deep space scan observations, it is found that the antenna reflector losses play an important role in calibration and dominates the scan angle dependent features in the ATMS antenna temperatures. Since the losses are small, they are difficult to measure by traditional means. However, they can be assessed directly from pitch over observations by using deep space radiation measured at different scan angle. This paper describes a physical model developed for the correction of reflector emissivity, which incorporates the angular dependent terms derived from the pitch-over maneuver data. Based on the pitch-maneuver data, the expected V/H polarization emissivity value is in the range of 0.002 to 0.0065. Considering the facts that ATMS is heritage of historical NOAA series microwave sounding instruments like MSU and AMSU, on which the reflector emissivity correction model can also be used to improve TDR/SDR data quality.

The Special Sensor Microwave Imager/Sounder (SSMIS) aboard the Defense Meteorological Satellite Program F-16 satellite measures the Earth-emitted radiation at frequencies from 19 to 183 GHz. Compared with the Special Sensor Microwave/Imager (SSM/I), SSMIS has similar imaging channels except for two at 85.5 GHz replaced by the 91.655-GHz frequency. After the Naval Research Laboratory calibration of SSMIS imager channels, the temperature data record can be utilized operationally to derive both atmospheric and surface parameters. In this paper, several products are developed from the SSM/I heritage algorithms, including total precipitable water (TPW), cloud liquid water path (LWP), snow cover, sea ice cover, rain rate, and land surface temperature (LST). Some new products are also derived from the SSMIS, such as land emissivity. The retrieved products from F-15 SSM/I and F-16 SSMIS are intercompared to quantify the mean bias and standard deviation. It is found that because of both the relatively small mean bias and standard deviation, the F-16 SSMIS products, such as TPW, cloud LWP, snow, and sea ice, may replace the SSM/I products for operational use. However, discrepancies remain in the global rainfall estimates, LST, and land emissivity produced by each sensor. This is likely due to the imperfect F-16 SSM/I-like channels to F-15 SSM/I channels' linear mapping, particularly for 91.655-GHz channels, whose frequency is shifted from 85.5 GHz in SSM/I.