Event-based Vision Sensors (EVS) gain popularity in en-hancing CMOS Image Sensor (CIS) video capture. Nonide-alities of EVS such as pixel or readout latency can significantly influence the quality of the enhanced images and warrant dedicated consideration in the design of fusion algorithms. A novel approach for jointly computing de-blurred, rolling-shutter artifact corrected high-speed videos with frame rates up to 10000 FPS using inherently blurry rolling shutter CIS frames of 120 FPS to 150 FPS in conjunction with EVS data from a hybrid CIS-EVS sensor is presented. EVS pixel latency, readout latency and the sensor's refractory period are explicitly incorporated into the measurement model. This inverse function problem is solved on a per-pixel manner using an optimization-based framework. The interpolated images are subsequently processed by a novel refinement network. The proposed method is evaluated using simulated and measured datasets, under natural and controlled environments. Extensive experiments show reduced shadowing effect, a 4 dB increment in PSNR, and a 12 % improvement in LPIPS score compared to state-of-the-art methods.

Surface waves investigation and monitoring (SWIM) can provide global wave spectra, but under small sea conditions, the presence of parasitic peaks at low wavenumbers, surfboard effects, and residual speckle noise lead to performance degradation of SWIM wave height spectrum products. To reduce the impacts of the above factors on the SWIM wave height spectrum, in this article, a convolution neural network (CNN) method based on BU-Net is proposed for calibrating SWIM omnidirectional wave height spectra with buoy measurements under sea states (wind wave mainly/swell mainly) and sea surface conditions (wind speed from 9 to 19 m/s, and significant wave height (SWH) from 0.8 to 3.4–4.2 m). The calibration results show that the impact of the above factors on the SWIM omnidirectional wave height spectrum can be corrected. The correlation coefficients between the corrected SWIM beams 6°, 8°, and 10° and the buoy mean omnidirectional wave height spectrum are all greater than 0.90, and the relative error of the peak wavenumber is within 10%. The relative error of the integrated energy is mostly less than 20%. In addition, the performance of spectral integration parameters (effective wave height$H_{s}$, and energy wave period$T_{m-10}$) of each spectral beam of SWIM has been verified using Meteo-France WAve Model (MFWAM) reanalysis data. The validation results show that RMSE of$H_{s}$and$T_{m-10}$, for the corrected SWIM beam 6° (8°, 10°) under wind wave sea conditions are 0.31 m (0.32, 0.25 m) and 0.50 s (0.51, 0.49 s), respectively; those for swell cases are 0.16 m (0.16, 0.13 m) and 0.87 s (0.77, 0.72 s), respectively.

Scatterometer wind data are critical for meteorological and oceanographic applications. The differences between scatterometer winds and buoy reference winds largely depend on the type of reference wind used in the fitting of the scatterometer’s geophysical model function (GMF). This study evaluates scatterometer winds using advanced buoy reference winds, specifically stress-equivalent winds (U10S), and equivalent-neutral winds (U10N). We utilized HSCAT-B scatterometer wind products retrieved using both NSCAT-4 and NSCAT-5 GMFs). NSCAT-4 winds were corrected to stress-equivalent winds, and these scatterometer winds were compared with various buoy reference winds, including true buoy winds, stress-equivalent winds, and equivalent-neutral winds. The results show that in extratropical regions, stress-equivalent winds provided a closer match to scatterometer winds, while in tropical regions, equivalent-neutral winds exhibited smaller errors. Scatterometer winds derived from the NSCAT-5 GMF demonstrated superior consistency with buoy reference winds, further reducing wind speed biases compared to NSCAT-4. An extended triple collocation (ETC) analysis was conducted to address the uncertainties arising from differences in spatial resolution between scatterometer and buoy measurements. The findings emphasize the importance of using appropriate wind correction methods for scatterometer wind validation, particularly in regions with significant atmospheric variability.

After over 12 years of development, the HY-2 series microwave scatterometers have been providing stable and reliable Ku-band observation data for operational forecasting departments and marine scientific research departments. The observation data of the satellite constellation comprising the HY-2B/C/D series satellites have played an important role in fields such as numerical forecasting models, typhoon monitoring, and polar sea ice edge identification. In 2019, the HY-2A scatterometer was retired after eight years of operation, having accumulated valuable experience for subsequent payloads and improvements in the processing algorithms of ground systems. Beginning from the HY-2B satellite, the performance of the scatterometer payload has been greatly improved, and the ground data processing system has also been improved accordingly. In addition, compared to the ECMWF Reanalysis v5 (ERA5) wind field, the wind speed accuracy has been increased from 1.35 to 0.9 m/s, and the wind direction accuracy has been increased from 27° to 12°, which is closely related to the improvement of the signal-to-noise ratio (SNR) of the observed data. In this article, the optimization process from experimental satellite payload to operational payload is introduced, then the calculation method of the normalized radar cross section (NRCS) is described in detail, and the consistency of observation data of four payloads is analyzed. The results show that the change in signal bandwidth, increase in signal slice, and improved slice finding and accumulation method have improved the data’s SNR reduced the measurement error, thus fundamentally ensuring the improvement of wind field inversion accuracy.

The HY-2 series scatterometers (HSCAT) are now providing global Ku-band radar observations. In order to build two-decade normalized radar cross section ($\sigma ^{\circ }$) datasets with high quality and high stability, increased attention should first be paid to the instrument variations caused by space environments. The HY-2B scatterometer (HSCAT-B) has operated to yield a two-year dataset in orbit. The monitoring of long-term ocean calibration results and telemetric temperatures indicate that beam radiometric imbalances and long-term instability exist in$\sigma ^{\circ }$due to the gain variations related to temperature changes. Such variations will result in estimated$\sigma ^{\circ }$biases with a peak-to-peak of approximately 0.5 dB. Gain-related calibration models depicting the functions of temperatures were developed using ocean calibration results. The beam radiometric imbalances were corrected using linear gain compensation models of antenna temperatures. The long-term instability was corrected using a linear dependence on microwave front-end and antenna temperatures. Following gain-related calibration, the beam imbalances and long-term instability of the HSCAT-B$\sigma ^{\circ }$were eliminated. The seasonal responses over the Amazon rainforest were also found to correspond to the QuikSCAT$\sigma ^{\circ }$measurements, with amplitudes of approximately 0.15 dB for the morning passes and approximately 0.1 dB for the evening passes. The corrected$\sigma ^{\circ }$will be more suitable for the generation of climate data records. In addition, with the exception of the prelaunch thermal vacuum test, the external calibrations using natural targets are considered to be alternative approaches to gain-related calibrations due to the temperature variations of radar electronics.

Calibration and validation (Cal/Val) of the sea surface height as measured by satellite radar altimeters is essential to understand altimeter biases, observation trends, and instrument aging. It also supports the long-term stability of the produced climate change records of sea level as determined by altimetry. In this article, we report the calibration of HY-2B and Jason-2/3 using the established research infrastructure and data sharing initiative introduced by the Altimetry Calibration Cooperation Plan (ACCP) of China. Currently, three ACCP calibration sites encompass the Wanshan Islands, and two national oceanic sites are located along the China coastline. For each Cal/Val site, the components of the facilities—the geodetic, sea level, and Global Navigation Satellite System (GNSS) infrastructure—and the followed monitoring procedures and calibration methods are described. The HY-2B performance was primarily evaluated using about two years data, which indicated a mean bias of −0.2 ± 4.2 cm. Confidence in the results is strong, because the HY-2B biases were cross compared and confirmed by all the three independent sites and the three satellite ground tracks. Compared with its predecessor HY-2A, HY-2B shows very stable observations with no linear drift at present. In addition, Jason-2 and Jason-3 were mainly assessed using Qianliyan site. Our results indicate that the Jason-3 sea-surface height bias is approximately 2–3 cm smaller than that of Jason-2 and that the long-term stability of Jason-2/3 shows no significant trend, which in good agreement with the international dedicated sites. The instrument noises of Jason-2/3 and HY-2B were estimated based on the ACCP sites. The results show that the instrument noise in the previous literature is underestimated. This was also consolidated by the result from wavenumber spectrum and global crossover point analysis. The code and Wanshan data used in these Cal/Val experiments are publicly available to facilitate further work in this domain (https://github.com/GenericAltimetryTools/CalAlti).

China has launched five satellites scatterometers, namely, the Haiyang-2A scatterometer (HSCAT-A), Haiyang-2B scatterometer (HSCAT-B), China-French Satellite scatterometer (CSCAT), Haiyang-2C scatterometer (HSCAT-C) and Haiyang-2D scatterometer (HSCAT-D). This article aims to introduce calibration and validation methods for products of these Chinese scatterometers. Active transponders are used for post-launch absolute calibration, while the Numerical Weather Prediction Ocean Calibration (NOC) method is applied for post-launch relative calibration for the sigma0 observed in these Chinese scatterometers. As a complement to NOC, a natural terrestrial target of the Amazon rainforest is chosen as a calibration site. A long time-series analysis of sigma0 over the Amazon rainforest is also used to assess the temporal stability. To validate the winds from these Chinese scatterometers, the HSCAT-A/B/C and CSCAT winds are compared to in-situ buoy, ECMWF and ASCAT winds, respectively. The comparison results show that all these four Chinese scatterometers winds are comparable and meet the mission requirements, i.e., the error is less than 2 m/s or 10% in terms of the speed and 20° in terms of the direction. HSCAT-B and HSCAT-C perform better than HSCAT-A and show similar qualities to that of ASCAT-A.

The HY-2B scatterometer (HSCAT-B) has now completed a one-year orbit. The instrument was declared operational after six months of in-orbit testing. The ocean wind field products are routinely being made available to the global science community. The HY-2B will work with the HY-2A to provide the Ku-band sea surface observations on a long-term scale, and this collaboration is expected to be important for disaster prevention and mitigation, as well as globally focused climate change research. However, to obtain reasonable evaluations of the system’s functional, performance, and instrument stability results, the temperature, internal calibration parameters, attitude angles, and normalized radar cross section (NRCS) of the instrument were rigorously analyzed during the in-orbit tests. This study provided an overview of the six-month in-orbit testing process results. The temperature levels of some important parts of the scatterometer were found to meet the design requirements. The internal calibration and noise power had shown similar trends and were both within the normal range. The attitude angles, which mainly included the roll and pitch, had displayed variations within a very small scope. The evaluation results of the Amazon rainforest observations indicated that the scatterometer instrument had met all the design requirements and had established a good database for geophysical processing.

The first rotating fan beam scatterometer onboard China-France Oceanography Satellite (CFOSAT) was successfully launched on October 29, 2018. CFOSAT SCATterometer (CSCAT) is dedicated to the monitoring of sea surface wind vectors but also provides valuable data for the applications over land and Polar Regions. This article provides an overview of the relevant procedures of CSCAT data processing, including onboard signal processing and operational ground processing. Then a post-launch analysis is carried out to evaluate the first results of CSCAT L1 and L2 products. It shows that the CSCAT instrument is generally stable in terms of noise measurements and internal calibration, unless there is any important change in the system configuration. Specifically, the CSCAT backscatter (σθ) precision and wind quality are studied using a set of collocated ancillary data. The σθprecision degrades as wind speed decreases, and it is relatively low at high incidence angles (e.g., θ >46°). In particular, backscatter estimation of the horizontally polarized beam should be further improved by correcting the noise subtraction factor. The retrieved CSCAT winds are in good agreement with the European Centre for Medium Range Weather Forecasts (ECMWF) winds, the Advanced Scatterometer (ASCAT) winds, as well as the buoy winds. However, due to unresolved calibration and interbeam consistency problems, the wind quality degrades remarkably for the out-swath and the nadir-region wind vector cells, implying that the σθcalibration should be improved in the future updates.

The absolute SSH (sea surface height) biases of three satellite altimeters Jason-2, Saral/AltiKa and HY-2 were determined using our GPS buoy at the Qian Li Yan Island of China, which are 9.3cm, 1.3cm and 66.8cm, respectively. In addition, the altimetry SWH (significant wave height) were assessed using GPS retrieved SWH, which shows good agreement between the GPS buoy and satellite altimeters. The detailed method and result are described in the paper.

The HY-2A launched in August 2011 is the first satellite for ocean dynamic environment measurement. The calibration of HY-2A altimeter is performed using cross-calibration methods with Jason-2 mission. Range absolute calibration activities is ongoing based on transponders. The main parameters in IGDR products are validated by in-suit NDBC buoys and Jason-2 measurements. The calibration of HY-2A scatterometer is implemented using open sea measurements, Amazon rainforest measurements and transponders. Wind vectors products are validated by NDBC buoy observations. The key results are as follows: The accuracy of the sea surface height is about 7.0cm by crossover analysis of HY-2A alone. Dual-crossover analysis with Jason-2 altimeter shows HY-2A altimeter total performances is close to the Jason-2. The calibration coefficients of sigma0 for scatterometer are 1.7dB for VV and HH polarization using ocean calibration technique, the monitoring result of the scatterometer measurement stability by Amazon rainforest shows that the instrument system is stable, the RMS of wind speed and wind direction retrieved by scatterometer are about 1.19m/s and 18.74°.