A Study on the Effect Produced by Instrumental Error of Automated Astronomical System on Landmark Azimuth Accuracy

The paper analyzes how random and systematic components of instrumental error of an automated astronomical system affect the accuracy of the landmark astronomical azimuth. The obtained results can be applied to construct the error mathematical model and to define the mutual orientation of the body axes when designing the system.

Outlier Detection: A Research and Modified Method using Fuzzy Clustering

Data mining is becoming increasingly popular in many application fields. Due to the advancement, Researchers show great interest to find unexpected behaviour over large amount of datasets. Outlier detection is studied extensively in data mining and developed for certain application domains, while others are generic in nature. It is one of the important and hottest topic in research which faces a series of new challenges. It occurs due to change in system behaviour, mechanical fault, human error, natural deviations and instrumental error. The purpose of this paper briefly provides a survey on outlier detection and a modified approach to detect outlier using Fuzzy clustering. Also, it provides a better understanding of different dimensions that applied in various substantive areas.

Contribution of future wide-swath altimetry missions to ocean analysis and forecasting

The impact of forthcoming wide-swath altimetry missions on the ocean analysis and forecasting system was investigated by means of OSSEs (observing system simulation experiments). These experiments were performed with a regional data assimilation system, implemented in the Iberian–Biscay–Ireland (IBI) region, at 1∕12∘ resolution using simulated observations derived from a fully eddy-resolving free simulation at 1∕36∘ resolution over the same region. The objective of the experiments was to assess the ability of different satellite constellations to constrain the ocean analyses and forecasts, considering both along-track altimeters and future wide-swath missions; consequently, the capability of the data assimilation techniques used in the Mercator Ocean operational system to effectively combine the different kinds of measurements was also investigated. These assessments were carried out as part of a European Space Agency (ESA) study on the potential role of wide-swath altimetry in future versions of the European Union Copernicus programme. The impact of future wide-swath altimetry data is evident for investigating the reliability of sea level values in OSSEs. The most significant results were obtained when looking at the sensitivity of the system to wide-swath instrumental error: considering a constellation of three nadir and two “accurate” (small instrumental error) wide-swath altimeters, the error in ocean analysis was reduced by up to 50 % compared to conventional altimeters. Investigating the impact of the repetitivity of the future measurements, the results showed that two wide-swath missions had a major impact on sea-level forecasting – increasing the accuracy over the entire time window of the 5-day forecasts – compared with a single wide-swath instrument. A spectral analysis underlined that the contributions of wide-swath altimetry data observed in ocean analyses and forecast statistics were mainly due to the more accurate resolution, compared with along-track data, of ocean variability at spatial scales smaller than 100 km. Considering the ocean currents, the results confirmed that the information provided by wide-swath measurements at the surface is propagated down the water column and has a considerable impact (30 %) on ocean currents (up to a depth of 300 m), compared with the present constellation of altimeters. The ocean analysis and forecasting systems used here are those currently used by the Copernicus Marine Environment and Monitoring Service (CMEMS) to provide operational services and ocean reanalysis. The results obtained in the OSSEs considering along-track altimeters were consistent with those derived from real data (observing system experiments, OSEs). OSSEs can also be used to assess the potential of new observing systems, and in this study the results showed that future constellations of altimeters will have a major impact on constraining the CMEMS ocean analysis and forecasting systems and their applications.

Contribution of future wide swath altimetry missions to ocean analysis and forecasting

The impact of forthcoming wide-swath altimetry missions on the ocean analysis and forecasting system was investigated by means of OSSEs (Observing System Simulation Experiments) performed with a regional data assimilation system, implemented in the Iberian-Biscay-Ireland (IBI) region, at 1/12° resolution using simulated observations derived from a fully eddy-resolving free simulations at 1/36° resolution over the same region. The objective was to asses the contribution of different satellite constellations to constrain the ocean analyses and forecasts, considering both along-track altimeters and future wide-swath missions, and as consequence the capability of the data assimilation techniques used in Mercator Ocean operational system to effectively combine the different kind of measurements. This was carried out as part of a European Space Agency (ESA) study on the potential role of wide-swath altimetry for the evolution of the European Union Copernicus programme. The impact of future wide-swath altimetry data is clearly evident investigating the reliability of sea-level in the OSSEs. The most significant results were obtained looking at the sensitivity of the system to wide-swath instrumental error: considering a constellation of three nadir and two accurate (small instrumental error) wide-swath altimeters, the error in the ocean analysis was reduced up to the 50 %, with respect to conventional altimeters. Investigating the impact of the repetitivity of the future measurements, the results showed that two wide-swath missions had a major impact on the the sea-level forecasting increasing the accuracy over the entire time-window of the 5-day forecasts, with respect to a single wide-swath instrument. A spectral analysis underlined that the contributions of wide-swath altimetry data observed in the ocean analyses and forecasts statistics were mainly due to resolve more accurately (up to > 25 %), with respect to along-track data, the ocean variability at spatial scales smaller than 100 km. Considering the ocean currents, the results confirmed that the information provided by wide-swath measurements at the surface is propagated also in the vertical and has a considerable impact (30 %) on the ocean currents (up to 300 metres), with respect to the present constellation of altimeters. The ocean analysis and forecasting systems used here are currently adopted by Copernicus Marine Environment and Monitoring Service (CMEMS) to provide operational services and ocean re-analysis. The results obtained in the OSSEs considering along-track altimeters were consistent with those derived with real data (observing system experiments, OSEs). OSSEs also allow to evaluate the potential of new observing systems and in this study the results showed that future constellations of altimeters will have a major impact to constrain the CMEMS ocean analysis and forecasting systems and their applications.