Fault detection and isolation

Erroneous measurements in multisensor navigation systems must be detected and isolated. A recursive estimator can find fast growing errors; a least squares batch estimator can find slow growing errors. This process is called fault detection. A protection radius can be calculated as a function of time for a given location. This protection radius can be used to guarantee the integrity of the navigation data. Fault isolation can be accomplished using either a snapshot method or by examining the history of the fault detection statistics

Initial validation of ozone measurements from the High Resolution Dynamics Limb Sounder

Comparisons of the latest High Resolution Dynamics Limb Sounder (HIRDLS) ozone retrievals (v2.04.09) are made with ozonesondes, ground-based lidars, airborne lidar measurements made during the Intercontinental Chemical Transport Experiment–B, and satellite observations. A large visual obstruction blocking over 80% of the HIRDLS field of view presents significant challenges to the data analysis methods and implementation, to the extent that the radiative properties of the obstruction must be accurately characterized in order to adequately correct measured radiances. The radiance correction algorithms updated as of August 2007 are used in the HIRDLS v2.04.09 data presented here. Comparisons indicate that HIRDLS ozone is recoverable between 1 and 100 hPa at middle and high latitudes and between 1 and 50 hPa at low latitudes. Accuracy of better than 10% is indicated between 1 and 30 hPa (HIRDLS generally low) by the majority of the comparisons with coincident measurements, and 5% is indicated between 2 and 10 hPa when compared with some lidars. Between 50 and 100 hPa, at middle and high latitudes, accuracy is 10–20%. The ozone precision is estimated to be generally 5–10% between 1 and 50 hPa. Comparisons with ozonesondes and lidars give strong indication that HIRDLS is capable of resolving fine vertical ozone features (1–2 km) in the region between 1 and 50 hPa. Development is continuing on the radiance correction and the cloud detection and filtering algorithms, and it is hoped that it will be possible to achieve a further reduction in the systematic bias and an increase in the measurement range downward to lower heights (at pressures greater than 50–100 hPa)

Initial validation of ozone measurements from the High Resolution Dynamics Limb Sounder

Comparisons of the latest High Resolution Dynamics Limb Sounder (HIRDLS) ozone retrievals (v2.04.09) are made with ozonesondes, ground-based lidars, airborne lidar measurements made during the Intercontinental Chemical Transport Experiment–B, and satellite observations. A large visual obstruction blocking over 80% of the HIRDLS field of view presents significant challenges to the data analysis methods and implementation, to the extent that the radiative properties of the obstruction must be accurately characterized in order to adequately correct measured radiances. The radiance correction algorithms updated as of August 2007 are used in the HIRDLS v2.04.09 data presented here. Comparisons indicate that HIRDLS ozone is recoverable between 1 and 100 hPa at middle and high latitudes and between 1 and 50 hPa at low latitudes. Accuracy of better than 10% is indicated between 1 and 30 hPa (HIRDLS generally low) by the majority of the comparisons with coincident measurements, and 5% is indicated between 2 and 10 hPa when compared with some lidars. Between 50 and 100 hPa, at middle and high latitudes, accuracy is 10–20%. The ozone precision is estimated to be generally 5–10% between 1 and 50 hPa. Comparisons with ozonesondes and lidars give strong indication that HIRDLS is capable of resolving fine vertical ozone features (1–2 km) in the region between 1 and 50 hPa. Development is continuing on the radiance correction and the cloud detection and filtering algorithms, and it is hoped that it will be possible to achieve a further reduction in the systematic bias and an increase in the measurement range downward to lower heights (at pressures greater than 50–100 hPa).Las comparaciones de las últimas recuperaciones de ozono de High Resolution Dynamics Limb Sounder (HIRDLS) (v2.04.09) se realizan con ozonosondas, lidar terrestres, mediciones lidar aerotransportadas realizadas durante el Experimento B de transporte químico intercontinental y observaciones satelitales. Una gran obstrucción visual que bloquea más del 80 % del campo de visión de HIRDLS presenta desafíos significativos para los métodos de análisis de datos y su implementación, en la medida en que las propiedades radiativas de la obstrucción deben caracterizarse con precisión para corregir adecuadamente las radiancias medidas. Los algoritmos de corrección de radiancia actualizados en agosto de 2007 se utilizan en los datos de HIRDLS v2.04.09 presentados aquí. Las comparaciones indican que el ozono HIRDLS es recuperable entre 1 y 100 hPa en latitudes medias y altas y entre 1 y 50 hPa en latitudes bajas. Se indica una precisión superior al 10 % entre 1 y 30 hPa (HIRDLS generalmente bajo) en la mayoría de las comparaciones con mediciones coincidentes, y se indica un 5 % entre 2 y 10 hPa cuando se compara con algunos lidars. Entre 50 y 100 hPa, en latitudes medias y altas, la precisión es del 10 al 20 %. Se estima que la precisión del ozono es generalmente del 5 al 10 % entre 1 y 50 hPa. Las comparaciones con ozonosondas y lidar dan una fuerte indicación de que HIRDLS es capaz de resolver características finas de ozono vertical (1–2 km) en la región entre 1 y 50 hPa. Se continúa desarrollando la corrección de radiancia y los algoritmos de filtrado y detección de nubes, y se espera que sea posible lograr una mayor reducción en el sesgo sistemático y un aumento en el rango de medición hacia abajo a alturas más bajas (a presiones superiores a 50 –100hPa).Universidad Nacional, Costa RicaEscuela de Químic