Long Term Performance Monitoring of ASCAT-A Intrument and Level 1 Products
Figa-Saldana, Julia; Anderson, C.; Bauch, H.; Duff, C.; Miller, J.; Wilson, J.

The Advanced SCATterometer (ASCAT) on METOP-A satellites is a real aperture, vertical polarisation, C-band radar designed primarily to provide global ocean winds operationally. The main application of these data is the assimilation into numerical weather prediction models. Its dense coverage makes the data also extremely useful for direct use by operational weather forecasters in near real time. The main measurement provided by the ASCAT is the normalised radar backscatter, for which other important applications have emerged in the recent years over land and sea ice areas, where it provides information on other parameters such as soil moisture and ice concentration and age.

Six years after the start of the ASCAT mission, a re-processing of the full mission is taking place and a long-term analysis of instrument performance and product quality is being carried out, covering instrument health events and trends, as well as an evaluation of the normalised radar backscatter calibration, accuracy and stability. This detailed long-loop performance analysis is summarised and provides an assessment of the long term available ASCAT data record, its continuity and how well it complements the long C-band scatterometer data record provided since 1991 by its predecessor, the ESA ERS scatterometers. This assessment is very important in order to evaluate the the long term data record of geophysical parameters derived from the ASCAT measurements.