This paper is Part 1 of a study concerned with the feasibility of using wind scatterometer data in a real-time data assimilation system. The potential that such a system offers for quality assurance and validation of scatterometer data is illustrated using Seasat A satellite scatterometer (SASS) data. The results of passive assimilations of scatterometer data (where the SASS data are passed to the assimilation system but not used), and of active assimilations of scatterometer data (where the data are used), are presented. It is shown that assimilation allows validation and quality assurance of the scatterometer data, through comparisons with collocated ship data and through comparison with the wind fields generated by the assimilation. Intercomparison can be carried out quickly and efficiently at an operational weather center where large amounts of data are collected, so allowing comprehensive quality assurance and validation of wind scatterometer data to be carried out in near-real-time. A number of comparisons are made which illustrate a speed-dependent bias between SASS and ship observtions and between SASS and forecast model, as well as directional irregularities in the SASS data. ¿ American Geophysical Union 1991