Presented at the 2014 Ocean Sciences MeetingThe Aquarius L-band radiometer/scatterometer system is designed to provide ocean surface salinity at an accuracy of 0.2 psu. This poses a challenge for the instrument design and calibration as much as for the salinity retrieval algorithm. Many sizeable spurious signals have to be removed. We discuss the most important ones and the methods for their mitigation: 1. Correcting effects of the wind roughened ocean surface. The Aquarius L-band scatterometer has proven to be an invaluable tool. 2. Correcting intruding celestial radiation, foremost from the galaxy. We then present a validation study for the new salinity product, which consists of an intercomparison between Aquarius, in-situ buoy salinity measurements and the HYCOM model salinity field. The analysis shows that the Aquarius salinity meets the aforementioned mission requirement of 0.2 psu. The Aquarius salinity shows a fresh bias in the tropics when compared to HYCOM and ARGO buoy measurements. This indicates that the Aquarius instrument can pick up rain freshening of the ocean surface.