Presented at the 2012 AGU Fall MeetingIn early November 2012, the SMOS mission will be celebrating 3 years in orbit. Since its launch, this mission has given many opportunities for breaking new grounds. Due to the very specific way in which it acquires brightness temperature measurements of the surface, advances were made in operating a two dimensional interferometric radiometer from space, and all the processing that is needed to reach satisfying accuracy requirements.On its side, at the end of 2012, Aquarius will be completing 18 months in orbit, acquiring brightness temperature measurements of the surface.Both missions highly rely on accurate estimates of absolute brightness temperature measurements to derive higher level products over ocean and land. Specifically, ocean salinity is very sensitive to this accuracy and its stability across time and space.Although both mission have developed different ways of calibrating and validating their own measurements, and since those are the only 2 space borne instruments operating at L-band, further cross validation can be found in the inter comparison of their measured brightness temperatures.This comparison can be done according to 2 complementary methods: i) selecting a stable target on the surface and monitoring its brightness temperature over time with both instruments. The selected target is a small area surrounding Dome Concordia in Antartica, already identified as stable and used in various calibration studies. ii) due to both satellites orbit characteristics, SMOS overflies Aquarius every 3 days, always at very low latitudes, all across the equator. From these simultaneous acquisitions, over various surfaces, and Aquarius acquisitions can be simulated based on interferometric acquisitions from SMOS, thus giving access to accurate inter comparison between the two instruments.Results of these methods will be presented and discussed, and overall conclusion with regard to both missions accuracy and stability will be drawn in this presentation.