Date: Thu, 24 Apr 2003 15:10:37 -0500 From: "John C. Ries" To: Pascal Willis , Jean-Paul Berthias Cc: Nikita Zelensky , Bruce J Haines , Martine Feissel , Gilles Tavernier , Pierre Sengenes , Flavien Mercier Subject: Re: JASON/DORIS oscillator - SAA effect on stations positioning Hi Pascal, At 10:39 AM -0700 4/23/03, Pascal Willis wrote: >Dear Jean-Paul, > >following my previous messages, new stations seem to be affected by >the SAA effect (see figure 1). In my presentation at the IDS >Workshop in Paris, I presented the PDMB stations as a possible >outlier. In fact, this is not the case, as now Toulouse seems now to >be also affected. PDMB is effectively affected by the same effect. I had been seeing both of these stations affected for some time. If I recall, they act in an opposite sense from the stations in the SAA. >My guess is that all stations who see the JASON satellite while in >the SAA region will be affected at some point in time. Yes, this seems to get steadily worse and the region affected larger. If the oscillator is becoming more and more sensitized, I wonder where this will lead. And I agree that estimating the global bias drift does not solve it (unfortunately), but only mitigate it for the non-SAA stations. My future strategy is a tight editing to automatically remove any pass acting 'strangely' (which effectively removes virtually all affected data) and then include the global bias drift. This will bother the estimation of station heights, so this is indeed only part mitigation. As the affected area grows, I'll lose more and more data, but what remains should be clean. And there is so much data remaining that the POD still looks good (for now). I don't see a problem in my runs, but I still need to process up to the latest cycles. I agree that if we lose a big enough geographic region, the POD has to start being affected even for the long arcs. Best regards, JR