[RADS] First Jason-2 GDRs arriving into RADS

Remko Scharroo remko at altimetrics.com
Wed Apr 1 22:27:14 CEST 2009

Dear RADS group,

Today, the first (temporary) GDRs for Jason-2 have been added to RADS,  
overwriting the data that was based on IGDRs.

What does this mean?

Short answer: very little.

Long answer: very little ... but note that:

1) The GDR data now in RADS are for Cycles 15 through 20 (inclusive).  
The Cycles prior to 15 are processed but under evaluation and are thus  
expected to arrive very soon. Cycles 21 and 22 are slated to be  
released soon as well, after which the baseline processing of GDRs, at  
approximately one-month delay can commence. Until then, the remaining  
Cycles of Jason-2 will be based on IGDRs.

As stated, the difference between GDRs and IGDRs is expected to be  
slight. The added value is an improved orbit and the occasional  
improved flagging of bad data.

2) As I've discussed before (see my mails of 23 and 27 Feb), there  
have been some updates recently both to the AMR data and the altimeter  
data in the IGDRs (since Cycle 23). I have already updated all Jason-2  
data to basically the same level as much as I could, in order to avoid  
any discontinuities in mean sea level extracted from the data prior to  
Cycle 23 and the data since. Obviously, the new GDR data incorporate  
the same improved ground processing. That means an even better  
consistency is obtained between the current and previous cycles. I'm  
looking forward to putting my fixes to the data aside.

3) Have a good look at these data before attending the OSTST meeting  
in Seattle at the end of June. But remember that some of the original  
corrections have been stripped off and replaced by my own (e.g. tide  
models, geoid, mean sea surface, land flagging). If you really want to  
be picking the data apart ... download the actual GDRs from CNES, JPL  
or NOAA.

4) This IS a temporary data set. The GDRs are expected to change after  
incorporating YOUR suggestions at the OSTST. So look at the data, make  
your wish list, speak out at the OSTST, or forever hold your peace :-)
If you are unable or unwilling to go to Seattle, or unhappy about  
speaking out .... please forward me, or the RADS user group, your  
suggestions, findings, pet peeves, musings, and I'll compile than and  
attempt to transmit them in Seattle.

The new Jason-2 data for Cycles 15-20 are now available on the Delft  
server. When more Cycles are released, they will appear there as well,  
overwriting the older IGDR data. So keep synching regularly!


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