Near-duplicate epochs in some mission data

[ludwigus]

Near-duplicate epochs in some mission data

[leuliett]

Ludwig,
Thanks for the question. Most of the near-duplicates are explained by leap seconds in UTC in the original data. In those cases, independent measurements were made, but the time-stamps are very close. There can be errors in the data either because of an error in the timing used for determining range or because errors when the orbits are generated. This can affect the data for several seconds to minutes before and after the leap second.

[ludwigus]

Hi Eric,
thanks for the fast response. I can understand that this is the first guess according to what I wrote but I don't think that explains this bug. I have reorganized the data in yearly database tables. Thats why I report the results per year and the first example I have shown is usually at the beginning of a year. However, the near duplicates occur all over the year, not only around January 1st or June 30th. Clearly, the first thing I have checked is if the near duplicates occur in the RADS NetCDFs as well and they do.
In c2p0377c004.nc I found 11 near duplicates:

2010-07-16T00:17:16.069441 2010-07-16T00:17:16.069442
2010-07-16T00:18:36.261586 2010-07-16T00:18:36.261587
2010-07-16T00:21:46.835860 2010-07-16T00:21:46.835861
2010-07-16T00:29:15.911872 2010-07-16T00:29:15.911873
2010-07-16T00:34:56.492629 2010-07-16T00:34:56.492630
2010-07-16T00:47:35.959414 2010-07-16T00:47:35.959415
2010-07-16T00:51:12.949924 2010-07-16T00:51:12.949925
2010-07-16T00:51:56.348026 2010-07-16T00:51:56.348027
2010-07-16T00:53:08.049239 2010-07-16T00:53:08.049240
2010-07-16T00:57:52.023776 2010-07-16T00:57:52.023777
2010-07-16T00:58:24.100634 2010-07-16T00:58:24.100635

However, in 2010 there was no leap second. Furthermore, these are no consecutive epochs. There are randomly scattered along the orbit. I fear the problem is somewhere else.

[remkos]

I finally took some time to look at this, and traced it down to the original CryoSat (GOP version C) products from ESA.
This is hopefully solved in the next release of there products, so that it also gets solved in RADS.

So I suggest we just live with the limitation and close this issue.