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Product History
October, 2009 — New time-series graphs for lake and reservoir water-levels measured by the Jason-2/OSTM satellite are now available. These new time-series graphs are preliminary and will be revised as the USDA/NASA GRLM project continues. The new time-series graphs have filenames called TPJO.1 (which stands for Topex/Poseidon/Jason/OSTM version 1). Users please note these TPJO.1 products also contain revised lake level estimates from the T/P and Jason-1 missions, i.e. there has been a revision of the old TPJ.2 products. See the reference section for details.
The Jason-2 or Ocean Surface Topography Mission (OSTM) was launched on June 20, 2008. It is the follow-on satellite to the Topex/Poseidon (1992-2002) and Jason-1 (2002-2008) missions, and continues the observations of surface water levels. The OSTM mission is a joint effort between NASA, CNES, NOAA and EUMETSAT with science objectives that focus on the ocean, as well as coastal and inland water regions. The new lake and reservoir water levels observed by the OSTM radar altimeter instrument will be continuously added to the existing time series on a weekly basis. Nevertheless, validation exercises, comparing TPJO.1 with ground based daily gauge data on the Great Lakes, USA are showing that the root mean square (rms) error on the current products are better than 10cm and this accuracy can be assumed for similar sized large lakes around the world.
Additional information on the Jason-2/OSTM mission can be found at:
August, 2009 — Data glitches delayed the release of updated graphs in June, but hopefully new graphs will be released in the next month or two.
March, 2009 — No Jason-1 product updates after January 2009 -- The lake level products in this data base have been derived from the NASA/CNES Topex/Poseidon (1992-2002) and Jason-1 (2002-2009) satellite missions. The Jason-1 mission reached the end of its nominal working phase at the beginning of 2009 and was shifted to a new orbit. Hence, there are no Jason-1 product updates after January 2009. However, the team are pleased to announce that the lake products will continue via data collected by the new Jason-2 (or OSTM) mission. In addition, many other lakes and reservoirs around the world are scheduled to be added to this data base via observations collected by the ESA ERS and ENVISAT missions. Look out for new OSTM products from April 2009 and new ERS/ENVISAT products towards the end of 2009.
August, 2007 — Jason-1 data modification --
Small modifications have recently been made to the lake level variations derived from the NASA/CNES Jason-1 mission. The update more accurately aligns the results of the Jason-1 mission to those of its predecessor Topex/Poseidon during the tandem phase (2002) and enables improved continuity from 2002 to the present day. Users are urged to utilize the revised Topex/Poseidon/Jason graphs and text files (TPJ.2 or Version 2) and to note that that new height offset between the missions (the 'relative bias') has been added to the header of the ascii text files.
August, 2007 — GFO data added --
Many of the lakes in the database are missing results derived from the Jason-1 mission. This is due to additional on-board and ground-based data filtering and out of the control of the reservoir project team. However, additional USDA and NASA funding is enabling the exploration of data from the US Navy's Geosat Follow On Mission (GFO). Preliminary GFO results are now provided here (TPJG.1 or Version 1) for a sub-set of the lakes. Users can access these results via clicking on the appropriate text next to the TPJ graphic products. Note that GFO samples each lake at a different location than Jason-1. Research continues to improve accuracy and consistency with respect to the NASA/CNES satellite data.
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