Klosko's Proposed Levels of ILRS Data Products

Editor's Note: These levels of data products were modeled after the levels described in Earth Sciences Reference Handbook/list which differ from Committee on Data Management, Archiving, and Computing (CODMAC) definitions. Currently SLR normal point data do not include the tropospheric refraction correction as noted in Level-1 below.

Level-0	Raw SLR data, uncorrected, uncalibrated, and unprossed. This is basically the time of flight recorded by the tracking station.
Level-1	SLR data as distributed by CDDIS, these data include tropospheric refraction corrections, time tag corrections to UTC/USNO obtained through GPS time transfer, information on internal calibrations, corrections to the optical axis.
Level-2	Daily/weekly parameters which are derived as part of the SLR data quality control process. These would include (daily) polar motion and geocenter variations and weekly station coordinates. Since an orbit is required for DQ, this is a value-added upgrade to routine operational efforts.
Level-2b	Observation equations relating each SLR observation to a set of parameters of geodetic/scientific interest. This opens SLR geodetic parameter recovery to a wide audience.
Level-3	Temporal gravity model parameters representing multiple satellites and many combinations of arcs; secular geopotential terms, tracking station velocity models, and normal equations for complex solutions which are contributed to by SLR.
Level-4	Geophysical and environmental models that can be forward modeled in the SLR analysis and perhaps are derived in conjunction with SLR studies. This would include a processing algorithm which ingests surface pressures from hindcast/forecast models and predicts a filtered estimate of temporal gravity changes from atmospheric mass redistribution, plate tectonic rotation axes and velocities, ice sheet mass imbalance models, models of post glacier rebound; these are models derived to explain the science basis for Level 3 products.

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