Orbital trajectory data on the thousands of satellites and debris objects in low-Earth orbit (LEO) provide one of the few long-term sources of information on the day-to-day variability, climate, and evolution of the thermosphere (Emmert, 2009(Emmert, , 2015a(Emmert, , 2015b. The atmospheric drag experienced by LEO objects is proportional to the mass density of the atmosphere, so that observed orbital changes contain information on the integrated density along the orbital path. Picone et al. ( 2005) developed a method for extracting density from two-line element sets (TLEs), which have been routinely compiled by the U.S. Air Force. Emmert (2009) applied this method to thousands of LEO objects to obtain a 1967-2007 data set of global average density as a function of altitude from 200 to 600 km altitude. Emmert (2015a) extended this data set to 2013.Starting around 2013, the Air Force changed the method used to generate TLEs. Previously, tracking observations were assimilated into an analytic, or "general perturbations" (GP), orbit propagation model, which consists of a truncated expansion of gravitational and atmospheric drag perturbations to Keplerian orbits. For LEO objects, the GP propagator is the SGP4 propagator (Hoots & Roehrich, 1988). Now, ephemerides from a higher fidelity numerical, or "special perturbations" (SP) orbit propagator (with assimilated tracking observations) are instead used to determine the GP model's orbital parameters. Because the ephemerides used to tune GP orbital parameters are projected into the future beyond the last observation fitted to the SP propagator, the new element sets are called "extrapolated GP", or eGP (they are still issued in the
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