Revisiting Spacetrack Report #3

Abstract

Over a quarter century ago, the United States Department of Defense (DoD) released the equations and source code used to predict satellite positions through SpaceTrack Report Number 3 (STR#3). Because the DoD's two-line element sets (TLEs) were the only source of orbital data, widely available through NASA, this code became commonplace among users needing accurate results. However, end users made code changes to correct the implementation of the equations and to handle rare cases encountered in operations. These changes migrated into numerous new versions and compiled programs outside the DoD. Changes made to the original STR#3 code have not been released in a comprehensive form to the public, so the code available to the public no longer matches the code used by DoD to produce the TLEs. Fortunately, independent efforts, technical papers, and source code enabled us to synthesize a non-proprietary version which we believe is up-to-date and accurate. This paper provides source code, test cases, results, and analysis of a version of SGP4 theory designed to be highly compatible with recent DoD versions.

Where Am I? A Simulated GPS Sensor for Outdoor Robotic Applications

“…The three governing North American aerospace institutions, namely the National Aeronautics and Space Administration (NASA), the North American Aerospace Defense Command (NORAD), and the Air Force Space Command (AFSPC), collectively promote the usage of the Simplified General Perturbations Satellite Orbit Model 4 (SGP4) for satellite tracking, the details of which are found in [7]. In fact, the SGP4 algorithm has gained a strong reputation among amateurs and professionals and quickly became the standard satellite tracking model, resulting in sustained research and constant improvements [8] [9].…”

Space Debris Removal: Learning to Cooperate and the Price of Anarchy

“…This is particularly important in LEO, where orbital progression is significant in the considered time frame. We use the SGP4 (Vallado et al, 2006) orbital propagator to calculate the evolution of the ephemeridis (i.e., position and velocity) of an orbiting object given its TLE description. Ephemerides of all objects are calculated at regular time intervals.…”

“…SGP4 uses averaged Keplerian orbital elements (Vallado et al, 2006) for its orbit representation. In that representation, and restricting ourselves to the LEO regime, we arrive at the following bounds for newly launched satellites: • Semi-major axis: a ∈ [300, 1200] +R E km (distribution from current data)…”

FLCNDEMF: An Event Metamodel for Flood Process Information Management under the Sensor Web Environment

“…Among all of the candidate datasets for precipitation monitoring, satellite TRMM and CMORPH are mostly used internationally, and satellite FY2 and FY3 are often used in China. After the candidate dataset is provided, users could use the simplified general perturbation version 4 (SGP4) model [34,35] and input the spatio-temporal range to quickly acquire the data meeting their demands. …”