Braxton selected the following components for integration into the AceFDS astrodynamics libraries:
LAPACK++ (Linear Algebra PACKage in C++) is a software library for numerical linear algebra that solves systems of linear equations and eigenvalue problems on high performance computer architectures. Computational support is provided for various matrix classes for vectors, non-symmetric matrices, SPD matrices, symmetric matrices, banded, triangular, and tridiagonal matrices; however, it does not include all of the capabilities of the original f77 LAPACK. Emphasis is given to routines for solving linear systems consisting of non-symmetric matrices, symmetric positive definite systems, and solving linear least-square systems. (Ref. 9)
SOFA (Standards of Fundamental Astronomy) operates under the auspices of the International Astronomical Union (IAU) to provide algorithms and software for use in astronomical computing. The initiative is managed by an international panel, the SOFA Board, appointed through IAU Division I. The Board obtains the latest IAU-approved models and theories from the fundamental-astronomy community, implements them as computer code and checks them for accuracy. SOFA also works closely with the International Earth Rotation and Reference Systems Service (IERS) and its reporting commission, IAU Commission 19 — “Rotation of the Earth”. (Ref. 5)
Jet Propulsion Lab DE405 Ephemeris: The JPL Solar System Ephemeris specifies the past and future positions of the Sun, Moon, and nine planets in three-dimensional space. Many versions of this ephemeris have been produced to include improved measurements of the positions of the Moon and planets and to conform to new and improved coordinate system definitions. The DE100-series ephemeris is in the B1950 coordinate system, the DE200 series is in the J2000 system, and the DE400 series is in the reference frame defined by the International Earth Rotation Service (IERS). DE200 has been the standard from which the Astronomical Almanac tables are computed since 1984. Updated planetary position accuracy is generally available in more than one series. For example, DE118 and DE200 are from the same data as are DE140 and DE400. As of this writing the latest data set is DE421. (Ref. 4)
NAIF JPL SPICE Libraries: NASA’s Navigation and Ancillary Information Facility (NAIF) offers NASA planetary flight projects and NASA funded planetary researchers an information system named “SPICE” to assist scientists in planning and interpreting scientific observations from space-based instruments. SPICE is also widely used in engineering tasks associated with planetary missions. SPICE is focused on solar system geometry (pdf). The SPICE system includes a large suite of software, mostly in the form of application program interfaces (APIs), that customers incorporate in their own application programs to read SPICE data files and, using those data, compute derived observation geometry, such as altitude, latitude/longitude, and lighting angles. SPICE data and software may be used within many popular computing environments. The software is offered in FORTRAN, C, IDL® and MATLAB®, with versions for Java Native Interface and Python planned for the future. (Ref. 22)
Modern Density Model from the Naval Research Lab (NRL): NRL has completed the new NRLMSISE-00 empirical model of the atmosphere for worldwide distribution to operational users and scientists. MSIS stands for Mass Spectrometer and Incoherent Scatter Radar, the two primary data sources underlying early versions of the model, and E indicates that the model extends from the ground to space, as opposed to early versions that covered only the upper atmosphere or “thermosphere” (altitude > 90 km). NRLMSISE-00 represents the culmination of an effort to preserve and radically extend NASA’s MSIS technology so that future military and scientific users could exploit the model’s advantages. The model calculates composition, temperature, and total mass density, and is the standard for international space research. Improvements have focused on the thermosphere, which offers the potential for a number of vital operational and scientific applications. (Ref. 6)
Open-source SGP4: code based on Revisiting Spacetrack Report #3: 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 the synthesization of a non-proprietary version which is believed to be up to date and accurate. The Revisiting Spacetrack Report #3 paper provides source code, test cases, results, and analysis of a version of SGP4 theory designed to be highly compatible with recent DoD versions.