Satellite Properties

Astro Standards Propagators

US Space Force (USSF) maintains its own implementation of various propagators. USSF provides an official, distributable versions of these propagators. STK supports the following propagator types and versions:

  • AFSPC_SP_V8
  • AFSPC_SGP4_V8
  • ASTROSTDS_SP_V9
  • ASTROSTDS_SGP4_V9

If you are supporting the US Government, you may request the USSF propagators. Contact AGI Support for information on how to obtain the propagators from USSF and install them for use in STK.

SGP4

For general information about the STK implementation of SGP4 and the use of SGP4 in STK, see the SGP4 Propagator Help topic. If you support the US Government, you may request Help documentation specifically regarding the USSF implementation of SGP4 from AGI Support.

SP Propagator

SP is an acronym for Special Perturbations, which is a general term used to describe the technique of numerically integrating a set of force models to generate ephemeris. Many individuals and organizations have created propagators that use this technique. STK's HPOP and Astrogator propagators are considered special perturbations propagators. However, within the US Space Force community, the term "SP propagator" refers to a particular implementation developed by USSF.

USSF provides input state vectors for the USSF SP propagator in Vector Covariance Messages (VCMs). AGI recommends that, if you want to propagate a VCM, you use the official SP propagator, as this will better ensure consistency with other USSF ephemeris generated from the same VCM.

If you support the US Government, you may request Help documentation regarding the USSF SP propagator from AGI Support.