Propagator Configuration

The propagator configuration setting defines a set of orbit propagation properties applying to special perturbations methods that can be applied to multiple orbit definitions. In other words, multiple Orbit types can be created with a single propagator definition. The keyword PropagatorConfig initiates this configuration type, followed by an assigned name that is referenced when defining an orbit. Multiple entries per definition can be entered with a semicolon marking the end as usual.

PropagatorConfig config_name ...

Before listing available options, an example entry will aid in clarifying the format:

PropagatorConfig  grav_srp   GravityModel  Standard 40 40
#                            GravityModel  Jn 3
                             MoonGravity  Meeus
                             SunGravity   Meeus
                             SRP Spherical 1.5 0.00008
                             Integrator  Adams4 Seconds 8.0;

Note the number of parameters following a configuration type depends on the entry. Two gravity models are shown, with the second commented out. The first is a standard rectangular gravity model requiring the degree and order. The commented out model model only requires entry of the number of zonal harmonics to include---in this case, J3. The format here indicates the type of model (central body gravity model), the specific model to use (degree and order vs. lower order zonals only), and then the configuration for that model. In contrast, the lunar gravity model only requires the specific type of model to activate as there are no other options.

Gravity Model

SP methods can select the gravity model to be used. The EGM 2008 gravity model is employed for all implementations. GravityModel Jn 0 is the default if not specified.

GravityModel Jn d

A simple zonal gravity model supporting up to degree (d) 4

GravityModel Standard degree order

Standard eom rectangular gravity model supporting degree and order d o such that order .LE. degree. The implementation is based primarily off equations from Vallado's Fundamentals of Astrodynamics and Applications, 3rd Ed.

GravityModel Gravt d o

GENPL option supporting degree and order d o. The model supports non-rectangular and sparse entries, but those options have not yet been configured through the eomx interface.

Moon Gravity Model

SP methods can select the model to be used for gravitational perturbations due to the moon. The default is to not incorporate lunar gravitational effects.

MoonGravity Meeus

Moon gravitational perturbations with lunar ephemeris resolved through the method from Chapter 47 of Meeus' "Astronomical Algorithms", 2nd Ed.

MoonGravity Ephemeris

This option interpolates JPL derived precision ephemerides of the moon (JPL Ephemerides).

Sun Gravity Model

SP methods can select the model to be used for gravitational perturbations due to the sun. The default is to not incorporate solar gravitational effects.

SunGravity Meeus

Sun gravitational perturbations with solar ephemeris resolved through the method from Chapter 25 of Meeus' "Astronomical Algorithms", 2nd Ed.

SunGravity Ephemeris

This option interpolates JPL derived precision ephemerides of the sun (JPL Ephemerides).

Planetary Gravity

OtherGravity

This option interpolates JPL derived precision ephemerides of the nine planets using JPL derived precision ephemerides (JPL Ephemerides). Planetary third body gravitational effects is currently an all or nothing option, for now.

Solar Radiation Pressure

SRP Spherical Cr AoM

A custom spherical solar radiation pressure model developed for use with the geodesy satellites. Cr is a reflectivity coefficient. The portion of the value from zero to one represents the proportion of the SRP acting along the incident ray direction. Zero would indicate a completly translucent, non-interactive body, essentially disabling SRP effects. Any portion of Cr in excess of one acts along the line from the satellite towards the center of the earth. Cr essentially dictates how the solar radiation pressure is distributed through a linear combination of the sun to satellite and satellite to earth vectors. This approach is showing promise for the 2 rev/day Etalon-1/2 spaceballs for which inclusion of SRP is essential to getting the 1 week orbit propagation error below 5 meters.

AoM is the effective area over mass ratio. Units are currently required to be square meters per kilogram.

A more detailed writeup on this model based on fitting precision SLR ephemerides will be created. For now, it should be understood Cr and AoM are fit parameters using a fixed 4.57e-6 N/m^2 solar radiation pressure value.

Numerical Integrator

SP methods can select the numerical integration method used to solve the equations of motion. Integrator RK4 is the default if not specified.

Integrator RK4 Duration

Standard Runge-Kutta integration method. Robust, but not efficient. The Duration is the integration step size to use. A Duration equivalent to zero will result in the use of a default integration step size.

Integrator RK4s Duration

Runge-Kutta with time regularization integration method. Still experimental---probably best to consider as a placeholder for more time regularization options.

Integrator Adams4 Duration

Fixed step size Adams-Bashforth predictor with Adams-Moulton corrector, primed via RK4. The Duration is the integration step size to use. A Duration equivalent to zero will result in the use of a default integration step size.

Integrator GJ Duration

GENPL option, highly efficient Gauss-Jackson 2nd order integrator with on-the-fly step size adjustment to minimize error while maximizing speed. The Duration entry is required by the parser, but the setting is currently ignored. Instead, a default initial integration step size is used and adjusted during propagation.

Integrator GJs Duration

GENPL option, GJ propagator employing time regularization. Better suited for elliptical orbits. As with the GJ propagation, Duration is ignored.

eomx User Guide Home