Available Parameters
The framework discussed in the previous section explains how the parameter_settings
list is populated. The goal of this section is to list the available parameters that can be used in the variational equations (and which are therefore available for estimation in a state estimation problem), what syntax they use, and explain to which environment models they are linked.
- Single Parameters
gravitational_parameter
Gravitational parameter of a body, linked to a
GravityFieldModel
object, which may be a point-mass or (time-dependent) spherical harmonic field. Parameter size: 1. Secondary identifer: None.estimation_setup.parameter.gravitational_parameter( "Earth" )
constant_drag_coefficient
Drag coefficient of a body that is constant, linked to a
CustomAerodynamicCoefficientInterface
object derived fromAerodynamicCoefficientInterface
, which must have 0 independent variables for the coefficients. Parameter size: 1. Secondary identifer: None.estimation_setup.parameter.constant_drag_coefficient( "Spacecraft" )
constant_rotation_rate
Rotation rate of a body around a fixed axis, linked to a
SimpleRotationalEphemeris
object derived fromRotationalEphemeris
. Parameter size: 1. Secondary identifer: None.estimation_setup.parameter.constant_rotation_rate( "Earth" )
radiation_pressure_coefficient
Constant radiation pressure coefficient of a body, linked to a
RadiationPressureInterface
object. Parameter size: 1. Secondary identifer: None.estimation_setup.parameter.radiation_pressure_coefficient( "Spacecraft" )
rotation_pole_position
Fixed rotation axis about which a body rotates with a fixed rotation rate, linked to a
SimpleRotationalEphemeris
object. Parameter size: 2 (denoting pole right ascension and declination). Secondary identifer: None.estimation_setup.parameter.rotation_pole_position( "Earth" )
ground_station_position
Fixed body-fixed position of a ground station on a body, linked to a
GroundStationState
object (requires aGroundStationState
class). Parameter size: 3 (denoting body-fixed x, y and z Cartesian position). Secondary identifer: Ground station name.estimation_setup.parameter.ground_station_position( "GroundStation" )
ppn_parameter_gamma
Parameter \(\gamma\) used in Parametric Post-Newtonian (PPN) framework, linked to a
PPNParameterSet
object (nominally the globalrelativity::ppnParameterSet
variable). Parameter size: 1. Note that the name of the associated body should be"global_metric"
. Secondary identifer: None.ppn_parameter_beta
Parameter \(\beta\) used in Parametric Post-Newtonian (PPN) framework, linked to a
PPNParameterSet
object (nominally the globalrelativity::ppnParameterSet
variable). Parameter size: 1. Note that the name of the associated body should be"global_metric"
. Secondary identifer: None.equivalence_principle_lpi_violation_parameter
Parameter used to compute influence of a gravitational potential on proper time rate, equals 0 in general relativity, not linked to any object, but instead the
equivalencePrincipleLpiViolationParameter
global variable (in namespacerelativity
. Parameter size: 1. Note that the name of the associated body should be"global_metric"
. Secondary identifer: None.
- Initial State Parameters
Warning
These functions return lists of parameters, which means that they can not be simply added in a list creation statement like [parameter_1, parameter_2, ...]
. Instead, this list needs to be concatenated to a list of ‘simple’ parameters, e.g. by using the +
operator: parameter_settings + estimation_setup.parameter.initial_states(...)
.
The factory function for initial states uses the propagator settings to determine which type is needed, e.g. if a translational propagator is defined, the function will automatically create the parameters for initial translational state.
initial_translational_state
initial_translational_state_from_ephemeris
arc_wise_initial_translational_state
arc_wise_initial_translational_state_from_ephemeris
initial_rotational_state
estimation_setup.parameter.initial_states( propagator_settings, bodies )
- Spherical Harmonic Parameters
spherical_harmonics_c_coefficients
Considers the cosine coefficients in the spherical harmonics gravity model for a body. There are two ways to specify which coefficients are to be used: giving min/max settings for degree and order, or giving block indices. The latter constitutes a list of tuples, where the first value is the degree and the second the order of the coefficient to be used. The length of this list can be arbitrary, as long as the pairs are unique.
estimation_setup.parameter.spherical_harmonics_c_coefficients( "Earth", minimum_degree, minimum_order, maximum_degree, maximum_order )
block_indices = [(1, 1), (2, 2), (3, 3)] estimation_setup.parameter.spherical_harmonics_c_coefficients( "Earth", block_indices )
spherical_harmonics_s_coefficients
Considers the sine coefficients in the spherical harmonics gravity model for a body. There are two ways to specify which coefficients are to be used: giving min/max settings for degree and order, or giving block indices:
estimation_setup.parameter.spherical_harmonics_s_coefficients( "Earth", minimum_degree, minimum_order, maximum_degree, maximum_order )
block_indices = [(1, 1), (2, 2), (3, 3)] estimation_setup.parameter.spherical_harmonics_s_coefficients( "Earth", block_indices )
- Tidal Love Number Parameters
full_degree_tidal_love_number
single_degree_variable_tidal_love_number
- Constant Observation Bias Parameters
constant_additive_observation_bias
arc_wise_constant_additive_observation_bias
constant_relative_observation_bias
arc_wise_constant_relative_observation_bias
- Empirical Acceleration Parameters
constant_empirical_acceleration_terms
estimation_setup.parameter.constant_empirical_acceleration_terms( body, central_body )
empirical_acceleration_coefficients
arc_wise_empirical_acceleration_coefficients