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 aGravityFieldModel
object, which may be a point-mass or (time-dependent) spherical harmonic field. Parameter size: 1. Secondary identifier: None.constant_drag_coefficient()
: Drag coefficient of a body that is constant, linked to aCustomAerodynamicCoefficientInterface
object derived fromAerodynamicCoefficientInterface
, which must have 0 independent variables for the coefficients. Parameter size: 1. Secondary identifier: None.estimation_setup.parameter.constant_drag_coefficient( "Spacecraft" )
constant_rotation_rate()
: Rotation rate of a body around a fixed axis, linked to aSimpleRotationalEphemeris
object derived fromRotationalEphemeris
. Parameter size: 1. Secondary identifier: None.radiation_pressure_coefficient()
: Constant radiation pressure coefficient of a body, linked to aRadiationPressureInterface
object. Parameter size: 1. Secondary identifier: 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 aSimpleRotationalEphemeris
object. Parameter size: 2 (denoting pole right ascension and declination). Secondary identifier: None.ground_station_position()
: Fixed body-fixed position of a ground station on a body, linked to aGroundStationState
object (requires aGroundStationState
class). Parameter size: 3 (denoting body-fixed x, y and z Cartesian position). Secondary identifier: Ground station name.estimation_setup.parameter.ground_station_position( "GroundStation" )
ppn_parameter_gamma()
: Parameter \(\gamma\) used in Parametric Post-Newtonian (PPN) framework, linked to aPPNParameterSet
object (nominally the globalrelativity::ppnParameterSet
variable). Parameter size: 1. Note that the name of the associated body should be"global_metric"
. Secondary identifier: None.ppn_parameter_beta()
: Parameter \(\beta\) used in Parametric Post-Newtonian (PPN) framework, linked to aPPNParameterSet
object (nominally the globalrelativity::ppnParameterSet
variable). Parameter size: 1. Note that the name of the associated body should be"global_metric"
. Secondary identifier: 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 theequivalencePrincipleLpiViolationParameter
global variable (in namespacerelativity
). Parameter size: 1. Note that the name of the associated body should be"global_metric"
. Secondary identifier: 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()