Central Body List

The central body list provides the means for configuration of non-Earth central bodies. You can gain access to this list by clicking next to the CentralBodyList attribute in the scenario properties. The list enables you to select from a specific list of gravity files and ground reflection models for each central body in ODTK's list (other than Earth). The name of the gravity file contains the degree and order of the gravity field specified therein. For example, "LP75D.grv" contains a 75x75 model for the lunar gravitational field. You can also choose to estimate corrections to the nominal ephemeris and gravitational parameter (GM) for the central body. Usually, you only enable estimation of corrections to the central body ephemeris or GM for small solar system objects, such as asteroids, for which high-accuracy ephemerides and mass estimates are not available.

Central Body List
Field	Description
Name	This is a read-only name containing the name of the central body.
GravityModel	Select a gravity field definition for the central body.
EclipsingAtmosAlt	Used for solar radiation pressure modeling. It is the height of the atmosphere on the central body that contributes to blocking the Sun. ODTK uses this for shadowing computations.
GroundReflectionModel	This is a text file containing model parameters for central body albedo (reflectivity) and thermal re-radiation (emissivity).
EstimateOrbitCorrection	Set this to true to estimate corrections to the central body ephemeris during Filter and Smoother processing. When set to true, output ephemeris options are exposed on Filter and Smoother objects. ODTK combines orbit correction with the nominal ephemeris solution to yield the final position and velocity of the estimated central body. ODTK uses a simple two-body model to propagate the corrections relative to the nonlinear nominal trajectory.
OrbitUncertainty	This is the initial orbit uncertainty expressed in sigma-correlation form in Radial/In-track/Cross-track (RIC) coordinates. The RIC coordinates are defined based on the position and velocity of the estimated central body relative to its parent central body. For example, when estimating corrections to the orbit of an asteroid, the RIC frame is defined by the nominal asteroid position and velocity relative to the Sun.
EstimateGM	Set this to true to estimate corrections to the central body gravitational parameter (GM) during Filter and Smoother processing. ODTK estimates GM corrections as a multiplicative scale factor of the nominal GM value. A nominal value of 1.0 for the scale factor indicates no correction to the a priori GM value.
GMScaleSigma	This is the initial uncertainty in the gravitational parameter scale factor. For example, a value of 0.3 represents a one-sigma uncertainty of 30% in the a priori value of GM.
LandmarkFilename	Select a file conforming to the Landmark file format. This file contains landmark data that ODTK uses in the simulation and processing of Optical Navigation (OpNav) landmark measurements.
LandmarkPosUncertainty	ODTK uses the LandmarkPosUncertainty values in the deweighting of Landmark OpNav measurements. ODTK provides default values for landmark position uncertainty, expressed in the topocentric frame: South, East, and Up. If you provide uncertainty information in the Landmark file (see LandmarkFilename), that data will override these default values. In the special case where the Landmark file only contains latitude and longitude uncertainty but not altitude uncertainty, ODTK will use the Up default value for the altitude uncertainty along with the Landmark file values for Latitude and longitude uncertainty.

Attempts to add gravity fields for other bodies will produce an error message.