Planet Properties
The Planet Properties node contains the parameters for the definition of the mass, radius and radiative properties.
Planet properties
The Planet Properties combo box is set to Earth by default. Selecting this option is equivalent to the User defined option with the following settings (Ref. 48):
Mass, M = 5.972e24[kg]
Radius, R = 6378[km]
Tilt angle, εtilt = 23.45[degC]
Rotation rate, Ω =1/24[h]
The position of the planet at t=0s can be defined from different parameters depending on the selected option for Planet longitude at start time. When Determined from GMT at start time is selected, define the Greenwich Mean Time that correspond to the planet position at t = 0 s. Select Longitude at subspacecraft point to define the initial planet position from the spacecraft position at t = 0 s. Choose Longitude facing Vernal point to define the initial planet position from the position of the Sun at t = 0 s.
Radiative Properties
Set Geographic position dependence to Constant when the radiative properties are assumed to be uniform all around the planet. In case they depend on the location on the planet, select the Latitude and longitude option.
When Geographic position dependence is set to Constant, the Albedo and Planet infrared flux can defined as None (default), User defined for each band or User defined distribution.
When User defined distribution option is selected for Albedo or Planet infrared flux, the expression is assumed to be a function of otl.lambda, where otl is the name of the physics interface. This distribution is integrated on each spectral band to obtain the albedo and planet infrared flux for each spectral band.
When Albedo or Planet infrared flux is set to User defined for each band, enter a value for each spectral band. Within a spectral band, each value is assumed to be independent of wavelength.
When Geographic position dependence is set to Latitude and longitude, the Albedo and Planet infrared flux can defined as None (default), or User defined for each band.
When User defined distribution option is selected for Albedo or Planet infrared flux, select a two argument function to define the corresponding property for each spectral band.
If the Wavelength dependence of radiative properties is set to Constant in the interface node, then the radiative properties are given as expressions or latitude and longitude functions that do not depend on the wavelength otl.lambda.
The planet is approximated via a set of radiation sources on a spherical cap representing the part of the planet that can be seen from the spacecraft. Under Planet discretization, set the Number of rings (default value 5) and the number of Points per ring (default value 10) to define the total number of points that should be used to discretize the planet and how they should be placed. The total number of points used is where Nm is the number of ring and Nn is the number of points per ring. If the radiative properties of the planet depend on the geographic position and an accurate interpretation of the data is expected, the number of points can be increased. Increasing the total number of points N, also increases the computational time.
See Modeling the Planet for more details about the planet discretization.
Location in User Interface
Context Menus
Ribbon
Physics tab with Orbital Thermal Loads selected: