Orbital Parameters
This feature contains all the information needed to define the spacecraft orbit.
Select an Orbit type among Elliptical (default), Equatorial elliptical, Circular, Equatorial circular, and User defined.
Elliptical is the most general option. It defines the orbit of the spacecraft from the six Keplerian elements as in Figure 6-5:
•
Semimajor axis, a (SI unit: m, default value otl.R_planet+1000[km] assuming otl is the interface name,
•
Eccentricity, e (dimensionless, default value 0) which is a value between 0 (included) and 1 (excluded),
•
Inclination, i (SI unit: rad, default value 0 deg), which is a positive angle between 0 and 180°,
•
The ascending node can be defined either from the Longitude of ascending node, Ω (SI unit: rad, default value 0 deg), or from the Local time at ascending node, tΩ (SI unit: s, default value 0 h),
•
Argument of periapsis, ω (SI unit: rad, default value 0 deg), and
•
True anomaly at start time, ν0 (SI unit: rad, default value 0 deg).
Figure 6-5: Definition of Keplerian elements.
Equatorial elliptical is similar to the Elliptical option with the Inclination, i, and the Longitude of Ascending Node, Ω, set to zero. In this configuration the Argument of periapsis, ω, is referred to as Longitude of periapsis, π.
The Circular option is another option with four orbital parameters. The Eccentricity, e, and the Argument of periapsis, ω, are set to zero. In this configuration the Radius, R, is equivalent to the semi-major axis, and the True anomaly at start time, ν0, is referred to as the Argument of latitude at start time, u0.
The Equatorial circular choice is the simplest option with only two parameters: the Radius, R, and True longitude at start time, λ0 (SI unit: rad, default value 0 deg).
The User defined option allows to freely define the position of the spacecraft in the equatorial coordinate system. Select a Spacecraft position source among Functions (default) and Local Table.
•
When Functions is selected, each coordinate is defined as a function of time. For User defined, enter a value or expression. Else, select a function defined under Global Definitions or Definitions. Only those whose argument and result units are respectively relative to time and length are available.
•
When Local table is selected, a table appears, where time and corresponding spacecraft coordinates can be specified or imported from a text file by clicking the Load from File () button under the table. Units can be specified for the Time and the Position. These data are then interpolated using a piecewise cubic method, and extrapolated linearly.
With User defined selected as Orbit type, orbit period is not defined and the Output times specification of Orbit Calculation, Orbital Temperature, and Orbit Thermal Loads studies must be set to Time steps.
Location in User Interface
Context Menus
Orbital Thermal Loads > Orbital Parameters
Ribbon
Physics tab with Orbital Thermal Loads selected:
Global > Orbital Parameters