Orbit – Sun Planet Characteristics

Planet Data
Planet Period	Sets the time it takes for the selected planet to complete one orbit around the sun.
Planet Rotation	Appears when Planet is set to Generic.Specifies the planet rotation for longitude-dependent calculations.ProgradeIndicates that the planet rotation is counterclockwise.RetrogradeIndicates that the planet rotation is clockwise.
Mean Radius	Sets the planet mean radius, as no planet is perfectly spherical. You should rarely need to change this value unless you select Generic from the Planet list.
Gravitational Constant	Sets the gravitational constant for the selected planet. The gravitational constant depends on the mass of the planet and its radius. You should rarely need to change this value unless you select Generic from the Planet list.
Sun-Planet Distance	Appears when Planet is set to Generic.Sets the distance between the generic body and the sun.
Account for Planet Flux and Albedo	Lets you specify albedo and infrared flux values for the planet.AlbedoSets the albedo for the planet. The albedo is the fraction of light that a planet reflects. You can define a constant value or a table field that varies the albedo with the angle (latitude or longitude), latitude and longitude, or time. For more information, see Additional magnitude options.To define albedo to vary with latitude or longitude, create a table that has angle as the independent variable. You indicate if angle is latitude or longitude in the Albedo Angle Dependence Uses list.When you use the explicit model, the thermal solver assigns a different albedo value that corresponds to the local latitude and longitude to each mesh element of the planet. This planet mesh is internal to the thermal solver and created from the values you specify in the Radial Mesh Density and Circumferential Mesh Density boxes.Planetary IR FluxSpecifies how the celestial body infrared flux is defined.SpecifyLets you define the celestial body infrared flux as a constant value or a table field where the IR flux varies with latitude or longitude, latitude and longitude, or time in the IR Flux box. For more information, see Additional magnitude options.Sunlight and Dark SideDefines the celestial body infrared fluxes for the sunlight side using the Sunlight Side Flux list and for the dark side using the Dark Side Flux list.Sunlight Side Flux and Dark Side FluxAppears when Planetary IR Flux is set to Sunlight and Dark Side.Define the celestial body infrared fluxes for the sunlight side and dark side, respectively.When you select IR Flux from the Sunlight Side Flux and Dark Side Flux lists, you can define different constant infrared fluxes emitted by the celestial body for the two sides in the IR Flux boxes.When you select Black Body Temperature from the Sunlight Side Flux and Dark Side Flux lists, the thermal solver computes the infrared fluxes emitted by the celestial body for the two sides using the black body temperature that you specify in the Black Body Temperature boxes.When you select Same as Sunlit Side from the Dark Side Flux list, the infrared flux from the dark side is the same as the infrared flux from the sunlight side. For some celestial bodies predefined values are automatically displayed.Radial Mesh DensitySets the density of the explicit mesh that models explicitly the orbited celestial object as a hemisphere that faces the satellite. The thermal solver arrays elements in a radial pattern centered on the closest point on the model you are analyzing. This value controls the number of elements between the pattern's center and its perimeter. This value contributes to the accuracy of the computed planet flux and albedo values. For higher accuracy, increase this value.Circumferential Mesh DensitySpecifies the number of elements around the circumference of the celestial object. This value contributes to the accuracy of the computed planet flux and albedo values. For higher accuracy, increase this value.Prime Meridian Initial Position Referenced fromDefines the longitude from which the prime meridian for the selected celestial body is referenced. You can select Local Noon, March Equinox, or Ascending Node.Prime Meridian Angle from ReferenceSets the angle from the reference longitude to the prime meridian. It is measured counterclockwise.Example: When you set Prime Meridian Initial Position Referenced from to Local Noon and Prime Meridian Angle from Reference to 75, the prime meridian is selected at a longitude that is 75 degrees counterclockwise from the local noon longitude at the start time of the solution.To model the orbited celestial object as a point, set the value in the Radial Mesh Density or Circumferential Mesh Density box to 1. This is referred to as the implicit model.
Solar Data
Sun Position	Appears when Planet is set to Earth.Specifies the time of year.Solar DeclinationComputes the solar flux using the value you set in the Solar Declination box.March Equinox, June Solstice, September Equinox, or December SolsticeUse the predefined value for the solar flux at these specified times of year.Sun Right AscensionComputes the solar flux using the value you set in the Sun Right Ascension box.Day NumberComputes the solar flux using the number of the day in the year you set in the Day Number box. Type a value from 1 to 365.GMT DateComputes the solar flux using the date and time you set in the GMT Date boxes. The time is in the Greenwich Mean Time time zone.Min Flux or Max FluxUses the predefined flux based on the time of year when the solar flux is lowest or highest, respectively. The predefined flux is displayed in the Solar Flux box.
Solar Declination	Sets the value between the solar vector and the equatorial plane. For all planets other than Earth, you must specify this value.
Sun Right Ascension	Available when Planet is set to a celestial body other than Earth.Sets the value for the angle that is measured eastwards from the vernal equinox vector to the projection of the sun vector on the equatorial plane for the selected planet.
Compute	Available when Planet is set to Earth.Computes the solar flux value using the information provided in previous options, and displays it in the Solar Flux box.
Solar Flux	Specifies the solar flux as a constant value or a field that varies with time, or displays the computed solar flux value when you click Compute. The software uses the solar flux to calculate solar heat loads.

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Orbit – Calculation Positions

Orbit – Spacecraft Attitude

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Understanding Classical, Sun Synchronous, Shuttle, and Molniya orbit type parameters

Sun Planet Vectors orbit type parameters

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