Central Body Constraints

Central Body constraints enable you to impose constraints based on the position of the Sun, planets, and the Moon.

The table below describes the sun constraints and lists the objects that they can be used to constrain access to.

When an access involves a child object (i.e., sensor, transmitter, receiver, antenna, or radar), use the child object's parent or grandparent in the table below to determine whether the constraint can be used for access to that child object. For example, if a constraint can be used for accesses to all vehicles, then that constraint can also be used for any child object of a vehicle.

In the following table, abbreviations in the Constraints used for accesses to... column are:

AT = area target

F = facility

LT = line target

P = planet

Pl = place

St = star

T = target

V = all vehicles

Constraint	Description	Constraint used for accesses to...
Boresight - Lunar Exclusion Angle	This defines the Lunar Exclusion Angle for sensors or their child objects, as measured from the object's boresight. It is the minimum angle between the boresight vector and the Moon vector for which access is considered valid. If the boresight vector is obstructed, such as when the Earth is between the boresight vector and the Moon, then the exclusion constraint is not applied. The Boresight Lunar and Solar Exclusion Angle constraints use the main access computation to apply the correct directionality of the light time delay. If the object that holds the constraint is being used in a receive sense, then a receive sense to the obstruction central body is used; if the object is being used in a transmit sense, then a transmit sense is used. This is consistent with the Object Exclusion angle constraint, which does the same thing.	AT, F, P, Pl, St, T, V
Boresight - Solar Exclusion Angle	This defines Solar Angle for sensors or their child objects, as measured from the object's boresight. It is the minimum angle between the boresight vector and the Sun vector for which access is considered valid. If the boresight vector is obstructed, such as when the Earth is between the boresight vector and the Sun, then the exclusion constraint is not applied.	AT, F, P, Pl, St, T, V
Boresight CB Exclusion Angle	It is the minimum angle between the boresight vector and the Central Body vector for which access is considered valid. If the boresight vector is obstructed, such as when the Earth is between the boresight vector and the Central Body, then the exclusion constraint is not applied.	AT, F, P, Pl, St, T, V
Central Body Obstruction	After choosing this constraint, select central bodies from the Available Central Bodies list and use the right blue arrow to move them to the Assigned Central Bodies list.	AT LT F Pl T P St V Sn
FOV Specular Point Exclusion	If you activate this, STK restricts access periods to times when the specular reflection point is outside the sensor field of view. The location of the solar specular reflection point on the surface of the central body is computed based on the position of the constrained object. The specular reflection point does not exist for instances where the constrained object is in umbra. The specular reflection point exists when the constrained object is sunlit, regardless of whether its location is on land, sea, etc. The FOV Specular Point Exclusion constraint is only available for sensors or sensor sub-objects.	F, P, Pl, St, T, V
Line Of Sight - Lunar Exclusion Angle	This defines the Lunar Exclusion Angles, as measured from the object's line of sight. It is the minimum angle between the line-of-sight vector to the object of interest and the Moon vector for which access is considered valid. If the line-of-sight vector is obstructed, such as when the Earth is between the line-of-sight vector and the Moon, then the exclusion constraint is not applied. Central Body The Line of Sight Lunar and Solar Exclusion Angle constraints now use the main access computation to apply the correct directionality of the light time delay. If the object that holds the constraint is being used in a receive sense, then a receive sense to the obstruction central body is used; if the object is being used in a transmit sense, then a transmit sense is used. This is consistent with the Object Exclusion angle constraint which does the same thing.	F, P, Pl, St, T, V
Line Of Sight - Solar Exclusion Angle	This defines the Solar Exclusion Angle, as measured from the object's line of sight. The minimum angle between the line-of-sight vector to the object of interest and the Sun vector for which access is considered valid. If the line-of-sight vector is obstructed, such as when the Earth is between the line-of-sight vector and the Sun, then the exclusion constraint is not applied.	F Pl T P St V

LOS Central Body Exclusion Angle	This defines the Central Body Exclusion Angle, as measured from the object's line of sight. It is the minimum angle between the line-of-sight vector to the object of interest and the Central Body vector for which access is considered valid. If the line-of-sight vector is obstructed, the Earth is between the line-of-sight vector and the Central Body, then the exclusion constraint is not applied.	F Pl T P St V
LOS Sun Illumination Angle	Min and Max values represent the illumination angle as measured from the object's line of sight to the apparent position of the Sun if it is not obstructed by the object’s central body. You must specify both a Min and Max value when enabling this constraint.	F Pl T P St V
Lunar Elevation Angle	Min and Max values represent the elevation angle to the apparent position of the Moon.	F Pl T AT P St V
Solar Beta Angle	The solar beta angle is the signed angle of the vector to the Sun relative to the orbital plane. The signed angle is positive when the vector to the Sun is in the direction of the orbit normal. The orbit normal is parallel to the orbital angular momentum vector, which is defined as the cross-product of the inertial position and velocity vectors.	F Pl T AT P St V
Sun Elevation Angle	Sun elevation angles are measured with respect to targets, places, and facilities. Min and Max values represent the Sun elevation angle in the VVLH frame that the target, place, or facility sees.	V
Sun Ground Elevation Angle	Sun ground elevation angles are measured with respect to targets, places, and facilities. Min and Max values represent the Sun elevation angle in the local horizontal frame that the target, place, or facility sees.	V
Sun Specular Point Exclusion	Access periods are restricted to times when the specular reflection point is at least the angle you specify from the line of sight between the constrained object and the secondary object. The location of the solar specular reflection point on the surface of the central body is computed based on the position of the constrained object. The specular reflection point does not exist for instances where the constrained object is in umbra. The specular reflection point exists when the constrained object is sunlit, regardless of whether its location is on land, sea, etc.	F Pl T P St V

If you do not activate any of the Line of Sight constraints, STK does not account for solar and lunar exclusion angles when an access line intersects the local central body.