Calc Object values, as a function of time. Each Calc Object contained in the Component Browser is available for use, including user defined Calc Objects. The Calc Objects listed here are representative.
| Name | Description |
|---|
| Top | Time measures. |
| Access | An Access calculation object that computes access between two objects. |
| Cartesian Elems | Calc Objects for the ephemeris of the object, expressed in Cartesian components. Each Calc Object allows a choice of coordinate systems. The default is Earth Centered Inertial. |
| Cartesian STM | The 36 position and velocity state transition matrix elements for use in combination with the State Transition Matrix propagator function and valid for Consecutive Propagate segments, Finite Maneuver segments, and Optimal Finite Maneuver segments in the Run Current Nodes mode. Expressed in Cartesian components, and allowing for choice of coordinate system. The default is Earth Centered Inertial. |
| Constants | Constant values used in astrodynamic calculations. |
| Curvilinear Relative Motion | Calc Objects for relative ephemeris between the satellite and reference satellite, expressed in curvilinear coordinates.
The relative ephemeris is computed using a reference ellipse that is defined as being the instantaneous keplerian orbit for either the satellite or reference satellite.
Crosstrack is the (signed) distance between an object's position and the plane of the reference ellipse. Crossrange is the (signed) closest distance
to the reference ellipse from the projection of an object's position into the plane of the reference ellipse. This closest point on the reference ellipse is called the
downrange position of the object. Downrange is the (signed) distance along the reference ellipse between two downrange positions. See Also Relative Motion. |
| Delaunay Elems | A set of canonical angle-action variables commonly used in general perturbation theories. An orbit is defined by a set of conjugate angle-action pairs. |
| Environment | Calc Objects for the satellite environment. |
| Equinoctial Elems | Calc Objects for the ephemeris of the object, expressed in equinoctial elements. Each Calc Object allows a choice of element type (Osculating elements, Kozai-Izsak Mean elements, Brouwer-Lyddane Mean elements using only short period terms, and Brouwer-Lyddane Mean elements using both short and long period terms). The default is osculating. Each Calc Object allows a choice of coordinate systems. The default is Earth Centered Inertial. |
| Formation | Calc Objects for relative motion and close approaches with respect to the master satellite or a specified vehicle. See also Relative Motion. The close approach X axis is the unit vector in the direction of the cross product of the relative velocity vector with the orbit momentum vector of the reference vehicle. The close approach Y axis is the unit vector in the direction of the cross product of the X axis and the relative velocity vector. The close approach plane is the plane spanned by the X and Y axes. The close approach vector is the relative position vector from the reference vehicle. |
| GeoStationary | Calc Objects that are useful for station keeping of geostationary satellites. The literature contains
a variety of metrics that have been found useful for describing and maintaining geosynchronous orbits. The elements are categorized as: (i) an angle representing
location in orbit; (ii) drift rate; (iii) eccentricity vector location within the orbit plane; and (iv) inclination vector. Some investigators (e.g, Soop) prefer
to use the unit angular momentum projection into the XY plane, rather then the lines of nodes, to set the direction of the inclination vector; however, we have
chosen to always align the inclination vector with the line of nodes and instead have provided the components of the unit angular momentum vector separately.
Each Calc Object allows a choice of a central body. The default is Earth.
Reference: Handbook of Geostationary Orbits, E. M. Soop, 1994, DOI 10.1007/978-94-015-8352-7. |
| Geodetic | Calc Objects for the ephemeris of the object, expressed in LLA elements. Each Calc Object allows a choice of a central body. The default is Earth. |
| Ground Track | Calc Objects for maintaining a repeating ground track. |
| Keplerian Elems | Calc Objects for the ephemeris of the object, expressed in keplerian (i.e., instantaneous two-body) elements. Each Calc Object allows a choice of element type (Osculating elements, Kozai-Izsak Mean elements, Brouwer-Lyddane Mean elements using only short period terms, and Brouwer-Lyddane Mean elements using both short and long period terms). The default is osculating. |
| Maneuver | Maneuver related Calc Objects. |
| Math | Used to perform functions on other Calc Objects. |
| Mean Elems | Calc Objects for the ephemeris of the object, expressed in Keplerian elements. Each Calc Object allows a choice of element type (Osculating elements, Kozai-Izsak Mean elements, Brouwer-Lyddane Mean elements using only short period terms, and Brouwer-Lyddane Mean elements using both short and long period terms).
The default is Kozai-Izsak mean elements. The mean elements are computed using mean element theory (not simply a numerical average of the element over a period), considering only gravity perturbations (J2 and for some theories J3 through J5). |
| MultiBody | Used for targeting a different central body. See also B-plane targeting under Astrogator help. |
| Other Orbit | Miscellaneous Calc Objects. |
| Power | Calc Objects that compute power. |
| Relative Motion | Calc Objects for relative ephemeris. The relative ephemeris is computed with respect to two rotating frames, the RIC
(Radial, In-Track, Cross-Track) frame and the NTC (Normal, Tangential, and Cross-Track) frames, that are defined using the primary's ephemeris.
Cross-track refers to the direction perpendicular to the position and inertial velocity; in-track refers to the direction perpendicular to both the radial
and cross-track (positive in the direction of motion); tangential refers to the direction along the velocity vector; and normal refers to the direction
perpendicular to the velocity and cross-track directions (positive outward along radial). Each Calc Object allows a choice of a central body. The default is Earth. See Also Formation. |
| SEET | Calc Objects utilizing computations provided by SEET. |
| STM Eigenvalues | The eigenvalues of the 6x6 cartesian State Transition Matrix (STM). The STM describes the effect of position-velocity
perturbations made at the start of propagation on the position-velocity state at the reported time. The coordinate system is a property of the calc objects.
Updated data is generated only for segments with a propagator that has a State Transition Matrix propagator function. When accessing after the MCS has been run,
the eigenvalues are sorted for consistency between ephemeris points. When accessing during an MCS run, the eigenvalues are sorted by absolute value of the real part. |
| STM Eigenvectors | The eigenvectors of the 6x6 cartesian State Transition Matrix (STM). The STM describes the effect of position-velocity
perturbations made at the start of propagation on the position-velocity state at the reported time. The coordinate system is a property of the calc objects.
Updated data is generated only for segments with a propagator that has a State Transition Matrix propagator function. When accessing after the MCS has been run,
the eigenvalues are sorted for consistency between ephemeris points. When accessing during an MCS run, the eigenvalues are sorted by absolute value of the real part.
The first eigenvector then corresponds to the first eigenvalue, etc. |
| Scalar | Scalar calculation component. |
| Scripts | Values from Astrogator plugin scripts. |
| Spacecraft Properties | Included are Drag, Radiation Pressure, and Solar Radiation Pressure coefficient and area values of a spacecraft. You can use these objects to report how a propagator plugin changes these values over time. When the value of one these objects changes, Astrogator applies the new value to subsequent propagation steps and segments in the MCS.
For built-in models that introduce time-varying areas and coefficients, namely the Variable Area and N-Plate models, the Drag and SRP calculation objects take on particular meanings as described below. Variable Area Drag and SRP models: The DragArea and SRPArea calculation objects reflect the associated areas used for a given time step in the ephemeris as prescribed by the corresponding file(s). Behavior of the Cd and Cr coefficients is unchanged from prior patterns by these models. Astrogator does not back-compute any quantities from the Variable Area Drag and SRP models; it keeps the values for area as per the original input. N-Plate Drag: For reporting purposes, Astrogator computes the DragArea calculation object by taking the "velocity-facing" area at a particular time step. Astrogator back-computes the Cd coefficient calculation object from the acceleration produced by the model only in the direction opposed to the velocity. Although such accounting generally captures the majority of the associated drag effects, neither of these scalar parameters completely reflect the contribution of the N-Plate Drag model to the total acceleration as experienced by the spacecraft under the numerical propagation. Astrogator neglects the perpendicular components in this reporting process. N-Plate SRP: Astrogator produces the SRPArea calculation object as the "Sun-facing" area for a particular ephemeris point. It back-computes the Cr coefficient calculation object only from the acceleration in the direction opposite to the Sun. Such accounting for reporting purposes in these scalar parameters does not capture the entire vector acceleration experienced by the spacecraft during numerical propagation. Unlike the case of a plugin changing the values, the various drag and coefficient values for these built-in models are applicable only for segments in which these models are active. Take the case, for example, where Astrogator propagates three subsequent segments in order. The first and third segments both use the DragArea parameter defined at the MCS level in some Initial State (or Update, etc.) segment. The second segment, between the first and third segments, uses the Variable Area Drag model. No plugins or other methods for changing the DragArea parameter are employed. In such a case, Astrogator will apply the constant MCS-level DragArea value to the first segment. For the second segment, it will use the Variable Area Drag model and report a varying value for DragArea. For the third segment, it will revert to the value of DragArea used in the first segment regardless of the DragArea value in effect at the end of the second segment. The behavior described in the Variable Area Drag model example — reverting parameters when the associated model is not employed — is consistent with how Astrogator reports all of the noted calculation objects for each of the built-in time-varying models described above. It is also consistent with the time of effect for the underlying models when Astrogator computes the full-vector accelerations consistent with constituent parameters (plates, coefficients, etc.). To have any value set by one of these models to persist into a subsequent segment, introduce an Update segment as appropriate. The effective drag and SRP area, as well as the effective Cd and Cr values, will be zero when the satellite altitude is outside the bounds of the density model, nominally -100 km to 2500 km. The effective Cr is also zero when the satellite is in shadow. |
| Spherical Elems | Calc Objects for the ephemeris of the object, expressed in spherical elements. |
| Target Vector | Data for incoming and outgoing asymptotes as well as C3 energy. |
| Time | Time related Calc Objects. |
| UserValues | User Variable related Calc Objects. |
| Vector | Vector-related Calc Objects. |
| Segment Data | Properties of each MCS segment in the Astrogator satellite. |
| Cartesian STM |
|---|
| Name | Dimension | Type | Description |
|---|
| Time | Date | Real Number or Text | Time. |
| STMPosXPosX | Unitless | Real Number | State transition function: delta(PosX,tf) = [this value] * delta(PosX,ti). |
| STMPosXPosY | Unitless | Real Number | State transition function: delta(PosX,tf) = [this value] * delta(PosY,ti). |
| STMPosXPosZ | Unitless | Real Number | State transition function: delta(PosX,tf) = [this value] * delta(PosZ,ti). |
| STMPosXVelX | Unitless | Real Number | State transition function: delta(PosX,tf) = [this value] * delta(VelX,ti). |
| STMPosXVelY | Unitless | Real Number | State transition function: delta(PosX,tf) = [this value] * delta(VelY,ti). |
| STMPosXVelZ | Unitless | Real Number | State transition function: delta(PosX,tf) = [this value] * delta(VelZ,ti). |
| STMPosYPosX | Unitless | Real Number | State transition function: delta(PosY,tf) = [this value] * delta(PosX,ti). |
| STMPosYPosY | Unitless | Real Number | State transition function: delta(PosY,tf) = [this value] * delta(PosY,ti). |
| STMPosYPosZ | Unitless | Real Number | State transition function: delta(PosY,tf) = [this value] * delta(PosZ,ti). |
| STMPosYVelX | Unitless | Real Number | State transition function: delta(PosY,tf) = [this value] * delta(VelX,ti). |
| STMPosYVelY | Unitless | Real Number | State transition function: delta(PosY,tf) = [this value] * delta(VelY,ti). |
| STMPosYVelZ | Unitless | Real Number | State transition function: delta(PosY,tf) = [this value] * delta(VelZ,ti). |
| STMPosZPosX | Unitless | Real Number | State transition function: delta(PosZ,tf) = [this value] * delta(PosX,ti). |
| STMPosZPosY | Unitless | Real Number | State transition function: delta(PosZ,tf) = [this value] * delta(PosY,ti). |
| STMPosZPosZ | Unitless | Real Number | State transition function: delta(PosZ,tf) = [this value] * delta(PosZ,ti). |
| STMPosZVelX | Unitless | Real Number | State transition function: delta(PosZ,tf) = [this value] * delta(VelX,ti). |
| STMPosZVelY | Unitless | Real Number | State transition function: delta(PosZ,tf) = [this value] * delta(VelY,ti). |
| STMPosZVelZ | Unitless | Real Number | State transition function: delta(PosZ,tf) = [this value] * delta(VelZ,ti). |
| STMVelXPosX | Unitless | Real Number | State transition function: delta(VelX,tf) = [this value] * delta(PosX,ti). |
| STMVelXPosY | Unitless | Real Number | State transition function: delta(VelX,tf) = [this value] * delta(PosY,ti). |
| STMVelXPosZ | Unitless | Real Number | State transition function: delta(VelX,tf) = [this value] * delta(PosZ,ti). |
| STMVelXVelX | Unitless | Real Number | State transition function: delta(VelX,tf) = [this value] * delta(VelX,ti). |
| STMVelXVelY | Unitless | Real Number | State transition function: delta(VelX,tf) = [this value] * delta(VelY,ti). |
| STMVelXVelZ | Unitless | Real Number | State transition function: delta(VelX,tf) = [this value] * delta(VelZ,ti). |
| STMVelYPosX | Unitless | Real Number | State transition function: delta(VelY,tf) = [this value] * delta(PosX,ti). |
| STMVelYPosY | Unitless | Real Number | State transition function: delta(VelY,tf) = [this value] * delta(PosY,ti). |
| STMVelYPosZ | Unitless | Real Number | State transition function: delta(VelY,tf) = [this value] * delta(PosZ,ti). |
| STMVelYVelX | Unitless | Real Number | State transition function: delta(VelY,tf) = [this value] * delta(VelX,ti). |
| STMVelYVelY | Unitless | Real Number | State transition function: delta(VelY,tf) = [this value] * delta(VelY,ti). |
| STMVelYVelZ | Unitless | Real Number | State transition function: delta(VelY,tf) = [this value] * delta(VelZ,ti). |
| STMVelZPosX | Unitless | Real Number | State transition function: delta(VelZ,tf) = [this value] * delta(PosX,ti). |
| STMVelZPosY | Unitless | Real Number | State transition function: delta(VelZ,tf) = [this value] * delta(PosY,ti). |
| STMVelZPosZ | Unitless | Real Number | State transition function: delta(VelZ,tf) = [this value] * delta(PosZ,ti). |
| STMVelZVelX | Unitless | Real Number | State transition function: delta(VelZ,tf) = [this value] * delta(VelX,ti). |
| STMVelZVelY | Unitless | Real Number | State transition function: delta(VelZ,tf) = [this value] * delta(VelY,ti). |
| STMVelZVelZ | Unitless | Real Number | State transition function: delta(VelZ,tf) = [this value] * delta(VelZ,ti). |
| GeoStationary |
|---|
| Name | Dimension | Type | Description |
|---|
| Time | Date | Real Number or Text | Time. |
| DriftRateFactor | Unitless | Real Number | A non-dimensional measure of mean longitudinal drift, defined as D = -1.5 * (semi-major axis - a_GEO)/a_GEO, where
a_GEO is the semi-major axis value whose mean motion is equal to the sidereal rotation rate of the Earth (360.985612287742 deg/day). The mean motion can be computed using only two-body motion (Point Mass) or include the effects of Earth oblateness represented
by J2 (Point Mass Plus J2). Soop includes only two-body motion and calls it drift rate. The drift rate, defined as the drift
rate factor multiplied by the sidereal rotation rate of the Earth, better approximates the rate of the mean longitude when oblateness is considered.
This Calc Object is only valid for the Earth central body. |
| EccentricityX | Unitless | Real Number | The component of the eccentricity vector, computed with respect to Earth TrueOfDate axes, along the X-axis of the equinoctial axes.
This is the same value as the element 'k' of equinoctial elements (Equinoctial k).
The eccentricity vector points from the center of the Earth to the location of perigee (as computed using osculating orbital elements at the current time)
with a magnitude equal to the eccentricity of the orbit. This Calc Object is only valid for the Earth central body. |
| EccentricityY | Unitless | Real Number | The component of the eccentricity vector, computed with respect to Earth TrueOfDate axes, along the Y-axis of the equinoctial axes.
This is the same value as the element 'h' of equinoctial elements (Equinoctial h).
The eccentricity vector points from the center of the Earth to the location of perigee (as computed using osculating orbital elements at the current time)
with a magnitude equal to the eccentricity of the orbit. This Calc Object is only valid for the Earth central body. |
| GeodeticMeanRightAscension | Longitude | Real Number or Text | The difference between Mean Right Ascension and Mean GHA.
The difference is a measure of location in orbit relative to the Earth Fixed X-axis. This Calc Object is only valid for the Earth central body. |
| GeodeticTrueLongitude | Longitude | Real Number or Text | The difference between True Longitude and Mean GHA. It is a measure of the position vector relative to the Earth
Fixed X-axis. Soop denotes this by lambda but calls it mean longitude. This Calc Object is only valid for the Earth central body. |
| GeodeticTrueLongitudeAtTimeOfPerigee | Longitude | Real Number or Text | The difference between True Longitude and Mean GHA, computed at the estimated time of perigee using
the current osculating elements. It is a measure of the position vector relative to the Earth Fixed X-axis. Soop denotes this by lambda_0 but calls it mean longitude
at epoch, where the epoch t_0 has been chosen here to be the time of perigee. This Calc Object is only valid for the Earth central body. |
| InclinationX | Unitless | Real Number | The component of the inclination vector, computed with respect to Earth TrueOfDate axes, along its X-axis.
The inclination vector lies along the line of nodes. Its magnitude is computed according to the setting of InclinationType. When InclinationType
is set to 'Inclination angle', then the units are in radians. This Calc Object is only valid for the Earth central body. |
| InclinationY | Unitless | Real Number | The component of the inclination vector, computed with respect to Earth TrueOfDate axes, along its Y-axis.
The inclination vector lies along the line of nodes. Its magnitude is computed according to the setting of InclinationType. When InclinationType
is set to 'Inclination angle', then the units are in radians. This Calc Object is only valid for the Earth central body. |
| Longitude_Drift_Rate | AngleRate | Real Number | The difference between the mean orbital rate and the central body rotation rate. The Calc Object allows a choice of element type (Osculating elements, Kozai-Izsak Mean elements, Brouwer-Lyddane Mean elements using only short period terms, and Brouwer-Lyddane Mean elements using both short and long period terms). The default is osculating. The mean orbital rate is computing using the element type and accounting for the effects of J2 of the central body. |
| MeanRightAscension | Longitude | Real Number or Text | Mean right ascension, defined as arctan(cos(inclination angle) * tan(mean longitude)),
computed with respect to Earth TrueOfDate axes. This Calc Object is only valid for the Earth central body. |
| Mean_Earth_Longitude | Angle | Real Number or Text | Mean longitude, computed in the True Of Date coordinate system, minus the Greenwich hour angle.
It is a measure of location in orbit relative to the Earth Fixed X-axis, but still based upon time.
This Calc Object is only valid for the Earth central body. |
| RectifiedLongitude | Angle | Real Number or Text | Two-body rectified longitude with respect to central body. The rectified motion moves nearly uniformally in true anomaly. The value is computed by first determining the two-body orbital elements, re-assigning the true anomaly value to the value of the mean anomaly, computing the cartesian position using these modified elements, and then computing the corresponding longitude from that position. |
| TrueLongitude | Longitude | Real Number or Text | True longitude, computed as the angle between the position vector and the X-axis of the equinoctial axes,
computed with respect to Earth TrueOfDate axes. The value is the sum of true anomaly, argument of perigee and raan. Soop denotes this by s but calls
it right ascension. This Calc Object is only valid for the Earth central body. |
| TwoBodyDriftRate | AngleRate | Real Number | The difference between Mean Motion and the sidereal rotation rate of the Earth (i.e., the mean GHA rate,
with value 360.985612287742 deg/day). This value is often used in lieu of the Semi-major Axis when describing geosynchronous motion;
however, it is only a fair approximation to the rate of the mean longitude because it ignores the secular drift caused by the oblateness of the Earth represented by J2.
This Calc Object is only valid for the Earth central body. |
| UnitAngularMomentumX | Unitless | Real Number | The component of the unit angular momentum vector (i.e, the unit vector along crossProduct(position, velocity))
along the X-axis of the Earth TrueOfDate axes. The value will equal sin(inclination angle)*sin(raan). This Calc Object is only valid for the Earth central body. |
| UnitAngularMomentumY | Unitless | Real Number | The component of the unit angular momentum vector (i.e, the unit vector along crossProduct(position, velocity))
along the Y-axis of the Earth TrueOfDate axes. The value will equal -sin(inclination angle)*cos(raan). This Calc Object is only valid for the Earth central body. |
| UnitAngularMomentumZ | Unitless | Real Number | The component of the unit angular momentum vector (i.e, the unit vector along crossProduct(position, velocity))
along the Z-axis of the Earth TrueOfDate axes. The value will equal cos(inclination angle). This Calc Object is only valid for the Earth central body. |
| Keplerian Elems |
|---|
| Name | Dimension | Type | Description |
|---|
| Time | Date | Real Number or Text | Time. |
| Altitude_Of_Apoapsis | Distance | Real Number | The difference between the radius of apoapsis and the central body's equatorial radius. The Calc Object allows a choice of a central body. The default is Earth. |
| Altitude_Of_Periapsis | Distance | Real Number | The difference between the radius of apoapsis and the central body's equatorial radius. The Calc Object allows a choice of a central body. The default is Earth. |
| Argument_of_Latitude | Angle | Real Number or Text | The sum of the argument of periapsis and true anomaly. The Calc Object allows a choice of coordinate systems. The default is Earth Centered Inertial. |
| Argument_of_Periapsis | Angle | Real Number or Text | The angle from the ascending node to the periapsis vector measured in the orbit plane in the direction of the object's motion.
The periapsis vector locates the closest point of the orbit. For a circular orbit, the value is defined to be zero (i.e., periapsis at the ascending node).
The Calc Object allows a choice of coordinate systems. The default is Earth Centered Inertial. |
| Eccentricity | Unitless | Real Number | A measure of the shape of the orbit. Values <1 indicate an ellipse (where zero is a circular orbit) and values >1 indicate a hyperbola. |
| Eccentric_Anomaly | Angle | Real Number or Text | An angle used for converting between true and mean anomaly. Has a geometrical definition as the angle between the line of apsides
and a line running from the center of the ellipse to a point Q on a circle circumscribed about the ellipse. The point Q is a projection of the satellite along a line parallel to the
minor axis of the ellipse. The Calc Object allows a choice of a central body. The default is Earth. |
| Inclination | Angle | Real Number or Text | The angle between the orbit plane and the XY plane of the coordinate system. |
| Longitude_Of_Ascending_Node | Angle | Real Number or Text | A measure of the right ascension of the ascending node, made in the Fixed frame. The value is the detic longitude of the orbit's ascending node. The ascending node crossing is assumed to be at, or prior to, the current position in the orbit in the same nodal revolution. The Calc Object allows a choice of a central body. The default is Earth. |
| MeanAnomaly | Angle | Real Number or Text | A measure of the time past periapsis passing, expressed as an angle. The Calc Object allows a choice of a central body. The default is Earth. |
| Mean_Motion | AngleRate | Real Number | A measure of the osculating period of the orbit, expressed as an angular rate. The value is 2pi rad / orbit_period.
The Calc Object allows a choice of a central body. The default is Earth. |
| Orbit_Period | Time | Real Number | Time required for a complete revolution as computed from osculating semi-major axis length. The Calc Object allows a choice of a central body. The default is Earth. |
| RAAN | Angle | Real Number or Text | The angle in the XY plane from the X axis to the ascending node, measured in a right-handed sense about the Z axis. in the equatorial plane.
For equatorial orbits, the ascending node is defined to be directed along the positive X axis, and thus the value is 0.0.
The Calc Object allows a choice of coordinate systems. The default is Earth Centered Inertial. |
| Radius_Of_Apoapsis | Distance | Real Number | The magnitude of the apoapsis vector. The apoapsis vector (defined only when the eccentricity is <1) locates the position in the orbit furthest from the central body. The Calc Object allows a choice of a central body. The default is Earth. |
| Radius_Of_Periapsis | Distance | Real Number | The magnitude of the periapsis vector. The periapsis vector locates the position in the orbit closest to the central body. The Calc Object allows a choice of a central body. The default is Earth. |
| Semimajor_Axis | Distance | Real Number | A measure of the size of the orbit. Orbits with eccentricity less than 1 are ellipses, with major and minor
axes identifying the symmetry axes of the ellipse, the major axis being the longer one. The value is half the length of the major axis.
The Calc Object allows a choice of a central body. The default is Earth. |
| Time_Past_Asc_Node | Time | Real Number | The elapsed time since passing the last ascending node crossing based on assumed two-body motion.. The Calc Object allows a choice of coordinate systems. The default is Earth Centered Inertial. |
| Time_Past_Periapsis | Time | Real Number | The elapsed time since passing the last periapsis crossing based on assumed two-body motion.. The Calc Object allows a choice of a central body. The default is Earth. |
| True_Anomaly | Angle | Real Number or Text | The angle from the periapsis vector, measured in the orbit plane in the direction of motion, to the position vector.
The Calc Object allows a choice of a central body. The default is Earth. |
| Mean Elems |
|---|
| Name | Dimension | Type | Description |
|---|
| Time | Date | Real Number or Text | Time. |
| Mean_Argument_of_Latitude | Angle | Real Number or Text | The sum of the argument of periapsis and true anomaly, where the angles are computed using Kozai-Izsak mean elements.
The Calc Object allows a choice of coordinate systems. The default is Earth Centered Inertial. |
| Mean_Argument_of_Perigee | Angle | Real Number or Text | The angle from the ascending node to the periapsis vector measured in the orbit plane in the direction of the object's motion.
The periapsis vector locates the closest point of the orbit. For a circular orbit, the value is defined to be zero (i.e., periapsis at the ascending node).
The ascending node and periapsis vector are computed using Kozai-Izsak mean elements. The Calc Object allows a choice of coordinate systems. The default is Earth Centered Inertial. |
| Mean_Eccentricity | Unitless | Real Number | A measure of the shape of the orbit. Values <1 indicate an ellipse (where zero is a circular orbit) and values >1 indicate a hyperbola.
The value is computed using Kozai-Izsak mean elements. The Calc Object allows a choice of a central body. The default is Earth. |
| Mean_Equinoctial_h | Unitless | Real Number | The value of 'h' from equinoctial elements, where h = eccentricity * sin(ascending node right ascension + periapsis argument),
as computed using Kozai-Izsak mean elements. The Calc Object allows a choice of coordinate systems. The default is Earth Centered Inertial. |
| Mean_Equinoctial_k | Unitless | Real Number | The value of 'k' from equinoctial elements, where k = eccentricity * cos(ascending node right ascension + periapsis argument),
as computed using Kozai-Izsak mean elements. The Calc Object allows a choice of coordinate systems. The default is Earth Centered Inertial. |
| Mean_Equinoctial_p | Unitless | Real Number | The value of 'p' from equinoctial elements, where p = tan(inclination / 2) * sin(ascending node right ascension),
as computed using Kozai-Izsak mean elements. The Calc Object allows a choice of coordinate systems. The default is Earth Centered Inertial. |
| Mean_Equinoctial_q | Unitless | Real Number | The value of 'q' from equinoctial elements, where p = tan(inclination / 2) * cos(ascending node right ascension),
as computed using Kozai-Izsak mean elements. The Calc Object allows a choice of coordinate systems. The default is Earth Centered Inertial. |
| Mean_Inclination | Angle | Real Number or Text | The angle between the orbit plane and the XY plane of the coordinate system, where the orbit angular momentum vector
is perpendicular to the orbit plane. The orbit angular momentum vector is computed using Kozai-Izsak mean elements. The Calc Object allows a choice of coordinate systems. The default is Earth Centered Inertial. |
| Mean_Mean_Anomaly | Angle | Real Number or Text | A measure of the time past periapsis passing, expressed as an angle. The periapsis direction is computed using Kozai-Izsak mean elements.
The Calc Object allows a choice of a central body. The default is Earth. |
| Mean_Mean_Longitude | Angle | Real Number or Text | The value of mean longitude, being the sum of right ascension of the ascending node, argument of periapse, and mean anomaly,
as computed using Kozai-Izsak mean elements. The Calc Object allows a choice of coordinate systems. The default is Earth Centered Inertial. |
| Mean_Orbit_Period | Time | Real Number | Time required for a complete revolution as computed from the mean semi-major axis length, computed using Kozai-Izsak mean elements.
The Calc Object allows a choice of a central body. The default is Earth. |
| Mean_RAAN | Angle | Real Number or Text | The angle in the XY plane from the X axis to the ascending node, measured in a right-handed sense about the Z axis. in the equatorial plane.
For equatorial orbits, the ascending node is defined to be directed along the positive X axis, and thus the value is 0.0. The ascending node vector is computed using Kozai-Izsak mean elements.
The Calc Object allows a choice of coordinate systems. The default is Earth Centered Inertial. |
| Mean_Semimajor_Axis | Distance | Real Number | A measure of the size of the orbit. Orbits with eccentricity <1 are ellipses, with major and minor axes identifying the
symmetry axes of the ellipse, the major axis being the longer one. The value is half the length of the major axis. The value is computed using Kozai-Izsak mean elements.
The Calc Object allows a choice of a central body. The default is Earth. |
| Mean_True_Anomaly | Angle | Real Number or Text | The angle from the periapsis vector, measured in the orbit plane in the direction of motion, to the position vector.
The periapsis vector and position vector are computed using Kozai-Izsak mean elements.
The Calc Object allows a choice of a central body. The default is Earth. |
| Relative Motion |
|---|
| Name | Dimension | Type | Description |
|---|
| Time | Date | Real Number or Text | Time. |
| CrossTrack | Distance | Real Number | The cross-track component of the relative position vector. |
| CrossTrackRate | Rate | Real Number | The cross-track component of the relative velocity vector as observed in the RIC rotating frame. |
| InTrack | Distance | Real Number | The in-track component of the relative position vector. |
| InTrackRate | Rate | Real Number | The in-track component of the relative velocity vector as observed in the RIC rotating frame. |
| Normal | Distance | Real Number | The normal component of the relative position vector. |
| NormalRate | Rate | Real Number | The normal component of the relative velocity vector as observed in the NTC rotating frame. |
| Radial | Distance | Real Number | The radial component of the relative position vector. |
| RadialRate | Rate | Real Number | The radial component of the relative velocity vector as observed in the RIC rotating frame. |
| Range | Distance | Real Number | The range (i.e., distance between the primary and secondary object) at the given time. |
| RangeRate | Rate | Real Number | The rate of change of the magnitude of the relative position vector. |
| Relative_Inclination | Angle | Real Number or Text | The angle between the orbit normals of the satellite and reference satellite. Each orbit normal allows a choice of orbit normal type
(Osculating elements, Kozai-Izsak Mean elements, Brouwer-Lyddane Mean elements using only short period terms,and Brouwer-Lyddane Mean elements using both short and long period terms). |
| Relative_Position_Declination_Angle | Angle | Real Number or Text | The angle between the relative position and an orbit plane. The relative position may be specified as either from the satellite to the reference satellite or the reverse.
The orbit plane may be specified as belonging to the satellite or the reference satellite, and allows a choice of orbit normal type
(Osculating elements, Kozai-Izsak Mean elements, Brouwer-Lyddane Mean elements using only short period terms,and Brouwer-Lyddane Mean elements using both short and long period terms). The sign
convention may be specified as being positive or negative when the relative position lies above the orbit plane. |
| Relative_Position_InPlane_Angle | Angle | Real Number or Text | The dihedral angle about the orbit plane normal from the reference direction to the relative position (i.e., angle to projection of relative position
into orbit plane from projection of reference direction into orbit plane). The relative position may be specified as either from the satellite to the reference satellite or the reverse.
The orbit plane may be specified as belonging to the satellite or the reference satellite, and allows a choice of orbit normal type
(Osculating elements, Kozai-Izsak Mean elements, Brouwer-Lyddane Mean elements using only short period terms,and Brouwer-Lyddane Mean elements using both short and long period terms).
The reference direction may be specified as being the satellite's or reference satellite's position or its opposite. Counter-clockwise rotation about the orbit normal may be specified
as being either a positive or negative value for the angle. |
| RICAzimuth | Angle | Real Number or Text | The angle measured in the plane formed by the in-track and cross-track directions, positive from the In-Track direction toward the Cross-Track direction. |
| RICAzimuthRate | AngleRate | Real Number | The rate of change of the RIC azimuth. |
| RICElevation | Angle | Real Number or Text | The angle measured perpendicular to the plane formed by the in-track and cross-track directions, positive toward the Radial direction. |
| RICElevationRate | AngleRate | Real Number | The rate of change of the RIC elevation. |
| Solar_Beta_Angle | Angle | Real Number or Text | The angle between the relative Sun position and an orbit plane. The relative Sun position may be specified as either apparent or true, as measured
from the satellite or from the reference satellite. The orbit plane may be specified as belonging to the satellite or the reference satellite, and allows a choice of orbit normal type
(Osculating elements, Kozai-Izsak Mean elements, Brouwer-Lyddane Mean elements using only short period terms,and Brouwer-Lyddane Mean elements using both short and long period terms). The sign
convention may be specified as being positive or negative when the relative Sun position lies above the orbit plane. |
| Solar_InPlane_Angle | Angle | Real Number or Text | The dihedral angle about the orbit plane normal from the reference direction to the relative Sun position (i.e., angle to projection of Sun
into orbit plane from projection of reference direction into orbit plane). The relative Sun position may be specified as either apparent or true, as measured
from the satellite or from the reference satellite. The orbit plane may be specified as belonging to the satellite or the reference satellite, and allows a choice of orbit normal type
(Osculating elements, Kozai-Izsak Mean elements, Brouwer-Lyddane Mean elements using only short period terms,and Brouwer-Lyddane Mean elements using both short and long period terms).
The reference direction may be specified as being the satellite's or reference satellite's position or its opposite. Counter-clockwise rotation about the orbit normal may be specified
as being either a positive or negative value for the angle. |
| Tangential | Distance | Real Number | The tangential component of the relative position vector. |
| TangentialRate | Rate | Real Number | The tangential component of the relative velocity vector as observed in the NTC rotating frame. |
| TimeDifference | Time | Real Number | Alternative measure for in-track position difference, computed as duration. The duration is computed by dividing the in-track component of the relative position vector by the inertial velocity of the primary object. |
| STM Eigenvectors |
|---|
| Name | Dimension | Type | Description |
|---|
| Time | Date | Real Number or Text | Time. |
| Lambda1PosXImag | Unitless | Real Number | The imaginary part of the PosX component of the first eigenvector (i.e., the eigenvector associated with the first eigenvalue lambda1). |
| Lambda1PosXReal | Unitless | Real Number | The real part of the PosX component of the first eigenvector (i.e., the eigenvector associated with the first eigenvalue lambda1). |
| Lambda1PosYImag | Unitless | Real Number | The imaginary part of the PosY component of the first eigenvector (i.e., the eigenvector associated with the first eigenvalue lambda1). |
| Lambda1PosYReal | Unitless | Real Number | The real part of the PosY component of the first eigenvector (i.e., the eigenvector associated with the first eigenvalue lambda1). |
| Lambda1PosZImag | Unitless | Real Number | The imaginary part of the PosZ component of the first eigenvector (i.e., the eigenvector associated with the first eigenvalue lambda1). |
| Lambda1PosZReal | Unitless | Real Number | The real part of the PosZ component of the first eigenvector (i.e., the eigenvector associated with the first eigenvalue lambda1). |
| Lambda1VelXImag | Unitless | Real Number | The imaginary part of the VelX component of the first eigenvector (i.e., the eigenvector associated with the first eigenvalue lambda1). |
| Lambda1VelXReal | Unitless | Real Number | The real part of the VelX component of the first eigenvector (i.e., the eigenvector associated with the first eigenvalue lambda1). |
| Lambda1VelYImag | Unitless | Real Number | The imaginary part of the VelY component of the first eigenvector (i.e., the eigenvector associated with the first eigenvalue lambda1). |
| Lambda1VelYReal | Unitless | Real Number | The real part of the VelY component of the first eigenvector (i.e., the eigenvector associated with the first eigenvalue lambda1). |
| Lambda1VelZImag | Unitless | Real Number | The imaginary part of the VelZ component of the first eigenvector (i.e., the eigenvector associated with the first eigenvalue lambda1). |
| Lambda1VelZReal | Unitless | Real Number | The real part of the VelZ component of the first eigenvector (i.e., the eigenvector associated with the first eigenvalue lambda1). |
| Lambda2PosXImag | Unitless | Real Number | The imaginary part of the PosX component of the second eigenvector (i.e., the eigenvector associated with the second eigenvalue lambda2). |
| Lambda2PosXReal | Unitless | Real Number | The real part of the PosX component of the second eigenvector (i.e., the eigenvector associated with the second eigenvalue lambda2). |
| Lambda2PosYImag | Unitless | Real Number | The imaginary part of the PosY component of the second eigenvector (i.e., the eigenvector associated with the second eigenvalue lambda2). |
| Lambda2PosYReal | Unitless | Real Number | The real part of the PosY component of the second eigenvector (i.e., the eigenvector associated with the second eigenvalue lambda2). |
| Lambda2PosZImag | Unitless | Real Number | The imaginary part of the PosZ component of the second eigenvector (i.e., the eigenvector associated with the second eigenvalue lambda2). |
| Lambda2PosZReal | Unitless | Real Number | The real part of the PosZ component of the second eigenvector (i.e., the eigenvector associated with the second eigenvalue lambda2). |
| Lambda2VelXImag | Unitless | Real Number | The imaginary part of the VelX component of the second eigenvector (i.e., the eigenvector associated with the second eigenvalue lambda2). |
| Lambda2VelXReal | Unitless | Real Number | The real part of the VelX component of the second eigenvector (i.e., the eigenvector associated with the second eigenvalue lambda2). |
| Lambda2VelYImag | Unitless | Real Number | The imaginary part of the VelY component of the second eigenvector (i.e., the eigenvector associated with the second eigenvalue lambda2). |
| Lambda2VelYReal | Unitless | Real Number | The real part of the VelY component of the second eigenvector (i.e., the eigenvector associated with the second eigenvalue lambda2). |
| Lambda2VelZImag | Unitless | Real Number | The imaginary part of the VelZ component of the second eigenvector (i.e., the eigenvector associated with the second eigenvalue lambda2). |
| Lambda2VelZReal | Unitless | Real Number | The real part of the VelZ component of the second eigenvector (i.e., the eigenvector associated with the second eigenvalue lambda2). |
| Lambda3PosXImag | Unitless | Real Number | The imaginary part of the PosX component of the third eigenvector (i.e., the eigenvector associated with the third eigenvalue lambda3). |
| Lambda3PosXReal | Unitless | Real Number | The real part of the PosX component of the third eigenvector (i.e., the eigenvector associated with the third eigenvalue lambda3). |
| Lambda3PosYImag | Unitless | Real Number | The imaginary part of the PosY component of the third eigenvector (i.e., the eigenvector associated with the third eigenvalue lambda3). |
| Lambda3PosYReal | Unitless | Real Number | The real part of the PosY component of the third eigenvector (i.e., the eigenvector associated with the third eigenvalue lambda3). |
| Lambda3PosZImag | Unitless | Real Number | The imaginary part of the PosZ component of the third eigenvector (i.e., the eigenvector associated with the third eigenvalue lambda3). |
| Lambda3PosZReal | Unitless | Real Number | The real part of the PosZ component of the third eigenvector (i.e., the eigenvector associated with the third eigenvalue lambda3). |
| Lambda3VelXImag | Unitless | Real Number | The imaginary part of the VelX component of the third eigenvector (i.e., the eigenvector associated with the third eigenvalue lambda3). |
| Lambda3VelXReal | Unitless | Real Number | The real part of the VelX component of the third eigenvector (i.e., the eigenvector associated with the third eigenvalue lambda3). |
| Lambda3VelYImag | Unitless | Real Number | The imaginary part of the VelY component of the third eigenvector (i.e., the eigenvector associated with the third eigenvalue lambda3). |
| Lambda3VelYReal | Unitless | Real Number | The real part of the VelY component of the third eigenvector (i.e., the eigenvector associated with the third eigenvalue lambda3). |
| Lambda3VelZImag | Unitless | Real Number | The imaginary part of the VelZ component of the third eigenvector (i.e., the eigenvector associated with the third eigenvalue lambda3). |
| Lambda3VelZReal | Unitless | Real Number | The real part of the VelZ component of the third eigenvector (i.e., the eigenvector associated with the third eigenvalue lambda3). |
| Lambda4PosXImag | Unitless | Real Number | The imaginary part of the PosX component of the fourth eigenvector (i.e., the eigenvector associated with the fourth eigenvalue lambda4). |
| Lambda4PosXReal | Unitless | Real Number | The real part of the PosX component of the fourth eigenvector (i.e., the eigenvector associated with the fourth eigenvalue lambda4). |
| Lambda4PosYImag | Unitless | Real Number | The imaginary part of the PosY component of the fourth eigenvector (i.e., the eigenvector associated with the fourth eigenvalue lambda4). |
| Lambda4PosYReal | Unitless | Real Number | The real part of the PosY component of the fourth eigenvector (i.e., the eigenvector associated with the fourth eigenvalue lambda4). |
| Lambda4PosZImag | Unitless | Real Number | The imaginary part of the PosZ component of the fourth eigenvector (i.e., the eigenvector associated with the fourth eigenvalue lambda4). |
| Lambda4PosZReal | Unitless | Real Number | The real part of the PosZ component of the fourth eigenvector (i.e., the eigenvector associated with the fourth eigenvalue lambda4). |
| Lambda4VelXImag | Unitless | Real Number | The imaginary part of the VelX component of the fourth eigenvector (i.e., the eigenvector associated with the fourth eigenvalue lambda4). |
| Lambda4VelXReal | Unitless | Real Number | The real part of the VelX component of the fourth eigenvector (i.e., the eigenvector associated with the fourth eigenvalue lambda4). |
| Lambda4VelYImag | Unitless | Real Number | The imaginary part of the VelY component of the fourth eigenvector (i.e., the eigenvector associated with the fourth eigenvalue lambda4). |
| Lambda4VelYReal | Unitless | Real Number | The real part of the VelY component of the fourth eigenvector (i.e., the eigenvector associated with the fourth eigenvalue lambda4). |
| Lambda4VelZImag | Unitless | Real Number | The imaginary part of the VelZ component of the fourth eigenvector (i.e., the eigenvector associated with the fourth eigenvalue lambda4). |
| Lambda4VelZReal | Unitless | Real Number | The real part of the VelZ component of the fourth eigenvector (i.e., the eigenvector associated with the fourth eigenvalue lambda4). |
| Lambda5PosXImag | Unitless | Real Number | The imaginary part of the PosX component of the fifth eigenvector (i.e., the eigenvector associated with the fifth eigenvalue lambda5). |
| Lambda5PosXReal | Unitless | Real Number | The real part of the PosX component of the fifth eigenvector (i.e., the eigenvector associated with the fifth eigenvalue lambda5). |
| Lambda5PosYImag | Unitless | Real Number | The imaginary part of the PosY component of the fifth eigenvector (i.e., the eigenvector associated with the fifth eigenvalue lambda5). |
| Lambda5PosYReal | Unitless | Real Number | The real part of the PosY component of the fifth eigenvector (i.e., the eigenvector associated with the fifth eigenvalue lambda5). |
| Lambda5PosZImag | Unitless | Real Number | The imaginary part of the PosZ component of the fifth eigenvector (i.e., the eigenvector associated with the fifth eigenvalue lambda5). |
| Lambda5PosZReal | Unitless | Real Number | The real part of the PosZ component of the fifth eigenvector (i.e., the eigenvector associated with the fifth eigenvalue lambda5). |
| Lambda5VelXImag | Unitless | Real Number | The imaginary part of the VelX component of the fifth eigenvector (i.e., the eigenvector associated with the fifth eigenvalue lambda5). |
| Lambda5VelXReal | Unitless | Real Number | The real part of the VelX component of the fifth eigenvector (i.e., the eigenvector associated with the fifth eigenvalue lambda5). |
| Lambda5VelYImag | Unitless | Real Number | The imaginary part of the VelY component of the fifth eigenvector (i.e., the eigenvector associated with the fifth eigenvalue lambda5). |
| Lambda5VelYReal | Unitless | Real Number | The real part of the VelY component of the fifth eigenvector (i.e., the eigenvector associated with the fifth eigenvalue lambda5). |
| Lambda5VelZImag | Unitless | Real Number | The imaginary part of the VelZ component of the fifth eigenvector (i.e., the eigenvector associated with the fifth eigenvalue lambda5). |
| Lambda5VelZReal | Unitless | Real Number | The real part of the VelZ component of the fifth eigenvector (i.e., the eigenvector associated with the fifth eigenvalue lambda5). |
| Lambda6PosXImag | Unitless | Real Number | The imaginary part of the PosX component of the sixth eigenvector (i.e., the eigenvector associated with the sixth eigenvalue lambda6). |
| Lambda6PosXReal | Unitless | Real Number | The real part of the PosX component of the sixth eigenvector (i.e., the eigenvector associated with the sixth eigenvalue lambda6). |
| Lambda6PosYImag | Unitless | Real Number | The imaginary part of the PosY component of the sixth eigenvector (i.e., the eigenvector associated with the sixth eigenvalue lambda6). |
| Lambda6PosYReal | Unitless | Real Number | The real part of the PosY component of the sixth eigenvector (i.e., the eigenvector associated with the sixth eigenvalue lambda6). |
| Lambda6PosZImag | Unitless | Real Number | The imaginary part of the PosZ component of the sixth eigenvector (i.e., the eigenvector associated with the sixth eigenvalue lambda6). |
| Lambda6PosZReal | Unitless | Real Number | The real part of the PosZ component of the sixth eigenvector (i.e., the eigenvector associated with the sixth eigenvalue lambda6). |
| Lambda6VelXImag | Unitless | Real Number | The imaginary part of the VelX component of the sixth eigenvector (i.e., the eigenvector associated with the sixth eigenvalue lambda6). |
| Lambda6VelXReal | Unitless | Real Number | The real part of the VelX component of the sixth eigenvector (i.e., the eigenvector associated with the sixth eigenvalue lambda6). |
| Lambda6VelYImag | Unitless | Real Number | The imaginary part of the VelY component of the sixth eigenvector (i.e., the eigenvector associated with the sixth eigenvalue lambda6). |
| Lambda6VelYReal | Unitless | Real Number | The real part of the VelY component of the sixth eigenvector (i.e., the eigenvector associated with the sixth eigenvalue lambda6). |
| Lambda6VelZImag | Unitless | Real Number | The imaginary part of the VelZ component of the sixth eigenvector (i.e., the eigenvector associated with the sixth eigenvalue lambda6). |
| Lambda6VelZReal | Unitless | Real Number | The real part of the VelZ component of the sixth eigenvector (i.e., the eigenvector associated with the sixth eigenvalue lambda6). |