STK/Attitude

• Analytical extension of STK - includes all STK functionality
• Vector constrained attitude
• Multiple segment profiles
• 3-D Attitude View
• Vector persistence
• Right ascension, declination and magnitude display
• Angular separation display
• Attitude simulation
• Multiple control modes
• User-defined integration steps
• Multiple integrators
• Visualization during propagation
• Propagation of user-defined variables

Multiple segments

Construct attitude profiles to align the vehicle's body axes with any axes or vector either predefined or built with the Vector Geometry Tool (e.g. aligned with the Sun for battery recharging). Multiple attitude segments can be threaded together over the vehicle ephemeris to represent multiple maneuver sequences or mission modes. Segments may be either coordinate-based, targeted, or file-driven. User-defined slew segments can be used to govern the transition between individual attitude modes.

Three-dimensional analysis

The 3-D Attitude View window allows an analyst to view pertinent information within a 3-D environment. The data source may be STK or an integrated legacy system. This output medium provides instant intuitive feedback when evaluating attitude profiles against mission requirements. 3-D Attitude View also builds on the Vector Geometry Tool by making any pre-defined or user-created vector/axes associated with the vehicle available for display. In addition, the arc connecting any two vectors or its projection into any plane (dihedral) defined by a third vector may be displayed along with its angular measure. Also available is an attitude sphere representing the right ascension and declination in any user-desired vehicle reference frame. Vectors can be traced over any period of time on or about the surface of the attitude sphere. In addition, the Earth limb, Sun, Moon, and any celestial objects included in a scenario, as well as any vehicle sensors, may be projected onto the sphere. Each vector/axis is also available for defining and constraining the users' view of the vehicle.

Attitude simulation

STK/Attitude also includes a simulation capability via MATLAB®, VBScript, or Perl plugins. Along with the various torque-free attitude modes of STK, the simulation capability lets the user introduce various disturbing forces such as atmospheric drag, solar radiation pressure, and gravity, as well as the effects of open- and closed-loop control on the resulting spacecraft attitude. All of STK's orbit propagation, environmental modeling, and geometric computation capabilities are available to the simulation interface. For maximum accuracy, it also takes advantage of proven STK integrators such as Runge-Kutta-Fehlberg 7(8) and 4(5) and Bulirsch-Stoer. Multiple plugins can be executed at various times and frequencies throughout the attitude simulation. Plugin computations may range from changing control gains or switching from one attitude control mode to another, to direct implementation of the control law itself. Plugins can even register additional variables to be integrated along with spacecraft attitude, essential for modeling dynamic compensators. The nature of the plugin interface is such that the user is free to define as simple or as complex a control law as desired. MATLAB plugins can take full advantage of MATLAB's analytical capabilities and users of the STK/MATLAB Interface can also utilize the capabilities of the STK Aerospace Tool Box. The plugins, created in several script languages mentioned above, can all share information through STK. For example, speed-critical scripts that are executed at high frequency can be tested in MATLAB and then compiled into DLLs, whereas other scripts that are not executed as often or may require frequent changes can be kept in a script form. These capabilities combine to provide the ultimate flexibility for quickly prototyping new controls or evaluating the performance of existing ones with accurate environmental, geometric, and position data.