Using Analysis Workbench for Interplanetary Spacecraft Attitude

Information

 
QuestionHow do you set nadir related attitude profiles for spacecraft not at Earth?
Answer

Using Analysis Workbench for Interplanetary Spacecraft Attitude

In STK, some of the built-in attitude profiles for a spacecraft are specific to the central body that is set as the reference for the satellite ephemeris.  This can cause complications in interplanetary missions where you may be traveling to multiple planets or moons.  Alternative attitude profiles can be used along with custom vectors and axes created in Analysis Workbench to solve this problem. 

For example, Nadir-aligned attitude profiles align the body z-axis of the spacecraft with the nadir vector and align the body x-axis of the spacecraft based on the constraint type (ECI velocity, ECF velocity, or orbit normal).  These profiles will only work for the reference central body, but not at other bodies.  For example, when you set a satellite at Mars to be Nadir aligned with ECI velocity constraint, the body z-axis will point toward Earth still, and the body x-axis will align with the spacecraft velocity in the Earth inertial frame if Earth is set at the ephemeris reference.  


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How to Create an Attitude Profile for a Spacecraft that Works with other Central Bodies

To create an Attitude profile for a spacecraft that works with other central bodies, use alternative attitude profiles along with custom vectors and axes created in Analysis Workbench.
  1. In lieu of using one of the built-in nadir profiles, instead, use the aligned and constrained profile, as shown below:  
 
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Now, the spacecraft is Nadir aligned with the velocity constraint, but for Mars:
 
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  1. To create the vector used in this example:
    1. Open Analysis Workbench to create a vector from the satellite to Mars. 
    2. In the Vector Geometry tab, select your satellite, and  create a new vector with the following properties:
Option
Value
Type
Displacement
Name
Mars
Origin Point
Satellite center
Destination Point
Mars center

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Similarly, there is a spin about nadir profile that only works properly at the central body defined by the ephemeris reference.  Instead, the spin aligned attitude profile can be used and the Mars vector that you created can be used as the reference vector.  In fact, the aligned and constrained and spin aligned attitude profiles combined with Analysis Workbench allow for endless possibilities in spacecraft attitude!
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