Parametric Analysis Using STK Attitude & STK Coverage

1. Parametric Analysis Using STK Attitude & STK Coverage Sergei Tanygin

2. What is it? “I SPY” attitude coverage

3. Content at a glance • Attitude coverage is a top level analysis tool that takes advantage of many other STK tools and modules • Access • Coverage • Attitude • Communication • Vector Geometry Tool

4. Example: Angle to sun

5. Coverage

6. Coverage analysis • Coverage analysis includes • Grid object • Grid • Assets • Figure of Merit (FOM) • Coverage analysis involves • Evaluating visibility and FOM for a given location of the grid object • Collecting and depicting FOM values throughout the grid Provides its properties, most importantly location and Access constraints, for visibility and Figure of Merit computations Scalar valued function of grid object’s and assets’ properties indicating quality of Access Identifies possible locations for grid object in central body fixed Lat-Lon space Other objects involved in visibility and Figure of Merit computations

7. Coverage as parametric analysis • Visibility and FOM can be functions of • Time • Specific properties of grid object and assets • Location of grid object • Coverage analysis is an example of 2D parametric analysis in central body fixed lat-lon space Coverage explicitly changes location of grid object throughout Lat-Lon grid

8. Attitude coverage Evaluate, collect and depict attitude dependent visibility and FOM on attitude grid Challenge What form of attitude grid and which attitude parameters can be used to provide meaningful depiction of collected coverage data?

9. Attitude coverage grid • Solution to grid challenge • Define attitude grid in Ra-Dec space of spatial directions • Limitation • Does not incorporate complete attitude • Advantages • Permits clear and meaningful depiction in 3D space • Well-suited for many practical problems • Supplies many ways of relating to complete attitude

10. Grid form • Grid’s spatial directions can be interpreted as points on attitude sphere • Grid size and shape as well as angular separation between grid points are configurable

11. Grid location • Grid centered on grid object • Grid object can be stationary or dynamic

12. Grid orientation • Grid can be attached to any set of coordinate axes available in Vector Geometry Tool • Grid is fixed within its axes... but axes can be dynamic

13. From direction to attitude • A direct dependency… • Boresight pointing of sub-object • Sensor • Comm object antenna • …or a long and winding road through Vector Geometry Tool

14. Vector Geometry Tool (VGT)

15. Manages geometric components such as Angles Axes Points Coordinate systems Planes Vectors Permits addition of new user-defined components via GUI or Connect Serves components for use in Vehicle attitude definitions Sensor pointing Import/export of ephemeris and attitude data files Access constraints Plug-ins Positioning in 3D windows Reports and graphs Attitude Coverage Many uses of VGT

16. From direction to attitude via VGT • Vehicle attitude • Spin Aligned • Aligned and Constrained • Fixed in Axes • Sensor pointing • Fixed in Axes

17. What about assets and visibility? • Coverage determines visibility from assets to grid object • Attitude coverage generally determines visibility from grid object to Assets – more on this later • Both run Access Tool “under the hood”

18. Access tool

19. Visibility via access tool • One object is considered visible to another object if visibility Constraints are satisfied • Constraint is what limits visibility • Constraints are scalar valued functions of time and specific properties of the two objects involved • Most commonly the objects’ relative position and attitude

20. Lots of constraints

21. Use of constraints in access • One-Point-Access determines visibility at a single moment in time by evaluating Constraints at this time • Access determines time intervals of visibility by judicious sampling and iterative sub-sampling of Constraints

22. Sources of constraints • Constraints are supplied by objects • Constraints in attitude coverage may come from • Assets • Grid object • Pointing object

23. Access in attitude coverage • No assets • Do not run Access • Assets / No attitude dependent constraints • Only run access once • Assets / attitude dependent constraints • Run access for each new pointing on coverage grid • Most attitude dependent constraints come from pointing objects

24. Example: Spinner access

25. Attitude FOM • Attitude FOM is a scalar valued function that among other variables depends on a spatial direction within attitude grid • Very similar to attitude dependent access constraint • Categories of attitude FOMs • Derived from access intervals • Attitude dependent access constraint • Special

26. Pointing accuracy FOM • Evaluates pointing accuracy based on line-of-sight (LOS) measurements from grid object to visible Assets • FOM value represents angular pointing error in selected grid direction given angular errors of LOS measurements

27. Pointing accuracy computations LOS measurements Attitude errors Attitude Determination Pointing error Error mapping

28. Example: Pointing accuracy

29. Attitude coverage analysis • Attitude Coverage analysis includes • Grid object • Pointing Object • Grid • Pointing Vector • Assets • Attitude FOM • Attitude Coverage analysis involves • varying direction of the grid vector within the grid • Attitude Coverage analysis is an example of 2D parametric analysis in Ra-Dec directional space Centers grid, provides object’s properties for visibility and Figure of Merit computations Provides attitude dependent properties for visibility and Figure of Merit computations Identifies possible pointing directions in a specific set of axes Other objects involved in visibility and Figure of Merit computations Gets assigned along directions throughout grid and provides flexible gateway for influencing attitude and pointing of objects Scalar valued function of grid direction as well as grid object’s and assets’ properties

30. Example: Interference analysis

31. Summary • Attitude coverage is a top level parametric analysis tool that combines capabilities of • Coverage/access • Attitude • Vector Geometry Tool • Communication • Attitude coverage provides • Flexible means for configuring parametric analysis • Informative visualization and reporting of results