1. Pg 1 of 31 AGI www.agiuc.com Parametric Analysis Using STK Attitude & STK Coverage Sergei Tanygin

2. Pg 2 of 31 AGI www.agiuc.com What is it? “I SPY” attitude coverage

3. Pg 3 of 31 AGI www.agiuc.com 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. Pg 4 of 31 AGI www.agiuc.com Example: Angle to sun

5. Pg 5 of 31 AGI www.agiuc.com Coverage

6. Pg 6 of 31 AGI www.agiuc.com 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 Identifies possible locations for grid object in central body fixed Lat-Lon space Provides its properties, most importantly location and Access constraints, for visibility and Figure of Merit computations Other objects involved in visibility and Figure of Merit computations Scalar valued function of grid object’s and assets’ properties indicating quality of Access

7. Pg 7 of 31 AGI www.agiuc.com 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. Pg 8 of 31 AGI www.agiuc.com 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. Pg 9 of 31 AGI www.agiuc.com 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. Pg 10 of 31 AGI www.agiuc.com 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. Pg 11 of 31 AGI www.agiuc.com Grid location Grid centered on grid object –Grid object can be stationary or dynamic

12. Pg 12 of 31 AGI www.agiuc.com 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. Pg 13 of 31 AGI www.agiuc.com 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. Pg 14 of 31 AGI www.agiuc.com Vector Geometry Tool (VGT)

15. Pg 15 of 31 AGI www.agiuc.com Many uses of VGT 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

16. Pg 16 of 31 AGI www.agiuc.com From direction to attitude via VGT Vehicle attitude –Spin Aligned –Aligned and Constrained –Fixed in Axes Sensor pointing –Fixed in Axes

17. Pg 17 of 31 AGI www.agiuc.com 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. Pg 18 of 31 AGI www.agiuc.com Access tool

19. Pg 19 of 31 AGI www.agiuc.com 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. Pg 20 of 31 AGI www.agiuc.com Lots of constraints

21. Pg 21 of 31 AGI www.agiuc.com 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. Pg 22 of 31 AGI www.agiuc.com Sources of constraints Constraints are supplied by objects Constraints in attitude coverage may come from –Assets –Grid object –Pointing object

23. Pg 23 of 31 AGI www.agiuc.com 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. Pg 24 of 31 AGI www.agiuc.com Example: Spinner access

25. Pg 25 of 31 AGI www.agiuc.com 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. Pg 26 of 31 AGI www.agiuc.com 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. Pg 27 of 31 AGI www.agiuc.com Pointing accuracy computations LOS measurements Attitude errors Pointing error Attitude Determination Error mapping

28. Pg 28 of 31 AGI www.agiuc.com Example: Pointing accuracy

29. Pg 29 of 31 AGI www.agiuc.com 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 Identifies possible pointing directions in a specific set of axes Provides attitude dependent properties for visibility and Figure of Merit computations Gets assigned along directions throughout grid and provides flexible gateway for influencing attitude and pointing of objects Other objects involved in visibility and Figure of Merit computations Scalar valued function of grid direction as well as grid object’s and assets’ properties

30. Pg 30 of 31 AGI www.agiuc.com Example: Interference analysis

31. Pg 31 of 31 AGI www.agiuc.com 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