Pg 1 of 31 AGI Parametric Analysis Using STK Attitude & STK Coverage Sergei Tanygin

Pg 2 of 31 AGI What is it? “I SPY” attitude coverage

Pg 3 of 31 AGI 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

Pg 4 of 31 AGI Example: Angle to sun

Pg 5 of 31 AGI Coverage

Pg 6 of 31 AGI 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

Pg 7 of 31 AGI 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

Pg 8 of 31 AGI 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?

Pg 9 of 31 AGI 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

Pg 10 of 31 AGI 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

Pg 11 of 31 AGI Grid location Grid centered on grid object –Grid object can be stationary or dynamic

Pg 12 of 31 AGI 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

Pg 13 of 31 AGI 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

Pg 14 of 31 AGI Vector Geometry Tool (VGT)

Pg 15 of 31 AGI 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

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

Pg 17 of 31 AGI 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”

Pg 18 of 31 AGI Access tool

Pg 19 of 31 AGI 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

Pg 20 of 31 AGI Lots of constraints

Pg 21 of 31 AGI 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

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

Pg 23 of 31 AGI 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

Pg 24 of 31 AGI Example: Spinner access

Pg 25 of 31 AGI 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

Pg 26 of 31 AGI 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

Pg 27 of 31 AGI Pointing accuracy computations LOS measurements Attitude errors Pointing error Attitude Determination Error mapping

Pg 28 of 31 AGI Example: Pointing accuracy

Pg 29 of 31 AGI 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

Pg 30 of 31 AGI Example: Interference analysis

Pg 31 of 31 AGI 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