The Satellite Collection Object

The Satellite Collection object () models a group of satellites as a single object in the Object Browser. The associated satellites do not appear in the Object Browser, but are available for analysis purposes within other computational tools such as STK's Coverage capability, CommSystem, DeckAccess, and AdvCAT.

Creating a satellite collection

If you want to create a Satellite Collection object from a (seed) satellite in your scenario, use the Walker Tool.

If you want to create a Satellite Collection object without using a seed satellite, use the STK Insert Object tool to create one. In its Properties browser, use the Basic and Graphics sections to set attributes for the Satellite Collection object.

Satellite collection subsets and members

Members of a satellite collection have unique names that identify the members in reporting and graphics. Member names also appear in the output of analysis tools operating on the content of satellite collections.

The Satellite Collection object primarily serves as a data store that STK uses, like a recipe, to generate the members of the collection and descriptive information about them. You can categorize the members of the satellite collection into subsets for use in STK analyses, where a subset is a group of some or all of the satellites in the collection.

Metadata for a satellite collection provides additional descriptive information of its members. You can generate metadata through a definitional algorithm, and you can extend it by specifying a supplemental metadata file. You format the supplemental metadata file in a similar way to the custom orbit specification file, with header information that describes the tabular data followed by a comma-separated table of data values for each satellite collection member. If you include subset fields in the metadata, STK will automatically generate those subsets. You can't view metadata in the user interface, but you can generate a report of it with the Subset Listing data provider.

When you use an entry of a satellite collection in your analysis, that entry will inherit the properties of a reference object. By default, the reference object is simply the default satellite object. However, if you choose a default subset reference object, STK will associate the entries with that specific satellite in the scenario. Using a specified satellite provides a way to customize settings (attitude, access constraints, etc.) when you use the satellite collection member in an analysis. Moreover, when the reference object contains child objects (sensors, transmitters, receivers, etc.), STK also associates these children with the satellite entry. You can then use these children in the analysis tools.

Creating analysis components for satellite collection entries

It is impractical to automatically create a set of components for every entry in a Satellite Collection object because there may be thousands of entries. Rather, STK creates a small set of Vector Geometry, Time, and Calculation components automatically for a satellite collection, all related to the same entry of the satellite collection. These components all have the prefix name "Exemplar" and serve as examples of useful components that you may want to construct for particular satellite entries of interest.

Using STK's Analysis Workbench capability, you can construct the location of any satellite collection entry as a Vector Geometry Tool (VGT) point. Select the satellite collection in the Analysis Workbench browser, select the Vector geometry tab, and click the Point button. Choose the SatelliteCollection Entry point type, and then select an entry name from the satellite name selector. The VGT Point named "Exemplar" was constructed in exactly the same way, using one of the satellite entry names.

With the VGT Point defined, other geometrical components are simple to construct. For example, the position vector is a true displacement vector from the satellite collection central body origin to the satellite collection entry Point (use Exemplar_Position as a guide). The velocity vector is the derivative of the position vector using the satellite collection central body's inertial frame as the Reference Axes (use Exemplar_Velocity as a guide). The Topocentric axes associated with the entry are constructed as Surface Axes based upon the entry's VGT Point (use Exemplar_Topocentric as a guide). Under the Calculation tab, you can construct orbital elements for a satellite entry as a set of Calc Scalars, defined by constructing a new Parameter Set of type Orbit and selecting an entry's VGT Point (use Exemplar_Orbit as a guide).

There is no Time Interval type that can obtain the ephemeris span of a specified Satellite Collection entry. If you need a Time Interval, then construct a Fixed Interval, obtaining the start and stop values using the Subset Listing data provider.

Basic properties

Property	Description
Definition	Under Type, choose the method for creating the satellite collection object. You can then specify the properties for the chosen type, including subsets of satellites for special analysis. For guidance on defining these, see Satellite Collection Definition.
Routing	Use a routing file to apply linking rules between subset entries within the satellite collection as well as to/from subset entries from/to other objects directly before and after the subset in a chain.
Description	Record useful information about the satellite collection.

Graphics properties

Property	Description
Attributes	Choose whether or not to show a satellite collection, either the whole collection or just specific subsets, in the 2D and 3D Graphics windows. Choose whether or not to show the following for each subset: marker, label, and 3D orbit lines. Also specify certain settings particular to either the 2D Graphics window or the 3D Graphics window.