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Insert Spacecraft Using the Standard Object Database
Use the Standard Object Database tool to query a locally installed Spacecraft database, an online Spacecraft database, or both for a set of space objects from which to create new satellites in STK.
The Standard Object Database tool is available from the Insert menu.
The tool performs two distinct steps:
- Searches the database file for space objects meeting all criteria you specify
- Creates and propagates the objects based on GP data (e.g., TLEs) obtained from an external file or from the AGI Online Server for each of your selected space objects
Both the satellite database file and the corresponding TLE file evolve over time, so you need to update them as needed.
The Standard Object Database tool is restricted to five-digit SSC numbers. GP data using nine-digit SSC numbers are not listed.
Background
The United States Air Force (USAF) continually tracks man-made space objects (i.e., spacecraft and orbital debris) as part of its mission. As of August 2020, they were tracking more than 46,000 space objects. These objects constitute the space object catalog. While most of the catalog is made available to the public, some information is restricted. AGI provides the publically released information for use with STK in the form of satellite database files and two-line mean element files (TLEs).
Search
A satellite database file is an ASCII file of a specified format, with file extension .sd, that contains information on space objects. AGI provides four database files:
Each file contains identification information (official name, common name, owner, mission type, etc.) and orbital characteristics (period, inclination, altitude) keyed to the unique identifier for each object, its SSC number. These files are updated daily on the AGI website. Updated files contain information on newly cataloged objects (new launches and newly found debris) as well as updates to the orbital characteristics for existing objects.
Propagate
Corresponding to each of the satellite database files are TLE files (files with extension *.tce) that contain ephemeris information for the space objects identified in the *.sd file. For example, stkAllTLE.tce contains TLE information for the space objects listed in stkAllTLE.sd. Because of information restrictions to the public, objects that are restricted for their ephemeris information but not restricted for identification purposes may be listed in a satellite database file even though no TLE is publically available for them and they do not appear in their corresponding *.tce file.
A TLE contains mean elements that STK uses in conjunction with the SGP4 propagator to produce ephemeris for the space object. The ephemeris produced by SGP4 is generally valid for a few days around the epoch contained in the TLE. (No official validity interval is provided by USSTRATCOM.) New TLEs for space objects are produced on a continual basis. Important objects, such as the International Space Station and Shuttle flights, have TLEs generated several times per day. Some debris objects may have newly generated TLEs only every several days or weeks (or possibly longer if the object is “lost” for a time). The AGI website updates its TLE files at least daily.
Searching the Satellite Database
Under Data Sources, you can choose to query either the Online database, the Local database, or both.
You can then select one, some, or all of the following search criteria parameters.
| Search Criteria | Description |
|---|---|
| Name or ID | Enter the common name of the object, the official name of the satellite, or the SSC number of the object. If you do not know the exact name, you can enter a partial name or use the wildcard character *. The Local database option also includes searching International Designator. |
| Owner | Select the country that owns the satellite. |
| Mission | Select the primary mission that the satellite performs. |
| Periapsis Altitude: Min/Max | You can limit the search to a specified Min value, Max value, or range (Min and Max both specified). |
| Launch Site | Select from a list of three-letter site acronyms. You can only search this in the Online database. |
| Launch Date | Enter a Begin date, End date, or both. The format is YYYY-MM-DD. You can only search this in the Online database. |
| Apoapsis Altitude: Min/Max | You can limit the search to a specified Min value, Max value, or range of values (Min and Max both specified). |
| Period: Min/Max | You can limit the search to a specified Min value, Max value, or range (Min and Max both specified). |
| Inclination: Min/Max | You can limit the search to a specified Min value, Max value, or range (Min and Max both specified). |
| Operational Status |
Designate the satellite status as Active or Inactive, or select Unknown if you are not sure. In general, the status of a satellite is not available from the AGI Satellite database. Status is listed where there is a reliable source for that information. No status is listed where there is no published, reliable source. |
| Advanced... | The Advanced options enable you to set the analysis time period, the propagation step size, the TLE source, and other TLE-related options. |
Click to update the list of satellites that meet your specific criteria.
Search results
The tool searches through a satellite database file, applying your search filters, and lists those objects meeting all the criteria. The results are sorted by Common Name. To sort the results by a different column, double-click the column heading The direction that the aircraft is pointing.. To hide or display additional columns, right-click a column heading.
If more than one item results from the search, you can select one or more items in the list to be inserted into your scenario. Use the Shift or Ctrl key to select more than one item. Use Ctrl+A to select all items.
The satellite database file that is searched is set on the Scenario’s Database properties page. AGI recommends using stkAllTLE.sd because it contains a listing of both debris and satellites objects that actually have TLE data and thus can be inserted as a Satellite object.
Propagation TLE source
The search process identifies a set of space objects for you to consider for insertion as a Satellite object. The ephemeris information for a space object consists of a set of TLEs for that object. While there may be many TLEs available for a space object, the most appropriate set of TLEs to use for propagation are those that have an epoch near the Time Period of propagation. By default, the Time Period will be the Scenario interval; however, you may choose a different interval.
AGI recommends that the TLE source be set to the AGI Online Server, because the correct set of TLEs will be obtained for space objects for the propagation time period. However, you may choose to load GP data (e.g., TLEs) from a file instead if you are unable to connect to the server or you want to use a specific file.
You can select a different file source; the Propagation TLE Source panel of the Spacecraft Insert Options dialog box provides options for this.
When using a file as the TLE source, you should ensure that the epochs for the GP data are appropriate for the propagation time period. You can choose to filter TLE source results to ensure this; see the Spacecraft Insert Options topic.
Inserting satellites
Select rows from the table (one or more) and click to create a satellite object for each selection. Use the SHIFT or CTRL key to select more than one item. When you click , information for the inserted satellite appears on the satellite's Basic Description page of its properties window.
Updating the Satellite Database files
When using this tool, it is important to use files that are appropriate for the propagation time period being used, which is the Scenario Interval by default.
Within STK, you can update the satellite database and TLE files from the AGI website using the Data Update Utility or from the Scenario’s Database properties page. Both the satellite database file (*.sd file) and the TLE file (*.tce) will be updated (as well as several database support files), overwriting the existing files.
Satellite database files contain both identification information and orbital characteristics. While the identification information does not change often over time, the orbital characteristics do. Thus, if you are searching for space objects with certain orbital characteristics, you should first obtain an appropriately dated satellite database file. You can do this on the Scenario’s Database properties page by clicking . If you are doing an analysis for a past time period, the appropriate file will not be the most current file, but rather an archived database dated near the propagation time period.
The archived database and TLE files simply overwrite any existing files; hence, if you choose another propagation time period, you may need to update the database files once again.
If you are not searching using orbital characteristics, then an appropriately dated satellite database file is less of a concern, unless the most recently available objects are of interest. In that case, the most recent satellite database may suffice.
However, while the date of the satellite database file may be a concern for finding a space object of interest, the epoch for any TLEs used for ephemeris generation for that object is always a concern. Using the AGI Online Server as the TLE source removes the burden of obtaining correctly dated TLEs for objects.
Additional options
Modifying the color of the selected satellites
Select the color choice or select the Auto Select Color check box to allow STK to choose colors sequentially.
Modifying the analysis time period
To propagate ephemeris using a different time period than the scenario time period, click Advanced....
Creating a constellation of satellites
You can group satellites into a single unit called a Constellation object. To create a constellation of satellites:
- Select one or more satellites to add to the constellation.
- Select the Create Constellation from Selected check box under Insert Options and enter a name for the constellation.
- Click to create the constellation. STK will add the constellation to the Object Browser.