Generate OEM (Orbit Ephemeris Message) files from state vectors. OEM files contain predicted satellite positions over a specified time range, useful for mission planning, conjunction analysis, or sharing with external systems.
Access: Click Generate Ephemerides on the State Vectors page top-right corner.
Modal Overview
The Generate Ephemerides modal guides you through four steps:
Step 1: State Vector Selection
Select Spacecraft
Choose a spacecraft from the dropdown. The list shows spacecraft names with colored satellite icons.
Select State Vector
After selecting a spacecraft, choose a state vector from the dropdown. Each option shows the state vector ID and epoch date/time.
Empty State: If no state vectors are available for the selected spacecraft in the last 30 days, you can:
- Click Import State Vector to open the import dialog
- Click Run Orbit Determination to configure OD
Include Covariance Data
Toggle whether to include covariance matrix in the OEM file:
| Option | Effect |
|---|
| Yes | Includes covariance matrix; enables covariance frame selection in Step 3 |
| No | Excludes covariance data (default) |
Step 2: Time Range Configuration
Time Step
Use the slider to set the interval between data points (1–60 minutes).
- Smaller step = more data points, larger file
- Larger step = fewer data points, smaller file
Start Date & Time
Select the start date from the 7-day calendar (use arrows to navigate weeks) and enter the start time in 24-hour UTC format (e.g., “08:30”).
Default: 00:00 UTC
End Date & Time
Select the end date and enter the end time.
Default: 23:59 UTC
Dates are limited to ±30 days from the state vector epoch. Total duration cannot exceed 30 days.
Step 3: Reference Frames
Time System
| Value | Description |
|---|
| UTC | Coordinated Universal Time (default) |
| TAI | International Atomic Time |
| TT | Terrestrial Time |
| TDB | Barycentric Dynamical Time |
| TCG | Geocentric Coordinate Time |
| TCB | Barycentric Coordinate Time |
| GPS | GPS Time |
Ephemerides Reference Frame
| Value | Description |
|---|
| GCRF | Geocentric Celestial Reference Frame (default) |
| EME2000 | Earth Mean Equator and Equinox of J2000 |
| ITRF | International Terrestrial Reference Frame |
| TOD | True of Date |
| MOD | Mean of Date |
| TEME | True Equator Mean Equinox |
Covariance Reference Frame
Only available when covariance is enabled in Step 1.
| Value | Description |
|---|
| RTN | Radial-Tangential-Normal (default) |
| TNW | Tangential-Normal-Out-of-plane |
Step 4: Review & Generate
Review your configuration before generating:
State Vector Card
- Spacecraft name
- State Vector ID
- Epoch date and time
Time Range Card
- Start and end date/time (UTC)
- Time step in minutes
- Calculated number of data points
Reference Frames Card
- Time system
- Ephemerides frame
- Covariance frame (if enabled)
Click the Edit button (pencil icon) on any card to jump back to that step.
Generate OEM
Click Generate OEM to create and download the file.
Loading states:
- “Sending request to server…”
- “Downloading file…”
On success:
- Toast notification: “OEM generated successfully”
- File downloads automatically
- Modal closes
Navigation
- Step tabs: Click any step name to jump directly to it
- Next: Validates current step and proceeds
- Back: Returns to previous step (hidden on Step 1)
- Cancel: Closes modal without generating
Error Handling
| Error | Message |
|---|
| 422 (Validation) | Field-specific messages from server |
| 400 (Bad Request) | “Please check your configuration” |
| 404 (Not Found) | “The state vector may have been deleted” |
| 500 (Server Error) | “An error occurred during OEM generation. Please try again.” |
Output
Format: OEM (Orbit Ephemeris Message), CCSDS standard text format
Filename: oem_{stateVectorId}_{timestamp}.txt
Constraints
| Constraint | Value |
|---|
| Date range from epoch | ±30 days |
| Maximum duration | 30 days |
| Minimum time step | 1 minute |
| Maximum time step | 60 minutes |
Related Pages
