Orbital Elements History
The Orbital Elements History section on the Orbital Analysis tab displays charts showing how the satellite’s orbital parameters evolve over time.
Understanding Orbital Elements
Orbital elements (also called Keplerian elements) are parameters that define a satellite’s orbit. Tracking how these elements change over time reveals important information about the satellite’s behavior, including natural orbital evolution, atmospheric drag effects, and deliberate maneuvers.
Time Range Selection
Select the time range for the orbital element charts:
| Option | Description |
|---|---|
| 7 Days | Recent week of data |
| 30 Days | Last month (default) |
| 90 Days | Last quarter |
Filters
Status Filter
The status filter is available to Government tier users and above. Standard users only see approved element sets.
Filter element sets by review status:
- Approved - Only approved elsets (default for all users)
- Pending - Elsets awaiting review (Government+ only)
- Rejected - Rejected elsets (Government+ only)
Type Filter
Filter element sets by propagation type:
- SGP4 - Standard SGP4 propagation element sets
- SGP4-XP - Extended Precision (SGP4-XP) element sets
SGP4-XP is selected by default when available. If no SGP4-XP element sets exist for the satellite, SGP4 is selected instead.
Charts
Orbital Period and Altitude
This combined chart shows two related orbital parameters:
Orbital Period (left axis)
- Time for the satellite to complete one orbit
- Measured in minutes
- Decreasing period indicates the orbit is lowering (often due to drag)
Perigee and Apogee Altitude (right axis)
- Perigee: Lowest point in the orbit
- Apogee: Highest point in the orbit
- Measured in kilometers above Earth’s surface
Semi-Major Axis
The semi-major axis represents the orbit’s size:
- Measured in kilometers
- Half the longest diameter of the elliptical orbit
- A decreasing semi-major axis indicates orbital decay due to atmospheric drag
- Sudden changes may indicate maneuvers
Inclination
The orbital inclination is the tilt of the orbit relative to Earth’s equator:
- Measured in degrees (0° = equatorial, 90° = polar)
- Typically very stable for most satellites
- Small drifts occur due to gravitational perturbations from the Sun and Moon
- Sudden changes may indicate plane-change maneuvers
Right Ascension of Ascending Node (RAAN)
RAAN describes the orientation of the orbit in space:
- Measured in degrees (0° to 360°)
- Indicates where the satellite crosses the equator going northbound
- Naturally drifts due to Earth’s oblateness (J2 effect)
- Drift rate depends on orbit altitude and inclination
Interacting with Charts
Hover Information
Hover over any data point to see:
- Elset epoch (date/time)
- Exact element value
- Source information
- Review status
Elset Selection
Click on any data point to select that element set:
- The selected elset is highlighted across all charts
- The Observation Residuals chart updates to show residuals for the selected elset
- The Element Sets grid scrolls to show the selected elset
Zoom and Pan
- Zoom: Use mouse wheel or pinch gestures
- Pan: Click and drag on the chart
- Reset: Double-click to reset the view
Key Insights
| Pattern | Possible Interpretation |
|---|---|
| Gradual altitude decrease | Atmospheric drag causing orbital decay |
| Sudden altitude change | Orbital maneuver (boost or de-orbit) |
| RAAN precessing steadily | Normal J2 precession effect |
| Inclination jump | Plane-change maneuver |
| Consistent elset quality | Stable, well-tracked satellite |
| Scattered data points | Possible tracking issues or analyst-generated fits |