Keplerian Elements

For the complete documentation index, see llms.txt.

The Keplerian Elements page displays time-series visualizations of the six classical orbital elements for your spacecraft. Each element is shown in its own chart card, and you can filter by spacecraft and reorder the cards to customize your view. Route: /state-vectors/keplerian-elements

Orbit sources

Open Orbit sources to display Precise orbits, Public orbits · SGP4, or both. Use automatic sources restores the automatic choice for each spacecraft. Read any source-availability notices before interpreting missing series. These controls change the display, not the stored states or an OD result’s approval.

Page Layout

Orbital Elements Displayed

The page shows 6 Keplerian orbital elements in a 2-column grid:

Spacecraft Filter

Filter which spacecraft are plotted on all charts. Actions:

• Click to open popover dropdown
• Check/uncheck spacecraft to display
• Click Apply to confirm selection
• Click Clear All to deselect all
• Remove individual spacecraft via X button on badges

Effect:

• Filters which spacecraft are plotted on all charts
• Each spacecraft shown as separate colored line
• URL updates to persist selection

Element Cards

Card Structure

Each orbital element is displayed in a card containing: Header Elements:

• Element Name: e.g., “Semi-major Axis”
• Unit: e.g., “km” or “deg”
• Reference Frame Indicator: A small chip showing the frame the element values are expressed in (e.g., GCRF). Hover for the full frame name; click Learn more to open the reference frame catalog. The badge appears on every element card on this page.
• Drag Handle: Grip icon for reordering

Chart Visualization

Each chart displays: X-Axis: Time (UTC)

• 5 evenly-spaced tick labels
• Shows date/time labels

Y-Axis: Element value

• Auto-scaled to fit data
• Formatted by element type:
  • Semi-major axis: Integer km values
  • Eccentricity: 4 decimal places
  • Angular elements: 2 decimal places with °

Lines:

• One line per selected spacecraft
• Color-coded by spacecraft
• Smooth curve interpolation
• No dots on data points (clean lines)

Drag-and-Drop Reordering

How to Reorder Cards

Each card has a grip icon in the top-right corner. To reorder:

1. Hover over the drag handle - cursor changes to grab
2. Click and hold the drag handle
3. Drag the card to desired position
4. Release to drop

Visual Feedback:

• Dragged card shows preview overlay
• Original position becomes semi-transparent (30% opacity)
• “Chart hidden during reordering” message displays
• Smooth animation when cards swap positions

Keyboard Support

• Use arrow keys to rearrange cards (when focused on drag handle)
• Tab to navigate between drag handles

Order Persistence

• Your custom order is automatically saved to browser storage
• Persists across page reloads and sessions
• Stored with key keplerian-elements-order

Default Order

1. Semi-major Axis
2. Eccentricity
3. Inclination
4. RAAN
5. Argument of Perigee
6. True Anomaly

Chart Interactions

Hover Tooltip

Hover over any point on a chart line to see values: Value Formatting:

• Semi-major Axis: Localized number with “km” (e.g., “7,012.34 km”)
• Eccentricity: 4 decimal places (e.g., “0.0012”)
• Angular elements: 2 decimal places with ° (e.g., “98.52°“)

Active Point Indicator

When hovering:

• Small filled circle appears at exact data point
• Circle matches spacecraft color
• White border for visibility

Cursor Line

• Dashed vertical line follows cursor
• Helps align values across time axis

Angular Element Handling

For angular elements (Inclination, RAAN, Argument of Perigee, True Anomaly): Discontinuity Handling:

• Charts automatically detect wrapping at 0°/360° boundaries
• Line breaks at discontinuities to prevent unrealistic connections
• Thresholds:
  • Inclination: 90° jump threshold
  • RAAN, Arg. of Perigee, True Anomaly: 180° jump threshold

Data & Time Range

Default Data Range

Data Resolution

• Time step: 5 minutes (300 seconds)
• Sufficient detail for orbital trends without overwhelming the charts

Data Caching

• Results cached per spacecraft/time range
• Prevents redundant API calls when switching views

When the orbit is stale or unusable

The charts plot each spacecraft from a fresh orbit. A spacecraft’s orbit age is measured from its latest state vector — the position and velocity at an epoch you provide through orbit determination, an OPM import, or manual entry. As that age grows it crosses two levels in turn — the degraded level, then the stale level — and the page reacts differently at each. The charts normally compute the moment you open the page; on a stale orbit they wait for you to choose to proceed. What you see depends on the selected spacecraft’s orbit age: Both N values are whole days — the spacecraft’s actual orbit age and your configured stale level. The stale and degraded levels are workspace-wide values set once in Settings → Orbits → Orbit age (stale level default 14 days); the same values govern the ground-track map and AOI overflight, so “stale” means one consistent thing across all three. See Orbit age for the workspace-wide policy and the block message.

Loading & Error States

Color Coding

Each spacecraft has a unique color that is consistent across:

• Chart lines
• Tooltip indicators (colored dots)
• Spacecraft filter badges

Colors are assigned from a predefined palette and retrieved from the spacecraft context. While there’s no separate legend component, spacecraft colors are visible through selected spacecraft badges in the filter and tooltip color indicators when hovering on charts.

Quick Reference

Understanding Keplerian Elements

Keplerian elements are six parameters that uniquely define an orbit:

1. Semi-major Axis (a): Determines the size of the orbit
2. Eccentricity (e): Determines the shape (0=circle, 0-1=ellipse)
3. Inclination (i): Tilt relative to Earth’s equator
4. RAAN (Ω): Orientation of where orbit crosses equator
5. Argument of Perigee (ω): Orientation of closest approach point
6. True Anomaly (ν): Current position along the orbit

Why Track These Over Time?

• Detect orbital drift: Semi-major axis changes indicate altitude changes
• Monitor stability: Eccentricity variations show orbit shape changes
• Track precession: RAAN and Argument of Perigee naturally precess
• Verify maneuvers: Changes in elements after planned burns
• Predict decay: Long-term trends in semi-major axis

Flight Plan orbital overview

In Operations → Flight Plan, select a spacecraft to review its orbital history and planned waypoint values in one plot. Choose an element, then Quarter, Year or Mission. Quarter and Year look three and twelve calendar months ahead, keeping recent history visible. Mission fits the available mission dates. Your choices are remembered. The grey line is recorded orbit history. The green line and shaded area connect supported forecast waypoint values. Forecast starts at the latest orbit used by that calculation, which can be earlier than Now. Hollow green circles are planned values, including historical targets; they do not confirm arrival. Waypoints are labeled directly and are not clickable on this plot. Use the waypoint and phase cards below to edit or review them. Hover, focus or tap the diamond at the latest orbit to inspect only its orbit ID, six Keplerian elements and mass. Public orbits show their PO identifier. Values match the plot’s compatible representation; mean anomaly is labeled explicitly. Missing values remain unavailable. AOP, RAAN and MA lines break at 0°/360° wraps. MA means mean anomaly; its forecast connects the source and waypoint values, omitting dense propagation samples. These connectors are a planning guide, not continuous orbital motion. All six elements use the same mean-element representation. Missing values and coverage gaps are not filled, and forecasts stop at terminal outcomes. Dates alone appear as time markers. Forecast and history loading or failure notices remain visible independently of the plot.