LESSON 03 OF 6

Raise/lower orbit

Intermediate ~10 min Slide deck Free

When a satellite changes altitude, the TLE fields update to reflect the new orbit. Knowing exactly which fields change — and in which direction — lets you read maneuver signatures directly from raw element sets, without any visualisation.

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What this lesson covers

The Two Fields That Change Immediately

Two TLE fields respond directly and reliably to an altitude change: mean motion and eccentricity.

Real Change vs Stale TLE Artefact

Not every apparent jump in TLE elements represents a real maneuver. Stale TLEs create prediction errors that look like jumps when fresh data arrives.

Practical Reading: What to Check

A step-by-step approach for reading maneuver signatures from a sequence of TLEs.

Key facts

💡A 50 km altitude raise at 500 km drops mean motion by roughly 0.5 rev/day. A 200 km raise drops it by about 2 rev/day. These are detectable by simple comparison of successive TLEs.

💡For a decaying LEO object, the natural drift in mean motion due to drag can easily reach 0.1–0.5 rev/day per week — which looks similar to a small maneuver in the element record.

💡Space-Track's Conjunction Data Messages (CDMs) already encode maneuver detection flags — but doing it yourself from raw TLEs builds the intuition that makes CDM outputs interpretable.

Watch mean motion — it's the fastest 'altitude changed' signal in tracking data.

Mean motion up = orbit lower. Mean motion down = orbit higher. Eccentricity spike = transfer in progress. These three rules let you read a significant fraction of maneuver activity directly from raw TLE comparisons — no specialised tools required.

All lessons in Orbital Maneuvers & Station-Keeping

01What a maneuver is~10 min 02Hohmann transfers~10 min 03Raise/lower orbit~10 min 04Inclination changes~10 min 05GEO station-keeping~10 min 06De-orbit & end-of-life~10 min

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