Take a real example. ASTRID 2, a small Swedish research satellite launched in 1998, shows up in the inspector with NORAD number 25568, an altitude of 988 km, a period of 105 minutes and an inclination of 82.95°. Here is what each of those tells you.
Altitude
Height above Earth's surface. Straightforward, with one catch worth knowing: the physics works from the centre of the Earth, not the surface. When you do any calculation, add Earth's radius - about 6,371 km - first.
For ASTRID 2 that gives an orbital radius of roughly 6,371 + 988 = 7,359 km.
Period
How long one full orbit takes. It is not a free parameter - it is fixed by the size of the orbit. Kepler's third law gives the relationship:
T = 2π × √(r³ / μ)
where r is the orbital radius and μ, Earth's gravitational parameter, is 398,600 km³/s².
Plug in ASTRID 2's radius of 7,359 km. r³ is about 3.985 × 10¹¹; divide by 398,600 and you get about 999,800; the square root is about 1,000; multiply by 2π and you get roughly 6,280 seconds, or 104.7 minutes. The inspector says 105. They agree.
That check is worth doing once, because it turns two numbers on a screen into a relationship you understand. Try it on the Space Station: 6,371 + 420 = 6,791 km gives about 93 minutes, which matches what trackers show.
Speed
For a near-circular orbit, speed also follows from radius alone: v = √(μ / r). For ASTRID 2 that is √(398,600 / 7,359), about 7.36 km/s - more than 26,000 km/h. Lower orbits are faster; higher ones slower. The Moon, far out, dawdles along at about 1 km/s.
Inclination
The tilt of the orbit against the equator, from 0° to 180°.
- 0° - directly over the equator, moving east with Earth's rotation.
- Around 51.6° - the Space Station, which is why it only passes over latitudes up to about 51.6° north and south.
- 90° - a polar orbit, crossing both poles.
- Above 90° - retrograde, travelling against Earth's rotation. Sun-synchronous orbits sit here, at about 98°.
The inclination sets the furthest latitude a satellite's ground track reaches. ASTRID 2's 82.95° takes it close to both poles, so over time it passes above almost the entire planet.
Apogee and perigee
An orbit is rarely a perfect circle. Apogee is its highest point, perigee its lowest. When the two are close, "altitude" is a fair single summary. When they are far apart, a single altitude hides a lot.
The gap between them gives the eccentricity - how stretched the orbit is. Using radii from the centre of the Earth:
e = (rapogee − rperigee) / (rapogee + rperigee)
A value near 0 is almost circular. Transfer orbits and Molniya orbits run far higher.
Country and launch year
Not orbital numbers, but often the most revealing. A piece of debris launched decades ago and still up there tells you its orbit is high enough that drag barely touches it. A cluster of fragments sharing a launch year and country usually traces back to one breakup.
Why the numbers can drift
Every value comes from an element set measured at a particular moment. Over time, especially for low orbits, drag lowers the altitude and shortens the period together - the relationship holds, the orbit just gets smaller. Checking the element age tells you how fresh the snapshot is.