Calculator Inputs
Choose the known orbit data. The page supports circular, radius-based, elliptical, and vis-viva calculations.
Example Data Table
| Case | Central Body | Known Input | Expected Altitude | Use Method |
|---|---|---|---|---|
| Low Earth orbit | Earth | Period: 92.68 minutes | About 400 km | From orbital period |
| Low Earth circular speed | Earth | Speed: 7.67 km/s | About 400 km | From circular orbital speed |
| Geostationary height | Earth | Radius: 42,164 km | About 35,786 km | From orbital radius |
| Medium orbit example | Earth | Semi-major axis: 26,560 km | About 20,182 km mean height | From semi-major axis and eccentricity |
Formula Used
Altitude from radius: h = r − R
Here, h is altitude, r is orbital radius, and R is the selected body radius.
From period: r = cuberoot( μ × (T / 2π)² )
From circular speed: r = μ / v²
From elliptical data: rp = a(1 − e) and ra = a(1 + e)
From vis-viva: v² = μ(2/r − 1/a)
The calculator converts entered units first. Then it calculates radius. Finally, it subtracts the body radius to report altitude.
How to Use This Calculator
- Select the central body. Choose custom if your body is not listed.
- Select the calculation method that matches your known value.
- Enter the required field for that method.
- Check the unit beside each value.
- Press the calculate button.
- Review the result section above the form.
- Use CSV or PDF export for reports and records.
Understanding Satellite Altitude
Satellite altitude describes the height of a spacecraft above the chosen body. It is not the same as orbital radius. Radius is measured from the body center. Altitude is measured from the surface. This small difference matters in every orbit estimate.
Why Orbit Height Matters
Altitude affects coverage, speed, signal delay, and mission cost. A low satellite moves fast and circles Earth many times each day. It can capture sharp images. It also sees a smaller ground area. A higher satellite moves slower. It covers more area, but needs more launch energy. Around Earth, communications missions often use high orbits. Observation missions often use low orbits.
Main Inputs
This calculator supports several practical inputs. Use period when you know how long one orbit takes. Use circular speed when you know the orbital velocity. Use orbital radius when a source gives distance from the center. Use the elliptical option for perigee and apogee heights. Use custom body data when the mission is not around Earth. The gravitational parameter and mean radius control the result.
Accuracy Notes
The formulas assume a two body model. That means the satellite and central body dominate the motion. It ignores drag, thrust, uneven gravity, sunlight pressure, and third body pulls. For many planning tasks, this is a helpful first estimate. For launch design, collision checks, or precise tracking, use professional orbit software and current ephemeris data.
Good Workflow
Start by selecting the central body. Choose the method that matches your known data. Enter values in the provided units. Press calculate. Review the altitude, orbital radius, period, and speed. Then export the result for records or reports. Compare your answer with the example table. This helps catch unit mistakes. If the altitude is negative, the orbit is below the surface. If it is very low around Earth, drag may end the orbit quickly.
A clear altitude estimate helps mission teams compare options. It also helps students connect equations with real orbital behavior.
Use With Care
Always check units before trusting any answer. Minutes, hours, meters, and kilometers can change a result greatly. Save the export after each important run for quick comparison later safely.
FAQs
1. What is satellite altitude?
Satellite altitude is the height above the surface of the selected central body. It equals orbital radius minus body radius. The calculator reports this value in kilometers and miles.
2. Is orbital radius the same as altitude?
No. Orbital radius is measured from the body center. Altitude is measured from the surface. For Earth, altitude equals orbital radius minus about 6,378 kilometers.
3. Which method should I choose?
Choose the method that matches your known data. Use period for orbit time. Use speed for circular velocity. Use radius when center distance is known. Use elliptical mode for perigee and apogee.
4. What does μ mean?
μ is the standard gravitational parameter. It combines the gravitational constant and body mass. The calculator uses km³/s². Larger μ values create faster orbits at the same radius.
5. Can I use this for the Moon or Mars?
Yes. Select Moon, Mars, or another preset. You can also choose custom body and enter your own radius and gravitational parameter for other worlds.
6. Why can altitude be negative?
A negative altitude means the calculated orbital radius is smaller than the body radius. This usually indicates wrong units, unrealistic speed, or an impossible orbit path.
7. Does this include atmospheric drag?
No. The calculator uses ideal two body equations. It does not include atmospheric drag, thrust, uneven gravity, solar pressure, or third body effects.
8. Can I export the results?
Yes. After calculation, use the CSV button for spreadsheet data. Use the PDF button for a simple report containing the result, formula, and calculation steps.