You need to specify which object is orbiting Jupiter to determine the semi-major axis of its orbit.

The semi-major axis is a key parameter in describing an elliptical orbit. It represents half of the longest diameter of the ellipse, effectively defining the average distance between the orbiting object and Jupiter.

Here's how to find the semi-major axis:

1. Identify the object: Tell me what object is orbiting Jupiter (e.g., Ganymede, Europa, a spacecraft, etc.).

2. Look up the orbital data: You can find the semi-major axis in astronomical databases or websites like NASA's Planetary Fact Sheet.

Example:

* Object: Ganymede (Jupiter's largest moon)

* Semi-major axis: 1,070,400 km (664,800 miles)

Once you provide the object you're interested in, I can help you find its semi-major axis.