Orbit controlled by virtual joystick

I currently have a planet in my scene located at the origin. I have a space ship placed at (0, 0, -10) which shows my ship in the center of the screen and just outside of the planet.

I am using the Dual Joysticks included in the Standard Assets (Mobile) package for my Android game. I am trying to get the joystick to control the direction the ship moves, so that the ship will orbit the planet continuously in the direction the joystick is pointing. I have tried Transform.RotateAround() by passing in arbitrary values (between -1 and 1) and it works. But I can't seem to get the joystick to control the rotation axis correctly. Any ideas?

If this doesn't make sense, let me know and I will try to explain it differently. Thanks!

Edit:

Here is my current hierarchy:

• Camera

  • Directional light

• EmptyGameObject

  • Ship

• Planet

Here is my code so far that seems to almost work. When I move the joystick a lot the ship seems to rotate around it's local axis on it's own. Also when I attach the camera to move with the ship by putting it under the ship in the hierarchy, the camera keeps flipping and starts restricting movement quite a bit.

 private const float MOVE_SPEED = 50.0f;
 private Vector3 rotationAxis;
 
 if (moveJoystick.IsFingerDown())
 {
     rotationAxis.Set(moveJoystick.position.y, -moveJoystick.position.x, 0.0f);
     transform.RotateAround(Vector3.zero, rotationAxis, MOVE_SPEED*Time.deltaTime);
 }