I wanted to have the camera rotate so that the planet center would always be straight down. I realized that I could only rotate the camera by a given amount of degrees, not set an absolute angle. This made things a bit harder, so I thought I would share how I did it.
//As center of planet is in (0, 0), it is enough to fetch the current position of the camera to get the correct angle. Vector2 shipPlanetVector = new Vector2(m_camera.position.x, m_camera.position.y); //Fetch vector up for camera. The angle between these two is how much we need to rotate the camera. Vector2 cameraUp = new Vector2(m_camera.up.x, m_camera.up.y); m_camera.rotate(cameraUp.angle() - shipPlanetVector.angle());