That was the first thing I looked at, the angle vs. the movement. It doesn't necessarily have to be something on the camera, it could be internal interreflections.
The entire optical system is shielded from the environment by a transparent cover, probably spherical for a large field of view. Optical systems usually have some degree of internal interreflection that you try to suppress with anti-reflection coatings on the internal lenses. Usually, these coatings are highly angle-dependent. Specifically for very shallow incidence, almost parallel to the optical surface, you can't do much, there will be reflection. Another source of interreflection is the housing of the optical system - you usually try and suppress that by making surfaces 'black' but a very broad spectrum, brilliant light source can still produce a significant amount of reflected radiance.
The system was probably made with some requirements on these artifacts but it's always possible that for a certain off-axis angle, light gets coupled into the external, curved cover and then through the imaging system. Some of it makes it through at an angle that actually hits the sensor, in this case a virtual image or just some caustic from an object way off-axis.
Maybe it's the reflection of the sun from the sea. It is pretty static in terms of global incoming angle and does turn just right in relation to a turning aircraft to still hit the sensor - especially if you turn to still track it and keep it in the optical system's field of view.
The entire optical system is shielded from the environment by a transparent cover, probably spherical for a large field of view. Optical systems usually have some degree of internal interreflection that you try to suppress with anti-reflection coatings on the internal lenses. Usually, these coatings are highly angle-dependent. Specifically for very shallow incidence, almost parallel to the optical surface, you can't do much, there will be reflection. Another source of interreflection is the housing of the optical system - you usually try and suppress that by making surfaces 'black' but a very broad spectrum, brilliant light source can still produce a significant amount of reflected radiance.
The system was probably made with some requirements on these artifacts but it's always possible that for a certain off-axis angle, light gets coupled into the external, curved cover and then through the imaging system. Some of it makes it through at an angle that actually hits the sensor, in this case a virtual image or just some caustic from an object way off-axis.
Maybe it's the reflection of the sun from the sea. It is pretty static in terms of global incoming angle and does turn just right in relation to a turning aircraft to still hit the sensor - especially if you turn to still track it and keep it in the optical system's field of view.