[Wavytone]

Two solutions used in the rail industry - we have machine vision camera equipment embedded in the ballast looking up at the undersides of rolling stock to inspect brake pads and wheel wear. As you might expect it’s a dirty environment in addition to ordinary dust, rain, leaves, litter and other debris that can fall on the gear.

1. Use a mechanical shutter that protects the window from dirt and only opens before and closes after a picture is taken.

2. Windscreen wipers with fluid to wash the window before a shot is taken. Wipers have advantage that they will push small items off (leaves, etc) but also more of a maintenance problem in requiring regular replacement of the blades, water, and fail frequently.

3. Don’t face the camera up - place horizontally with wide angle lens and a hood over it, and accept the camera cannot view directly overhead.

Anything with moving parts or requiring consumables (wash liquid) is prone to failure and a maintenance headache. Making these solutions work this reliably long-term is neither trivial nor cheap.

Tear-off protectors are also used on motorcycle helmet visors.

Questions for you:

1. do you really need continuous video or would it be ok to take images periodically ?
2. Is this expected to operate automatically at a location which is unmanned for long periods or will there be someone nearby ?

As I hinted before I think you really should be talking to companies that do this for weather stations because what you’re proposing is not new, and has been solved before.