Earth orbit and space applications – where do I need radiation tolerant lenses?
Satellites are not launched any higher than is needed for a particular mission, because to get them to stay there takes a lot more launch energy and therefore a bigger rocket which costs much more money.
Many Earth observation satellites are launched into geosynchronous orbit, 36,000 miles up, because this lets them orbit at the same rate as the Earth rotates, appearing stationary over a particular spot as the planet revolves with them. In this high orbit, satellites are exposed to far more radiation from the sun. By comparison, space platforms such as the International Space Station orbit at only about 250 miles, below most of the radiation and low enough to be easier to reach for resupply.
The cosmic radiation emitted during solar events such as sunspots, solar flares, coronal mass ejections and proton storms is well known to have a deteriorating effect on orbiting equipment in space as well as astronauts.
If you are looking to launch a satellite into low Earth orbit it may not be necessary to use lenses made from radiation tolerant materials because the Earth’s atmosphere works like a shield, keeping out substantial amounts of this radiation. However, if the duration of your low Earth orbit mission is years rather than weeks or a few months then using radiation tolerant optical materials is recommended to minimise loss of optical performance.
As you move to the higher orbits, and exposure to radiation increases, using radiation tolerant optical materials becomes necessary. Apart from fused silica or quartz – all standard glasses turn dark when exposed to radiation. This means that if you are using a standard lens in higher Earth orbit within weeks or a few months at most, you will start to lose your image.
The widely accepted solution to this is to use non-browning glasses that have Cerium Oxide added which retards the darkening of the glass when exposed to radiation. A non-browning lens will continue to work until it has exceeded its accumulative dose of radiation. In the case of Resolve Optics radiation tolerant lenses, they are rated for one hundred million rad so depending on the level of radiation they are exposed to daily you could expect a space ready lens to have a life of around 10 years.
To discuss your application and determine the requirement for radiation tolerant lenses please click here.