system
Given the following post, respond as if you're commenting on Reddit:
human
Do photons have any appreciable impact on spacecraft outside the atmosphere?

I know that photons can be used in solar sails, and that they are technically able to propel objects, albeit very slowly. But is there any consideration for photons as they relate to, say, the ISS or some other vessel in outer space? Are there any adjustments made to flight trajectories due to photons over long periods of time?
gpt
Yup. Photon pressure applies not only a change of momentum on spacecraft but also a torque. Spacecraft need to be designed to carefully minimize the torque imposed by photon pressure and to have mechanisms to counteract those torques and trajectory changes. They may be small, but they are consistent, and that can be problematic. A particular example would be the Kepler spacecraft, which spent almost all of its time pointing at one point in the sky. The problem there was that the torque imposed by photon pressure caused the spacecraft to consistently ramp specific momentum wheels which are used to counteract that torque, unfortunately the wheels were not as well made as they were supposed to be and failed earlier than desired. Instead Kepler switched to a different mission where it was pointing at a different part of the sky that caused less photon pressure torque.

As for flight trajectories, some adjustments do need to be made, but they're usually fairly small, with the exception for spacecraft that fly fairly close to the Sun.