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I don’t think that’s quite true. There are actually some interesting patents related to the star sensor in the devices, particularly related sky background gra
by labcomputer 3y ago
I don’t think that’s quite true.
There are actually some interesting patents related to the star sensor in the devices, particularly related sky background gradients. Northrop’s patents are more interesting than Lockheed’s, IMHO. In all cases the patents mention using an IR-pass filter to improve contrast.
The sensor is essentially an analog lock-in/synchronous detector with a rotating shutter and a wedge prism that nutates the star field about the boresight. the patented component in most cases is the shutter (there are different patterns, and Northrop came up with some clever designs).
You end up with a frequency modulated signal from the photomultiplier tube (carrier is from the shutter, modulation frequency the difference between the prism and shutter).
By measuring the phase and magnitude of the modulated signal, you can steer the telescope onto the star, and the “coding gain” from the lock-in is substantial.
Edit, previous comments:
https://news.ycombinator.com/item?id=27084261 https://news.ycombinator.com/item?id=27084261
https://news.ycombinator.com/item?id=23238437 https://news.ycombinator.com/item?id=23238437
- pyinstallwoes 3y agoI have recently been bitten by the modular synthesis bug, and it is wild to me how these terms seem to have correspondence even though I am learning it from the audio domain. I guess a signal is a signal and that is the power of analog. For context: learning about carriers, modulation frequency in relation to audio synthesis [acknowledging there is more than one type of 'FM' in relation to audio but nonetheless similar]).