I have the ephemeris for an Earth observing satellite from a TLE, so I can get the location of the satellite (lat/lon). The documentation has a nice example for the ISS, showing how that is done.
However, what I am actually after is the location of the point of the Earth's surface that the satellite's sensor is pointing at. Assume that the sensor is pointing perpendicular to the flight direction, so I should be able to calculate the azimuth direction using the satellite's inclination. Then I have an idea of the angle the satellite's sensor is using to point to the ground. Some simple geometry should give me the altitude I need.
The question is now: How do I string these two things together? The compute(observer) calculation example returns altitude and azimuth for a location (lat/lon). However, I could not find anything that does that the other way around. Any thoughts how to go about this? Any clues are much appreciated.