The foundation of the satellite branch, and nothing above it yet: where a
satellite is (SGP4 from akhenakh/sgp4, Apache-2.0 and pure Go, so the
no-cgo rule holds), where it will be (passes with an elevation floor,
because a three-degree scrape is a line in a table that will never be a
QSO), and what its motion does to a frequency.
The Doppler pair is the part worth being careful about: the two
corrections go in OPPOSITE directions. The downlink arrives shifted and
we tune to meet it; the uplink must LEAVE shifted the other way to land
on the transponder's nominal input. A test pins the signs and the size —
7 km/s on 2 m is about 3.4 kHz.
Elements keep their raw lines beside the parsed form: that is what the
cache stores and what an operator pastes by hand for a bird no feed
carries yet, which is exactly when everyone wants to hear it.
