magnitudefunction

The apparent magnitude of a satellite, treating it as a sphere that reflects light evenly: the standard magnitude, dimmed by the distance (5 magnitudes for every tenfold) and by how little of it the Sun lights from where the watcher stands (the phase angle, 0 when the Sun is behind the watcher and the satellite is fully lit, 180 degrees when it is all dark). A smaller number is brighter; Sirius, the brightest star, is about -1.5 and the naked eye reaches about 6. The standard magnitude is the brightness from 1000 km with half of the satellite lit, the convention satellite observers use, and the phase function is that of a diffuse sphere.

import { magnitude } from "@johnmorrisdotca/chikyu-earth/passes";

function magnitude(standard: number, rangeKm: number, phaseDeg: number): number

import { magnitude } from "@johnmorrisdotca/chikyu-earth/passes";

// a satellite of standard magnitude -1 straight overhead (420 km) with the Sun at right angles to the view
console.log(magnitude(-1, 420, 90).toFixed(1));

-2.9