closeApproachfunction

The closest the two satellites come between from and to. The span is sampled every stepMs (60 seconds when left out), and the moment of the closest sample is then refined between its two neighbours, to a tenth of a second, because two satellites close in at several kilometres a second and the closest sample alone can be hundreds of kilometres too far. The uncertainty is the elements' own: the square root of the sum of the squares of the two satellites' rough uncertainties (1 km, and 1 km more for each day the elements have aged at that moment), not a published covariance. Two SGP4 calls a sample, and about 20 more for the refinement. It does not run again by itself.

import { closeApproach } from "@johnmorrisdotca/chikyu-earth/satellites";

function closeApproach(group: Satellites, a: number, b: number, from: number, to: number, stepMs?: number): { at: number; kilometres: number; uncertaintyKm: number; } | null

import { closeApproach, createSatellites } from "@johnmorrisdotca/chikyu-earth/satellites";

const group = createSatellites([]);
console.log(closeApproach(group, 0, 1, 0, 60_000));

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