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Chikyu Earth地球

A line-drawn globe of the world's countries that turns at the Earth's own rate, with an optional realistic Earth from space and markers for any place.

Chikyu is the Japanese word 地球 for the Earth. About the name

Contents

Reference · Passes: when a satellite crosses the sky over a place

satelliteAtfunction

Where one satellite is in the sky over a place at one moment, and what the light is like: its direction and height, its distance, whether the Sun lights it, how high the Sun is, and how bright it looks.

Import it

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

Definition

function satelliteAt(set: ElementSet, observer: Observer, ms: number, options?: Pick<PassOptions, "magnitudes">): (PassPoint & { sunlit: boolean; sunAltitude: number; magnitude: number | undefined; }) | undefined

Parameters

NameTypeDescription
setElementSet

The satellite's elements.

observerObserver

Where the watcher stands.

msnumber

The moment, milliseconds since the Unix epoch.

options (optional)Pick<PassOptions, "magnitudes">

magnitudes for your own standard magnitudes (the ISS, Tianhe and Hubble are known).

Returns

(PassPoint & { sunlit: boolean; sunAltitude: number; magnitude: number | undefined; }) | undefined

Its place in the sky (altitude below 0 means below the horizon), sunlit, the Sun's altitude and the magnitude (undefined when it is in shadow or its standard magnitude is not known); undefined where SGP4 gives no place.

Examples

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

const iss = {
  OBJECT_NAME: "ISS (ZARYA)",
  EPOCH: "2026-11-02T10:25:21.580320",
  MEAN_MOTION: 15.49150046,
  ECCENTRICITY: 0.0007139,
  INCLINATION: 51.6332,
  RA_OF_ASC_NODE: 335.9757,
  ARG_OF_PERICENTER: 339.3739,
  MEAN_ANOMALY: 20.6961,
  NORAD_CAT_ID: 25544,
  BSTAR: 0.00012,
  MEAN_MOTION_DOT: 0.0001,
  MEAN_MOTION_DDOT: 0,
};
const where = satelliteAt(iss, { latitude: 51.5, longitude: -0.13 }, Date.UTC(2026, 10, 3, 12));
console.log(where?.compass, where?.altitude.toFixed(0));
WSW -38

What it prints (run when this page was built)

View sourceEdit on GitHubMade from the source of @johnmorrisdotca/chikyu-earth 0.51.1.