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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

standardMagnitudefunction

The standard magnitude of a satellite worked out from its size: the brightness, from 1000 km away with half of it lit by the Sun, of a sphere with the same average cross-section that reflects albedo of the light that falls on it evenly in every direction. It is the model of this package's own, from the Sun's magnitude, and not a measurement: a real satellite is not a sphere (a station is mostly solar panels, which can flash when they catch the Sun), and its albedo is a guess, so the answer can be a magnitude or two off.

Import it

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

Definition

function standardMagnitude(crossSectionM2: number, albedo?: number): number

Parameters

NameTypeDescription
crossSectionM2number

The average area the satellite shows to someone looking at it, in square metres (for a shape with no hollows, a quarter of its whole surface).

albedo (optional)number

The share of the light that falls on it that it sends back, 0 to 1 (0.2 by default, about what dull metal and solar cells do).

Returns

number

The standard magnitude: smaller is brighter.

Examples

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

// a 10 square metre satellite
console.log(standardMagnitude(10).toFixed(1));
5.0

What it prints (run when this page was built)

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