静止衛星は赤道の上でしか止まって見えない/en

#0022 Science & nature

Fact rank

S

Raised from the expected A to S: primary sources (ESA, the maker of Michibiki) state the altitude and the figure eight, and the altitude agrees with a calculation

Wow rank

B

Geostationary satellites are well known, but the figure eight of a tilted orbit is a small surprise

Usefulness

—

A fact worth knowing for its own sake

Verification: Supported by evidence

Posted by: — ・ Verified: 2026-10-29 ・ Method: AI + human ・ On Wikipedia?: Already on Wikipedia

AI verification reports the evidence it found; it does not guarantee that a claim is true.

A geostationary satellite appears fixed in the sky from the ground. If the orbit is tilted from the equator, the satellite traces a figure eight in the sky even with the same period (Japan's Michibiki quasi-zenith satellites use this kind of orbit).

Why

It circles 35,786 km above the equator with the same period as the Earth's rotation.

Evidence

Primary ESA, "Types of orbits". GEO satellites fly above the equator at an altitude of 35,786 km, keeping pace with Earth's spin, and appear stationary over one spot. Calculating from the period (one sidereal day) also gives 35,786 km (checked by calculation) link

Secondary Explainer by the Calgary Centre of the Royal Astronomical Society of Canada. A satellite in an inclined geosynchronous orbit appears to trace a more or less distorted figure eight in the sky link

Primary Explanation by Mitsubishi Electric, which built Michibiki. Michibiki's orbit traces a figure eight, passing over the Japanese islands in the north and Australia in the south link

Notes and limits

Michibiki's figure eight is lopsided because its orbit is tilted about 40 degrees and also made elliptical. With a small tilt the figure eight becomes long and narrow. Geostationary satellites and the figure-eight motion are in the English Wikipedia article "Geosynchronous orbit", so the text is kept short.

Derivations

Derived from: 体重計の数字は緯度が高いほど大きく出る

Derived facts: —