静止衛星は赤道の上でしか止まって見えない/enのソースを表示

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{{豆知識
|番号=0022
|投稿者=まめち編集部
|本文=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).
|なぜ=It circles 35,786 km above the equator with the same period as the Earth's rotation.
|ジャンル=科学・自然
|ファクト度=S
|ファクト度の根拠=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
|ネタ度=B
|ネタ度の根拠=Geostationary satellites are well known, but the figure eight of a tilted orbit is a small surprise
|便利度=該当なし
|便利度の根拠=A fact worth knowing for its own sake
|検証ステータス=根拠あり
|根拠1URL=https://www.esa.int/Enabling_Support/Space_Transportation/Types_of_orbits
|根拠1要約=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)
|根拠1格付け=一次
|根拠2URL=https://calgary.rasc.ca/geo_orbits.htm
|根拠2要約=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
|根拠2格付け=二次
|根拠3URL=https://www.mitsubishielectric.co.jp/society/space/qzss/
|根拠3要約=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
|根拠3格付け=一次
|補足=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.
|検証日時=2026-10-29
|検証方式=AI＋人
|本家既出チェック=本家に既出
|本家の該当ページ=https://en.wikipedia.org/wiki/Geosynchronous_orbit
|派生元=体重計の数字は緯度が高いほど大きく出る
}}