近地点




近地点（Perigee）是一个天文学上的用语，用来指地球卫星在绕地飞行时与地球最近的距离。


地球卫星包括月球以及为数众多的人造卫星。根据天文物理学和数学原理，卫星在绕主星運行时的轨道是一个椭圆。


地球位于椭圆的两个焦点位置中的一个。以椭圆的两个焦点为横轴画一条直线，其与卫星轨道产生两个交点，其中距离地球最近的称为近地点，距离地球最远的称为远地点；通常在近地點時，衛星運行的角速度最快。



相關條目



  • 拱點

  • 橢圓軌道








-

Popular posts from this blog

Y

Image
This article is about the letter of the alphabet. For other uses, see Y (disambiguation). See also: Wye (disambiguation) Y Y y (See below) Usage Writing system Latin script Type Alphabetic and Logographic Language of origin Latin language Phonetic usage [ y ] [ ɨ ] [ j ] [ iː ] [ ɪ ] [ ɘ ] [ ə ] [ ɯ ] [ ɛː ] [ j ] [ ɥ ] [ ɣ̟ ] / w aɪ / / aɪ / Unicode value U+0059, U+0079 Alphabetical position 25 History Development Υ υ 𐌖 Y y Time period 54 to present Descendants  • U  • V  • W  • Ỿ  • ¥  • Ꮙ  • Ꮍ  • Ꭹ Sisters F Ѵ У Ў Ұ Ү ו و ܘ וּ וֹ ࠅ 𐎆 𐡅 ወ વ ૂ ુ उ Variations (See below) Other Other letters commonly used with y(x), ly, ny This article contains IPA phonetic symbols. Without proper rendering support, you may see question marks, boxes, or other symbols instead of Unicode characters. For an introductory guide on IPA symbols, see Help:IPA. ISO basic Latin alphabet Aa Bb Cc D...
Read more

Mount Tamalpais

Image
Mount Tamalpais Mount Tamalpais, viewed from the south Highest point Elevation 2,571 ft (784 m)   NAVD 88 [1] Prominence 2,456 ft (749 m)  [1] Listing California county high points 55th Coordinates 37°55′45″N 122°34′40″W  /  37.929088°N 122.577829°W  / 37.929088; -122.577829 Coordinates: 37°55′45″N 122°34′40″W  /  37.929088°N 122.577829°W  / 37.929088; -122.577829   [1] Geography Mount Tamalpais Marin County, California, U.S. Show map of California Mount Tamalpais Mount Tamalpais (the US) Show map of the US Parent range California Coast Ranges Topo map USGS San Rafael Geology Mountain type Sedimentary Climbing First ascent 1830s by Jacob P. Leese (first recorded ascent) [2] Easiest route Railroad Grade fire trail Mount Tamalpais ( / t æ m əl ˈ p aɪ . ɪ s / ; TAM -əl- PY -iss ; Coast Miwok: /t̪ɑmɑlˈpɑis̺/ , known locally as Mount Tam ) is a peak in Marin County, California, United State...
Read more

Indian Forest Service

Image
Indian Forest Service Service Overview Preceding service Imperial Forest Service (1864 to 1935) Year of Constitution 1966 Country India Staff College Indira Gandhi National Forest Academy (IGNFA), Dehradun, Uttarakhand Cadre Controlling Authority Ministry of Environment, Forests and Climate Change Legal personality Governmental: Government service General nature Administration of Forest and Wildlife resources Cadre strength 3131 (2182 Direct Recruits and 949 Promotion Posts) Website ifs.nic.in Service Chief Director General of Forests Siddhanth Das, IFS (1982 Batch, Odisha Cadre) [1] Head of the All India Civil Services Cabinet Secretary Pradeep Kumar Sinha, IAS Indian Forest Service (भारतीय वन सेवा) [2] is one of the three All India Services of the Government of India. The other two All India Services being the Indian Administrative Service (IAS) and the Indian Police Service (IPS). [3] [4] [5] It was constituted in...
Read more