Menu
Home
People
Places
Arts
History
Plants & Animals
Science
Life & Culture
Technology
Reference.org
Parking orbit
open-in-new
<h2 id="reasons-for-use">Reasons for use</h2> <h3>Geostationary spacecraft</h3> <p><a href="/facts/Geostationary_orbit/VBq1v5Kr">Geostationary</a> spacecraft require an orbit in the plane of the equator. Getting there requires a <a href="/facts/Geostationary_transfer_orbit/1WwL0SPz">geostationary transfer orbit</a> with an apogee directly above the equator. Unless the launch site itself is quite close to the equator, it requires an impractically large amount of fuel to launch a spacecraft directly into such an orbit. Instead, the craft is placed with an upper stage in an inclined parking orbit. When the craft crosses the equator, the upper stage is fired to raise the spacecraft's <a href="/facts/Apogee/VaL6ow9w">apogee</a> to geostationary altitude (and often reduce the inclination of the transfer orbit, as well). Finally, a <a href="/facts/Circular_orbit/sSFMzmBv">circularization</a> burn is required to raise the <a href="/facts/Perigee/VaL6ow9w">perigee</a> to the same altitude and remove any remaining inclination.<a class="footnote-ref" id="fnref:1" href="#fn:1"><sup>1</sup></a> </p> <h3>Translunar or interplanetary spacecraft</h3> <p>In order to reach the Moon or a planet at a desired time, the spacecraft must be launched within a limited range of times known as a <a href="/facts/Launch_window/h2P1T5n0">launch window</a>. Using a preliminary parking orbit before final injection can widen this window from seconds or minutes, to several hours.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a><a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> For the <a href="/facts/Apollo_program/IC1Ek1Ao">Apollo program</a>'s crewed lunar missions, a parking orbit allowed time for spacecraft checkout while still close to home, before committing to the lunar trip.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> </p> <h2 id="design-challenges">Design challenges</h2> <p>The use of a parking orbit can lead to a number of technical challenges. For example, during the development <a href="/facts/Centaur_(rocket_stage)/ryg96uIF">Centaur</a> upper stage, the following problems were noted and had to be addressed:<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> </p> <ul><li>The injection burn occurs under <a href="/facts/Weightlessness/GrhveURG">zero g</a> conditions.</li> <li>If the same upper stage which performs the parking orbit injection is used for the final injection burn, a restartable <a href="/facts/Liquid-propellant_rocket/TAonrVDn">liquid-propellant rocket</a> engine is required.</li> <li>During the parking orbit coast, the propellants will drift away from the bottom of the tank and the pump inlets. This must be dealt with through the use of tank diaphragms, or <a href="/facts/Ullage_motor/JMocbdlB">ullage rockets</a> to settle the propellant back to the bottom of the tank.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a></li> <li>A <a href="/facts/Reaction_control_system/YfqBrd7h">reaction control system</a> is needed to orient the stage properly for the final burn, and perhaps to establish a suitable thermal orientation during coast.</li> <li><a href="/facts/Cryogenics/cw7dHAkp">Cryogenic</a> propellants must be stored in well-insulated tanks, to prevent excessive boiloff during coast.</li> <li>Battery life and other consumables must be sufficient for the duration of the parking coast and final injection.</li></ul> <p>The Centaur and <a href="/facts/RM-81_Agena/mRvYKtC1">Agena</a> families of upper stages were <a href="/facts/Centaur_(rocket_stage)/ryg96uIF">designed for restarts</a> and have <a href="/facts/Atlas_V/5SNgegyt">often been used in missions using parking orbits</a>. The last Agena flew in 1987, but Centaur is still in production. The <a href="/facts/Briz_(rocket_stage)/nPncWv0Q">Briz-M</a> is also capable of coasts and restarts, and <a href="/facts/Briz_(rocket_stage)/nPncWv0Q">often performs the same role</a> for Russian rockets.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> </p> <h2 id="examples">Examples</h2> <ul><li>The Apollo program used parking orbits, for all the reasons mentioned above except those that pertain to geostationary orbits.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a><a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a></li> <li>When the <a href="/facts/Space_Shuttle_orbiter/pD50Txk9">Space Shuttle orbiter</a> launched interplanetary probes such as <a href="/facts/Galileo_(spacecraft)/H57agAgz">Galileo</a>, it used a parking orbit to deliver the probe to the right injection spot.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a></li> <li>The <a href="/facts/Ariane_5/H78wlLG4">Ariane 5</a> does not usually use parking orbits.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> This simplifies the launcher since multiple restart is not needed, and the penalty is small for their typical <a href="/facts/Geostationary_transfer_orbit/1WwL0SPz">GTO</a> mission, as their launch site is close to the equator. A less commonly used second stage, the <a href="/facts/Ariane_5/H78wlLG4">Ariane-5ES</a> has multiple restart capability, and has been used for missions such as the <a href="/facts/Automated_Transfer_Vehicle/sHdKC0wv">Automated Transfer Vehicle</a> (ATV) that use parking orbits.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> The <a href="/facts/Ariane_6/4JJaWjfb">Ariane 6</a> upper stage supports multiple restarts and can be used with missions that require parking orbits.</li> <li>In a literal example of a parking orbit, the <a href="/facts/Automated_Transfer_Vehicle/sHdKC0wv">Automated Transfer Vehicle</a> could park for several months in orbit while waiting to rendezvous with the <a href="/facts/International_Space_Station/VNPUBz9m">International Space Station</a>. For safety reasons, the ATV could not approach the station while a Space Shuttle was docked or when a <a href="/facts/Soyuz_(spacecraft)/meooRg7U">Soyuz</a> or <a href="/facts/Progress_spacecraft/l9GvvKLs">Progress</a> was maneuvering to dock or depart.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Charles D. Brown (1998). Spacecraft Mission Design. AIAA. p. 83. ISBN 978-1-60086-115-4. <a href="978-1-60086-115-4" target="_blank">978-1-60086-115-4</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Hall, R. Cargill (1977). LUNAR IMPACT - A History of Project Ranger. NASA History Series (Technical report). National Aeronautics and Space Administration. NASA SP-4210. Retrieved 2011-11-11. <a href="https://history.nasa.gov/SP-4210/pages/TOC.htm" target="_blank">https://history.nasa.gov/SP-4210/pages/TOC.htm</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Cortright, E. M. (January 1975). "Apollo Expeditions to the Moon". Chapter 3.4 <a href="https://history.nasa.gov/SP-350/toc.html" target="_blank">https://history.nasa.gov/SP-350/toc.html</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Cortright, E. M. (January 1975). "Apollo Expeditions to the Moon". Chapter 3.4 <a href="https://history.nasa.gov/SP-350/toc.html" target="_blank">https://history.nasa.gov/SP-350/toc.html</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>"Taming liquid hydrogen: the Centaur upper stage rocket 1958-2002" (PDF). NASA. <a href="https://ntrs.nasa.gov/api/citations/20050070711/downloads/20050070711.pdf" target="_blank">https://ntrs.nasa.gov/api/citations/20050070711/downloads/20050070711.pdf</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Krivetsky, A.; Bauer, W.H.; Loucks, H.L.; Padlog, J. & Robinson, J.V. (1962). Research on Zero-Gravity Expulsion Techniques (PDF) (Technical report). Defense Technical Information Center. Archived (PDF) from the original on July 18, 2021. <a href="https://apps.dtic.mil/sti/pdfs/AD0274044.pdf" target="_blank">https://apps.dtic.mil/sti/pdfs/AD0274044.pdf</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>"Briz-M: Russia's workhorse space tug". <a href="http://www.russianspaceweb.com/briz-m.html" target="_blank">http://www.russianspaceweb.com/briz-m.html</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>"Apollo lunar landing launch window: The controlling factors and constraints". NASA. <a href="https://history.nasa.gov/afj/launchwindow/lw1.html" target="_blank">https://history.nasa.gov/afj/launchwindow/lw1.html</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>"Apollo Flight Journal - Apollo 8, Day 1: Earth Orbit and Translunar Injection". NASA. Archived from the original on 2008-02-18. <a href="https://web.archive.org/web/20080218181006/https://history.nasa.gov/ap08fj/02earth_orbit_tli.htm" target="_blank">https://web.archive.org/web/20080218181006/https://history.nasa.gov/ap08fj/02earth_orbit_tli.htm</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>d'Amario, Louisa.; Bright, Larrye.; Wolf, Arona. (1992). "Galileo trajectory design". Space Science Reviews. 60 (1–4): 23. Bibcode:1992SSRv...60...23D. doi:10.1007/BF00216849. S2CID 122388506. <a href="https://link.springer.com/article/10.1007/BF00216849" target="_blank">https://link.springer.com/article/10.1007/BF00216849</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Chris Gebhardt (Feb 18, 2020). "Ariane 5 lifts Japanese, South Korean satellites to Geostationary Transfer Orbit". NasaSpaceFlight.com. <a href="https://www.nasaspaceflight.com/2020/02/ariane-5-japanese-south-korean-satellites-gto/" target="_blank">https://www.nasaspaceflight.com/2020/02/ariane-5-japanese-south-korean-satellites-gto/</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>"Ariane-5ES". <a href="https://space.skyrocket.de/doc_lau_det/ariane-5es.htm" target="_blank">https://space.skyrocket.de/doc_lau_det/ariane-5es.htm</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>Stephen Clark. "Maiden launch of Europe's resupply ship gets new date". Spaceflight Now. <a href="http://www.spaceflightnow.com/news/n0802/10atv1/" target="_blank">http://www.spaceflightnow.com/news/n0802/10atv1/</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> </ol>