| 词条 | Ekspress AM4 |
| 释义 |
}}{{Infobox spaceflight | name = Ekspress AM4 | image = | image_caption = | mission_type = Communications | operator = FGUP | COSPAR_ID = 2011-045A | SATCAT = 37798 | mission_duration = 15 years planned Launch failure | spacecraft_bus = EADS Astrium | manufacturer = Eurostar-3000 | launch_mass = {{convert|5775|kg|lb}} | power = 14 kilowatts | launch_date = {{start-date|17 August 2011, 21:25:01|timezone=yes}} UTC[1] | launch_rocket = Proton-M/Briz-M | launch_site = Baikonur 200/39 | launch_contractor = Khrunichev | disposal_type = Deorbited | decay_date = {{end-date|25 March 2012}} | orbit_epoch = 25 August 2011[2] | orbit_reference = Geocentric | orbit_regime = Medium Earth Geostationary planned | orbit_periapsis = {{convert|695|km|mi}} | orbit_apoapsis = {{convert|20239|km|mi}} | orbit_inclination = 51.1 degrees | orbit_period = 6.04 hours | orbit_longitude = 80° east planned | apsis = gee | trans_band = | trans_frequency = | trans_bandwidth = | trans_capacity = | trans_coverage = | trans_TWTA = | trans_EIRP = | trans_HPBW = }}Ekspress AM4 was a communications satellite placed into the wrong orbit from a faulty Briz-M rocket stage. This satellite was to be part of the Ekspress series of geostationary communications satellites owned by Russian State Company for Satellite Communications. The satellite was de-orbited on 28 March 2012 into the Pacific Ocean, in spite of efforts of it being used for Antarctic broadband purposes.[3] Although there have been several satellites de-orbited over the years, Ekspress AM4 would have been able to provide broadband services to the Antarctic for the first time.[4] LaunchThe Ekspress AM4 satellite was launched on 18 August 2011 on a Russian Proton rocket from Kazakhstan, which included a Briz-M stage.[5] It was just after launch that the Briz-M stage did not separate from the Ekspress satellite, causing it to fall into the wrong orbit.[6] SpacecraftThe total mass of the Ekspress AM4 satellite was 5,800 kg, and the spacecraft had 64 transponders. The onboard antennas were capable of broadcasting in the C, Ku, L, and Ka bands. The satellite's orbit was measured at 1,007 by 20,317 km altitude, with an inclination orbit of 51.3 degrees. Though the satellite was placed in the wrong orbit, there was no damage to the satellite, meaning that it became the subject of numerous reuse proposals. Reuse proposalsOne of the most notable{{citation needed|date=April 2012}} reuse proposals came from a company called Polar Broadband Systems, which was established in December 2011. Its objectives were to submit proposals for the reuse of semi-retired and retired satellites for use with communications over the Antarctic. The company notes that it would not have been feasible to build a dedicated satellite for the region as the population would not justify the expense, however Ekspress AM4 would suffice as it could have been maneuvered into the required orbit. There was enough fuel on board for it to be operational for ten years, with giving the Antarctic region 16 hours of broadband access a day.[7] DeorbitDennis Pivnyuk, chief financial officer of the Russian Satellite Communications Co, informed on 15 March 2012 that the satellite would be decommissioned and deorbited. He stated that the descent phase would start on 20 March, with the spacecraft reentering over the Pacific Ocean around 26 March. The spacecraft was destroyed during reentry on 28 March.[8] References1. ^{{cite web|url=http://planet4589.org/space/log/launchlog.txt|title=Launch Log|first=Jonathan|last=McDowell|work=Jonathan's Space Page|accessdate=30 October 2013}} 2. ^{{cite web|url=http://planet4589.org/space/log/satcat.txt|title=Satellite Catalog|first=Jonathan|last=McDowell|work=Jonathan's Space Page|accessdate=30 October 2013}} 3. ^[https://archive.is/20120720054857/http://news.sciencemag.org/scienceinsider/2012/03/second-life-for-failed-russian-s.html?ref=em "Second Life for Failed Russian Satellite."] Retrieved 1 April 2012 4. ^"Fiery Death of Wayward Russian Satellite Mourned by Company." Retrieved 1 April 2012 5. ^{{cite news|first1=Tom|last1=Parfitt|accessdate=2018-12-31|title=Russian satellite missing within hours of takeoff|url=https://www.theguardian.com/world/2011/aug/18/russian-satellite-goes-missing|newspaper=The Guardian|date=18 August 2011|issn=0261-3077|via=www.theguardian.com}} 6. ^"Repurposing Express-AM4: Mission Possible: Recycling Space Junk into Antarctic Science Treasure." Retrieved 1 April 2012 7. ^"Lost Russian Communications Satellite Found in Wrong Orbit." Retrieved 1 April 2012 8. ^"Dead Russian Satellite to Fall From Space." {{webarchive|url=https://archive.is/20130223130916/http://www.uk.amsat.org/5893 |date=23 February 2013 }} Retrieved 1 April 2012 External links{{Portal|Spaceflight}}
6 : Ekspress satellites|Satellite launch failures|Spacecraft launched in 2011|Spacecraft which reentered in 2012|2011 in Russia|Satellites using the Eurostar bus |
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