A-train (satellite constellation)

As of 2018, the A-Train consists of five satellites and two no longer officially part of the constellation.

The A-train (from Afternoon Train) is a satellite constellation of five Earth observation satellites of varied nationality in sun-synchronous orbit at an altitude of 705 km (438 mi) above the Earth.[1]

The orbit, at an inclination of 98.14°, crosses the equator each day at around 1:30 pm solar time, giving the constellation its name (the "A" stands for "afternoon"[2]) and crosses the equator again on the night side of the Earth, at around 1:30 am.

They are spaced a few minutes apart from each other so their collective observations may be used to build high-definition three-dimensional images of the Earth's atmosphere and surface.

Satellites

Active

The train, as of April 2018,[3][4] consists of five active satellites:

  • OCO-2, lead spacecraft in formation, replaces the failed OCO and was launched for NASA on July 2, 2014.
  • GCOM-W1 "SHIZUKU", follows OCO-2 by 11 minutes, launched by JAXA on May 18, 2012.
  • Aqua, runs 4 minutes behind GCOM-W1, launched for NASA on May 4, 2002.
  • CALIPSO, a joint effort of CNES and NASA, follows CloudSat by no more than 15 seconds, launched on April 28, 2006.
  • Aura, a multi-national satellite, lags Aqua by 15 minutes, crossing the equator 8 minutes behind due to different orbital track to allow for synergy with Aqua, launched for NASA on July 15, 2004.

Past

  • PARASOL, launched by CNES on December 18, 2004 and moved to another (lower) orbit on December 2, 2009.[5]
  • CloudSat, launched with CALIPSO on April 28, 2006 and moved to another (lower) orbit on February 22, 2018.[4]

Failed

  • OCO,[6] destroyed by a launch vehicle failure on February 24, 2009,[7] and was replaced by OCO-2.
  • Glory,[8] failed during launch on a Taurus XL rocket on March 4, 2011, and would have flown between CALIPSO and Aura.

References

  1. ↑ «A-train Symposium October 2007: Constellation keeps its promises», CNESMAG, January 2008
  2. ↑ NASA, Introducing the A-Train, 10.26.10 (accessed April 30 2012)
  3. ↑ "Individual A-Train Missions". June 5, 2012. Retrieved 2013-11-15.
  4. 1 2 Greicius, Tony (2018-02-23). "CloudSat Exits the "A-Train"". NASA. Retrieved 2018-04-01.
  5. ↑ CNES News on Calipso
  6. ↑ OCO homepage
  7. ↑ Media Briefing Scheduled To Discuss Orbiting Carbon Observatory Mission
  8. ↑ Glory homepage Archived 2008-09-16 at the Wayback Machine.
  • NASA A-Train Portal
  • NASA satellite program impacted
  • NASA Program Page
  • Orbital Sciences Program Page
  • L'Ecuyer, T.S.; Jiang, J.H. (2010). "Touring the atmosphere aboard the A-Train". Physics Today. 63 (7): 36–41. Bibcode:2010PhT....63g..36L. doi:10.1063/1.3463626. Archived from the original on 2013-02-24.
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