A-train
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A-train (satellite constellation)
For the subway, see A (New York City Subway service). For other uses, see A Train (disambiguation).
The A-train (from Afternoon Train) is a satellite constellation of four French and American Earth observation satellites in sun-synchronous orbit at an altitude of 690 kilometers 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.
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Contents
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Satellites
Active
The train currently consists of four active satellites:
- Aqua, lead spacecraft in formation, launched by NASA on May 4, 2002
- CloudSat, a cooperative effort between NASA and the Canadian Space Agency, runs 2 minutes and 30 seconds behind Aqua, launched with CALIPSO on April 28, 2006
- 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 by NASA on July 15, 2004
Past
- PARASOL (Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar'),[3] launched by CNES on December 18, 2004; moved to other (lower) orbit on 2 December 2009[4]
Failed
- OCO,[5] destroyed by a launch vehicle failure on February 24, 2009,[6] and would have preceded Aqua by 15 minutes
- Glory,[7] failed during launch on a Taurus XL rocket on March 4, 2011, and would have flown between CALIPSO and Aura
References
- ^ «A-train Symposium October 2007: Constellation keeps its promises», CNESMAG, January 2008
- ^ NASA, Introducing the A-Train, 10.26.10 (accessed April 30 2012)
- ^ PARASOL page (accessed 30 April 2012)
- ^ CNES News on Calipso
- ^ OCO homepage
- ^ Media Briefing Scheduled To Discuss Orbiting Carbon Observatory Mission
- ^ Glory homepage
External links
- 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. http://ptonline.aip.org/journals/doc/PHTOAD-ft/vol_63/iss_7/36_1.shtml.
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