French
DeutschA-train (satellite constellation)
The A-train (from Afternoon Train) is a satellite constellation of four Earth observation satellites of varied nationality in Sun-synchronous orbit at an altitude that is slightly variable for each satellite.[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 Earth's atmosphere and surface.
Satellites
[edit]Active
[edit]
The train, as of January 2022[update],[3][4][5] consists of three 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.
- Aura, a multi-national satellite, lags OCO-2 by 19 minutes, launched for NASA on July 15, 2004.
Past
[edit]- PARASOL, launched by CNES on December 18, 2004 and moved to another (lower) orbit on December 2, 2009. PARASOL was deactivated in 2013[6]
- CloudSat, launched with CALIPSO on April 28, 2006 and moved to another (lower) orbit on February 22, 2018.[5] Now part of the C-train.
- CALIPSO, launched on April 28, 2006, is a joint effort of CNES and NASA. It follows CloudSat by no more than 8.5 seconds. CALIPSO was moved to CloudSat's new orbit in September 2018.[7] It was then part of the C-train with Cloudsat until it was officially decommissioned on August 1, 2023.
- Aqua, used to run 4 minutes behind GCOM-W1, launched for NASA on May 4, 2002. In January 2022, it descended from the A-Train to save fuel and now is in a free-drift mode, wherein its equatorial crossing time is slowly drifting to later times.
Failed
[edit]- OCO,[8] destroyed by a launch vehicle failure on February 24, 2009,[9] and was replaced by OCO-2.
- Glory,[10] failed during launch on a Taurus XL rocket on March 4, 2011, and would have flown between CALIPSO and Aura.
References
[edit]- ^ «A-train Symposium October 2007: Constellation keeps its promises», CNESMAG, January 2008
- ^ NASA, Introducing the A-Train, 10.26.10 (accessed April 30 2012)
- ^ Smith, Joseph M. (4 May 2022). "Aqua Turns 20".
- ^ "Individual A-Train Missions". June 5, 2012. Retrieved 2013-11-15.
- ^ a b Greicius, Tony (2018-02-23). "CloudSat Exits the "A-Train"". NASA. Retrieved 2018-04-01.
- ^ CNES News on Calipso
- ^ Sister Satellites, Briefly Separated, Working Together Again
- ^ "OCO homepage". Archived from the original on 2018-09-09. Retrieved 2008-02-10.
- ^ Media Briefing Scheduled To Discuss Orbiting Carbon Observatory Mission
- ^ Glory homepage Archived 2008-09-16 at the Wayback Machine
External links
[edit]- 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.