API VERSION: 1.2
API SOURCE: NASA/JPL Horizons API

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 Revised: Apr 03, 2015           MESSENGER Spacecraft                      -236
                            http://messenger.jhuapl.edu/

 BACKGROUND:
  MESSENGER was launched from Cape Canaveral Air Force Station, Fla., on 
  August 3, 2004. It returned to Earth for a gravity boost 2005-Aug-2, 
  (2,347 kilometers over central Mongolia at 3:13 p.m. EDT), then flew past 
  Venus twice, on October 24, 2006 and June 2007. Mercury orbit insertion  
  occurred March 18, 2011.

  Three Mercury flybys, each followed about two months later by a course 
  correction maneuver, put MESSENGER in position to enter Mercury orbit in 
  March 2011. During the flybys - set for January 14, 2008 (19:05 UTC, 
  200.6 km altitude), October 2008, and September 29, 2009 (21:56 UTC, 228 km
  altitude) - MESSENGER will map nearly the entire planet in color, image 
  most of the areas unseen by Mariner 10, and measure the composition of the 
  surface, atmosphere and magnetosphere. 

  MESSENGER's 12-month orbit covers two Mercury solar days; one Mercury solar 
  day, from sunrise to sunrise, is equal to 176 Earth days. The first solar 
  day is focused on obtaining global map products from the different 
  instruments, and the second focuses on targeted science investigations.

 MESSENGER SPACECRAFT:
  http://messenger.jhuapl.edu/the_mission/spacecraft_design.html

 SPACECRAFT TRAJECTORY:
  A switch from DE405 to DE423 occurs at 2009-Dec-07 23:59:00 UTC

  CAUTION: Osculating elements (only) may not be suitable for high precision 
  applications like reduction of spacecraft measurements because Horizons uses
  mass parameters (GM) from DE431 to determine osculating elements. This issue
  does NOT affect Horizons vector or observer tables over the spacecraft 
  mission interval.

  Trajectory provided by JHU/APL on Apr 02, 2015:
  File/Model                            Start         Stop
  --------------------------------      -----------   -----------
  msgr_20040803_20150501_od423sc_0      2004 AUG 03   2015 May 01 
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