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TRMM Satellite Operating Altitude Change

The average operating altitude for TRMM was changed from 350 to 403 km during the period of August 7-24, 2001. This orbit boost maneuver extended the mission life significantly. All post-boost data products had been released by the TRMM Science Project, as of early December 2001. All TRMM data products (post- and pre-boost) are available via the TRMM data search-and-order system at The time period before August 7, 2001 is referred to as pre-boost, and the time period after August 24, 2001 is referred to as post-boost.

The characteristics of the three rain instruments for pre- and post-boost are shown in following table:

Characteristics of TRMM Instruments
  Swath Width (km) Ground Resolution (km)
Pre-boost Post-boost Pre-boost Post-boost
VIRS 720 833 2.2 2.4
TMI 760 878   4.4*   5.1*
PR 215 247 4.3 5.0
* Ground resolutions of TMI are those at 85.5 GHz (highest resolution).

The pre- and post-boost characteristics of TRMM data are different; their details are listed in the Data Characteristics table for each orbital product. Some caveats associated with post-boost TRMM Precipitation Radar (PR) products have been released by the PR algorithm scientists and are available at

For TRMM version 5 products, the post-boost filenames all have a "5A" in the product version part of the name, compared with a "5" in pre-boost filenames. For version 6, the filenames have no differences for pre-boost and post-boost.
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Last updated: Sep 18, 2009 10:32 AM ET