Wednesday, June 17, 2015

Tropical Rainfall Measuring Mission Spacecraft Falls to Earth

Visualization of the TRMM satellite in space over a tropical cyclone. Credit: NASA

A satellite, built jointly by NASA and the Japan Aerospace Exploration Agency (JAXA), to measure the amount of rainfall on Earth has ended its long-lasting mission in a fiery demise. According to the U.S. Strategic Command’s Joint Functional Component Command for Space, the Tropical Rainfall Measuring Mission (TRMM) spacecraft re-entered the Earth’s atmosphere on June 15, 2015, at 11:55 p.m. EDT, over the South Indian Ocean.

Most of the spacecraft burned up in the atmosphere during its uncontrolled re-entry. NASA estimates that 12 components of the TRMM spacecraft could survive reentry. These objects include two propellant tanks, a nitrogen pressurant tank, four Reaction Wheel Assembly (RWA) flywheels, two Solar Array Drive Assembly (SADA) actuators, a High Gain Antenna (HGA) boom bracket, a HGA antenna bracket, and a TRMM Microwave Imager (TMI) Bearing and Power Transfer Assembly (BAPTA) housing and shaft. Surviving objects are metallic (titanium alloys), and are not toxic.

“Any sightings of suspected TRMM debris should be reported to local authorities,” NASA said in a statement. “Debris could have sharp edges and should not be touched or handled, in the unlikely event someone were to find TRMM fragments.”

NASA becalms that the chance of one of these pieces striking someone is approximately 1 in 4,200, which is a relatively low chance. Total mass of objects expected to survive is estimated to be 247 lbs. (112 kg).

NASA, conferring with the U.S. Government and some foreign space agencies even limits the risk from reentering space objects to less than 1 in 10,000.

TRMM is a moderate-sized space object. Uncontrolled reentries of objects more massive than TRMM are not frequent, but neither are they unusual. Since the beginning of the space age, there has been no confirmed report of an injury resulting from reentering space objects.

The U.S. Space Surveillance Network, operated by the Defense Department's Joint Space Operations Center (JSpOC), had been closely monitoring TRMM’s descent since the mission was ended in April.

TRMM was a research satellite designed to improve our understanding of the distribution and variability of precipitation within the tropics as part of the water cycle in the current climate system.

The satellite was launched H-II rocket from Japan's Tanegashima spaceport in 1997 for a planned three-year mission, but managed to be fully operational for 17 years. In 2001, the mission was given extensions until 2005, when residual propellant would reach the minimum required for controlled reentry from 400 km altitude. 

After considerable analysis and review, TRMM was relieved of the controlled reentry requirement to prolong its mission until the Global Precipitation Measurement (GPM) spacecraft could be launched (then predicted to be 2010, actually launched in February 2014).

NASA ceased station-keeping maneuvers of TRMM near the end of the spacecraft’s fuel supply in July 2014. The instruments on the satellite were finally turned off on Apr. 8, 2015 and the spacecraft will slowly descend from its orbit.

“The TRMM dataset will continue to be used for research to improve global weather and climate models. The data meet exacting standards for data preservation, so that future scientists will be able to use the data. The dataset also is being processed to make up one continuous climate data record with the follow-on GPM, also a joint project between the U.S. and Japan,” NASA said.

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