Leonard David's INSIDE OUTER SPACE

Incoming: Tropical Rainfall Measuring Mission (TRMM) spacecraft.
Credit: NASA/GSFC

The Tropical Rainfall Measuring Mission (TRMM) spacecraft is nearing its uncontrolled re-entry, diving into the atmosphere in a destructive plunge next week.TRMM was a joint mission of NASA and the Japan Aerospace Exploration Agency (JAXA).

NASA/Goddard Space Flight Center (GSFC) provided the satellite, four passive sensors, and mission operations.

Roughly 12 pieces of debris from the nearly 3-ton (2,630 kilograms) TRMM spacecraft are expected to survive the heated re-entry and reach the surface of the Earth.

Pre-launch TRMM spacecraft assembly.
Credit: NASA/GSFC

Odds are…

NASA’s Orbital Debris Program Office estimates about a dozen components of the TRMM spacecraft could survive reentry. The chance that one of these pieces would strike someone is approximately 1 in 4,200, which is a relatively low chance.

As its name suggests, TRMM’s orbit brings it over the tropics between 35 degrees North latitude and 35 degrees South latitude.

The scientific satellite was launched on November 27, 1997, from Tanegashima, Japan. TRMM produced over 17 years of scientific data.

An expected re-entry date is June 17.

Credit: NASA/GSFC

Leftovers

The “potentially hazardous objects” due to TRMM’s fiery fall that are expected to survive include:

Two propellant tanks, a nitrogen pressurant tank, four Reaction Wheel Assembly flywheels, two Solar Array Drive Assembly actuators, a High Gain Antenna (HGA) boom bracket, and a TRMM Microwave Imager Bearing and Power Transfer Assembly housing and shaft.

The surviving objects are metallic (titanium alloys), nothing toxic. Total mass of objects expected to survive equates to 247 pounds (112 kilograms) – roughly four percent of the dry mass of TRMM.

Who should be called if someone suspects they found TRMM leftovers?

NASA advises that they should call their local authorities.

“The pieces of TRMM expected to survive re-entry are made of titanium or stainless steel. Although these materials are not toxic, they could have sharp edges and should not be touched or handled by private individuals,” according to a NASA Frequently Asked Questions list.

Credit: NASA

Estimated risk

According to the NASA Orbital Debris Program Office the estimated human injury risk (updated in 2015) is roughly one in 4,200. One in 4,200 means that if the same reentry were to occur repeatedly 4,200 times, the expectation is that that only one person on Earth would be harmed.

Due to TRMM’s orbit, the chances of spacecraft debris harming human life or property is slim, although the exact location of the re-entry cannot be predicted.

The U.S. Department of Defense and NASA are monitoring the decay and re-entry of TRMM.

Credit: NASA

The official source of reentry predictions for uncontrolled space objects is USSTRATCOM’s Joint Space Operations Center (JSpOC).