WASHINGTON — The impending reentry of a defunct European satellite serves as a reminder of the hazards posed by existing objects even as agencies work to mitigate the growth of orbital debris.
The European Space Agency’s European Remote Sensing (ERS) 2 satellite is expected to reenter on Feb. 21 after nearly two decades in orbit. The latest update by ESA Feb. 20 predicted the satellite will reenter at 11:32 a.m. Eastern, with a margin of error of plus or minus 4.61 hours.
The spacecraft, weighing nearly 2,300 kilograms, launched in 1995 to provide Earth science data with a set of instruments that included a radar altimeter and synthetic aperture radar (SAR) mapper. The spacecraft was shut down in 2011 but lacked the propellant to perform a controlled reentry.
Some components of ERS-2 will survive reentry, said Mirko Albani, heritage space program and missions manager for ESA’s Earth Observation program, at a Feb. 13 briefing. That includes four fuel tanks and some internal panels. The largest single component expected to survive reentry is the SAR antenna, weighing 52 kilograms.
The risk of falling debris injuring someone is extremely low, although ESA did not quantify the risks from this specific reentry. Albani added that none of the debris from ERS-2 contains toxic or radioactive materials.
When ESA decided to end ERS-2 operations in 2011, it used the remaining propellant to lower the spacecraft’s orbit from 785 to 573 kilometers, and then passivated onboard systems like batteries to prevent a debris-generating explosion. However, the spacecraft lacked the propellant to go lower, and constraints in the spacecraft’s design would have prevented it from operating below about 560 kilometers, said Tim Flohrer, director of ESA’s Space Debris Office.
ERS-2 complies with earlier debris mitigation guidelines, which call for deorbiting satellites within 25 years of the end of their lives. However, ESA published a new orbital debris…
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