European Satellite ERS-2 Set to Reenter Orbit, Highlighting Hazards of Space Debris
In a stark reminder of the dangers posed by space debris, the European Space Agency’s (ESA) European Remote Sensing (ERS) 2 satellite is set to reenter Earth’s orbit after nearly two decades. The impending reentry of this defunct satellite serves as a wake-up call for space agencies worldwide, highlighting the urgent need to address the issue of orbital debris.
Expected to reenter on February 21, the ERS-2 satellite weighs a staggering 2,300 kilograms and was launched in 1995 with the purpose of providing Earth science data. Equipped with advanced instruments like a radar altimeter and synthetic aperture radar (SAR) mapper, the spacecraft played a crucial role in gathering valuable information about our planet. However, in 2011, the satellite was shut down due to a lack of propellant to perform a controlled reentry.
Mirko Albani, the heritage space program and missions manager for ESA’s Earth Observation program, revealed that some components of the ERS-2 satellite will survive reentry. This includes four fuel tanks and several internal panels. The largest single component expected to make it through reentry is the SAR antenna, weighing a substantial 52 kilograms. While the risk of falling debris causing harm to individuals is minimal, ESA has not provided specific details regarding the risks associated with this particular reentry. Albani did assure that none of the debris from ERS-2 contains toxic or radioactive materials.
When ESA made the decision to terminate ERS-2 operations in 2011, they utilized the remaining propellant to lower the spacecraft’s orbit from 785 to 573 kilometers. Additionally, they passivated onboard systems like batteries to prevent any explosion that could generate debris. Unfortunately, due to insufficient propellant, the spacecraft couldn’t descend any further. Tim Flohrer, the director of ESA’s Space Debris Office, explained that the spacecraft’s design limitations prevented it from operating below approximately 560 kilometers.
Although ERS-2 adhered to earlier debris mitigation guidelines, which required satellites to be deorbited within 25 years of the end of their operational lives, ESA published a new orbital debris mitigation policy in November. This policy aims to reduce the post-mission disposal timeframe from 25 to 5 years. Francesca Letizia, an ESA space debris mitigation and reentry safety engineer, described this policy as part of ESA’s “zero-debris vision.” The updated guidelines also mandate that spacecraft not classified as “low risk” must be prepared for removal through the addition of an interface that would allow for active debris removal missions.
However, the implementation of this new policy is still in its early stages. Letizia clarified that they do not expect to fully implement all the measures for zero-debris on missions currently being launched. Instead, they plan to gradually introduce these measures throughout the decade. She emphasized that this is just the beginning of a journey towards achieving zero-debris and that they will assess how well these measures work.
It is important to note that the new policy does not apply retroactively to spacecraft already in orbit. Albani confirmed that ESA will establish a space debris mitigation assessment board to review on a case-by-case basis how the rules should be applied to older missions. However, for future missions, the goal is to achieve zero-debris by 2030 onwards.
The new policy is based on the lessons learned from previous failed missions. ERS-1, a satellite similar to ERS-2, experienced a malfunction in orbit in 2000, leaving it stranded at an altitude of nearly 800 kilometers. Albani revealed that ERS-1 is likely to remain in orbit for at least 100 years. Another example is the Envisat satellite, a larger ESA Earth science mission that suffered an on-orbit malfunction in 2011. Weighing eight tons, Envisat is considered one of the most hazardous space debris objects apart from rocket bodies. It is also expected to remain in orbit for a century or more.
While technology has advanced significantly since the design of ERS-2 in the ’90s, Tim Flohrer acknowledged that the necessary technology was not available at the time. However, with the increasing number of satellites being launched into space, it is crucial to address the issue of space debris promptly and effectively.
The impending reentry of the ERS-2 satellite serves as a timely reminder of the hazards posed by existing objects in space. As space agencies work towards mitigating the growth of orbital debris, it is imperative to implement stringent policies and guidelines to ensure the safe disposal of satellites and prevent further cluttering of Earth’s orbit. The journey towards achieving zero-debris is just beginning, and it is essential for all stakeholders to collaborate and prioritize the sustainability of space activities for future generations.
