October 4, 2022 will be a significant day for humanity as it celebrates the 65th anniversary the Space Age began. It all began in 1957 when the Soviet satellite Sputnik-1 was launched into orbit. This was the first artificial satellite to be sent to orbit. About 900 satellites have been launched to orbit since then. 8,900 satellitesMore than 40 countries have launched spacecraft from their orbits. There are growing concerns about space debris and its potential hazard to future constellations, spacecraft and habitats in Low Earth Orbit (LEO).
This has led to many proposed solutions for cleaning up “space junk,” as well as satellite designs that would allow them to deorbit and burn up. There are still questions about the sustainability of a planet surrounded with mega-constellations. A Recent studyJames A. Blake, a University of Warwick research fellow, studied the evolution of LEO’s debris environment and assessed whether future space operations could be sustained.
Blake was a Ph.D. candidate and focused on the imaging, tracking, and monitoring of space debris at geosynchronous Earth orbits (GEOs), which are located around 36,000 km (22.370 miles) above the Equator. Satellites in this region of space follow the Earth’s rotation and have the same orbital period. This makes it highly desirable for telecommunications. This region has limited space, which could cause serious problems with overcrowding or debris.
In particular, Blake’s main body of work was a survey of faint geosynchronous debris carried out using the Isaac Newton TelescopeAt the Roque de los Muchachos ObservatoryLa Palma. His work was summarized in a study titled “DebrisWatch I: A survey of faint geosynchronous debris,” which appeared in January 2021 in the journal Advances in Space Research. This study shows that GEO’s debris population is not well-controlled, but is a growing problem.
A Historical Problem
According to the ESA’s Space Debris Office(SDO), approximately 12,720 satellites were launched to Earth orbit in 2022 since Sputnik-1. An estimated 7,810 satellites are still in orbit, with approximately 5,200 remaining operational. All in all, approximately 29860 debris objects are in LEO and are regularly tracked by Earth based observation networks.
Previously, it was thought that the population of debris in GEO would be fairly negligible because of the strict spacing regulations that are meant to ensure satellites don’t collide. However, the recent apparent destruction of communications satellites – AMC-9, owned by Luxembourg-based telecom SES S.A., and Lockheed Martin’s Telkom-1 – has provided clear evidence that a debris field exists in GEO. This has implications for future constellations in GEO.
Blake stated via email that it is vital to chart the evolution of space debris in order to mitigate future hazards.
“Sputnik 1 was the first of thousands of satellites to be launched into Earth orbit over the past six decades, and that number continues to grow rapidly. Some have re-entered Earth’s atmosphere while others are still in orbit and pose a threat to the satellites we depend on.
“Over time, the orbital debris population has grown due to accidental explosions and collisions, alongside intentional anti-satellite tests. The vast majority of debris produced by these events remains invisible to us, too small to be detected by our current generation of surveillance networks, yet still holding the potential to severely damage spacecraft.”
According to Blake, there’s a lesson to be learned from humanity’s exploitation of the near-Earth environment. In keeping with the interconnected nature of space exploration and life on Earth, this same lesson applies equally to humanity’s activities on the ground. In short, humanity needs to act sustainably so that future generations can enjoy and benefit from the freedoms we’ve enjoyed since the dawn of the Space Age. Blake says collision avoidance is essential to achieve this goal.
“Effective collision avoidance requires timely and accurate information. As satellite and debris catalogs grow ever larger, surveillance networks are being tasked with monitoring more and more objects to provide sufficient warning to operators, who can then opt to maneuver their craft out of harm’s way.”
Monitoring and Mitigating
The current strategy for preventing an uncontrollable debris environment in orbit involves a two-pronged approach: tracking and “passivating.” The task of tracking satellites and debris is handled by several space agencies and government offices worldwide. For example, the Joint Space Operation CenterVanderburg Air Force Base (JSpOC), California, uses the Space Surveillance Networks(SSNs) – A combination of radar and optical sensors to monitor satellites and debris in orbit.
The NASA Orbital Debris Program OfficeThe Johnson Space Center’s Orbital Debris Environment Monitoring Observatory (ODPO), measures the environment and develops control measures. The Office of Safety and Mission AssuranceNASA HQ in Washington D.C. is home to the Office of Space Management Administration (OSMA), which is responsible for developing and implementing agency-wide policies and procedures that ensure safety, reliability, sustainability, and the environment.
There’s also the aforementioned ESA’s Space Debris Office (SDO) – located at the European Space Operations Center (ESOC) in Darmstadt, Germany – which is responsible for measuring and modeling the orbital debris environment and developing protection and mitigation strategies. It also coordinates activities and research efforts with the ESA’s constituent agencies, which form the European Network of Competences on Space Debris (SD NoC).
At the international level, there’s the Inter-Agency Space Debris Coordination Committee(IADC), which is a forum that includes 13 national space agencies (including NASA and Roscosmos), as well as the ESA and the Indian and Chinese satellite agencies. This body was created 2001 GuidelinesThey have been revised multiple times, the most recent in 2020, and have since been adopted. United Nations Committee on the Peaceful uses of Outer Spatial Space (UNCOPUOS).
On the other end of things, there’s the famous “25-year rule,” where operators are encouraged to dispose of satellites within 25 years of mission completion via atmospheric re-entry. Low-altitude satellites may already have the ability to do this. To accelerate the deorbiting process, non-compliant satellites can be equipped with drag sails, thrusters, and other instruments. Blake explained:
“Operators are encouraged to passivate spacecraft at the end of their mission, by depleting or saving any remnant sources of internal energy onboard the satellite or rocket body, thus reducing the chances of explosion. Adherence to the 25-year rule for deorbiting spacecraft in low Earth orbit is still concerningly low, and a boost to cooperation on an international scale will be paramount to tackling the debris problem.”
A Problem of Policy
Blake concludes that policy is the greatest obstacle to sustainability in space. UNCOUPOUS adopted the IADC guidelines over the past decades as the basis for international standard mitigation practices. These guidelines are voluntary, meaning they are not legally binding, and some space-faring states have chosen to not include them in their national regulatory structures.
In addition, adherence to the “25-years rule” remains very low in LEO, and the process of re-entry is not a viable option for objects in the high-altitude GSO region. As a result, operators will typically attempt to raise decommissioned satellites into so-called “Graveyard” orbits well beyond GSO – or what is known as a Supersynchronous Orbit (SSO). Although this has the effect of clearing orbit for future satellites’ use, it can still pose a threat for spacecraft that are destined for deep-space or the Moon.
Blake suggests that a policy of Active Debris Removal is required, which should be accompanied by stricter compliance to regulations for debris mitigation.
“Ultimately, well want to conduct regular removal missions to actively dispose of dead spacecraft and debris, though a number of technological hurdles are yet to be cleared. As evidenced by the recent Russian ASAT test back in November 2021, there is also a need for internationally recognized, legally binding regulations, to sanction against reckless behavior.”
ADR systems are being tested by NASA and the ESA as well as the China National Space Agency, CNSA, and other space agencies. There are many concepts, including Earth-based directed energy arrays (lasers), spacecraft equipped to carry plasma beams, harpoons, nets, or magnetic space tugs. In recent years, says Blake, there have also been efforts to formulate a “Space Sustainability Rating” that would incentivize operators to adhere to safe practices and debris mitigation. However, several questions remain unanswered.
How can a regulatory framework be used to compare University-led CubeSat research to commercial constellations (a la Starlink), in light of increasing access to space? What liability will lawmakers assign in the event that a collision involves uncontrolled debris? What mechanisms will be used to ensure equal playing fields between the emerging space agencies as well as those with a long history in space?
These questions are being debated and solutions are being sought. It has also led the Space Court Foundation (SCF), a non-profit organization, to rise. Space Generation Advisory Council (SGAC). There are also the tried-and-true efforts to formulate and clarify policy by the Institute of Air & Space Law(IASL), McGill University and The United Nations Office for Outer Space Affairs (UNOOSA).
As space expands, we can expect to see spirited debate, resolutions and innovative ideas in the years ahead. As usual, the driving force behind these developments is a simple matter of necessity. Humanity’s future in space depends upon accessibility and safety, something that cannot happen with huge debris fields in orbit!
Further Reading: arXiv
