FEATURE
SPACE TRAFFIC MANAGEMENT: ESSENTIAL YET ELUSIVE? MATTHEW STUBBS, ASSOCIATE PROFESSOR, ADELAIDE LAW SCHOOL AND CHAIR, SPACE LAW COMMITTEE
INTRODUCTION: THE MIRACLE OF TRAFFIC MANAGEMENT, AND THE MORASS OF UNMANAGED TRAFFIC IN OUTER SPACE
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ost of us take traffic management for granted. It is a problem that has largely been solved on the roads, and even in airspace. But it is one of the great unresolved challenges of humankind’s burgeoning use and exploration of outer space. Once we have learned the rules of the road and obtained a driver’s licence, it becomes second nature to drive on the formed road within the marked lanes, to give way to other vehicles which have the right of way (including at devices such as roundabouts which are designed to use the right of way as an ordering system) and otherwise to follow the various Australian Road Rules, and to obey traffic control devices such as traffic lights. Each of these is an element of the architecture of road traffic management which is essential to our ability to use the road but which we do not stop to think about, except perhaps if we are in a long queue at the traffic lights. When we fly in an aircraft, we also devote little thought to air traffic management. But typically we fly in aircraft whose pilots are following pre-filed flight plans, with access to standardised information-sharing regimes, using designated air lanes, in aircraft with transponders transmitting identifying information to facilitate radar tracking, whose movements are controlled by active air traffic control in order to reduce the possibility of collision even in congested airspace.1 This is a highly sophisticated system for air traffic management. In outer space, there is no equivalent system of traffic management. Moreover, an object orbiting at an altitude of 400km (as the international space station does)
18 THE BULLETIN June 2022
will be travelling at just under 28,000 kilometres per hour. At that speed, there will be no such thing as a ‘fender bender’ or minor collision. In the absence of space traffic management, James Rendleman has memorably said that satellites in low earth orbit are like ‘cars driving blindly through a corn field, at top speeds, in all directions at once.’2 This is a problem which will only become more acute, as the number of objects in low-earth orbit is increasing exponentially. At the end of 2016, there were just over 2,000 payloads and nearly 10,000 pieces of debris greater than 10cm in size in low-earth orbit.3 By the end of 2021, that had risen to around 6,000 payloads and 12,000 pieces of debris.4 The number of payloads is projected to increase rapidly to 100,000 in coming years.5 The cornfield is becoming much more crowded, and thus collisions much more likely.
EXISTING PRINCIPLES AND PRACTICE: HOW SPACE LAW HAS ORDERED ACCESS TO DATE To date, users of outer space have relied on a practice which amounts to self-help, and on broad principles whose application to the problem is not entirely clear. The practice is that, where space domain awareness enables the tracking of objects, it may be possible to calculate the likelihood of collisions between tracked objects. In such a case, a conjunction warning can be issued when a risk of collision is identified.6 If there is such a warning, individual operators will need to choose whether to heed the warning and take evasive action, which necessarily burns fuel and reduces the lifespan of an expensive satellite.7 The limits of this system are easily demonstrable through the example of a major satellite collision. On 10 February, 2009, there was no conjunction warning
issued to Iridium that its Iridium 33 satellite was going to pass close to the defunct Cosmos 2251, and publicly available data (of which the operator was unaware) put the risk of collision outside the top 10 conjunction warnings for the day. In fact, the satellites did collide, creating more than 2,000 pieces of space debris greater than 10cm in size, and a great many more smaller pieces.8 This illustrates the problems of the track and avoid system we have today: tracking capabilities leave gaps in space domain awareness, and the lack of data sharing arrangements further hamper the identification of collision risks; and even where risks are identified, there may be limited capacity to respond, and imperfect information may mean that poor judgements are made about the need for response where there is a capability to take evasive action. The precise application of the legal framework is also uncertain. The Outer Space Treaty of 19679 – the constitution of outer space –10 establishes important principles which guide the exploration and use of outer space. Relevantly, these principles include: • Freedom of exploration and use (art I); • Due regard for the interests of other states and the avoidance of harmful interference with their space activities (where possible) (art 9). Inevitably, due regard and the avoidance of harmful interference must operate as a limit on the general freedom of exploration and use of outer space. However, it is not clear how the balancing of these considerations is to be carried out in practice.
PRACTICAL PATHWAYS TO THE FUTURE: WALK BEFORE YOU RUN; DON’T BITE OFF MORE THAN YOU CAN CHEW
