Space is increasingly a contested ^[1] operational domain. A major contributor to this is the development and testing of counterspace capabilities (also referred to as anti-satellite weapons or ASATs) by some countries. ASATs are designed to destroy an opponent’s critical satellites in a crisis or during wartime.

China ^[2], India ^[3] and, most recently, Russia ^[4] have all tested purpose-designed direct-ascent ASATs ^[5], which are ground-launched missiles that collide with, or explode next to, a target satellite, physically destroying it. A Russian test ^[6] in November last year created a huge cloud of space debris that directly threatened the International Space Station, China’s Tiangong space station, and numerous satellites. The debris cloud still threatens satellites, and the ISS recently had to shift orbit to avoid a collision with debris created in that test.

In February 2008, the US used ^[7] a significantly modified version of its ship-based SM-3 surface-to-air missile to destroy a malfunctioning satellite in Operation Burnt Frost ^[7]. This test highlighted the dual-role potential of ballistic-missile-defence capabilities for ASAT roles. The operation was undertaken in part to prevent an uncontrolled re-entry that could have spread toxic fuel to overpopulated areas, but also as a response to China’s test of a dedicated direct-ascent ASAT in January 2007. That Chinese test, like the recent Russian test, created a huge cloud of space debris that remains a threat to this day. China has subsequently operationally deployed a direct-ascent ASAT to target US and allied satellites in low-earth orbit. These developments were a wake-up call to the US and its allies that assured access to space was increasingly contested.

The reality of counterspace capabilities and space as a contested operational domain is reflected In the Australian Defence Force’s 2022 space strategy ^[8]. The goal is to develop a space architecture that is resilient, can be defended if under attack and can be reconstituted if compromised. Defence is not under illusion that Australia can always enjoy assured access to space, or that space is a peaceful sanctuary untouched by terrestrial competition and conflict below. Resilient space capabilities and responsive and assured access to space launch are vital steps as Australia’s approach to the use of space for defence and national security gathers momentum.

Part of the solution to the challenge of counterspace threats is to raise the political, economic and potentially military cost of using ASATs to unacceptable levels through a strategy of deterrence by denial. Such a strategy requires resilient space architectures, a high level of space domain awareness to ensure attribution of activity and denial of opacity for would-be aggressors, and an ability for rapid reconstitution of lost capability in a crisis. The more sensitive issue of space-control capabilities—be they passive, such as an ability to shift orbits of a satellite under threat, or active, such as an ability to engage in non-kinetic direct defence of a satellite under attack—also needs to be considered in a way that is consistent with Australia’s commitment to be a responsible actor in space.

It is therefore entirely appropriate that Australia has announced ^[9] that it will join a multinational ban ^[10] on testing of destructive, direct-ascent ASATs to strengthen global norms of responsible behavior in space. As Deputy Prime Minister and Minister for Defence Richard Marles explained ^[9]: ‘Destructive testing of direct-ascent anti-satellite missiles threatens the security of vital systems in space, which Australia and other nations depend on every day. With this pledge, the Government is demonstrating Australia’s commitment to act responsibly to protect our national security interests.’

Joining the ban on testing of destructive ASATs is an easy move and a sensible step for Australia. Australia hasn’t been looking to acquire such a capability and has no plans to do so. Discussions about space control in Defence are occurring in the context of Australia’s interest in pursuing norms of responsible behaviour in space. We are part of the UN open-ended working group on responsible behaviour in space ^[11], and this move strengthens our commitment to promoting norms of responsible behaviour in space and, through diplomacy and legal mechanisms, reducing the incentive for states to pursue direct-ascent ASATs.

Australia will be joining the US, Canada, Japan, New Zealand and other liberal democracies in signing up to the ASAT ban. However, there’s no guarantee that other states will follow suit. Continued testing of destructive ASATs will only add to the congestion of space, further imperilling humanity’s ability to use this vital domain, not just for defence and national security, but also for broad international public-good uses.

One problem with the ban is that it’s a unilateral moratorium, not an international treaty. It’s relatively easy to join, but for those outside, there are no enforcement mechanisms. And, as demonstrated in the aftermath of Russia’s 2021 ASAT test, there’s little in the way of penalties beyond diplomatic demarches for such actions. Staying outside the ban is a low-cost policy option for some states, such as China and Russia, that are not answerable to, or less likely to be affected by, strong diplomatic language and minimally effective sanctions.

Another issue is that the ban applies only to destructive, direct-ascent ASATs and fails to address co-orbital ASAT capabilities ^[12], which some states are developing directly, or at least demonstrating ^[13] the relevant technology for. It also doesn’t address ground-based counterspace capabilities such as uplink and downlink jamming, laser dazzling and cyberattacks ^[14] on satellites.

The ASAT ban is thus the start of a solution rather than an end to itself. It’s a step forward on a long path that is now being explored by the UN working group. It’s a good move for Australia to join the ban, but it needs to be followed by a concerted international effort towards a true multilateral treaty that is enforceable under international law. This should be the next step for proponents of space law that seek to reduce the likelihood that space moves from a contested operational domain to a warfighting domain at the outset of a future conflict.