Seeing Clearly – the Importance of SDA
The importance of Space Domain Awareness (SDA) is rising logarithmically with the number of objects in Space. Systems that enable better understanding of the orbital environment are increasingly crucial to all activity above the Kármán Line and the consequences they generate for life on Earth. But plotting paths to orbit, penetrating through to beyond, knowing where things came from, predicting where they are going, avoiding unintentional interactions, and calling out malign activity are difficult but foundational to safe Space activity. So, we need to be better at all of it and quickly.
Space Domain Awareness captures the detection, tracking, cataloguing and identification of objects in Space. It involves space surveillance and tracking (SST - sensor tasking and management, orbit determination and propagation, catalogue maintenance, launch and manoeuvre detection) and space situational awareness (SSA - attribution, characterisation, jamming analysis, capability and behavioural analysis, and threat modelling). Together, these enable civil, commercial, and military space leaders to act safely with confidence in Space.
But the need to better at SDA is rising dramatically. There are some 40,000 visible objects in Space and around 170 million that we cannot see. There are plans to launch 17,000 new satellites this decade and China’s Starlink challenger will fire another 13,000 into Space in the same timeframe. Getting to high orbits requires penetrating this congested belt, which has the feel of a hypersonic Indiana Jones dash today, but will be worse tomorrow. Whilst Space is big and the intra-object distances are, by terrestrial measures, huge, orbit velocities of 20,000 kph mean that we are never that far away from a calamity. A collision with a 10-cm object could be catastrophic for a satellite, a 1-cm fragment could disable a spacecraft, and even a 1-mm fleck could cause damage. Addressing this is vital if Space is to continue to be a safe place and its benefits for all mankind are to be protected.
So, what should we be doing?
Seeing clearly is obviously crucial to navigating safely, so we need to develop better ways to identify and track what’s there. This will demand enhanced sensor resolution to pick out and track the sub 10cm pieces that we cannot see and could damage billion-pound satellites. Surface-based optical, radio and electro-magnetic sensors are part of the answer, but very soon we will need on-orbit methods of sensing and tracking. Stable orbital geometry suggests that we don’t need to see everything all the time, rather we can simply ‘check-in’ with debris occasionally at the times / places where it should be. But as volumes increase, collisions are increasingly more probable and therefore secondary effects and changes to trajectory are likely to become ever more complex. So, we urgently need to up our game on sensing and tracking.
We also need to accelerate geometry prediction and enhance the computational power to process and predict where things will be, days, months, and years ahead, and enhance security for the data that is generated. Computing where an object travelling at 20k kph a few weeks ahead is tough, especially when minor astronomical nutations (orbital wobbles) are factored into calculations. But when synchronised with the other 170 million objects, the challenge overwhelms current computing power and will be even worse with increasing object numbers. So, new generations of technology will be needed to keep us safe. The pace and scale of Quantum may enable that breakthrough, as it might also contribute to the challenges of detection through Quantum Gravity Sensing. Processing data and predicting the future is a key SDA development strand.
Ground segments that capture, store, and distribute Space data is an equally important area needing focus. Better interaction between civil, commercial, and military orbit management teams would help generate a single rectified and ratified data set – a Recognised Space Picture – that should be made freely available to all those acting in the orbit highways. The approach that the seven Combined Space Operating nations have taken to sharing data is a great start, but it should be broadened to all those active in Space. Such is the importance of SDA data, that it should be collected and curated by sovereign nations but rationalised and harmonised in a supra-national body, perhaps under the United Nations. Difficult policy work is required to find better ways to collate international SDA data, share it more routinely, and enable better and faster co-ordination.
But if we can capture and compute the data, how can we be sure that it has not been corrupted, either by stellar weather, background electro-magnetic friction or intentionally through malign actors seeking competitive advantage. Disruption of the orbital almanac / Recognised Space Picture would be highly destructive to confidence, force delays to launch, and unwittingly facilitate avoidable collisions. This suggests two technologies need to be deployed into the architecture. Some form of encryption to secure data being moved between authorised locations, such as Quantum Key Encryption, and a date stamp system to secure a permanent dependable point of reference, such as blockchain. Urgent work is required to raise levels of confidence in the data and protect the systems that currently keep us (only just) safe.
Personnel in the International Space Station are routinely crowded into the escape module as debris storms pass uncomfortably close, but there are real capital risks through irreparable damage to satellites on orbit as well. These are significant, growing with increasing Space activity and so tracked carefully by the insurance markets. At the top end, the liability is enormous, a day without Space is almost uninsurable, so we accept the risks to life and property on orbit but are largely ignorant of the indirect effects to our way of life on Earth. The costs of upgrading our systems to address this are far outweighed by the costs of the consequences. So, perhaps an external impetus from the capital markets, rather than from Government intervention, is going to be the trigger to get after crucial SDA enhancements; hopefully ahead of the inevitable calamity.
Knowing more prompts another canon of work centred on doing something about it. In the first instance, we need to actively stop the growth of objects on orbit. Extending satellite’s life, refuelling in orbit and de-orbiting dead bits are all key changes to Space behaviour. We absolutely need to cease kinetic satellite events – data and simulation can assure governments that anti-satellite systems are functional, removing the need for live tests to prove theoretical physics. But there are no technological solutions to ‘grapple’ the 170 million or so 1cm and smaller objects, so we need a new generation of Space hoovers to clean up space. Much more work is required in this area if we are to make Space a safer place to operate.
Space’s utility to life on Earth is critical, growing, but increasingly threatened by orbital congestion. So we must break this cycle and develop policy, science, technology, and better international co-ordination to make Space a safe place to operate. Put simply, we need to accept there is a huge and growing problem, come together and get on with solving it.