Interviews Low earth Orbit Satellite Space News

How space situational awareness has changed in the past decade

Due to the proximity to Earth, huge constellations are required to maintain coverage in LEO, so congestion is predictably going to get much worse, says Pascal Wauthier.
Pascal Wauthier.

Pascal Wauthier is Chairman of Space Data Association.

This year we mark ten years since the Space Data Association (SDA) became operational via the Space Data Center (SDC). Indeed, ten years ago, satellite operators recognised a need to protect the space environment by sharing essential data for collision avoidance.

A lot has changed since then and continues to do so at a rapid pace. Whether it’s technical innovations or new opportunities via non-traditional markets, new challenges to the safety of flight present themselves continuously. So, in light of this important milestone, together with SDA Directors (Brian Swinburne from Airbus, Jean-Luc Froelinger from Intelsat, Lorenzo Arona from Avanti ) and AGI Expert (Dan Oltrogge), we are describing the most significant changes shaping the industry right now and in the near future, and how these are impacting upon all-important Space Situational Awareness (SSA).

Changing markets and a busier space

An increase in broadband demands has triggered the development and launch of non-geostationary orbiting satellites (NSGSOs).

Certain commercial entities are capitalising on the demand for LEO-enabled broadband services. Currently, there are around 1,300 satellites in orbit in LEO, but planned launches could see that number rise by as much as ten times in the next decade.

Due to the proximity to Earth, huge constellations are required to maintain coverage in LEO, so congestion is predictably going to get much worse. The assertion that ‘space is a big place’ is no longer a valid excuse when it comes to SSA

The space population has dramatically increased over the past decade in all orbits. This is true both for debris fragments driven primarily by an estimated average of over ten fragmentation events per year, including several catastrophic collision events and explosions, as well as for active spacecraft, which during this new space era have already put us on track to double the number of active spacecraft this year over that of 2010.

What’s particularly concerning when it comes to these fragmentation events is that LEO is already the most debris-filled region, and current trends point to a worsening of the situation.

Over two years ago, NASA estimated that at the time there were around 23,000 large objects of ‘junk’ in LEO, with another 7,000 untracked objects of significant size. But when it comes to the smaller pieces of debris in all orbits, the ESA predicts that there are currently 900,000 objects from greater than 1cm to 10cm in size and 128m objects from greater than 1mm to 1cm.

Even pieces as small as this can cause horrendous damage to equipment, putting whole satellite operations at risk. On top of this, any debris-causing event has the potential to set off a chain reaction whereby each piece of debris causes another debris-causing episode, and so on (the infamous Kessler Effect).

The problem of debris in LEO could become so severe that it threatens our ability to operate in LEO at all. The world relies on space-based infrastructure for essential services each day, so this is not just a problem for the satellite world.

As LEO becomes more populated by new satellites, the problem of congestion and debris is likely to worsen. At the moment, there is very little enforcement of de-orbiting regulations during the last decade; only around 15-25% payloads reaching end-of-life in LEO attempt to comply, and only 5-15% are even successful.

Current estimates predict that there are already over 3,000 defunct satellites in space, hurtling unchecked amongst our valuable assets. Couple this with a lack of on-board propulsion amongst newer LEO satellites, meaning no ability to perform collision avoidance measures, and it becomes difficult to see how we can even attempt to keep space clean going forward.

To this end, new innovations in tracking technology should be considered, particularly those that would allow us to track objects smaller than 10cm in diameter in LEO. In LEO, the ability to track smaller objects could offer operators valuable data with which to action collision avoidance maneuvres, preventing further debris from being created.

Current figures suggest that even in GEO, where we have less debris (although still a problem), the ability to track objects between 20cm-1m in size would increase the number of tracked objects by 50%.

Improvements to SSA

On a more positive note, SSA options have improved over the past ten years and continue to do so.

Prior to 2010, very little data sharing was happening, and few CA (Collision Avoidance) manoeuvres were undertaken. Some operators did rely on publicly available data or had separate agreements in space with services like JSpOC.

In many cases, operators undertook their own personal arrangements between various Flight Dynamics groups. Using free, legacy services did offer operators the ability to monitor close approaches, but they would not consider actioning CA manoeuvres as the warnings were not always reliable.

The SDA has been able to work with operators since its inception to pool authoritative space data, provide an interface to this, and ‘normalize’ data by validating conversions into standard reference frames, timing systems, units and elements. This has worked to provide actionable data to operators which is reliable and comprehensive enough to make collision avoidance measures a reality.

SSA policies, on the whole, have been slow-moving as they are developed by consensus across nations. There has, however, been a tangible transition in the past few years from a focus on collision avoidance through to the development of SSA and the emergence of the concept of Space Flight Safety and Space Traffic Management (STM).

Commercial SSA and STM services have emerged, pairing new sensor technology with advanced data fusion algorithms to dramatically improve SSA solutions and predictions. Services such as AGI’s ComSpOC have focused not only on sensor observations, but on the multi-sensor data fusion problem, on-the-fly non-cooperative manoeuvre detection and characterisation, and on error covariances that are commensurate with observed positional product precision and accuracy.

The commercial viability of new SSA services like the above is also symbolic in that it shows that the industry is on-board with tackling the problem and as mentioned already, are now committed to preserving the safety of flight.

Where will SSA take us?

There is, however, a long way to go.

It’s clear that current flight safety policies are not yet equipped to accommodate the rapid change associated with New Space’s large constellations, and improved SSA sensors and enlarged space catalogues.

Since 2010, we have continued to have thousands or perhaps even hundreds of thousands of conjunctions which could have been justifiably ignored as collision threats, if we had just incorporated better and more comprehensive SSA and operator data.

Missed manoeuvres, unrealistic error covariance profiles, errant object sizes and shapes, and errant observational and orbit associations with the objects they are meant to represent, all currently contribute to misleading or errant threat warnings.

To this end, continued and complete data sharing is critical to enable more actionable warnings, which will be an enabler for new tools and perhaps even those which work autonomously to protect the safety of flight.

Through its SDC system, the SDA has demonstrated during the last 10 years that effective SSA relies on using the best possible available data to manage collision avoidance and on closely monitoring their quality by comparing information.

Multi-national governmental cooperation will always be somewhat of a challenge, but it is most definitely something we at SDA consider to be the next step in SSA. We have shown that successful international cooperation between operators is possible, and international government-led SSA surely is too.

We would like to see national agencies shoulder some of the responsibility for SSA/STM, especially given that it is arguably an environmental issue and the detrimental effect of an unsafe space environment could affect us all.

The cost of SSA is also a huge burden on the spacecraft operator, and which many of our members believe should be shared by national governments.

The involvement of national agencies has evolved over the past few years; in the US the plan to transfer SSA services from 18SPCS to the Department of Commerce illustrates this.

But there is currently very little international responsibility, and no organization which can support SSA on behalf of all nations. There is also the question of standardisation of SSA/STM regulations among countries – a long-standing talking point and something which could see a more cohesive approach across the industry’s efforts in SSA.

Over the next decade, we would also like to see a more holistic approach to SSA, including multiple tools and sources. SSA, as well as flight safety and STM, could be greatly expanded by incorporating existing and planned SSA algorithms with commercial SSA services, crowdsourcing on a global scale, sensor-agnostic data fusion, and new government SSA and STM initiatives.

The SDA has clearly demonstrated that spacecraft operators are willing to invest in improving the safety of flight, and we believe that the SDA (and the operators it represents) can work with governments and other operators to bring about the changes needed over the next ten, or even five, years.

We would also like to see increased cooperation between commercial and military operations, something which is rarely happening now. Very little military data is shared with the commercial space, and of course, this is for very legitimate security reasons, but sooner or later could lead to exacerbated collision risks which could have been avoided.

Clearly, a lot has changed since the SDC was ‘switched on’ in 2010, and we can see that further significant changes are on the horizon. We do, however, have a clear vision of what needs to happen in response to these challenges – whether it’s the continued sharing of reliable data,  the development of new technology,  or assisting in the development of a more rounded, holistic and international approach to SSA so governments would take-over the role to ensure the sustainability of space operations – and will continue to work towards making these a reality.

Pascal Wauthier is Chairman of Space Data Association.