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Like the internet, the space domain underpins many essential services to everyday life and is an critical part of the international infrastructure. Its security is threatened by unco-ordinated space activity by countries in competition with each other.
Alex Drake, Research Analyst, RUSI
There is a growing, unseen dependence on satellites in the UK across all sectors of society. In 2007, the Centre for the Protection of National Infrastructure outlined areas of services that are essential for day-to-day life. These areas include the obvious - Communications, Government - but also sectors such as the Emergency Services, Transport, Finance and Health. Space, like the cyber domain, is not explicitly named in the list but underpins all of these services and is very much a critical part of the international infrastructure. The global reliance on the GPS network, for example, is staggering: in 2010, there were around 57 million civilian GPS devices; according to ABI research, that number is expected to reach 370 million by 2015.
A list of threats to space services were outlined in the 2010 Strategic Defence and Security Review,  which states that 'risks include the potential effects of interference, cyber attack, physical damage and electromagnetic pulse (whether natural or deliberate) on satellites or their ground stations critical to our security and the economy.' This article will examine some of the more serious threats and the means to build resilience into the space infrastructure.
Space is a naturally harsh environment. Satellites are already hardened to protect sensitive components from solar flares and rare high-energy particles, but this may not be enough in the event of a severe geomagnetic storm. Such events are caused by the sun releasing large amounts of matter and electromagnetic radiation into space which then interacts with the Earth's magnetosphere. It is the mechanism responsible for the auroras (Northern and Southern Lights). Particularly strong geomagnetic storms can cause disruption in radio signals, and have been known to interfere with the GPS constellation for seconds or minutes. In extreme cases, it would be similar to an electromagnetic pulse attack on a satellite, potentially completely disabling it.
Fortunately these events can be predicted and their effects are rarely permanent. When they do, it is usually due to damaged solar panels. Solar panels can be damaged by one-off events, but also degrade over time due to constant bombardment from solar particles. These particles can accumulate on the surface of the panels which leads to large potential differences with parts of the satellite that are isolated and can result in major damage to sensitive components when they discharge. The best way to protect against these effects is to use a nuclear power source, as electromagnetic events have little, if any, effect on them. A nuclear power source would be contained within the satellite itself as the large energy density of nuclear fuel reduces the amount of fuel needed, removing the need for solar panels and dramatically reducing the dimensions of the satellite. This would however, require a revision of the Nuclear Power Source Principles and there would likely be public opposition to a nuclear device orbiting the Earth.
Further worries surround cyber-attacks as these are hard to defend against over long periods of time and can take many forms. Not only are the satellites themselves at risk, but ground stations and radio transmissions are susceptible to cyber-attack. Indeed, given their physical location on the earth they are much easier to target and interfere with.
The military is increasingly reliant on commercial space services but many private organisations do not have the same security requirements and are therefore much more vulnerable to attack. Both the cyber domain and space domain are seen as global environments and rely heavily on each other. Thus to secure both domains, common standards must be found and international collaboration must take place.
Denial of service is the simplest form of cyber-attack and has recently been employed by 'hacktivist' groups such as Anonymous and Lulzsec. Such attacks would not cause any long term effects on space services but could block networks long enough to cause immediate problems. An attack on the GPS constellation would cause the most disruption due to its widespread use, however, as it is a military network, the service is more robust than many commercial networks.
Attacks from state sponsored intelligence or military organisations are more likely to have serious and prolonged effects on space systems. Threats from such agencies range from signals intelligence (hacking into secure communications) to intercepting command and control links and reprogramming the satellite. Loss of control of satellites - such as the failed and now rebooted Intelsat Galaxy-15, (dubbed 'zombie-sat') - is of particular concern as there is the potential for such systems to be used as a 'weapon' to interfere with other satellites or even to take other systems out completely.
Physical damage to a satellite is also a risk and can be caused by several factors, the most likely of which is space debris. Meteorite impacts, man-made space debris and even particles from previous collisions can cause substantial damage. While most debris has the effect of sandblasting satellites, collisions with objects greater than 10 cm can cause the satellite to lose fragments of 1kg or more.
Such large-scale damage is generally rare but significant effort is undertaken to track such objects and, if necessary, manoeuvre the satellite away from the object's trajectory. In January 2007, China conducted an anti-satellite missile test. The defunct FY-1C polar orbit weather satellite was destroyed by a kinetic kill vehicle at an altitude of 865 kilometres. This created large amounts of space debris which orbits between 200 and 4000km altitude and at least 2,500 pieces of which are of trackable size (golf ball and larger).
A more recent collision between a Russian military satellite and an Iridium commercial communications satellite caused a similar debris cloud. Several countries are undertaking ground based space surveillance programmes to help improve tracking of space based objects and governments are increasingly willing to share more information about movements of national and commercial satellites to help mitigate the risk of such collisions in the future. Further cluttering of the space environment through collisions is largely seen as detrimental to all in spite of the traditional secrecy surrounding national space assets.
One solution is to launch a network of smaller satellites instead of one large device. This increases the reliance of the service as there is no one single point of failure. From a military perspective, smaller satellites are not only much cheaper, but are also harder to track and therefore to hit. Small satellites are also more responsive as they can be reproduced in a more timely manner, allowing constellations to be rapidly augmented or regenerated in the event of an attack (or environmental catastrophe).
Further design modifications could lead to the implementation of stealth technologies for satellites, again making them harder to track. This could be implemented over the whole constellation or on a selected number of satellites in order to keep costs down and maintain a skeleton service in the event of an attack. Maintaining a hardened core alongside a less secure network would allow for cheaper acquisition of SATCOM in an era when funds are limited but demand is high. It may also be possible use stealthy satellites as 'Guardian Angels' for a network, which would only come into play if a threat was detected, intercepting or destroying the threat before it could do any damage.
However, 'Guardian Angels' could equally be used as stealthy 'demons' conducting surveillance operations or disrupting the services of other operators. Many nations are therefore likely to see the use of stealth spacecraft as an aggressive act and this could initiate a 'space-race' similar to the arms race of the Twentieth Century. It is therefore in the common interest for nations to be open about their use of space.
An alternative solution to avoiding space debris damage would be to improve ground tracking methods. International collaboration on debris tracking would allow for an in-depth register of all space debris and provide enough information for nations to manoeuvre a satellite before a collision occurred. Such a programme could also allow for a larger debris - spent rocket stages, defunct spacecraft - to be removed from orbit and thereby improving safety in cluttered orbits. Space, after all, is a truly international environment and several nations have the capability to track these objects. Even if international programmes are not to be pursued, there must be common standards and guidelines in the long-term.
Looking into the future, another technique for ensuring space security would be to have the capability to readily replace satellites if and when they are taken out of play, or to launch secure systems as and when needed. For this to happen, launch costs must first decrease. These costs currently stand at £70-£80 million per launch and must be planned a long time in advance. Reaction Engines Ltd claims to have a solution to such a problem which could be available as soon as 2020. Their SKYLON space-plane will use a conventional runway for take-off and landing and use hydrogen fuel and breathing air, SKYLON can reach a velocity of Mach 5.5 before reverting to stored oxygen for the final boost into orbit. It is being designed to deliver up to 10 tonnes to an orbit of 460km (the same altitude as the International Space Station). The team are also designing a structure for the payload bay to allow for a constellation of up to ten micro-satellites to be delivered into the same orbit. Reaction Engines Ltd believes that this can be done for as little as $10 million per launch.
Space as a Global Common
Other security options rely less on hardware and more on collaboration. Space congestion is of particular concern as more and more nations are launching satellites. Some orbits are running out of physical space while frequency management is also becoming problematic. The worst space congestion can be seen in Low-Earth Orbits where there are many communication satellites. To provide continuous coverage, a network of satellites is required, which increases the congestion each time a new communications network is launched. This can be prevented by international and commercial co-operation on such networks. Questions arise regarding secure communications, but these could be overcome if each country were to use the hardened core system suggested previously and allow all other communications to go through a joint network. Such an effort may be easier than previously thought, with recent agreements between the UK and US over information sharing and the 2010 Anglo-French agreement providing a suitable platform for NATO based co-operation. However, with countries such as Brazil and India building up their space assets, co-operation on a larger scale - preferably through the UN - is paramount. The International Telecommunication Union (ITU), an agency of the UN, coordinates the global use of the radio spectrum and is now responsible for the promotion of international cooperation in the allocation of satellite orbits. However, this work is progressing slowly and not all satellite orbits are declared prior to launch.
To protect essential services, satellite security must be increased. In order to do this, innovative ideas and new and alternative technologies must be implemented. In some areas, security must first be 'decreased' in order to provide a safer space environment - nations must make their activities in space much more transparent. Both the space and cyber domains are global commons and therefore international collaboration is a key element to securing these areas. Initial work towards space congestion and debris tracking should be the way forward for further co-operation, paving the way for a mutual space paradigm and enhancing the long-term sustainability of outer space activities.
The issues outlined here emerged from RUSI's recent Space and UK National Security Conference.
1. Securing Britain in an Age of Uncertainty: The Strategic Defence and Security Review
2. Elizabeth Quintana, 'Space and the UK's Critical National Infrastructure', RUSI Defence Systems, Spring 2011
3. '"Zombie' satellite prompts orbital waltz', BBC News, 25 May 2010, http://www.bbc.co.uk/news/10150614