Airbus Defence and Space paves the way
Inner space plays a vital role in our Earthly activities, affecting aspects as varied as the economy, politics, defence, security, to name but a few. This is why it is important to be able to detect and assess any dangers that could threaten satellites in orbit and look at ways of acquiring the technologies which will enable us to mitigate this threat. Airbus Defence and Space is already getting prepared.
In 2008, Airbus Defence and Space launched and internally funded an R&T programme called ‘Space Police’, which is part of a broader strategic framework known as SiS (Security in Space), combining all related Airbus Defence and Space activities, not only in the field of space surveillance, but also in the longer-term fields of active de-orbiting of space debris (both large and small), space deterrence (lasers and interceptors) and a rapid space-based response (on-demand launches for military missions).
At a European level, the Space Police activity is preparing the space debris surveillance part of the European dual SSA (Space Situational Awareness) programme of the European Space Agency (ESA), which encompasses a whole gamut of aspects, including space surveillance (from orbital debris to near-Earth objects), third-party satellites, and space weather.
“As a manufacturer of launchers and satellites and a supplier of space services, Airbus Defence and Space has for a long time now been concerned by the problem of space debris and what to do about it,” says Sophie Vial, Head of the SSA Programme at Airbus Defence and Space. “Moreover, we have expertise that can help us deal with this subject.”
The optical route
Since late 2008, the Space Police programme has comprised two parts: optical surveillance of the skies from the ground, and radar observation – necessary counterparts as radar range remains limited to about 1,000 km and therefore to low Earth orbit (LEO) only. The first part consisted of the development of algorithms for processing space surveillance images, in order to detect the various objects, the propagation of the debris orbitography and even the simulation of objects in orbit, in order to assess the image processing required for detecting and tracking them. The purpose of the second part was to test these theoretical developments and software using technology demonstrators.
The first technology demonstrator is a small aperture (<1°) tracking telescope based in Airbus Defence and Space’s Les Mureaux site near Paris called D2R2. It has been in service since May 2008 and is designed to track objects in the sky with great precision in order to collect detailed data about their orbits. “It takes dated photos of the object, also showing the star constellations,” explains Sophie. “As we know the sighting angle of the telescope, we can identify the constellations and thus accurately locate the object in space for calculation of its orbit. We have been able to precisely determine medium Earth orbits and geostationary orbits.”
Sophie considers that the results obtained with D2R2 are highly satisfactory, but a tracking telescope can only follow objects that have already been detected, which is why another telescope, MEDOC (French acronym for space observation resource) was inaugurated at Airbus Defence and Space’s Aquitaine site in June this year. It has a wider aperture (4°) and its mission is to scan the skies to detect objects. In this case, several images are taken each time the telescope is pointed, in order to detect points of light passing across the space background. An algorithm then localises these points, links them from image to image and deduces the trajectory of the object.
“None of these demonstrators is designed to become an operational system and the aim is primarily to validate the concepts,” Sophie makes clear. “But with the feedback obtained on implementation and on the image processing systems, we have acquired good experience which will help us progress to the next step.”
“Observation by optical means is certainly dependent on weather conditions, but we can get round this problem by establishing a global network,” she says. “We have developed the tools to design such a network.”
European Space Surveillance Programme
Airbus Defence and Space has pooled the strengths of its Space Transportation and Satellites Business Units in order to compete for the design of the surveillance system architecture, which would combine a radar system for low Earth orbit and optical means for higher orbits. The assembly would be linked to processing centres based on a bid-winning service-oriented architecture (SOA) developed by Airbus Defence and Space in Bremen, built around its Asteria prototype. This architecture allows processing of data from different independently-designed systems, eliminating compatibility constraints and enabling a large number of highly diverse sources – catalogues of orbital parameters, data collected by telescopes or radar operated by other systems – to be interconnected. Services can then be introduced by adding various data-processing software modules. This SOA architecture will make it possible to ensure confidentiality of the data shared by the various civil and military users from a number of European states.
The goal of this initial European programme is to prepare the ground rather than to aim for the performance of a fully operational system. “Its development will to a large extent depend on the funding allocated at the next ESA ministerial meeting in late 2012, and/or on the future financial situation of the European Union,” explains Sophie.
ESA is not alone in taking an interest in space surveillance. The military and even satellite operators are keen to protect their satellites. To deepen understanding of their particular requirements, Airbus Defence and Space has developed a technical-operational laboratory to explore the network performance requirements and the man-machine interfaces. Sophie says: “This is an interactive simulator running a detection and recording scenario from a catalogue, but it enables us to determine what information the customer needs, when they need it, at what intervals and in what format, as well as when and how they should receive alert messages.”
The benefits of lasers
Airbus Defence and Space is already aiming higher, looking at another means of high-precision orbitography: the laser. A partnership was created in 2010 with the Côte d’Azur Observatory, which is equipped with a laser which targets reflectors on board satellites or positioned on the surface of the moon for geodetic and astronomical purposes, as part of the ILRS (International Laser Ranging Service) network. After a series of tests on ‘cooperative’ targets (those equipped with reflectors), there will be a campaign on ‘non-cooperative’ targets, in this case launcher upper stages, which will use a more powerful laser. By precisely measuring the time the photons reflected by the launcher stage take to return to the emitter telescope, it should be possible to achieve an accuracy of about one metre for low Earth orbit.
This laser telemetry ushers in a new era of active surveillance. In the future, lasers could be used to de-orbit small debris, as proposed by the Clean Space project, a study under the 7th EU R&D framework programme, co-financed by the European Commission and AIRBUS Group. In the longer term, it might even be possible to ‘nudge’ or ‘shunt’ satellites into a more appropriate position.