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Score for a ‘space symphony’

The ATV, satellite communications system, ground control centres, ISS and its crew – all in perfect harmony

Artist’s impression of the ATV launch from Kourou on Ariane 5 (© ESA).What have a symphony for orchestra and the ATV in common?

Little at first sight, except perhaps that the ‘score’ is indeed a fantastic one. Between its launch on Ariane 5 and its final deorbiting procedure, the ATV puts together independent orbital flight phases, flight phases coordinated with the ISS (rendezvous, docking, de-docking and departure), and also phases integrated with the Space Station during which it operates as another ISS module. Like counterpoint, data and command signals travel, via satellites, between the ATV, ground control stations, the ISS and the ISS crew.

Highly orchestrated

The ATV is the most sophisticated spacecraft ever built in Europe. For Airbus Defence and Space, the ATV prime contractor for the European Space Agency (ESA), the challenge was not limited to design and integration of the vehicle. Working with its many partners, the company also had to establish how the vehicle was to be monitored and controlled from the ground at the Toulouse-based ATV Control Centre (ATV-CC), managed by the French space agency CNES for and on behalf of ESA, and by the ISS and its crew for the months when the ATV will form an integral part of the Station.

The Toulouse Control Centre teams take charge of the ATV on injection of the vehicle into orbit by Ariane 5, or about 60 minutes after lift-off. Their mission will only terminate on destruction of the cargo vehicle on its atmospheric re-entry around six months later. In the meantime, the Toulouse Centre is responsible for ATV stabilisation and orbit transfer operations, its approach to the ISS, docking and in-service maintenance while attached to the Station, under ISS control for orbit adjustment or the transfer of propellant, and finally de-docking and de-orbiting of the vehicle at the end of its mission.

During all these operations, the Toulouse Centre works constantly in close collaboration with:

View of the NASA International Space Station Control Centre in Houston  (© NASA) the NASA Control Centre in Houston, supreme authority for all operations relating to the ISS and which also controls the TDRS relay satellites to be used by ATV
View of the Russian ISS Control Centre in Korolev near Moscow (© NASA) the Korolev Control Centre near Moscow, responsible for the Russian part of the ISS where the ATV docks

The ISS team offloads the freight ferried up by the ATV (© ESA/NASA)

the ISS team, which offloads the freight ferried up by the ATV
View of the Columbus Control Centre, Oberpfaffenhofen (© DLR) the Columbus Control Centre (COL-CC) at Oberpfaffenhofen in Germany, which controls the ESA ground network interconnected with the ISS network
Redu Control Centre in Belgium (© ESA) the Redu Control Centre in Belgium, which controls the Artemis relay satellite

Once docked with the Station, the ATV will be switched to the ‘dormant’ mode. (This does not mean that the ATV is Off, but rather that it is in an automated mode, with systems all active. During this period, the ATV-CC permanently monitors the ATV, and adapts the vehicle’s solar array and power configurations to the constraints or requirements imposed by the ISS.)

View of the ATV Control Centre in Toulouse (© CNES)The ATV is frequently activated at the request of the ISS crew: to access the ‘dry cargo’ in its pressurised module, and to unload water or gas for replenishing the ISS’ internal atmosphere. This activation by the crew is rather limited, but always coordinated with and monitored from the ground, i.e. the Toulouse centre for ATV aspects and the Houston or Moscow centres for ISS and on-board crew aspects. The ATV-CC operators consequently have to ‘wake up’ the ATV, check its condition, activate the necessary utility systems and transmit authorisation to the Station for initiating operations. The ATV is also called upon to execute manoeuvres to boost the orbit or adjust the attitude of the ISS. In the latter case, having first activated the propulsion systems, the ATV-CC teams hand over control to the Station which then uses the ATV as its own propulsion module. During the attached phase, the Station crew transfers water and oxygen from the ATV’s tanks, while gradually loading waste from the orbital complex into the vehicle. One of the last functions of the ATV is refuelling the ISS, a typical combined operation involving the ATV-CC, the ISS’ propulsion systems and the Moscow centre, which takes place in general at the end of the ATV’s sojourn attached to the Station, just before it undocks and departs.

On completion of its mission, and under the control of the Toulouse Control Centre, the ATV will be de-orbited and will then disintegrate in the atmosphere (© ESA)And then it will be time to leave. This time, the Control Centre wake up the ATV with all its utility systems, including its integrated intelligence. This will be reactivated to ensure smooth separation from the Station. The ATV will then function again in the autonomous orbital mode to distance itself from the ISS, after which it will respond to command signals from the Control Centre to commence its return journey into the atmosphere and disintegration.

All these information exchanges in real time, throughout the mission, involve the immediate transfer of telemetry and an efficient communications network, based on the American TDRS satellites, the European Artemis satellite and a direct RF communications ‘proximity link’ between the ATV and the Station. Surprisingly for such an incredibly complex mission, the ‘score’ is really rather pared down: as a fully autonomous spacecraft, the ATV must be capable of being flown only with a limited data rate to and from the ground. Herein lies the beauty of the symphonic poem – it is composed of not many notes, but they are all perfectly harmonised.

The teams at the CNES ATV Control Centre (ATV-CC) based at Toulouse will take charge of the ATV after it has been placed into orbit by Ariane 5. Their mission will continue until the cargo vehicle is destroyed on its atmospheric re-entry six months later (© CNES)

The teams at the CNES ATV Control Centre (ATV-CC) based at Toulouse will take charge of the ATV after it has been placed into orbit by Ariane 5. Their mission will continue until the cargo vehicle is destroyed on its atmospheric re-entry six months later. © CNES

Many players, close-part harmony

Thus we can see that, in parallel with the design and qualification of the vehicle, it is this intricately woven ‘score’ involving the ATV, the satellite communications system, the ATV and ISS Control Centres, the orbital station and its crew – the complete mission, including a multitude of events, failures or other problems – that Airbus Defence and Space has had to define and simulate in its minutest detail for the ground operators and Station crew.

Working with ESA and all partners in the programme, Russian, American or European, the Airbus Defence and Space team had to determine how the ATV would operate and how to monitor the vehicle and react in any situation. They also had to establish how to share tasks between the ATV, the various Control Centres and the ISS crew at all stages of the mission. All this was based on different stored experience and cultures, and consequently methods.

The ATV has been designed for integration in a vast system with a multitude of components, whether emanating from ESA (ATV flight and ground segment, Ariane 5 and Artemis) or NASA and RSC-Energia (ISS flight and ground segments, ISS crew and TDRS satellites). The Airbus Defence and Space team had to define not only the sharing of functions, but also operations plans for the Control Centres of the ATV (Toulouse) and the ISS (Houston and Moscow), and the Station crew throughout the mission. This ATV System Operations Reference now represents a written ‘constitution’ covering each phase of the mission.

As regards the ATV itself, the Airbus Defence and Space teams have described all the operational procedures and instructions in detail. This enables each operator at the Toulouse Control Centre to know exactly what he or she has to monitor and how to control the vehicle throughout its mission. These instructions constitute the Operations Manual, a veritable electronic encyclopaedia amounting to several gigabytes, the core element of which is constituted by the 19 principal volumes concerning the sub-systems (such as the propulsion system) and the nine volumes dealing with general operation of the vehicle (such as OB power and energy management).

During the delicate ISS docking phase, the Control Centres in Toulouse, Houston and Moscow and the Station crew will all be in close contact (© Airbus Defence and Space)

During the delicate ISS docking phase, the Control Centres in Toulouse, Houston and Moscow and the Station crew will all be in close contact © Airbus Defence and Space

In addition, the teams transcribed and supplied all the instructions relating to transmission of command signals from the Centre to the ATV, in the form of computer electronic procedures which can be used directly by the Centre operators. Over 1,000 procedures and around 100 command sequence plans have been delivered in this way. And that is not all. Airbus Defence and Space has also produced 1,300 computation micro-programs, 1,400 alarm signals for vehicle monitoring by the ATV-CC operators, and tens of thousands of ATV-related characteristics data (necessary to operate the vehicle, such as the thousands of thermal control set-points on the ATV). A titanic task, regularly updated and delivered to the Toulouse Control Centre stage by stage since 2002.

Music, maestro!

The great ‘score’ is now to be played again with the mission of ATV-3 ‘Edoardo Amaldi’. Airbus Defence and Space experts will remain in the front line throughout the mission, ready to assist operators at the Toulouse Control Centre and backed by the combined rear base team at Bremen in northern Germany and Les Mureaux, near Paris, which in turn will be able to call, if necessary, on the skills, expertise and resources of the ATV industrial team. All of these people, each in their own way, are the members of the orchestra playing one of the most fantastic space symphonies of all time.

Artemis relay satellite Control Centre in Belgium (© ESA

ATV