The European Space Agency’s Operations Control Centre (or ESA’s OCC, if you want to be acronymic about it…) is located at ESOC, the Agency’s Operations Centre in Darmstadt, Germany. The centre is used to control (unmanned) satellites whilst they are in orbit. This includes monitoring where they are in the sky, keeping them correctly positioned within their orbit, and ensuring that data from the satellite is getting back to Earth safely. The centre also does most of the preliminary processing to the data, before sending it on to end-users around the world.

Before we go any further, I should point out that the OCC is not the same as mission control. Although the rooms look pretty similar, mission control is a NASA-specific term for the controlling ground station during manned spaceflights (that is, missions with astronauts). The Operations Control Centre, on the other hand, is an ESA-specific term for the controlling ground station during unmanned missions (normal satellites). The space industry is nothing if not inconsistent.

The OCC is not the only element within ESA’s ground segment. There are receiving stations scattered across the globe, in an attempt to optimise the speed that a satellite can relay data (it would take a long time if you always had to wait until it was directly above Darmstadt), but the OCC is where all the data eventually comes to, and is in charge of regulating the entire process. Once the data has been gathered from the various ground stations, the OCC consolidates the data (they have some seriously large storage capacity) and then send the relevant pieces on to customers (that is, universities, research institutions and private companies that are working with ESA on a project).

The centre’s operations are divided among several distinct rooms, each of which uses SUN workstations (which in turn use Solaris and using a Silicon Graphics ONYX workstation) installed in a three module console configuration.

Main Control Room (MCR)

This is the room you’ve seen on television (except you haven’t, because ESA’s activities rarely make it into the mainstream press). There are banks of computers lined up in neat rows, all facing a wall filled with monitors. Remember the scene in Apollo 13, with the ‘Houston, we've had a problem’ line? Well, imagine a modern version of the room in that film, and you’re pretty close.

To be more specific, the room contains 14 workstations (it was upgraded in 1994), each fitted with headsets to allow voice communication with the other ground stations. The monitors on the wall are network-controlled, and display general information concerning the status of the satellite, as well as a collection of timers (GMT, local network time, countdown clock, etc.), and any videos or slides that the operators need to see whilst working (these are often time-synched to the launch process, so everyone can be sure of where they are in the countdown).

The MCR is the largest of the available control rooms, and where most of the action takes place, before, during, and after launch. Before the launch, extensive simulations are carried out, under ‘live’ conditions. That is, everything is as it would be during launch, from the behaviour of the satellites gyro’s to the behaviour of the controllers’ bladders. Everything needs to be rehearsed several times before they are ready for launch. During the launch itself, the OCC shares control of the satellite with the ground station at the launch site (usually Europe’s Spaceport, French Guiana). This sharing of responsibility continues until the satellite has separated from the rocket, at which point the OCC is in full control. This period is known as LEOP (Launch and Early Orbit Phase), and is by far the most dangerous period of a satellite’s life. The stress in the room is usually olfactible, and the frantic coffee-drinking and toe-tapping don’t quite cover up the sweat dripping from the controllers’ brows. Still, most of the time, everything goes without problem, and the satellite is safely placed into the correct orbit.

After launch, control of the satellite is usually passed to one of the smaller Dedicated Control rooms (DCR) and the MCR is prepared for the next task. Outside of the launch process, the MCR is also used during emergencies, and sometimes during important periods in a satellites lifetime after launch (for example, if a satellite needs to perform a gravity swingby during a deep space mission).

Dedicated Control Room (DCR)

The OCC contains several of these rooms, and can expand the number as necessary. Basically, they are just smaller versions of the MCR, used for the day-to-day operations required on a particular satellite. At the moment, there are four DCRs in operation, one for Cluster, one for Huygens, one for all ERS and Envisat activities, plus a room for the various telecommunications satellites (currently, mainly Artemis).

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