What does the Telemetry mission consist of?

Telemetry has to adapt to each customer's specifications, which vary according to the mission

In the run-up to the launch (which for a standard mission is in an easterly direction), preparation of the telemetry system begins at between D-15 and D-10 days, then technical testing takes place at around D-7 days, with the Base Preparation Review at D-4 days and the Final Rehearsal at D-3 days.

Arianespace, the first-level customer, requires all telemetry data to be recorded, both to ensure the success of the European launcher's mission and to confirm this for its satellite customers. This mainly involves monitoring the launcher's performance, specifically the chain of events which determine whether or not the mission succeeds (engine ignition, separation of stages, fairing and satellites, extinction, etc).

Flight Safety uses around fifty internal launcher measurements in its decision-making process, including factors relating to launcher operations, the status of the flight control systems, etc. The aim is twofold: to permanently control availability of the launcher's abort telecommand chain, and to confirm information received from the tracking and location system.

The Telemetry system therefore makes a direct contribution to the Tracking and Location mission: it processes 'position' and 'velocity' data from the launcher's inertial units, then transmits them to the Tracking and Location data processing centre in a signal similar to those transmitted by radar, so that the two sources may be correlated.

Lastly, Telemetry is continuously supported by the Telecommunications network which is in charge of carrying the information and therefore has to provide an adequate telecommunications configuration.

Telemetry Preparation

During the launch preparation phase, Arianespace, Flight Safety and the Measurement Assistant* provide the mission characteristics to the Telemetry system; this data is used to configure the telemetry stations and SET (Telemetry Operating System).. Each station manager must report on his equipment's status and operational configuration to the Telemetry Manager (RTM) . Once the entire network is operational, the station managers take part in technical testing at the Launch Base, before transmitting their operational elements to the Telemetry Manager, who summarises them for a general presentation of the Telemetry system during the Base Preparation Review (RPB) Phase 2. Following this review, the configurations of all the systems are 'frozen'.

Which measurements?

To deal with so many missions, the parameters are recorded continuously, from the propulsion phase until launcher passivation. The telemetry signal is transmitted from the launcher to the ground. Transmitters located in the equipment bay send an enormous quantity of information from the sensors and inertial measurement units. The information gathered during the different stages mainly relates to:

- pressure, temperature, vibrations

- voltages, currents

- results from the flight control computer

- nozzle positions

- digital messages from the onboard computer (OBC)

* The Measurement Assistant's role

A member of the Measurement Acquisition Department within the Operations Sub-Directorate, the Measurement Assistant (AME) is a key player in the system. He is responsible for performing mission analyses for each launch, which are needed for specifying the design and architecture of the launcher tracking facilities. Working closely with the Director of Operations (DDO) and the Operations Quality Assistant (AQO), he is based at the Jupiter 2 Control Centre during countdown operations. During campaigns, the Measurement Assistant coordinates all the people responsible for the measurement system; the Telemetry Manager (RTM), the Tracking and Location Manager (RLOC), the Optronics and Special Resources Manager (ROMS) and the Telecommunications Manager (RTEL).

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