Measurements related to launches

The Measurement system consists of :

• the tracking and location system (LOC) which determines the trajectory in real time and displays it for safety purposes to handle assignment of sensors and telecommands and finally, to record the trajectory for later analysis.
• the telecommand system (TSAR) which is the only system which can destroy the launcher and abort its mission if it endangers life or property.
• the telemetry system (TLM) which is used to acquire, record and restore both in real time and later any information transmitted by the launcher.
• the control centre system (CDC) installed at Jupiter II, used to control operations during the countdown and to centralize the ‘No go/go’ state for the different systems.
• the synchronization system controlled from the Jupiter II control centre, used to synchronize all of the Ariane Launch Base (BLA) systems, to precisely time-tag some events (such as the Lift-off Signal) and to distribute universal time (UT), lift-off signal (TD), and T0 to all BLA sites
• the optics/video system for producing technical images in real time
• the weather forecasting system (MTO) which provides various weather forecasting services for the launching of Satellites and for Range Safety (on the Ground and In-flight) the telecommunications system, used to link all of the CSG systems and downrange stations used for a launch

Missions and services

Telemetry is information recorded on the launcher by sensors then formatted and transmitted to the ground trough a radioelectrical link.

Once decoded, this information on the different launcher components during the flight is either processed and exploited immediately on the ground (real-time control known as ‘immediate visual control’ [CVI]), or recorded for more thorough analysis later (offline analysis known as ‘offline visual control’ [CVD]).

CSG thus has a system for acquiring, recording, transmitting and processing Ariane telemetry. This includes :

• recording all telemetry from the freeing of the inertial measurement units until the end of the launcher mission and transmission to a processing centre located in metropolitan France,
• real-time control by Arianespace of launcher operations and of the sequence of programmed events (mainly separations),
• drawing-up of a ‘satellite positioning report’ indicating the orbits and attitudes of satellites after positioning.

Flight Safety officers also use some telemetry information to :

• permanently control the availability of each abort telecommand chain,
• to confirm information they receive from the tracking system with elements on the launcher’s propulsion.

In addition, the telemetry system contributes directly to the tracking and location mission; it processes the ‘position and velocity’ information received from the inertial measurement units and transmits them to the tracking and location data processing centre – CTDL – in a similar form to that transmitted by radars.

Finally, during the launcher integration campaign, the telemetry system is used for some tests and for launcher qualification.

Tracking and acquisition systems

The current configuration of the network of stations for launches towards the east and which is displayed in the diagram of the telemetry chain is based on the following stations :

• Kourou-Galliot: Stella 43 and for back-up, Star 45 (TTC station, part of the CNES 2GHz network)
• Natal: Stella 43, set-up by CNES (owned by IAE, managed by the Brazilian Space agency),
• Ascension Island: Stella 35, owned by ESA, managed by CSG,
• Libreville-N'Koltang: Stella 43, owned by ESA, managed by CSG,
• Malindi (Kenya): Datron antenna, owned by ESA, managed by CSG and CRPSM (Rome University)

For a launch countdown (summary)

Functions
Acquire TM
Real-time supply of TM from nominal inertial measurement unit (CIN) & CIS to TRACKING
Real-time supply of CVI TM to ARIANESPACE
Real-time supply of safety TM to CVI SVG
Supply of a satellite positioning report
Off-line supply of TM to CTTM in Toulouse

Functioning

Before the flight
The Department for Coordination of Downrange Telemetry Stations (SCS) sends the stations the launcher’s nominal trajectory when within visibility of each station.
The stations continually provide the SCS with the status of their equipment.

During the flight
The telemetry signal is received by telemetry stations distributed along the launcher’s trajectory. The telemetry stations process the signal and send the CVI part in real-time to SCET. The SCET processes the CVI part and provides the different subsystems, TRACKING, ARIANESPACE* and SAFETY, with the corresponding relevant information. The MITE system acts as interface with TRACKING.
At the same time and still via MITE, TRACKING send information describing the objective to DODO which are relayed to all stations.
Furthermore, for comparison, MITE also sends SCET the tracking data provided by radars.

After the flight
Stations provide the CTTM (CNES Toulouse) with all of their telemetry.

* The customer experts room, known as the Arianespace room, is the ARIANESPACE control centre for the launcher flight. Installed near to SCS (at Montagne des Pères, near the Galliot station), it is equipped with terminals for the CVI computers.

Missions and services

The tracking system, whose main function is to determine the launcher’s trajectory for safety purposes is the heart of the measurement system on the launch base.

Missions before flight :

• Prepare the mission configuration to be used during operations
• Participate in operations necessary for validating and preparing the whole measurement system during the campaign (campaign tests, safety training).

Missions during the flight :

• Identify all of the measurement observations, telemetry and telecommand facilities
• Transmit the General Public Image (IGP) to the operational image wall (in the Jupiter 2 Control and Command Centre)
• Send the tracking data from the best radar to CVI Arianespace
• Record all tracking data
• Display the point d’impact frotté in the flight safety room

Missions after the flight :

• Restore the generated and reference trajectories
• Supply the generated trajectory and raw tracking measurement data to Arianespace
• Supply, if necessary, the data required for the Internal Operations Plan (location and velocity of the launcher at the time of the explosion)
• Supply the mission reports and measurement file

Description of the tracking and location system

The tracking and location system is described in the following block diagram. Tracking and location data are provided by :

• radars (Bretagne 1 & 2, Adour),
• information from the inertial measurement units, sent with the launcher telemetry.

Processing :

The tracking and location system is designed around two independent trajectographs (TR1 & TR2 computers) which receive the data from radars and the inertial measurement units in real-time. Each trajectograph is connected to a single back-up machine to which it transmits the position and velocity of the launcher calculated from the different sensors thus creating two independent tracking chains.

The Centre for Coordination and Exploitation for Tracking (CCEL), is responsible for centralizing control of the tracking and location system.