Tracking, location and measurement systems

From lift-off until the end of its mission, the launcher and its payload (satellite) are tracked and located by a system of telemetry, radar and optical tracking and location equipment linked to several monitoring screens through computers.

Radio-electric linking between the launcher and the ground are used :

• to receive continuous telemetry information on the launcher operation,
• to send queries to radar transponders on the launcher to locate it on its trajectory,
• to abort its flight by destroying it with a telecommand if it poses any threat to life and property flown over.

This measurement system tracks and locates the launcher by processing the position or velocity information provided by the two inertial measurement units. This tracking and location mission is mainly intended for Flight Safety.

Downrange Stations

• Northern downrange Stations

The downrange stations network to the north varies depending on trajectories and is defined ahead of each launch. The first telemetry station along the trajectory of the Ariane launcher is the Galliot site on the Montagne des Pères which is used both for launches towards the north and to the east.

• The Eastern downrange Stations

The Galliot station (Kourou)

This is the first telemetry station along the eastwards trajectory of the Ariane launcher.

The Natal station (Brazil)

The Natal telemetry station is located at the extreme eastern point of Brazil below the equator. This is the second downrange station along the trajectory of the Ariane station. With its Stella 43 telemetry antenna, it offers visibility of the launcher for 8 minutes.

The Ascension Island station

The Ascension Island station in the South Atlantic is the third in the network of eastern downrange stations. Its geographic location allows for visibility of significant mission events such as the end of propulsion of the third stage, the injection or even the separation of the payload (satellite). The average visibility offered by the station is 7 minutes.

The Libreville station (Gabon)

The Libreville station is located at N'Koltang, 30 km from Libreville (Gabon). This is the fourth operational station; it tracks the Ariane launcher for about 15 minutes. Its unique geographic location on the equator in the West of Africa means that it can cover the most significant mission events such as the end of propulsion of the third stage, the injection and the separation of payloads (satellites).

The Malindi station (Kenya)

The Malindi station is the last station in the network arranged along the launcher’s trajectory. Located on the equator in Kenya, Africa, this station is able to cover separation of payloads (satellites), their injection in orbit and the end of the launcher mission.

The Galliot site (Montagne des Pères)

Located on the southern horn of the Montagne des Pères at Kourou, about 20 km from the launch complexes, the Galliot site is the first telemetry station along the trajectory of the Ariane launcher both for eastward and northward launches. It uses the Stella 43 and Star 45 antennas, and its equipment enables it to cover the trajectory between 313 and 91° north with an average visibility window of about 10 minutes.

Equipment

• The Acquisition-Receiving station: this station was designed to receive, record and process radioelectric telemetry signals transmitted by the Ariane launcher. It can receive simultaneous measurements on three separate telemetry channels and is able to demodulate the signals and store the information on magnetic tape.
• The CNES-Kourou 98 station is used to transmit and receive radioelectric signals, telemetry, telecommand signals, tracking and location signals (for measuring the range and the radial velocity of satellites) transmitting data to and receiving data from the Control Centre.
  All of these data are used to monitor the evolution of the launcher until 12 minutes after lift-off.

• The telemetry evaluation system (SET)

This system is used before, during and after launch.

• Before: for launcher control operations
• During: it is used for Immediate Visual Checks (CVI), in other words, it provides parameters for the different flight phases, sends some launcher parameters to the flight safety officers (on propulsion, attitude, separation, among others) and transmits trajectory parameters to the Toulouse Space Centre
• After: it is used off-line for later visual checks (CVD), by evaluating the quality of telemetry recordings and analysing all of the flight parameters.

The Diane Station

Introduction

The Diane station, also known as Kourou 93, is the last site located on the route de l’espace, 5 km to the northwest of the launch complexes. It belongs to the European Space Agency (ESA), and is managed for operations and technical matters by the European centre for Space operations (ESOC).
This tracking and telemetry station was built in the 1970’s to provide support for the first launch performed from the Guiana Space Centre.

Missions

The Diane station is implemented in direct contact with the Guiana Space Centre each time that a satellite is launched on behalf of the European Space Agency (ESA). The station can carry out 4 types of mission:

• Launch and orbiting missions (Leop mission)
• Routine phases
• Recovering missions
• Ranging missions

Since 1990, the Diane station has been part of the network of satellite control stations belonging to the European Space Agency. These stations are at:

• Villafranca, Maspalomas (Spain)
• Malindi (Africa)
• Redu (Belgium)
• Perth (Australia)
• Fucino (Italy)
• and, if needed, the Goldstone and Canberra stations (NASA).

The whole network is coordinated from the European centre for Space operations (ESOC) located at Darmstadt (in Germany), which plans operations while developing new scientific satellite projects for the European Space Agency.

The tracking and location system uses three trajectography radars: Adour 2, Bretagne 1 and Bretagne 2. The radars emit electromagnetic waves which are returned by the launcher and it is then possible to locate the launcher in Space by determining the angles and range.

• Adour 2 (Kourou weather forecasting site)
• Bretagne 1 - Grand Leblond (Montagne des Pères)

This trajectography radar is used for launcher tracking and location missions. It provides information on the position of the launcher in Space.

• Bretagne 2 - Montabo hill station(Cayenne)

The Montabo hill is at Cayenne, 60 km from the city of Kourou. It is equipped with a trajectography radar, Bretagne 2, which is used for the launcher tracking and location mission along with two other radars, Adour 2 and Bretagne 1.

Launches depend greatly on favourable weather. When crossing a cloud mass (cumulonimbi and big cumuli) the launcher risks being struck by lightning. In order to anticipate such risks, the Guiana Space Centre built a weather forecasting station when it first began its activities in 1968. This station is located about 8 km from the technical centre on the route de l’espace leading to the launch complexes.

The weather forecasting station at the Guiana Space Centre is entirely devoted to the Ariane launcher and is also involved in all planning and launch operations (launcher assembly and transfer, review of launcher countdown, transporting satellites and propellant, among others). It provides weather forecasts for rain, wind, lightning and cloud masses. Since 1968, ground observations are completed with measurements taken from balloon-probes, aircraft and probe-rockets. Balloons continue to be released before Ariane launch campaigns.

During satellite campaigns, weather forecasts are mainly intended to protect the launcher. Their principle objective is to evaluate the risk of storms occurring as well as rain, but also the direction of the predominating wind and potential gusts. In the short term, these forecasts are performed :

• for any dynamic operations which might prove risky for satellite transfers,
• for unpacking equipment from containers, purging of pipelines, transporting propellant,
• for transferring the launcher from ZP to ZL.

For all countdown sequences such as those performed for the launcher systems review, the general rehearsal, the weather briefing sessions on D-2 and D-1 and the final countdown, the forecasts provide information on specific criteria. The briefing sessions are held for the Director of Operations and the Director of the CSG.
Weather forecasting also attempts to determine potential risks related to storms, rain as well as the direction and strength of the wind and is done more and more frequently for different operations such as :

• the burning-off of propellant at the UPG,
• ARTA tests,
• the transfer of segments, stages, launchers, satellites or propellant tanks,
• any work done off the ground.

Under the terms of the agreement between the CSG and Météo-France and as part of the standard services provided to Arianespace, the CSG weather forecasting department has to continually gather data to determine the meteorological parameters necessary for drawing-up monthly climatology tables and reports on launches.

Two kinds of measurement are systematically taken during countdowns in order to study the behaviour of launchers on the ground and in flight in relation to wind stress. These involve :

• continuous recording of wind data on masts (ELA and probe-rockets), respectively for levels at 20, 35, 50 and 60, 75, 100 metres,
• radio-sounding before and after launch in order to determine profiles for temperature, pressure, humidity and wind from ground level up to the bursting altitude for balloons at about 30 km.

Equipment

• A meteorological radar is used to identify large clouds within a radius of 250 km
• An acoustic sounder is used to measure wind in lower layers of the atmosphere
• There is a system for detecting lightning and storm discharges
• There are systems for receiving satellite photographs and weather maps
• An automatic radio-sounding bay is used to obtain profiles for temperature, humidity and pressure as well as wind direction and speed at high altitudes, by dropping a probe from a balloon
• There is a network for measuring the surrounding electrical field
• There are two masts (on the Ariane and Probe-rocket launch complexes) fitted with sensors for measuring wind direction and speed
• There are three other automatic observation stations (at île Royale, Dégrad Saramaka and Kourou beach) for measuring conventional weather parameters (temperature, humidity, quantity and duration of rainfall as well as wind direction and speed)
• There is a buoy at sea for measuring wind speed and direction.

The meteorological equipment is used for

The CSG weather forecasting radar

The ROMUALD radar is on the Montagne des Pères about 5 km from the Space Base. It covers the inhabited areas of the coast from Saint-Laurent to the boundaries of Brazil including the CSG and the commune of Saint-Georges. ROMUALD is continuously controlled by personnel at the CNES/CSG Meteorology Department who analyse weather forecasts for Ariane launches and during all risk-related operations performed at the launch base.
Every 5 minutes, it also provides forecasters at the Météo-France centre, located at the Cayenne Rochambeau airport, with rainfall measurements; these are essential for observing the atmosphere and for very short-term weather forecasts.

In addition, this radar is used for early detection of intense rainfall within a radius of 150 to 200 km and especially to gain one or two precious hours for warning the population ahead of time.
ROMUALD was designed to be integrated into a set of nine radars which are part of a network covering the larger Caribbean area in order to better forecast intense rain and cyclones.

The Salvation Islands were named for the Kourou expedition of 1763. There are three of them, located about 30 km to the north of the city of Kourou.

In 1965, they were recognized as being of strategic interest to the State due to the trajectory of the launchers and became CNES property in 1971. They are reached by sea from the port at Balourous in Kourou and have become a favourite tourist destination, welcoming about 50,000 visitors per year.

L'île Royale

This is the biggest of the three islands with a surface area of 62 hectares. Its highest point is at an elevation of about 47 metres. Between 1971 and 1975, it was used as a launch area for atmospheric balloons.
In 1969, a cinetheodolite was installed there; this is an optical instrument for trajectography tracking which is used to cover the main events in a launcher’s flight, from lift-off until the third stage is ignited. The cinetheodolite has now been transformed into a cinetelescope whose task is to observe flight events in the visible and infrared ranges.