An Arianespace Soyuz ST-B has successfully launched another pair of Galileo satellites from the European Spaceport in Kourou, French Guiana on Friday. The lofting of the FM03 and FM04 satellites took place on schedule at 21:46 UTC, as Europe’s Global Navigation Satellite System (GNSS) constellation continues construction in orbit.
Following the launch of four satellites Galileo In-Orbit Validation (IOV) satellites, forming the operational nucleus of the full 30-satellite constellation – FM01 and FM02 were then launched as the first two “Full Operational Capability (FOC) birds to head into orbit.
Their launch didn’t go to plan as they ended up in an elongated orbit travelling up to 25,900 km above Earth and back down to 13,713 km.
Their orbits have since been modified by making them more circular and raising their perigee by more than 3500 km, allowing their navigation payloads to be switched on throughout their orbits.
The decision whether to use the two satellites as part of the Galileo constellation will be taken by the European Commission based on the results of in-orbit testing.
The complete Galileo constellation will consist of 30 satellites along three orbital planes in medium Earth orbit (including two spares per orbit). The result will be Europe’s largest ever fleet of satellites, operating in the new environment of medium-Earth orbit.
The 700 kgs birds sport two Passive Hydrogen Maser atomic clocks; two Rubidium atomic clocks; Clock monitoring and control unit; Navigation signal generator unit; L-band antenna for navigation signal transmission, C-band antenna for uplink signal detection, two S-band antennas for telemetry and tele-commands and a search and rescue antenna.
Galileo’s highly-accurate atomic clocks will provide the accuracy of the system. Each satellite emits a signal containing the time it was transmitted and the satellite’s orbital position.
The Galileo program is Europe’s initiative for satellite navigation, providing a highly accurate global positioning system under civilian control, along with European control centers and a worldwide network of sensor and uplink stations.
The launch campaign began with the launch of the first two experimental satellites, Giove-A and Giove-B, orbited by Arianespace’s Starsem affiliate on Soyuz launchers from Baikonur Cosmodrome in 2005 and 2008.
The remaining Galileo constellation satellites will be orbited using Soyuz vehicles carrying two spacecraft each, along with three Ariane 5 ES rockets configured with four per launch.
Designated Soyuz Flight VS11 in Arianespace’s numbering system, this mission was Arianespace’s second mission performed in 2015, following a lightweight Vega launch in February with the IXV spaceplane. It was also be the 11th Soyuz liftoff performed from French Guiana.
The mission profile calls for the two satellites to be deployed after a flight lasting approximately three hours and 47 minutes. This proved to be a successful mission to separation.
The payload dispenser for Galileo was developed by RUAG Space Sweden for Arianespace, and carries one satellite on each side.
It deployed the spacecraft during their Soyuz launch by firing a pyrotechnic separation system to release them in opposite directions at the orbital insertion point.
The target is a circular orbit at an altitude of 23,522 km., inclined 55.04 degrees to the equator.
The more powerful Soyuz-ST configuration is the standard version launched from French Guiana, with the additional performance provided by the Soyuz ST-B variant – including a Fregat-MT upper stage.
Two variants are currently in service; the Soyuz-2-1a, and the Soyuz-2-1b which features an RD-0124 third stage engine which provides additional thrust. The RD-0124 was declared operational on 3 May 2011.
A third configuration, the Soyuz-2-1v, has also debuted, featuring the NK-33 engine in place of the RD-108A used on the core stages of the other configurations, and does not include the strapon boosters used by other configurations.
The Soyuz-2 forms the basis for the Soyuz-ST rocket, which is optimised to fly from Kourou, and also incorporates a flight termination system and a modified telemetry system.
With the Soyuz ST-B utilizing the RD-0124 third stage engine, an additional 34 seconds of specific impulse (Isp) significantly increases the vehicle’s overall launch performance.
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The RD-0124 is a staged-combustion engine powered by a multi-stage turbopump, which is spun by gas from combustion of the main propellants in a gas generator. These oxygen-rich combustion gases are recovered to feed the four main combustion chambers where kerosene – coming from the regenerative cooling circuit – is injected.
Attitude control is provided by main engine activation along one axis in two planes. Liquid oxygen (LOX) and kerosene tanks are pressurized by the heating and evaporation of helium coming from storage vessels located in the LOX tank.
Avionics for the Soyuz launcher are carried in the vehicle’s third stage, and are located in an intermediate bay between the oxidizer and fuel tanks.
As part of the Soyuz’ upgrades for its operations from the Spaceport, the launcher’s flight control system is modernized with a digital control system.
This system incorporates a digital computer and inertial measurement unit that are based on proven technology – giving the Soyuz improved navigation accuracy and control capability.
The new digital control system provides a more flexible and efficient attitude control system, and it gives the additional flight control authority required for the new, enlarged Soyuz ST payload fairing.
In addition, it improves flight accuracy for the Soyuz’ first three stages, and provides the ability to perform in-flight roll maneuvers as well as in-plane yaw steering (dog-leg) maneuvers.
The Fregat upper stage is an autonomous and flexible upper stage designed to operate as an orbital vehicle. Flight qualified in 2000, it extends the Soyuz launcher’s capability to provide access to a full range of orbits (medium-Earth orbit, Sun-synchronous orbit, geostationary transfer orbit, and Earth escape trajectories).
Fregat consists of six spherical tanks arrayed in a circle (four for propellant, two containing the avionics), with trusses passing through the tanks to provide structural support. The stage is independent from the Soyuz’ lower three stages, having its own guidance, navigation, control, tracking, and telemetry systems.
The Fregat uses storable propellants (UDMH/NTO) and can be restarted up to 20 times in flight – enabling it to carry out complex mission profiles. It can provide 3-axis stabilization or perform a spin-up of the spacecraft payload.
The Fregat first flew in 2000, and has been used on Soyuz-U, Soyuz-FG, Soyuz-2 and Zenit rockets.
The launch was performed from the purpose-built ZLS launch facility for Soyuz – located in the Spaceport’s northern sector near the city of Sinnamary.
Construction of the launch site began in 2007, as Arianespace advanced their plans to add two launch vehicles to their family. (See large set of construction photos in L2).
The Spaceport’s Soyuz launch site combines the proven design elements from the long-existing site at Baikonur Cosmodrome with satellite integration procedures that are in concert with the spacecraft processing used for Ariane missions.
Located 12 kilometers northwest from the existing Ariane 5 launch complex, the new Soyuz facility extends the Spaceport’s operational zone further up the French Guiana coastline.
The launch vehicle’s assembly building is 92 meters long, 41 meters wide, and 22 meters tall, allowing the vehicle to be assembles horizontally, prior to rolling out to the launch site, which is configured after the Russian Baikonur and Plesetsk Cosmodromes, albeit with a new mobile launch service tower.
The Soyuz’ transfer to the Spaceport’s launch zone is performed with the launcher riding horizontally atop a transporter/erector rail car.
Soyuz was then raised into position on the pad, and in contrast with the Baikonur Cosmodrome processing flow, is protected by a gantry that moves into place for payload integration.
(Images via Arianespace, O3b and L2.)