December 2, 2015: The European Space Agency’s LISA Pathfinder mission launched atop a Vega rocket, beginning a year-long mission to demonstrate technologies that could be used for future missions to observe gravity waves.Conceived as a precursor mission to the now-cancelled Laser Interferometer Space Antenna (LISA) – a joint mission between the European Space Agency (ESA) and NASA, LISA Pathfinder is intended to prove a concept which scientists believe will allow gravitational waves – a phenomenon predicted by Albert Einstein’s theory of General Relativity but which has never been proven – to be observed by studying differences between perturbations in the orbit of a constellation of satellites.LISA Pathfinder’s main experiment, the LISA Technology Package (LTP), contains two test masses, 4.6 centimetre (1.8 inch) cubes of a gold-platinum alloy, which will be allowed to float freely in an environment with minimal gravitational interference. As the masses move within the spacecraft, LTP uses a laser interferometer to identify changes of position on the order of picometres.Pathfinder’s experiment is designed to validate the spacecraft can accurately measure the movements of these test masses and maneuver accordingly. It is a scaled-down form of the experiment that would have been flown by LISA, using two masses within the same spacecraft instead of three masses in separate spacecraft orbiting at great distances.Upon the spacecraft reaching its operational halo orbit around the Earth-Sun L1 Lagrangian point, the propulsion module will separate and manoeuvre away from the experiment module. In a 500,000 by 800,000 kilometre (300,000 by 500,000 mile) orbit around the Lagrangian Point, the spacecraft will operate for around half a year – spending three months testing the LISA Technology Package, two months testing the Disturbance Reduction System and then finally a month operating the two systems together. A further six-month extension to the mission has been proposed.The mission lifted off from the Ensemble de Lancement Vega (ELV) launch pad at the Centre Spatial Guyanais (CSG) or Guiana Space Centre, at Kourou, French Guiana.The four-stage Vega consists of three solid-fuelled stages, burning hydroxyl-terminated polybutadiene propellant, with a liquid propellant upper stage to provide for more precise orbit insertion.Two hours and forty minutes before liftoff, the pad gantry was retracted away from the rocket, a process which can take up to 45 minutes. Following the tower’s retraction a second round of alignment and checkout were conducted on the guidance system. Seventy five minutes before launch the rocket’s transponders were turned on.The Vega’s first stage, powered by a P80FW motor, began the ascent and burned for 110 seconds. Three seconds later the spent stage was jettisoned, and a second after that the second stage ignited to begin its own burn. Using a Zefiro-23 motor, the second stage burn edfor approximately 77 seconds before the mission entered a brief coast phase. The second stage separated 103 seconds after its engine ignited.Twelve seconds after staging, the third stage’s Zefiro-9 motor lit to begin a 119-second burn. The vehicle’s payload fairing separated four minutes and three seconds into flight, or fourteen seconds after third stage ignition.At the end of the third stage burn, VV06 coasted for forty two seconds before the final stage separation event. The fourth stage, the Attitude Vernier Upper Module or AVUM, ignited – for its first burn fifty nine seconds later.Powered by a Ukrainian RD-869 engine, originally developed for the post-boost stage of the R-36M2 missile, AVUM burns unsymmetrical dimethylhydrazine propellant oxidised by dinitrogen tetroxide.Thursday’s launch was the third of the year for Vega – following February’s mission that deployed ESA’s Intermediate Experimental Vehicle (IXV) demonstrator and June’s launch of the Sentinel 2A Earth science satellite – and the eleventh of 2015 for Arianespace.Aside from Vega, Arianespace’s previous launches this year have been flown using two Russian Soyuz rockets and six Ariane 5 vehicles. The company has one further launch scheduled for 2015, with a Soyuz slated to loft a pair of Galileo navigation satellites on 17 December.The next Vega launch is expected to occur no later than July, with PeruSat-1 as its primary payload. Another launch towards the end of the year will carry Turkey’s Göktürk 1. ABOUT GTD AT KOUROU SPACE CENTERSince 2003, each time an Ariane 5, a Soyuz or a VEGA are launched from the spaceport in Guiana, as well as the payload, many hours of work are required from GTD’s technical teams.GTD supplies services and software in practically all steps of an Ariane 5 mission – from the launcher's flight program to the responsibility of ground systems that control the launching operations, as well as the radars, telemetry and mission control systems.Each launch is also a challenge for GTD’s team, who is responsible for all the computer systems at the launch site. Each launch is a fresh new project; there is no routine, which means our engineers always embark on an adventure than goes beyond technical jobs that require a lot of responsibility.Countdown: The campaign to prepare a launcher takes about 22 - 30 working days, and a campaign to prepare the payload (satellite) takes from 4 weeks to 5 months (depending on the mission and its magnitude). Our teams are currently able to launch up to seven double Ariane 5, up to four soyuz and up to two Vega per year, that is, 14 telecom satellites and 4 to 6 EO and scientific spacecraft every year.Launch day: The end of the countdown is near. The final operations to fill the liquid propellants on the Ariane 5, and then the ground operation tests are carried out on the launcher. During this stage, gtd's staff is working hard all round the Spaceport. In the launch site's bunker, the technical centre, in Des Pêres Mountain where the radar and telemetry installations are, in the meteorological centre where the last conditions before the launch is authorised.At the same time, a support team is configuring a backup of the computer systems in Barcelona, 8,000 km away from the Ariane 5, which is already letting out oxygen steam.Ariane is launched: Once the launcher is in the air, it is controlled on board (by the embedded computer) and from the Jupiter Control Centre (CDC). These two systems were also designed by GTD’s engineers and are currently being operated by GTD’s engineers, too. Once the launcher releases the payloads (at a height of 500 - 600 km), everyone breathes a sigh of relief and starts clapping and cheering and congratulating each other; but our engineers are already thinking about the next mission that starts the following morning...
