Arianespace—the Paris, France-headquartered launch services organization, which operates Ariane, Vega, and Soyuz vehicles from the Guiana Space Centre in Kourou, French Guiana—has successfully lofted Europe’s Sentinel-1A radar-imaging satellite into orbit. Liftoff of Arianespace’s seventh Soyuz booster, equipped with a Fregat upper stage, occurred precisely on time at 6:02:26 p.m. GFT (5:02:26 p.m. EDT) Thursday from the Ensemble de Lancement Soyouz (ELS) complex. Timing of this launch was particularly critical and initiated a 23-minute mission to insert Sentinel-1A into a Sun-synchronous polar orbit of about 435 miles (700 km) for its planned seven years of operational life. Once it has been tested, the satellite will provide imagery of the Home Planet in all lighting and weather conditions, utilizing a powerful C-band synthetic aperture radar.
Today’s mission was the seventh flight of a Soyuz booster from the South American spaceport, the first of which flew back in October 2011. Since then, Galileo navigational satellites, Pléiades civil/military imaging satellites, French-built ELISA electronic intelligence satellites, low-orbiting communications satellites, and an Earth observation satellite on behalf of Chile have been delivered successfully aloft. Most recently, in December 2013, a Soyuz vehicle lofted ESA’s Gaia space observatory into a distant “Lissajous” orbit, around the Earth-Sun L2 Lagrangian Point, a position about 930,000 miles (1.5 million km) beyond our planet.
Preparations for today’s launch ran like clockwork, with the Soyuz booster and its Fregat upper stage confirmed as fully fueled about 60 minutes ahead of launch time. The mobile gantry was retracted to a distance of 330 feet (100 meters) from pad, exposing the vehicle to the elements. Similar in design to the Soyuz vehicles which, four times yearly, deliver crews of astronauts and cosmonauts to the International Space Station (ISS), this rocket consists of three main stages. Its central core, fed by a single RD-108A engine, was surrounded by four tapering boosters, each powered by an RD-107A engine. All were fueled with a mixture of cryogenic liquid oxygen and a refined form of rocket-grade kerosene, known as “RP-1.”
The second stage was connected to its lower counterpart by a lattice-like framework, and its single RD-0110 engine was timed to ignite a couple of seconds after the separation of the first stage. Finally, the Fregat upper stage—powered by unsymmetrical dimethyl hydrazine and nitrogen tetroxide and capable of restarting up to 20 times in flight, but planned for just two discrete “burns” on this mission—was powered by the storable propellants unsymmetrical dimethyl hydrazine and nitrogen tetroxide. Its inclusion in the vehicle allows the Soyuz to deliver payloads to a range of orbits from low, medium, and geostationary altitudes and onto Earth-escape trajectories.
Five minutes before liftoff, at 5:57 p.m. GFT (4:57 p.m. EDT), the Launch Key—a physical key which transfers control to the Soyuz systems, activates ground and vehicle telemetry, and allows the final stages of the countdown to proceed—was inserted. Nitrogen purging to remove contaminants from fuel lines and engine combustion chambers followed, and at 6:00 p.m. GFT (4:00 a.m. EST), at T-2 minutes, as planned, umbilical connectors were severed between the Sentinel-1A payload and the ground control system. All fuel tanks were confirmed at flight pressure, and the final topping-off of cryogenic propellants was terminated shortly afterward.
Sixty seconds later, at 6:01 p.m. GFT (5:01 p.m. EDT), the Soyuz transitioned to internal power and the autosequencer got underway, commanding all vehicle critical functions through liftoff. According to AmericaSpace’s Launch Tracker, the first stage ignition got underway at 6:02:06 p.m. GFT (5:02:06 p.m. EDT), and after final umbilical disconnects and confirmation that all turbopumps were operating at full speed and all engines at full power, the vehicle lifted off precisely on time at 6:02:26 p.m. GFT (5:02:26 p.m. EDT).
In the seconds after leaving the pad, the vehicle executed a combined pitch, roll, and yaw program maneuver to establish itself onto the proper flight azimuth for the injection of Sentinel-1A into space. Rising rapidly, it passed 1,100 mph (1,770 km/h) within a minute of liftoff. At 6:04:24 p.m. GFT (5:04:24 p.m. EDT), at an altitude of about 28 miles (45 km), the four tapering boosters exhausted their propellant and were jettisoned, leaving the central core and its single engine to continue the ascent. By two minutes into the flight, the vehicle was traveling at over 3,350 mph (5,390 km/h).
The payload fairing was jettisoned shortly afterward, and, five minutes after leaving Kourou, the core separated at an altitude of 105 miles (170 km) and the third and final stage ignited to boost the vehicle to a velocity in excess of 13,420 mph (21,600 km/h). By the time the third stage departed the vehicle, at 6:11 p.m. GFT (5:11 p.m. EDT), some nine minutes into the flight, Sentinel-1A was in space and ready for the two planned “burns” by the Fregat upper stage. The first burn began at 6:13:51 p.m. GFT (5:13:51 p.m. EDT) and served to lift the payload into orbit. “The Fregat … will ignite its engine a first time, lasting about 11 minutes,” noted Arianespace’s launch kit, “followed by a ballistic phase lasting about 39 minutes.” After the completion of the first burn, at 6:25:50 p.m. GFT (5:25:50 p.m. EDT), Sentinel-1A was declared to be in free flight at an inclination of 98.18 degrees to the equator. Following the completion of the Fregat’s ballistic phase, at 7:01 p.m. GFT (6:01 p.m. EDT), some 59 minutes after launch, the upper stage performed its second burn, lasting 81 seconds, to deorbit itself into the atmosphere.
Built by Thales Alenia Space, the Sentinel-1A payload arrived at Kourou on 25 February , having been flown to Félix Eboué International Airport, near French Guiana’s capital, Cayenne, aboard a chartered An-124 transport aircraft. After delivery by road to the space center, it underwent several weeks of checkout and fueling. On Tuesday, 2 April, the Soyuz vehicle emerged horizontally from its integration building in the northwestern sector of the space center and was transported by railcar to the ELS complex. It was subsequently raised to the vertical and suspended in place by four large supporting “arms.” Yesterday (Wednesday), Arianespace reported that Sentinel-1A had been installed atop the booster. “The activity occurred inside the [174-foot] 53-meter-tall mobile gantry that provides a protected environment for the vertical payload installation,” it was explained. “This is one of the main differences in launcher processing at the [Guiana] Spaceport compared to the horizontal processing of vehicles on Soyuz launch sites at the Baikonur Cosmodrome in Kazakhstan and Plesetsk Cosmodrome in Russia.”
Sentinel-1A represents the first radar-satellite component of Europe’s vast Copernicus Earth observation network. Developed by ESA, in partnership with the European Commission, its goal is to ensure European independence in the acquisition and management of environmental data in support of authorities and policy-makers. The Sentinel programs being developed by ESA within the scope of Copernicus include five satellite families. Sentinel-1 will ensure the continuity of earlier missions, including the two European Remote Sensing Satellites (ERS), launched in 1991 and 1995, and Envisat, launched in 2002, whilst Sentinel-2 and 3 are dedicated to Earth and ocean monitoring and Sentinel-4 and 5 for meteorology and climatology.
“Sentinel-1A opens a new page in the implementation of Copernicus, the second EU flagship space initiative, after the Galileo positioning system,” said ESA Director-General Jean-Jacques Dordain after today’s successful launch. “The Copernicus program will provide European citizens with the most ambitious space-based services in the world for environmental and security applications.” Mr. Dordain added that co-operation between the EU and the ESA Member States had placed Europe “at the forefront of utilization of space to benefit citizens, policymakers and the economy.”
The Sentinel-1A satellite has been built by Thales Alenia Space, based upon the Prima three-axis-stabilized spacecraft “bus.” It measures about 11.2 feet (3.4 meters) x 4.3 feet (1.3 meters) and weighed 5,100 pounds (2,300 kg) at launch. Immediately after insertion into orbit, the satellite began the 11-hour sequence to deploy its electricity-generating solar arrays and communications and other antennas. “After the initial Launch and Early Orbit Phase, the satellite will go into the Commissioning Phase,” explained ESA, “when all instruments will be checked and calibrated. The mission is expected to begin operations within three months.”