Arianespace Soyuz ST-A set for CSO-1 launch – NASASpaceFlight.com



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Arianespace will make its latest launch in 2018 on Tuesday using a Soyuz rocket to deploy a high-resolution satellite image to the French military. Soyuz is scheduled to take off from the Guyana Space Center – near Kourou, French Guiana – at 13:37:14 local time (16:37 UTC), rolling out its CSO-1 cargo just over an hour later.

Tuesday's launch will deploy the CSO-1, the first of three satellites to form the Spatiale Optique Composite (CSO) or Optical Space Component. These spacecraft will serve the French military, replacing the previous Helios reconnaissance satellites. To develop the constellation, the General Directorate of the French Armada (DGA) has signed a partnership with the national space agency, CNES.

Airbus Defense and Space is the lead contractor for the three CSO satellites, based on its AstroSat-1000 platform. Each satellite has a mass of 3,565 kg and must operate for at least ten years. The imaging systems were produced by Thales Alenia Space. From the synchronous orbit of the sun at an altitude of about 800 kilometers (492 miles, 432 nautical miles), CSO-1 is expected to be able to make images of Earth at resolutions of about 35 centimeters (14 inches) .

The CSO-1 is the first satellite of the third generation of recognition satellites in France, after two pairs of Helios spacecraft. The first dedicated French reconnaissance satellite was the Helios-1A, launched on an Ariane 4 rocket in July 1995.

The nearly identical Helios-1B was deployed in December 1999 to replace it. A second generation of Helios spacecraft with high-resolution imaging systems followed: Helios-2A was deployed by an Ariane 5G + on December 18, 2004 and Helios-2B launched aboard an Ariane 5GS five years later by the minute. Notably, CSO-1 is scheduled to take off on the anniversary of both launches, although the launch time for Tuesday's mission is eleven minutes later than for both Helios releases.

CSO-1 – via Arianespace

Once the three satellites have been launched, the CSO will operate with two satellites in the 800-km orbit, while CSO-2 will use a lower orbit for higher-resolution images. The mission of CSO-2 has been described as one of the identifying characteristics – distinctive observed by its sister satellites in the upper orbit. CSO-2 is currently scheduled for launch in 2020 or 2021, with CSO-3 joining the constellation a year or two later.

The CSO-1 will be launched by Arianespace, based in Paris, which has deployed all previous reconnaissance satellites in France. Arianespace operates a fleet of three different types of rockets: Vega is used to launch smaller satellites, Ariane 5 carries the heaviest loads – typically pairs of geostationary communication satellites – and the Russian Soyuz rocket fills the capacity gap between these two vehicles. Tuesday's mission will use Soyuz in its Soyuz ST-A configuration with a higher Fregat-M stage.

The Soyuz ST-A is based on the Soyuz-2-1a rocket, incorporating specific modifications to the use of the Arianespace launch site, the Center Spatial Guyanais (CSG), located near Kourou in French Guiana. The Soyuz-2-1a is one of three modernized versions of previous Soyuz rockets, derived from Sergei Korolev's R-7 missile that have been used for launches of Russian (and formerly Soviet) space planes and satellites since the 1960s.

Soyuz ST-A during preload integration – via Arianespace

The Soyuz-2-1a made its first suborbital test flight in 2004 and its first orbital launch two years later. It introduced the upgraded first and second stage engines on the previous generation Soyuz-U, as well as a digital flight control system and other enhancements. A second Soyuz-2 configuration, the Soyuz-2-1b (operated by Arianespace as the Soyuz ST-B) also has an updated third-stage engine. The smaller Soyuz-2-1v is designed to carry lighter loads, but this version of the rocket is not used by Arianespace.

Soyuz is a three-stage rocket, although the first and second stage fire together at launch. To achieve higher orbits or to perform more complex missions, the Soyuz can be used in conjunction with a higher stage. For Tuesday's mission, a Fregat-M will be used to insert the CSO-1 into its orbit synchronized with the sun. Fregat is the most common type of upper stage winged in the Soyuz; is based on the propulsion systems of the late interplanetary probes of the Soviet Union and can restart its engine several times over a long extended mission to ensure delivery of its payload into the required orbit.

Tuesday's launch will be the twentieth flight of a Soyuz from French Guiana. The Soyuz launch pad, the Soyuz Lancement Ensemble (ELS), was first used in October 2011 for the deployment of a pair of Galileo navigation satellites. Including the vehicle carrying out the CSO-1 mission, six Soyuz ST-A rockets and fourteen Soyuz ST-B rockets departed from Kourou. All but one of the Soyuz launched from Kourou – a Soyuz ST-B whose top Fregat stage was defective – completed their missions successfully.

Soyuz, Arianespace launch pad – via Arianespace

Soyuz launches also take place at the Baikonur Cosmodrome in Kazakhstan and the Plesetsk and Vostochny Cosmodrome in Russia.

Arianespace's designation for Tuesday's mission is VS20. The launch will start with the ignition of the first and second stage engines about sixteen seconds before launch. The first stage of the Soyuz ST-A vehicle consists of four boosters with RD-107A engines, grouped around the second stage which is powered by a single RD-108A.

The rocket engines will accumulate while the rocket is pressed, reaching full power in the second T-1 mark in the countdown. At zero, the swinging arms of the launch pad will open and the Soyuz will begin to ascend into space.

Soyuz ST-A during an earlier launch – via ESA

The first and second stages of the rocket will burn together for the first minute and fifty-eight seconds of climb. At this point, the four first-stage boosters will be turned off, releasing excess oxygen to keep their noses away from the rocket as they separate. The pattern made by the separation boosters is known as Korolev Cross, after the chief designer of the rocket.

After the first stage separates, Soyuz will continue to fly under the power of its second stage for another two minutes and 49 seconds. About thirty-two seconds before the end of the second stage flight, the payload fairing will be separated from the nose of the rocket.

The second and third stages are designed to separate while the second stage is still firing. The third stage lights up its RD-0110 engine while the RD-108A is still burning to ensure the propellant remains in the tanks of the third stage. The third stage will be fired for four minutes and two seconds before deploying Fregat to continue the journey from CSO-1 to orbit.

Sixty seconds after the separation of the third stage, Fregat will light up its S5.98M engine for the first of three planned burns. This will take eight minutes and fifty-two seconds, setting up an initial parking orbit. After a coastal phase of 35 minutes and 34 seconds, the Fregat will fire again for another 89 seconds, circling the orbit.

The CSO-1 will separate from Fregat five minutes after the end of the second firing – about one hour and 44 seconds after launch. Fregat will make its third and final burn four seconds after 51 minutes with this 55-second maneuver serving to dismiss the stage to keep unnecessary debris in orbit.

The launch of the CSO-1 is the eleventh and last Arianespace in 2018, after two previous Soyuz missions, two Vega launches and six Ariane 5s. Arianespace's next launch is scheduled for the end of January with the HS4-SGS1 and GSAT-31 on-board communications satellites and the Ariane 5, while the next launch of Kourou's Soyuz is expected to carry four O3b satellites in the first quarter of the new year .

Another Soyuz launch is expected from Russia before the end of the year: a Soyuz-2-1a / Fregat-M vehicle is scheduled to take off from Vostochny Cosmodrome on December 27 with its primary payload from a remote Kanopus-V . satellites.

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