Soyuz ST-A launches with Sentinel-1B at fourth attempt

by William Graham

Russia’s Soyuz ST-A rocket has launched with the European Space Agency’s Sentinel-1B spacecraft and four small satellites, following three delays – two relating to unacceptable weather for both Friday and Saturday’s attempts and then a technical scrub on Sunday. In what was the rocket’s first launch of the year from its South American launch site, liftoff occurred at 18:02:13 local time (21:02 UTC) on Monday.

Soyuz ST-A Launch:

Soyuz operates from the Centre Spatial Guyanais, in Kourou, French Guiana as part of a trio of rockets operated by Arianespace – alongside the smaller Vega and the larger Ariane 5.

The three rockets are used for commercial launches and in support of missions for the European Space Agency (ESA) and the governments and national space agencies of several European countries.

2016-04-22-134746The primary payload of the launch is ESA’s Sentinel-1B, a radar imaging satellite which forms part of the Global Monitoring for Environment and Security (GMES), or Copernicus, programme.

A partnership between ESA and the European Commission, Copernicus will use a fleet of satellites to study Earth and its environment. The spacecraft also have applications for aiding in the enforcement of civil security within European countries.

Sentinel is the space segment of Copernicus, consisting of six different types of satellite to study different aspects of the planet.

Sentinel-1 satellites carry radar imaging payloads, Sentinel-2 spacecraft are used for optical imaging, Sentinel-3 vehicles perform an oceanography mission, Sentinel-4 will study Earth’s atmospheric composition from geostationary orbit while Sentinel-5 will carry out the same mission in low Earth orbit.

Sentinel-6, which is a successor to the Franco-American Jason spacecraft, will carry radar altimeters to measure variations in the height of sea surfaces.

Z9Sentinel 1, 2, 3 and 6 are free-flying satellites, while Sentinel-4 and 5 will be payloads hosted aboard the next-generation Meteosat and METOP spacecraft respectively. At present, one satellite each of the Sentinel-1, 2 and 3 series are in orbit, with the remaining series due for introduction in the early 2020s.

An interim satellite, Sentinel-5 Precursor (Sentinel-5P) will be launched later this year to restore ESA’s ability to monitor atmospheric composition in the troposphere, which was lost after Envisat ceased operating in 2012.

Sentinel-1A was the first member of the constellation to be launched, riding a Soyuz to orbit in March 2014. It was joined by Sentinel-2A, which launched aboard a Vega in June 2015 and Sentinel-3A which was launched by a Rokot from the Plesetsk Cosmodrome this February.

2016-04-22-134950Sentinel-1B is a 2,164 kilogram (4,771 lb) satellite which was constructed by Thales Alenia Space. Based around the Piattaforma Italiana Multi-Applicativa (PRISMA) satellite bus, the spacecraft is designed for a seven-year mission in sun-synchronous low Earth orbit although it carries sufficient propellant and resources to operate for up to twelve years.

The satellite is equipped with a synthetic aperture radar operating in the C-band, which can image with a resolution of up to five by five metres (16 by 16 feet).

In addition to Sentinel-1B, this launch carries four secondary payloads. The first of these, Microsatellite à Traînée Compensée pour l’Observation du Principe d’Equivalence (Microscope), is a 303-kilogram (668 lb) microsatellite designed to demonstrate physics’ weak equivalence principle which holds that the inertial and gravitational masses of a body will be proportional, and therefore all bodies will experience the same gravitational acceleration in the same gravitational field. This is a key concept to Einstein’s theory of general relativity.

2016-04-22-135036Microscope was built and will be operated by the French national space agency, CNES. It is based on the agency’s Myriade small satellite bus. Two test masses are contained within the satellite; one made of a platinum alloy and the other of titanium. These will be maintained in separate test cells and accelerated such to keep them motionless relative to the satellite. The expected result is that the spacecraft will apply the same acceleration to each mass.

The remaining three payloads are single-unit CubeSats, which are being carried as part of the European Space Agency’s “Fly Your Satellite!” mission. AAUSAT-4 is a technology demonstration mission for Aalborg University in Denmark.

Equipped with Automated Identification System (AIS) receiver, its mission follows that of the AAUSAT-3 and AAUSAT-5 satellites, launched by a PSLV in 2013 and deployed from the International Space Station last year respectively.

2016-04-22-135125The Polytechnic University of Turin’s e-st@r 2 satellite is a replacement for the e-st@r satellite that was launched in February 2012 as part of the Vega rocket’s maiden flight. Uncontrolled tumbling of the original satellite prevented it from completing its mission, which was to have demonstrated a system to detect and control the spacecraft’s attitude. The reflight is expected to fulfil this objective.

Orbital Utility for Telecommunications and Technology Innovations 1 (OUFTI-1) is a demonstration and amateur radio satellite which will demonstrate the use of the D-STAR amateur radio protocol in orbit.

The launch made use of a Soyuz-STA rocket with a Fregat-M upper stage. A variant of the Soyuz-2-1a optimised for launches from French Guiana, the Soyuz-STA is a three-stage vehicle under the Russian schema which classifies its strap-on boosters as the first stage. The fourth stage, Fregat-M, will take over after the third stage separates, injecting the spacecraft into precise target orbits.

Soyuz is one of the oldest series of rockets still flying; having made its maiden flight in November 1966.

The current-generation version, Soyuz-2, made its first suborbital test flight in November 2004 ahead of its first orbital mission in October 2006.

The Soyuz-2-1a or Soyuz-STA is a modernisation of the previous-generation Soyuz-U.

The Soyuz-2-1b or STB introduces an upgraded and re-engined third stage to increase the rocket’s performance and the Soyuz-2-1v is a smaller version omitting the first stage of the Soyuz-2-1b to cater for lighter payloads. Only the STA and STB versions fly from Kourou.

The launch site at Kourou was constructed by French space agency CNES in the mid-1960s to replace its previous launch site at Hammaguir, Algeria, following Algeria gaining its independence from France.

French Guiana is an overseas territory of France, with an equatorial location making it suitable for launching to geosynchronous orbit.

The first launch from the facility was made by a Veronique sounding rocket in April 1968, with the first orbital launch occurring in March 1970 via a Diamant-B rocket.

2016-04-22-135301Kourou was selected as the equatorial launch site for the European Launcher Development Organisation’s (ELDO) Europa rocket, which made a single flight from a newly-built pad at the site in November 1971. This would be the Europa’s final flight, with the rocket failing to achieve orbit for the fourth time in as many attempts.

The program was subsequently abandoned, however its launch pad would be re-used for the next attempt at a pan-European space launch project, the Ariane 1. This first flew in December 1979.

The Ariane 1 launch pad, Ensemble de Lancement Ariane 1 (ELA-1) was subsequently used by Ariane 2 and 3 rockets, remaining in use until July 1989. More recently it was rebuilt for the solid-fuelled Vega rocket, returning to service as the Ensemble de Lancement Vega (ELV) or Zone de Lancement Vega (ZLV) with the type’s first flight in February 2012.

A second pad, ELA-2, was built for the Ariane 4 and also used by a small number of Ariane 2 and 3 vehicles. This pad was in service between 1986 and 2004. A third pad, ELA-3, has been used by the larger Ariane 5 since 1996. The Soyuz pad, Ensemble de Lancement Soyouz (ELS), is located about ten kilometres (6 miles) to the Northwest of the other launch pads.

This launch was the fourteenth launch from ELS; the first of which came in October 2011 when a Soyuz-STB deployed a pair of Galileo In-Orbit Validation (IOV) spacecraft.

Arianespace designated this launch as VS14.

2016-04-22-135334Sentinel-1B arrived at the launch site on 8 March, and was joined by Microscope two days later, with the CubeSats arriving on 25 March. The CubeSats and Microscope were installed respectively upon the rocket’s auxiliary payload adaptor on 5 and 6 April, with this being mounted atop the Fregat on 13 April. A day later, the Sentinel satellite was attached to this stack, with encapsulation in the payload fairing occurring the day after this.

On 19 April the rocket and the integrated stack of Fregat, payload and fairing, or “Upper Composite”, were transported to the launch pad and the Upper Composite was mounted atop the Soyuz.

Final countdown operations for the launch began five hours before launch, with a meeting to authorise fuelling of the rocket. Fuelling commenced thirty minutes later, continuing until about 95 minutes before the scheduled liftoff. The launch pad’s mobile gantry was moved away from the rocket 70 minutes before launch.

2016-04-22-160245The terminal count began at the five minute, ten second mark, with a key being turned to enable the final stage of the countdown to begin. At five minutes before launch the Fregat switched to internal power.

Umbilicals connecting the upper composite to the launch pad disconnected two minutes and 25 seconds before launch. The mast upon which these are mounted retracted about a minute and fifty seconds later, followed by a lower umbilical mast which retracted upon ignition of the first stage.

Soyuz transfered to internal power at the forty second mark in the countdown.

2016-04-22-160318Soyuz has one of the longest times of any rocket between ignition and liftoff, with the first and second stages igniting together seventeen seconds before launch, reaching full thrust in fourteen seconds. Once the countdown reached zero the four swing arms holding the rocket in place opened and Soyuz began its ascent to orbit.

The first stage consists of four liquid boosters, each powered by an RD-107A engine, clustered around the core – or second stage – which has a single RD-108A engine. The two types of engine, which are closely related, have four combustion chambers each and burn refined petroleum propellant oxidised by liquid oxygen. Hydrogen peroxide is used to power the rocket’s turbopumps.

2016-04-22-160352First stage flight lasted one minute and fifty-eight seconds, before the four boosters separated from the core vehicle – forming a pattern in the sky which has become known as the “Korolev Cross” after the rocket’s designer – Soviet engineer Sergei Korolev.

Following first stage separation, the core or second stage continued to power Soyuz towards orbit. The payload fairing separated from the nose of the vehicle at three minutes and 29 seconds elapsed time, with the rocket clear of the dense lower regions of Earth’s atmosphere.

Separation of the second stage occurred four minutes and 48 seconds after launch, with the third stage igniting shortly beforehand. Separation occurs with both stages burning.

2016-04-22-160417Powered by an RD-0110 engine, the third stage propelled the launch for four minutes and one second before it shut down and separated. Ignition of the Fregat occurred one minute after staging, beginning a ten-minute, fifteen-second burn to reach Sentinel-1B’s deployment orbit.

Separation of the Sentinel-1B satellite from the Fregat occurred three minutes and 21 seconds after the end of its first burn. At separation the spacecraft will be in a circular sun-synchronous orbit at an altitude of 686 kilometres (426 miles, 370 nautical miles) and an inclination of 98.18 degrees.

The Fregat performed a second burn beginning 96 minutes and 30 seconds after the separation of Sentinel-1B. Lasting thirteen seconds, this burn reduced the perigee of the orbit to 453 kilometres (281 miles, 244 nautical miles) and the apogee to 665 kilometres (413 miles, 359 nautical miles).

2016-04-22-160500While the vehicle is in this orbit the CubeSats separated, 47 minutes and 53 seconds after the end of the second burn. The auxiliary payload adaptor separated forty seconds later leaving just Microscope attached to the Fregat.

Three hours, 32 minutes and 35 seconds after liftoff – about three quarters of an hour after CubeSat separation, the Fregat began its third burn. Lasting twelve seconds, this raised the vehicle’s orbit. A second short of twenty-five minutes later the stage fired again, this time for sixteen seconds, to circularise its orbit.

Separation of the Microscope satellite occurred two minutes and fifty seconds after the end of the fourth burn, into a circular orbit at an altitude of 711 kilometres (442 miles, 384 nautical miles) and an inclination of 98.23 degrees.

Fifteen minutes and three seconds after Microscope’s separation, the Fregat ignited for a fifth and final time to deorbit itself. The deorbit burn lasted twenty-nine seconds. Launch operations concluded ten seconds after the burn was completed.

2016-04-22-160600In addition to Kourou, Soyuz rockets also launch from the Baikonur Cosmodrome in Kazakhstan and the Plesetsk Cosmodrome in Northwest Russia. Soyuz will also be able to fly from the new Vostochny Cosmodrome in the Southeast; the inaugural launch from that site will be made by a Soyuz-2 rocket and is expected to occur as early as next week.

Although this mission was marked as the first Soyuz launch of 2016 for Arianespace, it had already flown five missions from Baikonur and Plesetsk since the beginning of the year. These include the launches of a Glonass navigation satellite in February, the Resurs-P Earth observation spacecraft, the manned Soyuz TMA-20M mission, a Bars-M reconnaissance satellite and a Progress resupply mission to the International Space Station in March.

The next Soyuz launch is currently expected to be that of the Mikhailo Lomonosov research satellite from Vostochny – a mission currently scheduled for Wednesday morning.

Arianespace, which has conducted two missions so far in 2016 – both using its flagship Ariane 5 rocket – has scheduled its next launch for 24 May. Another Soyuz mission, this will orbit two Galileo navigation satellites.

(Images via ESA, CNES and Arianespace).

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