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A Russian Soyuz-2-1b rocket will launch Saturday night from the Plesetsk Cosmodrome, deploying a replacement satellite for the GLONASS navigation system with the help of an Fregat-M top floor. The takeoff must take place at 23:17 Moscow time (20:17 UTC), which corresponds to a trip of three and a half hours to the spacecraft's destination orbit.
The Russian navigation system GLONASS is served by a constellation of satellites named Uragan, which means hurricane. Uragan-M spacecraft of the current generation are designed for seven years of service. New satellites are being launched as needed to replace defective gears in orbit. Saturday's launch will feature Uragan-M No. 757 – the forty-eighth Uragan-M satellite and the 137th GLONASS satellite in total.
Like the US global positioning system and Galileo in Europe, GLONASS uses satellites in medium Earth orbit to broadcast extremely precise timing signals that receivers can use to triangulate their positions. The GLONASS satellites emit four navigation signals in the L-band: unrestricted L1 and L2 signals for civil use and equivalent restricted signals for the Russian army.
Precise synchronization is maintained for these signals by the cesium atomic clocks onboard the satellites. GLONASS requires twenty-four satellites, stationed in three planes of eight satellites each, to provide a global service. The launch of Saturday seems to target the second shot of the constellation.
Russia has not identified the Uragan-M No.757 spacecraft to replace. It was assumed that it could replace Uragan-M No.723 – or Kosmos 2436 – which had been launched in December 2007. This satellite had already been removed, but was put back into service following the blackout. another spacecraft.
Other candidates include the two oldest GLONASS satellites still in service: Nos. 716 and 717 (Kosmos 2425 and 2426), which shared their journey in orbit at the top of a Proton rocket on December 25, 2006. A third satellite was already been launched aboard the same decommissioned rocket.
The GLONASS program was launched by the Soviet Union in the 1970s. The first satellite was put into orbit in 1982. Under the control of the Russian government, the network reached its initial operational capability in 1993 before becoming totally operational in 1996.
The first-generation Uragan satellites were designed to operate for only three years. The system therefore required frequent replenishment launches. Shortly after GLONASS became operational, the old satellites began to fail faster than the replacements could be deployed, and the system fell into ruin. In 2001, fewer than ten satellites were usable.
Recognizing its importance, the then president, Boris Yeltsin, ordered in 1999 that the GLONASS system be maintained and upgraded. Since he became president, Vladimir Putin has also shown a personal interest in the program.
To reverse the decline of GLONASS, the second-generation Uragan-M satellite was introduced at the end of 2001. Offering five times the accuracy and improved lifetime in orbit, Uragan-M can be launched in trios aboard Proton rockets. The launch of Saturday – alone on a Soyuz. Each Uragan-M has a weight of 1,415 kilograms (3,120 lbs).
A new generation of Uragan-K satellites is being developed, with two first spacecraft already in orbit. Other Uragan-K launches are scheduled for next year via the Soyuz and Proton-M rockets.
Saturday's launch will use a Soyuz-2-1b rocket with a Fregat-M upper stage. The Soyuz-2-1b is a modernized version of the Soyuz rocket family, which traces their story to Sergei Korolev's R-7, the world's first intercontinental ballistic missile. The R-7, which flew for the first time in 1957, was also used to launch the world's first satellite – Sputnik – and formed the base of the rockets that brought Yuri Gagarin's Vostok 1 mission into orbit and deployed the first probes of the planets.
While maintaining the basic design of the previous rockets, the Soyuz-2 series was designed to improve performance and reliability. Digital flight control systems replace the analog equipment used on previous Soyuz versions, while the first and second stage engines have also been upgraded. Three versions of the Soyuz-2 have been developed: the Soyuz-2-1a is closer to the Soyuz-U of the previous generation, while the Soyuz-2-1b also replaces the third-floor engine with the more powerful RD-0124 . The third version, Soyuz-2-1v, is designed to carry smaller payloads at lower cost: it is a two-stage rocket based on the second and third floors of Soyuz-2- 1b.
The first flight of Soyuz-2 took place in November 2004, while Soyuz-2-1a was performing a suborbital test flight. The first Soyuz-2-1b was launched at the end of 2006.
While the standard Soyuz-2-1b is a three-stage vehicle, the upper stages can be used to carry satellites in higher orbits than the main vehicle or to inject payloads into more precise orbits. Several versions of the Fregat – Frigate – upper stage were used with Soyuz-2, while the Soyuz-2-1a and 2-1v models also flew with the smaller Volga upper stage. For Saturday's launch, a Fregat-M will be used, allowing the deployment of the Uragan-M satellite directly into its operational orbit.
Soyuz will be launched from the 43/4 site at the Plesetsk Cosmodrome in northwestern Russia. Plesetsk is one of four Soyuz launch sites in the world – alongside the Vostochny Cosmodrome in eastern Russia, the Baikonur Cosmodrome in Kazakhstan and the Guyanese Space Center in Kourou, French Guiana.
The 43/4 site is the only operational Soyuz launching complex in Plesetsk – although the 43/3 and 16/2 sites are being renovated to support future Soyuz-2 rockets. A fourth platform, the 41/1 site, was last used in 1989 and has since been dismantled.
The Soyuz rockets are assembled horizontally, in an assembly building – MIK – far from the platform. The rocket is then deployed and erected on the launching ramp, arms raised to allow the vehicle to support. The rocket that will be used for the launch of Saturday arrived Wednesday on the platform. The tests of the rocket and the probe were successfully carried out the next day.
About sixteen seconds before take-off, Soyuz will light up his engines on the first and second floors. The first floor consists of four boosters, each powered by an RD-107A engine, which are clustered around the second floor. The second stage is powered by an RD-108A, a version of the RD-107A that incorporates additional vernier motors to help control the rocket's ascent. The first three stages all use an RG-1 propellant – a refined petroleum product – oxidized by liquid oxygen.
Once the engines have reached maximum cruising speed, Soyuz will be released and begin to climb into orbit. The first and second stages will burn together during the first 118 seconds of the mission, before the first stage exhausts its propellant and separates. The four boosters are released from the core to the outside, evacuating the residual oxidant away from the second stage to avoid any undesirable contact after separation. The failure of one of the first stage boosters to release the oxidizer during separation – and the subsequent contact between it and the second stage – was the cause of the failure of last month's launch at of the Soyuz MS-10 mission.
The second step will continue to propel Soyuz into orbit for an additional 170 seconds after the separation of the first leg. Shortly before the end of the second leg, the third leg – Blok I – will turn on its RD-0124 engine and separate from the second leg. Known as "separation in the hole," the third-stage engine is fired while the second stage is burning, keeping the thruster in place in the third floor. The rocket therefore does not need additional engines. The third stage will last between four and five minutes.
In order to protect the Uragan-M satellite from the Earth's atmosphere and preserve the aerodynamic characteristics of the rocket, the Fregat-M probe and upper stage are encapsulated in a payload fairing located at the nose of the rocket . Once in space, this structure is no longer needed and will be removed to gain weight. For Soyuz launches, the separation of the fairing usually occurs towards the end of the second combustion stage or shortly after the second and third stages.
Fregat will separate from the third leg shortly after the end of the third leg. Powered by a restartable S5.98M engine, which burns dimethylhydrazine and dinitrogen tetroxide asymmetrically, Fregat will use three burns spread over about three and a half hours. Uragan-M No. 757 will separate from Fregat shortly after the end of the third fire. Once in orbit, the satellite should be renamed Kosmos 2529, in accordance with the standard designation scheme for Russian military satellites.
Saturday's launch targets a medium Earth orbit (MEO), located approximately 19,100 km above the planet, at an inclination of 64.8 degrees.
The launch of Uragan-M No. 757 is the second Soyuz mission since an old Soyuz-FG rocket malfunctioned at the launch of Soyuz MS-10 at the International Space Station last month. A state commission has completed its investigation of this failure a few days ago. His report was published last Thursday.
While Soyuz was launched while the investigation was underway (returning to flight Oct. 25 with the launch of a military intelligence satellite Lotos-S1), the results of the investigation and the Saturday's launch will restore confidence before the next launch of the ship's crew. International Space Station early December.
From here, two or three other unmanned Soyuz launches are expected. The first of these will take place on Wednesday (Tuesday at its launch site in French Guiana), with the European MetOp-C weather satellite. Progress MS-10, a cargo launch for the International Space Station, will take place in Baikonur in mid-November. A military launch from Plesetsk with a Neitron satellite could also take place in November or December.
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