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<\/p>\nA Russian Soyuz-2-1b rocket launched from the Plesetsk Cosmodrome Saturday night, deploying a replacement satellite for the GLONASS navigation system with the aid of a Fregat-M upper stage. Liftoff is due to take place at 23:17 Moscow Time (20:17 UTC), beginning a three-and-a-half hour journey to the spacecraft\u2019s destination orbit.
\nRussia\u2019s GLONASS navigation system is served by a constellation of satellites named Uragan, meaning Hurricane. The current-generation Uragan-M spacecraft are designed for seven years of service, with new satellites being launched as needed to replace failing spacecraft on orbit. Saturday\u2019s launch deployed Uragan-M No.757 \u2013 the forty-eighth Uragan-M and the 137th GLONASS satellite overall.<\/p>\n
Like the US Global Positioning System and Europe\u2019s Galileo, GLONASS uses satellites in medium Earth orbit broadcasting highly-accurate timing signals which receivers can use to triangulate their locations. GLONASS satellites broadcast four navigation signals in the L-band: unrestricted L1 and L2 signals for civilian use, and equivalent restricted signals for the Russian military.<\/p>\n
Accurate timing is maintained for these signals by caesium atomic clocks aboard the satellites. GLONASS requires twenty-four satellites, stationed in three planes of eight spacecraft each, to provide worldwide service. Saturday\u2019s launch appears to be targeting the second plane of the constellation.<\/p>\n
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A GLONASS satellite \u2013 via Roscosmos<\/p>\n
Russia has not identified which spacecraft Uragan-M No.757 will replace. It has been speculated that it might replace Uragan-M No.723 \u2013 or Kosmos 2436 \u2013 which was launched in December 2007. This satellite was previously withdrawn, only to be pressed back into service after another spacecraft failed.<\/p>\n
Other candidates include the two oldest GLONASS spacecraft still in service: Nos. 716 and 717 (Kosmos 2425 and 2426), which shared their ride to orbit atop a Proton rocket on 25 December 2006. A third satellite launched aboard the same rocket has already been decommissioned.<\/p>\n
The GLONASS program was initiated by the Soviet Union in the 1970s, with the first satellite reaching orbit in 1982. Under the control of the Russian government, the network achieved initial operational capability in 1993, before becoming fully operational in 1996.<\/p>\n
First-generation Uragan satellites were only designed to operate for three years, so the system required frequent replenishment launches. Soon after GLONASS became operational, older satellites started to fail faster than replacements could be deployed, and the system fell into disrepair. By 2001, fewer than ten satellites were serviceable.<\/p>\n
Recognizing its importance, then-President Boris Yeltsin directed in 1999 that the GLONASS system must be maintained and upgraded. Since becoming president, Vladimir Putin has also taken a personal interest in the program.<\/p>\n
Spaceflight history books (adsbygoogle = window.adsbygoogle || []).push({});<\/p>\n To reverse the decline of GLONASS, second-generation Uragan-M spacecraft were introduced in late 2001. Offering a fivefold increase in accuracy and an improved on-orbit lifespan, Uragan-M can be launched in trios aboard Proton rockets, or \u2013 as with Saturday\u2019s launch \u2013 alone atop a Soyuz. Each Uragan-M has a mass of 1,415 kilograms (3,120 lb).<\/p>\n A new generation of Uragan-K satellites is under development, with two initial spacecraft already in orbit. Further Uragan-K launches are expected next year via Soyuz and Proton-M rockets.<\/p>\n Saturday\u2019s launch made use of a Soyuz-2-1b rocket with a Fregat-M upper stage. The Soyuz-2-1b is a modernized version of the Soyuz family of rockets, which trace their history back to Sergei Korolev\u2019s R-7, the world\u2019s first intercontinental ballistic missile. The R-7, which first flew in 1957, was also used to launch the world\u2019s first satellite \u2013 Sputnik \u2013 and formed the basis of the rockets that carried Yuri Gagarin\u2019s Vostok 1 mission into orbit and deployed the Soviet Union\u2019s earliest probes to the Moon and the planets.<\/p>\n The variant of Soyuz rocket used by Arianespace<\/p>\n While retaining the basic design of the earlier rockets, the Soyuz-2 series was engineered to improve performance and reliability. Digital flight control systems replace the analog equipment used on earlier versions of the Soyuz, while the first and second stage engines have also been upgraded.<\/p>\n Three versions of the Soyuz-2 have been developed: the Soyuz-2-1a is closest to the previous-generation Soyuz-U, while the Soyuz-2-1b also replaces the third-stage 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 stages of Soyuz-2-1b.<\/p>\n Soyuz-2 first flew in November 2004, with the Soyuz-2-1a performing a suborbital test flight. The first Soyuz-2-1b was launched at the end of 2006.<\/p>\n While the standard Soyuz-2-1b is a three-stage vehicle, upper stages can be used to carry satellites into higher orbits than the core vehicle could reach, or to inject payloads into more precise orbits. Several versions of the Fregat \u2013 Frigate \u2013 upper stage have been used in conjunction with Soyuz-2, while the Soyuz-2-1a and 2-1v have also flown with the smaller Volga upper stage. For Saturday\u2019s launch a Fregat-M was used, allowing deployment of the Uragan-M satellite directly into its operational orbit.<\/p>\n Soyuz launched from Site 43\/4 at the Plesetsk Cosmodrome in Northwest Russia. Plesetsk is one of four Soyuz launch sites worldwide \u2013 alongside the Vostochny Cosmodrome in Eastern Russia, the Baikonur Cosmodrome in Kazakhstan and the Centre Spatial Guyanais in Kourou, French Guiana.<\/p>\n<\/p>\n![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2018\/11\/2018-11-03-17_41_58-Window.jpg\")
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