Soyuz 2-1B successfully launches latest GLONASS-M mission

by William Graham

A Soyuz 2-1B rocket has conducted a launch in support of Russia’s GLONASS satellite navigation system in the early hours of Friday local time, carrying the Uragan-M No.52S spacecraft on a path to its destination orbit. Liftoff from the Plesetsk Cosmodrome in northern Russia was on schedule at 03:02 Moscow Time (00:02 UTC).

Russian Launch:

The first GLONASS launch in over a year, Thursday’s launch deployed a spacecraft to replenish the operational constellation in medium Earth orbit. Such launches are regularly undertaken using Soyuz or Proton rockets to deliver single spacecraft and groups of three respectively.

The Soviet Union began development of GLONASS in the 1970s, with the first satellite launching in 1982. Like the American Global Positioning System, GLONASS uses spacecraft in medium Earth orbits (MEO) to broadcast highly-accurate timing signals which receivers can then use to triangulate their position relative to satellites overhead of their location. GLONASS satellites are known as Uragan, meaning Hurricane.

The GLONASS constellation consists of three planes of eight satellites, for a full constellation of twenty-four spacecraft, although limited operation is possible with at least eighteen. The system achieved initial operational capability in 1993, and full capability in early 1996.

Russia had taken over the program following the Soviet Union’s dissolution in December 1991. With new satellites not being launched as quickly as old ones failed, by 2001 GLONASS had fallen into disrepair with fewer than ten serviceable spacecraft.

Boris Yeltsin gave a directive in 1999 that GLONASS should be maintained and upgraded, and since becoming President for the first time in 2000, Vladimir Putin has taken a personal interest in the system. Second-generation GLONASS satellites, Uragan-M, began to launch in December 2001. It is a Uragan-M spacecraft that is to be deployed on Friday.

Uragan-M satellites broadcast four L-band navigation signals – restricted-access L1 and L2 signals for the Russian military, and equivalent open-access signals for civilian users. The first-generation satellites did not broadcast a civilian L1 signal. Uragan-M has also increased timing accuracy by a factor of five, while the satellites have an increased design life of seven years.

At the time of Friday’s launch, GLONASS has twenty-three operational satellites, with slot fourteen in plane two currently vacant after the removal of one of the system’s joint-oldest satellites in June. That spacecraft, one of three launched on 25 December 2006, remains in its slot and is officially listed as “under investigation” – a status normally reserved for satellites that are about to be decommissioned. The two satellites launched alongside it remain in service, also in plane two.

All of the operational GLONASS satellites bar one are of the Uragan-M model – the exception being Kosmos 2501, a prototype third-generation Uragan-K1 that was deployed in 2014. This is in slot nine of plane two. A second Uragan-K1 is co-located with an Uragan-M in slot twenty of plane three, but is not part of the operational constellation. Further Uragan-K1 satellites are expected to launch next year.

The spacecraft deployed by Friday’s mission, Uragan-M No.52S, is the forty-sixth Uragan-M to be launched, and overall the 135th spacecraft of the GLONASS program – excluding eight mass simulators flown of early Proton GLONASS launches. Including the spacecraft in slot fourteen, twenty-three Uragan-Ms are in operation prior to Friday’s launch. Six Uragan-M satellites – two pairs of three – were lost in launch failures.

The 1,415-kilogram (3,120 lb) Uragan-M satellite will operate in a circular 19,100-kilometre (11,900 miles, 10,300 nautical miles), at an inclination of 64.8 degrees.

Friday’s launch was the first in support of the GLONASS constellation since the end of last May. The Uragan-M No.53 satellite, now known as Kosmos 2516, was launched atop a Soyuz-2-1b/Fregat on 29 May. Despite the third stage cutting off early, Fregat was able to make up the shortfall and deliver its payload into its planned orbit.

The launch of Uragan-M No.52 made use of a Soyuz-2-1b rocket with a Fregat-M upper stage. The Soyuz-2-1b is a modernised version of Sergei Korolev’s original Soyuz rocket.

It is one of three Soyuz-2 configurations, which introduced modernised engines over the Soyuz-U series that they replaced, as well as a digital flight control system in place of earlier analogue systems.

The Soyuz-2-1a is otherwise fairly similar to its predecessors, while the Soyuz-2-1b uses a more powerful RD-0124 third-stage engine. The Soyuz-2-1v is intended as a more cost-effective solution for launching smaller payloads, removing the first stage and replacing the second stage engine – its first stage – with an NK-33.

Combined with the Fregat-M upper stage, Soyuz-2-1b is a four-stage vehicle under the Russian system of numbering stages. The first stage consists of four liquid-fuelled strap-on boosters, each powered by an RD-107A engine. The second, or core, stage is powered by an RD-108A that ignites at the same time as the first stage, about sixteen seconds before liftoff.

A little under two minutes after launch, the first stage separates, forming a pattern known as the Korolev Cross as they fall away from the rocket. The second stage continues to burn for around another 170 seconds, during which time the payload fairing will have separated from the nose of the rocket.

The third stage, or Blok-I, ignites just before second stage separation, while the second stage is still burning. It will have burned for a little over four and a half minutes before shutting down and separating from the Fregat.

The three stages of the Soyuz itself are fuelled by RG-1 propellant – refined petroleum similar to the western RP-1 – oxidised by liquid oxygen. Fregat’s S5.98M engine burns unsymmetrical dimethylhydrazine, oxidised by dinitrogen tetroxide. The restartable Fregat conducts a series of burns to deliver its payload directly into medium Earth orbit.

Friday’s launch was the eleventh of the year for Soyuz, and the fourteenth to be made by a Russian rocket – the other three having used the larger Proton. Russia’s next launch will take place on 28 September, with a Proton delivering the AsiaSat-9 communications satellite into orbit.

Soyuz will next fly at the end of October, carrying the Progress MS-07 spacecraft on a resupply mission to the International Space Station.

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