Proton-M successfully lofts Express-AT satellite duo

by Chris Bergin

A Russian Proton-M launch vehicle has launched from a freezing Baikonur Cosmodrome in Kazakhstan on Saturday. The mission is tasked with lofting the Ekspress-AT1 and Ekspress-AT2 (translated as Express) satellite duo en route to their geostationary orbit, which involved a nine hours of flight with the Briz-M Upper Stage.

Proton-M Launch:

The Proton booster launching the satellites was 4.1 m (13.5 ft) in diameter along its second and third stages, with a first stage diameter of 7.4 m (24.3 ft). Overall height of the three stages of the Proton booster is 42.3 m (138.8 ft).

The Proton vehicle has a heritage of nearly 400 launches since 1965 and is built by Khrunichev Research and State Production Center, one of the pillars of the global space industry and the majority owner of ILS.

Z4The first stage consists of a central tank containing the oxidizer surrounded by six outboard fuel tanks. Each fuel tank also carries one of the six RD-276 engines that provide first stage power.

Total first stage vacuum-rated level thrust is 11.0 MN (2,500,000 lbf).

Of a conventional cylindrical design, the second stage is powered by three RD-0210 engines plus one RD-0211 engine and develops a vacuum thrust of 2.4 MN (540,000 lbf).

Powered by one RD-0213 engine, the third stage develops thrust of 583 kN (131,000 lbf), and a four-nozzle vernier engine that produces thrust of 31 kN (7,000 lbf).

Guidance, navigation, and control of the Proton M during operation of the first three stages is carried out by a triple redundant closed-loop digital avionics system mounted in the Proton’s third stage.

The Briz-M upper stage is tasked with the bulk of the flight, with separation not expected until nine hours after launch.

ZFailure1As a workhorse, the Proton-M has suffered from its fair share of failures, none more dramatic than last year’s failure, when the rocket rolled from one side to the other, prior to crashing into the cosmodrome.

The Russian government launch was carrying three satellites for the GLONASS navigation system.

However, the vehicle now has several successful launches under its belt since the failure.

The Express-AT1 satellite is based on the Express-1000N platform.

With a mass of 1,800 kilograms, the spacecraft will have 5,600W of payload power and is equipped with 32 Ku-band transponders.

Z5The telecommunications spacecraft Express-AT2 isn’t identical to its companion for this mission, having being built around the Express-1000K platform.

The 1,250-kilogram satellite offers 2,850W of payload power and accommodates 16 Ku-band transponders.

Both birds are expected to enjoy 15 years of service life, serving eastern and western Russia, delivering modern communications, television broadcasting and data transmission services.

The launch occurred just a matter of months after the lofting of the Express-AM5 satellite. That satellite was launched with a mass of 3,200 kg and sports 30 C-band, 40 Ku-band, 12 Ka-band, 2 L-band transponders.

The Express-AM5 was the first satellite built around ISS-Reshetnev’s heavy-class Express-2000 platform. It was manufactured under a contract with the national operator RSCC (Russian Satellite Communications Company).

Academician M.F. Reshetnev Information Satellite Systems and the Russian Satellite Communication Company were involved with the contract for the construction of the two satellites launched on Saturday, with another – Express-AM8 – set to follow later this year, also via the Proton-M rocket.

Express-AM8 is based on the advanced platform Express-1000HTB, weighing in at 2,100 kilograms and a payload power rating of 5600 W. This satellite will carry 42 C-, Ku- and L-band transponders.

During the last week, International Launch Services (ILS) and ISS Reshetnev also announced they are evaluating the technical feasibility into launching two large satellites at the same time on a Proton-M launch vehicle.

(Images via ISS Reshetnev and Tsenki Webcast).

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