Post Tue Jul 19, 2011 9:48 am

The Glonass system hit by the loss of three satellites

On 5th of December 2010, at 10:25 GMT the Baikonur Cosmodrome hosted a new Proton launch having onboard three Glonass satellites: Kosmos 2470, 2471 and 2472.

The satellites built by JSC Information Satellite Systems/Reshetnev and NPO PM on an Uragan-M platform were three axes stabilized spacecrafts, 2.4 m x 3.7 m (solar wide span of 7.2 m), weighting 1415 kg and having a lifetime of 7 years.
The satellites were foreseen as an enforcement of the Russian satellite navigation system block M the one which is the basis of the Glonass before putting into operations the new block K (somewhere at the end of the month).
The flight, scheduled earlier 2010, has been delayed several times due to satellite problems and in the end has been carried out in December.

The Proton rocket entered the operation under the UR500 name on 16th of July 1965. Since then it has performed 362 flights with various scenarios: it has been used for Russian interplanetary missions to Moon, Mars, Venus or Haley comet, it flew to Mir and ISS stations, and last but not least it carried military or commercial spacecraft to orbit.

The Proton M version is 53 m long and weights 712 tons in nominal configuration. It is equipped with a booster system 42.3 m in length and a diameter varying between 4.1 and 7.4 m. Additionally we found on board the rocket special systems controlling the orbital injection –these ones different based on the mission’s specifics. For this flight the Russians were using the Blok DM 3 equipped with a RD 58 M engine having a thrust force of 85 kN.
The first stage of the rocket is powered by 6 RD275 type engines developing a total thrust of 10.5 MN, the second stage is equipped with 4 RD210 engines 2.3 MN of thrust and the third stage has a RD212 engine capable of developing 0.6 MN.
In this configuration the rocket is able to liftoff a payload of up to 22 tons for a LEO mission or 6 tons for a GTO.

If for the previous Glonass flights it has been used a Proton M Blok DM2 configuration, this time, as mentioned before, the configuration has been switched to Blok DM3. According to the flight plan, after third stage separation, two consecutive Blok DM3 activations should bring the satellites into the desired orbit (19.100 km altitude and 64.8 degrees inclination).

The Russian company Energia, the one which builds the Proton rocket has invested recently a large amount of money for buying the most part of the shares in the SeaLaunch operator which went to bankruptcy. There is a strategic reason for the long term improvements of the Blok M assembly considering this configuration will be used for commercial flights. Finding a test case financed with public money is therefore a good opportunity which cannot be missed.

For the moment is not sure why the launch failed, some sources speaking about an error on the Blok DM3 others about an error in the flight control software. Apparently the telemetry was good until the separation of the third stage, when the trajectory deviated from the desired attitude course with 8 degrees. Soon the satellites reentered the atmosphere and felled down to Earth somewhere 1500 km in the North-West of the Hawaii.
The event retained the attention of the Russian authorities, the president Medvedev asking for an investigation on the possible causes of the accident which affects the strategic interests of the country and on a large perspective over the spending in the aerospace industry sector.

The last failure of a Proton rocket dated from September 2007 when the first stage failed to separate and ended in the loss of the Japanese JSAT Corporation’s satellite JCSat 11.
In March 2008 another telecommunication satellite- AMC 14 part of the SES Americom fleet was left in a lower orbit than expected. However the geostationary transfer has been achieved using the onboard thrusters.

As mentioned previously, this has been the 362nd flight of the Russian launcher and the 43rd incident in its history (including the accidents and the sub-performed flights).

The Glonass system would have had, according to official information, 26 satellites in orbit. Theoretically the number is sufficient for a complete coverage of Russian teritory (at least 18 satellites) and more for global expansion of services (24 satellites). However should be said that 4 satellites are in technical maintenance and 2 –more than 2 years old- are now kept as a back-up, so only 20 would be fully operational.
Glonass system ("Globalnaya Navigationnaya Sputnikovaya Sistema” or “Global Orbiting Navigation Satellite System”) was put into operation for the first time in September 1993 with a group of 12 satellites and has reached the projected number of 24 for a global coverage in December 1995. However due to financial problems at that time and to the lack of new investment, some satellites have been retired without beeing replaced.
The system consists of three orbital planes, separated by 120 degrees with the satellites from the same orbital plane being separated by 45 degrees. Each satellite makes a circular orbit at a height of 19.100 km and an inclination of 64.8 degrees and has an orbital period of 11 hours and 15 minutes. Satellites are uniquely identified by the so-called "slot number"-the first orbital plane contains slots 1-8, second plane slots 9-16 and the third slots 17-24.
Each satellite transmits two types of signals, a standard one for commercial applications and a high-precision encoded one used by military applications. There are actually 25 channels separated by 0.5625 Mhz in the so-called L1 frequency bands:1602.5625-1615.5 Mhz and L2:1240-1260 Mhz.
According to official information, when the system will be complete, the maximum positioning error will be 70 m, both horizontally and vertically, and the speed erorr will stay at a value of 15cm/s (in the case of civil system), the error decreasing to 10-20 m in the case of military systems.
To keep pace with competing satellite navigation systems, the Glonass system will benefit from an investment of $ 2.6 billion hoping to reach a total of 30 operational satellites in 2011. This change of the system's conception is a result of studies from 2007, when it was decided to change the number of satellites from 24 to 30-meaning 8 operational satellites plus two spares will be reserved for each orbital plate.
The new generation of Glonass-K satellites to be launched starting 2011, benefit from an improved design that should increase their operating period (10 to 12 years), reliability, as well as smaller size and weight (750 kg) which would allow the replacement of the Proton-M launcher with the new Soyuz 2 (and almost a havling of the cost of lauch).