Post Tue Jul 19, 2011 9:46 am

US launches another military satellite

Friday, 11th of March 2011, at 23:38 UTC, US have launched from the complex 37 of the Cape Canaveral space centre a new military satellite. This holds the NROL-27 indicative and it is the newest platform of National Reconnaissance Office.

Despite the fact that as with all the programs of this kind very few information are made public, it is known that the new satellite is a geostationary platform part of the SDS- “Satellite Data System” which is facilitating the transmission of the data collected by the NRO satellites back to the ground stations when no direct visibility is possible.

SDS has reached today the third generation.
The first SDS 1 satellites (7 in total) have been launched between 1976 and 1987 aboard Titan 3 rockets, they were weighting 628 kg, have had a cylindrical shape and were relatively simple spin stabilized platforms.
Built on an Intelsat 4 spacecraft bus they were using from a Molnyia orbit (500 km x 39200 km x 57 degreees inclination) a 12 channels communication system with the ground station from Fort Belvoir, Virginia.

The second SDS generation had 4 launched satellites between 1989 and 1996, 3 aboard the Space Shuttle, and the fourth aboard a Titan 4 rocket. In this version, the platform has taken some design elements from Intelsat 6 spacecraft bus and weighted up to 3000 kg.
It was also operated an orbital change – 3 of the satellites were still flying in a Molnyia orbit (slightly modified compared with the previous generation 368 km x 39700 km x 63 degrees inclination) while the fourth has been sent to operate from a GEO orbit.

Finally, the third generation entered the service in 1998 and accumulated 5 launches until now: NROL 5 (USA 137) launched in 1998, NROL 10 (USA 155) launched in 2000, NROL 12 (USA 162) launched in 2001, NROL 1 (USA 179) launched in 2004 and NROL 24 (USA 198) launched in 2007. The first four have been launched aboard Atlas 2 rockets, while the last one has been put into orbit by an Atlas 5.
Satellites numbered 1, 4 and 5 use high Molnyia orbits but number 2 and 3 are geostationary platforms.
The command and control centre remains in Fort Belvoir, Virginia.

The flight from Friday, with the indicative 353, used a medium Delta 4 launcher. This is a two stages rocket- the first stage being powered by a RS 68 type engine and the second stage powered by a RL-10B2 engine.
They are helped for take off by a booster system composed from 2 solid fuel GEM-60 engines.
The medium Delta 4 rocket can carry up to 10430 kg in a LEO orbit, 5845 kg in a GTO orbit or 1611 kg in a GEO orbit.

NROL-27 is the third military satellite launched by United States since the beginning of the year. On 20th of January, another Delta 4 rocket, this time flown as a heavy version, left the Vandenberg space centre to put into orbit the NROL-49, a massive 15.000 kg satellite from the Keyhole KH-11 class.
On 6th of February, a Minotaur 1 rocket used the same Vandenberg base to launch in a SSO orbit the NROL-66 or Rapid Pathfinder Program- another small spy satellite.

The previous Delta 4 medium launch dated from Mai 2010 when the passenger was GPS 2F 1 (USA 213).
The next launch will be on 23rd of June when another GPS satellite- GPS 2F 5- will find its way to orbit.