GLONASS (satellite)

GLONASS (ГЛОНАСС-М), also known as Uragan (Ураган) (GRAU Index 11F654) are the first generation of Uragan satellite used as part of the Russian GLONASS radio-based satellite navigation system. Developed by Reshetnev Information Satellite Systems, it had its debut launch in 1983, with the last launched unit on 2005 and the retirement of the last unit Kosmos 2403 on April 30, 2009. I has been superseded by the GLONASS-M (GRAU Index 11F654M), the second-generation satellites.

Design
It used a 3-axis stabilized pressurized bus with two solar panels, a propulsion module and a payload module. It weights 1413 kg generates 1000W of power and had a limited design life of 3 years, but it was extended to 5 years in later models. It had a strict requirement of keeping the internal temperature at ±1°C. The previous design used an embedded liquid cooling system that weighted 340 kg. The Uragan implemented a gaseous cooling system that put most of the heat generating parts on the outside of the pressure vessel, simplifying the system and weighting just 40 kg.

The Uragan-M are usually launched in trios, and due to the close distance, the radios of the thee would interfere with each other, meaning that the ground segment can only command one satellite at a time. Setting sun pointing attitude for power and then Earth pointing attitude for communications for a single unit takes about 5 hours. Since the radio contact window with ground control is between 4 to 6 hours, ground control can not control all spacercafts in a single pass. The on board computer in the Uragan-M can put the spacecraft in sun pointing mode autonomously, and does many of the start up processes so the ground segment can take control and process the Earth pointing mode. The payload consisted of 3 L-Band navigation signals in 25 channels separated by 0.5625 MHz intervals in 2 frequency bands: 1602.5625 - 1615.5 MHz and 1240 - 1260 MHz. EIRP 25 to 27 dBW. Right hand circular polarized. It transmits the FDMA signals L1OF, L1SF and L2SF. It uses 2 Cs clocks with a clock stability of 5x10-13. And includes retroreflector for accurate orbit assessment by laser ranging.

History
The first generation Uragan spacecraft were created under ban of foreign radiation-hardened components and thus had an inferior expected design life of just 3 year. Given the realized average life was just 22 months, and the fleet should have 24 spacecraft, it was necessary to launch more than 7 spacecraft per year to keep the fleet in good health.

Versions
The Uragan series was both the first and most extensive model of the Uragan family. As such, it had at least four main versions:
 * Uragan Block I: First batch of 10 satellites. Only has an expected design life of 1 year, but averaged 14 months. Where launched between 1982 and 1985.
 * Uragan Block IIa: Second batch of 9 satellites. Same design life as Block I, but averaged 17 months. Added new time and frequency standards and improved clock stability by an order of magnitude. Launched between 1985 and 1989.
 * Uragan Block IIb: Third batch of 12 satellite. Had a 2 year design life time and averaged 22 months. Two launch failures meant that only 6 were operational. Launched between 1987 and 1988.
 * Uragan Block IIv: The last and most numerous batch of the Uragan design, it had 56 units built and launched. The initial design life was 3 years but later enhancements on radiation hardening increased that to 5 years. Launched between 1988 and 2005.