Scalable SIRU™ Inertial Reference Unit for Space
The high reliability Scalable SIRU™ ensures precision performance for critical space missions.
HRG – A Design with Proven Reliability
The Hemispherical Resonator Gyro (HRG) sensor is comprised of three simple machined quartz parts – a high-Q vibrating hemispherical resonator, and inner and outer shells which support the resonator within.
The quartz construction of the HRG is inherently stable, impervious to aging effects, and naturally radiation-hard. Operating in a completely evacuated hermetically sealed case, the HRG sensor is not affected by any phenomena that could make it wear out or limit its life – making it an ideal gyro for space applications.
Scalable SIRU™ Unique Benefits for Space Applications
The HRG-based Scalable SIRU™ incorporates unmatched features:
- Proven high reliability and long life, due to the simple HRG sensor design
- Fault-tolerant, redundant system architecture with cross-strapped HRGs and electronics, ensuring success for missions lasting 15 or more years
- Demonstrated gyro capability, providing an inertially stable, low noise, wide bandwidth reference
- Radiation hard sensors and electronics that operate reliably when subjected to long-term radiation exposure in space
Redundancy Ensures High Performance for Over 15 Years
The efficient and redundant architecture of the Scalable SIRU™ minimizes subassembly count. It contains:
- Four HRGs and four (optional) accelerometers, with associated loop control/ readout/ thermal control electronics, and sensing along the octahedral- tetrad axes
- Two power supplies and two sets of sensor processors with input/output electronics
Each of the four inertial sensor channels can be operated by either of the two power supply/processors, providing a probability of mission success of 0.996 for a 15 year mission.
Demonstrated Inertial Reference Performance
The Scalable SIRU™ features precision inertial rate measurements, characterized by extremely stable gyro bias, low noise, and precise scale factor. The tables on the reverse side illustrate these features.
Rad Hardness Can be Scaled for Varying Environments
Radiation hardness can be scaled by selecting specific parts and variable thickness bolt-on shielding for low total dose, high total dose, high dose rate [2E8 rad (Si/s], and SEU/SEL tolerance.
Applications
The Scalable SIRU™ is the spacecraft manufacturer’s choice for sensor pointing/stabilization and spacecraft attitude control on demanding long term space missions, including:
- Earth orbits at all altitudes/angles
- Interplanetary missions
- Deep space missions
Heritage
The space qualified Scalable SIRU™ evolved from the heritage Core SIRU™, which has operated in space since 1996 for over 4.5 million hours with 100% mission success. Over fifty NASA, Department of Defense, commercial, and international space applications use SIRU™ systems, including: Deep Impact, MESSENGER, Cassini, NEAR, GLAST, EOS, Geolite, Aura, Aqua, KOMPSAT 1, GOES, 601- HP, TDRS, XM, WGS, 702 bus, EchoStar, IKONOS, AEHF, A2100 bus, N-Star C, and PanAmSat.