SIRU - Scalable Inertial Reference Unit for Space

Scalable Inertial Reference Unit for Space 

The Scalable SIRU™ combines innovation and high reliability – with 100 percent mission success in over 40 million on-orbit hours – for precision performance on space missions.

The Hemispherical Resonator Gyro (HRG) sensor on the Scalable SIRU™ is composed of three simple machined quartz parts—an outer shell, a high-Q vibrating hemispherical resonator and an inner shell. The quartz construction of the HRG is inherently stable, impervious to aging effects, and naturally radiation hardened. Operating in a completely evacuated hermetically sealed case, the HRG sensor is the ideal gyro for space applications.

Scalable SIRU™ 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

Scalable SIRU™ advantages

  • Proven high reliability and long life, due to the simple HRG sensor design
  • Ultra-low angle random walk and inherent freedom from dead band
  • Fault-tolerant, redundant system architecture with cross-strapped HRGs and electronics, helping to ensure the success of missions lasting 15 or more years
  • Demonstrated gyro capability, providing an inertially stable, low noise, wide bandwidth reference
  • Radiation hardened sensors and electronics that operate reliably when subjected to long-term radiation exposure in space

Scalable SIRU™ heritage

The space-qualified Scalable SIRU™ evolved from the heritage Core SIRU™. Together, these systems have operated in space since 1996 for over 40 million hours with 100 percent mission success. Our heritage systems have been launched more than 170 times while used for NASA, Department of Defense, commercial and international space applications, including: Deep Impact, MESSENGER, Cassini, NEAR, GLAST, EOS, Geolite, Aura, Aqua, KOMPSAT 1, GOES, 601-HP, 702 bus, TDRS, GPM, WGS, EchoStar, IKONOS, AEHF, A2100 bus, 1300 bus, STAR bus, MUOS, SBSS, Worldview, Herschel, GeoEye, TerreStar and Landsat.

Scalable SIRU™-L Configuration

The Scalable SIRU™-L is a variant configuration that has the same hardware and associated reliability as the Scalable SIRU™. The Scalable SIRU™-L has streamlined calibration and test processes that lead to a shorter delivery schedule and lower cost compared with the standard Scalable SIRU™.

Scalable SIRU™-E Configuration

The Scalable SIRU™-E variant has the same overall hardware configuration as the standard Scalable SIRU™. A nominal increase in a sensor electronics component value improves the signal to noise ratio, resulting in tripled improvement in Angle White Noise. The Scalable SIRU™-E also has a software filter coefficient change that allows for a higher sample rate capability and significantly improved Angle Random Walk over the standard Scalable SIRU™.