SSIRU - Scalable Space Inertial Reference Unit

SSIRU - Scalable Space Inertial Reference Unit 

The SSIRU™ combines innovation and high reliability – with 100 percent mission success in over 50 million on-orbit hours – for precision performance on space missions.

The Hemispherical Resonator Gyro (HRG) sensor on the SSIRU™ 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.

SSIRU™ applications

The Scalable SIRU™ is the spacecraft manufacturer's choice for sensor pointing/stabilization and spacecraft attitude control on demanding space missions, including:

  • ISR
  • Early Warning
  • Communications (Protected & Commercial)
  • Earth Observation
  • Deep Space Exploration

SSIRU™ 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

SSIRU™ heritage

The space-qualified SSIRU™ evolved from the heritage Core SIRU™. Together, these systems have operated in space since 1996 for over 50 million hours with 100 percent mission success. Our heritage systems have been launched more than 200 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/GEO-KOMPSAT, GOES, 601-HP, 702 bus, TDRS, GPM, WGS 1-10, EchoStar, IKONOS, AEHF 1-5, A2100 bus, 1300 bus, STAR bus, GEOStar bus, MUOS 1-5, SBIRS, SBSS, Worldview, Herschel, GeoEye, TerreStar and Landsat.

SSIRU™-L Configuration

The SSIRU™-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™.

SSIRU™-E Configuration

The SSIRU™-E variant has the same overall hardware configuration as the standard SSIRU™. 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™.