A low cost ½ U CubeSat Compact Inertial Reference Unit (CIRU) is proposed comprising of a patent-pending, digitally-controlled, low power, ASIC-based, piezoelectrically-transduced, Coriolis Vibratory Gyroscope (CVG). Demonstrated at TRL 4 in a lab environment, it has very low Angle White Noise (AWN), Angle Random Walk (ARW) and Bias Stability enabling Attitude Determination with <0.1 arc second pointing and arc second level control. The small size is enabled by our Radiation Hard By Design (RHBD) commercial CMOS ASIC. This results in 4X smaller size, 4X lower weight, and 20X lower power vs. state of the art IRUs, (e.g. MIMU, NGC SIRU). The same ASIC also interfaces accelerometers to complete an IMU for relative or absolute navigation.
The macroscale PZT metal cylinder resonator's very low mechanical thermal noise, digitally controlled with our low-noise ASIC and patent-pending IWAG electronics overcomes the limited range and noise of current analog rate demodulation and digitization. Digital vs. analog control allows low-cost, parameter-based adaptation for more applications and modes of operation such as Whole Angle for high rates, IWAG self-precession for asymmetry detection and switched drive axis operation for bias self-calibration. Eliminating bulky discrete electronics yields a low-cost, lower power, compact CVG with lower parasitic impedance. Our ASIC is collocated and thermal-mechanically isolated with the resonator for precise temperature compensation/control. Gyros are mechanically tuned, balanced, and vibration isolated. The IMU also has vibration isolation for external source suppression.
The Phase 1 project will extend bias compensation and thermal mechanical packaging design to TRL 5 performance in a relevant environment. For Phase 2, we will build the newly designed mechanical package and integrate full RHBD ASIC electronics and optional accelerometers into a compact IRU/IMU assembly with the result being a TRL 6 CIRU/CIMU performance demonstration.
The CIRU enables spacecraft from CubeSat to mid-size to have the same sub-arc-second knowledge and control as large spacecraft at a fraction of the cost. Smaller size and lighter weight also benefits larger satellites and interplanetary missions by lowering cost and increasing payload. Telescope and other pointing payloads can also benefit from smaller mass IRU sensors. Entry, descent, and landing missions can also benefit from the lower cost, light weight, and high performance IMU.
Commercial low earth orbit, geosynchronous, and constellations of spacecraft can benefit from the CIRU smaller size, light weight, and performance at lower cost. Payload pointing, autonomous spacecraft safing, and other space applications are envisioned.
Terrestrial applications include aircraft attitude sensing, autonomous vehicles, north finding, down-hole navigation, and other pointing applications. The large quantity potential of terrestrial uses may further reduce cost for all users.