A new generation of IRS with innovative architecture based on HRG for satellite launch vehicles

The satellite launch vehicles’ evolution goes through a reduction of cost, weight and size of the IRS (Inertial Reference System), while keeping a very high level of performance and safety compatible with this kind of application. The classic approach leads to duplicate this equipment, so assuring a first level redundancy. But this solution is not favourable considering the previous criteria (cost, weight, size) and does not allow detecting a possible slow drift of performance of one of the two IRS because there is no possible majority vote. The approach proposed in this paper is based on a multisensor architecture, integrating 6 gyroscopes and 6 accelerometers, with a triplication of the common functions, which allows using a non-radiation hardened electronics. This integrated architecture facilitates the implementation of FDI techniques (Fault Detection and Isolation), and withstands straight failures and performance drifts of the inertial sensors, the whole being integrated into a single equipment, which allows reducing drastically cost, weight and size. In this context, the use of HRG (Hemispherical Resonant Gyroscope) is particularly relevant because of its low size and weight. As a result, the proposed architecture allows reaching high levels of accuracies, which makes it capable of a wide range of missions. This paper details the proposed inertial and electronic architecture, demonstrates the techniques used for the FDI function and shows the contribution of the HRG for this kind of architecture in terms of accuracy, safety and size.