The algorithm for estimating angular rate of spacecraft in survivability mode

The paper discusses the issue of ensuring survivability of Spacecraft (SC) in its long-term autonomous operation in space conditions for cases of critical failure of rate sensors. We presented an autonomous control loop in survivability mode in the form of a functional circuit and a mathematical model of control loop. On the spacecraft engineered by JSC ISS - Reshetnev, failures of an angular-rate sensor took place; these failures reduced a redundancy level and unfailing performance of SC; the failure of a standby angular rate sensor will lead to impossibility to use this mode. We came up with a solution to a problem of potential failures of angular rate sensors for spacecraft in operation in orbit using addi- tional control logic; this solution is the purpose of our work. We developed a mathematical model of control without using an angular rate sensor. We described the model in details and it included estimating the angular rate according to previously generated control actions, calculation of control actions and filtration of evaluation registration accord- ing to measuring of a solar sensor. We showed the purpose of each newly introduced block that gives such advantages as improving the noise immunity of control loop to measurement errors, providing search rotation in the case of failure of all rate sensors. Improved control algorithm was synthesized. Having improved the basic algorithm, we carried out ground and flight tests. We performed mathematical modeling in the environment called GNU Octave. Hybrid modeling was performed on rotary tables equipped with functional models of units and a functional model of onboard control subsystem. We conducted flight tests on real geostationary SC flying in orbit. For each test, we pro- vided description of initial conditions and presented graphs of measurement of angular rate. We carried out all the tests successfully, and the algorithm is applied on the SC engineered by JSC “ISS - Reshetnev Company”.