SPIRAL CONING MANOEUVRE FOR IN-ORBIT LOW THRUST CHARACTERISATION IN CUBESATS

The ability to accurately measure the level of thrust during in-orbit operations is fundamental to the characterisation
of emerging propulsion systems for nanosatellites. Many new CubeSat missions use propulsion systems with thrust levels
in the order of few micro-Newtons. Whilst laboratory sensing resources are able to resolve such low thrust values, in
complementary in-orbit characterisation are limited and in the main not compatible with the standard CubeSat mission.
Additionally, typical in-orbit assessment of micro-thrust is generally carried out through body angular speed changes,
the effectiveness of which is drastically reduced when external perturbations and sensor noise approach or exceed the
thruster action on the CubeSat. This investigation sets out to improve in-orbit micro-thrust characterisation via changes
in body angular velocity periodicity due to off-centred thrust action in nearly axisymmetric CubeSats. Unlike traditional
methods, the thrust magnitude is determined by the observed variation in angular velocity sweep-out natural frequencies.
Numerical simulations support the feasibility and adequacy of the proposed low-thrust gauging method, specially in weak
and noisy sensor signals. The robustness of the method allows for interchangeable analysed signal and enables the use of
conventional commercial-off-the-shelf rate sensors in fine micro-thrust characterisation.