Feasibility study of a PocketQube platform to host an ionospheric impedance probe

Since the advent of CubeSat spacecraft, universities and private entities have been successfully designing and launching satellites at a fraction of the traditional cost. These satellites still accommodate useful scientific payloads. Another recently established satellite format is the PocketQube (PQ) - one eighth the size of a CubeSat – with the aim of further reducing launching costs. However, this brings with it the challenge of working with substantially smaller power, mass and volume budgets. Accurate ionospheric modelling requires the use of electron density measurements at the topside of the ionosphere which could be obtained via distributed in-situ sensing. This makes a low cost PQ constellation ideal for this application. In order to assess the feasibility of the PQ format, a preliminary study was conducted about the design of a PQ technology demonstrator capable of carrying a scientific payload. In this paper, the design approaches are discussed, keeping in mind the design budget restrictions as well as the constraints imposed by the ionospheric sensor.The research work disclosed in this publication is funded by the ENDEAVOUR Scholarship Scheme (Malta). The scholarship is part-financed by the European Union – European Social Fund (ESF) under Operational Programme II – Cohesion Policy 2014-2020, “Investing in human capital to create more opportunities and promote the well-being of societypeer-reviewe

Feasibility study of a PocketQube platform to host an ionospheric impedance probe

Since the advent of CubeSat spacecraft, universities and private entities have been successfully designing and launching satellites at a fraction of the traditional cost. These satellites still accommodate useful scientific payloads. Another recently established satellite format is the PocketQube (PQ) - one eighth the size of a CubeSat – with the aim of further reducing launching costs. However, this brings with it the challenge of working with substantially smaller power, mass and volume budgets. Accurate ionospheric modelling requires the use of electron density measurements at the topside of the ionosphere which could be obtained via distributed in-situ sensing. This makes a low cost PQ constellation ideal for this application. In order to assess the feasibility of the PQ format, a preliminary study was conducted about the design of a PQ technology demonstrator capable of carrying a scientific payload. In this paper, the design approaches are discussed, keeping in mind the design budget restrictions as well as the constraints imposed by the ionospheric sensor.The research work disclosed in this publication is funded by the ENDEAVOUR Scholarship Scheme (Malta). The scholarship is part-financed by the European Union – European Social Fund (ESF) under Operational Programme II – Cohesion Policy 2014-2020, “Investing in human capital to create more opportunities and promote the well-being of societypeer-reviewe

Input Redundancy under Input and State Constraints (Extended version of the submission accepted to Automatica)

For a given unconstrained dynamical system, input redundancy has been recently redefined as the existence of distinct inputs producing identical output for the same initial state. By directly referring to signals, this definition readily applies to any input-to-output mapping. As an illustration of this potentiality, this paper tackles the case where input and state constraints are imposed on the system. This context is indeed of foremost importance since input redundancy has been historically regarded as a way to deal with input saturations. An example illustrating how constraints can challenge redundancy is offered right at the outset. A more complex phenomenology is highlighted. This motivates the enrichment of the existing framework on redundancy. Then, a sufficient condition for redundancy to be preserved when imposing constraints is offered in the most general context of arbitrary constraints. It is shown that redundancy can be destroyed only when input and state trajectories lie on the border of the set of constraints almost all the time. Finally, those results are specialized and expanded under the assumption that input and state constraints are linear

Reaction Wheels Desaturation Using Magnetorquers and Static Input Allocation

International audienceConsidering the most widely spread configuration of actuators for low orbit satellites, namely a set of reaction wheels and a set of magnetorquers, we revisit the classical " cross product control law " solution for achieving attitude stabilization and momentum dumping. We show how the classical solution has a quasi-cascade structure that, under a suitable input-to-state (ISS) assumption, can be stabilized by high gain, thereby making the actuators more inclined to saturate. Motivated by this, we propose a revisited version of this control law that transforms the quasi-cascade into a real cascade. Then we show that both strategies are such that the attitude control is affected by the momentum dumping, and that they both require a suitable ISS property. To overcome these drawbacks, we propose a new allocation-based controller which makes the attitude dynamics completely independent of the momentum dumping and induces global asymptotic stability without any ISS requirement. Several formal statements and simulation results support our discussions and highlight the pros and cons of the different control strategies