Estimation and Attitude Control in CONASAT's Nominal Operation Mode: An Approach for SDRE Filter and PID Control

CubeSat attracted interest of international community with numerous studies being developed in some universities, schools or even space enthusiastic. Miniaturization of components and use of conventional electronics reduced costs with space projects, that previously restricted access to space to only a few nations at costs of several million dollars. So, governments and space agencies, especially in developing nations, has begun to invest in small satellite projects, because now they can have space missions at low cost. Thus, the National Institute for Space Research (INPE), in Brazil, has planning some CubeSat missions as an academic tool to spread the space technology across the country to universities and researches. One of the missions in development is the Nanosatellite Constellation for Environmental Data Collection (CONASAT). This project intends to launch at least two small satellites to replace the SCD1 and SCD2 satellites of the Brazilian's environmental data collection system. The main objective of this paper is to propose state estimation technique, known as State-Dependent Riccati Equation (SDRE), together with a PID controller based on attitude error given by the Euler angle and axis for nominal mode attitude control of CONASAT. Simulations were performed using an open computational tool for attitude and orbit simulation.