Attitude control aspects for SCD1 and SCD2

CONASAT is being designed to gather environmental data like rain volume, temperature, humidity, air pollution, ocean streams, environmental hazards, etc. collected and transmitted to satellite by remote platforms on ground, and to retransmit them to the mission center. At least two identical satellites shall be launched, and, together with their antecessors SCD1 and SCD2 (Data Collecting Satellites 1 and 2, from Brazil) launched in 1993 and 1998, respectively, and still operating, they will provide large temporal resolution for environmental monitoring. In order to keep the costs low, CONASAT shall be based on CubeSat technologies. However, the large power required by onboard data transponder implied an arrangement of 8 CubeSat units in a single cubic one, with 230 mm size. All internal subsystems shall be duplicated in cold redundancy, in order to assure the reliability. In addition, in order to fulfill the power requirements, the attitude shall be Earth pointed, since the payload antenna will face to ground. Although there is no restraint in pointing requirements, a set of 3 off the shelf reaction wheels will be employed so as to assure satellite maneuverability and attitude stabilization. Attitude determination will rely in a set of 6 coarse sun sensors (one in each cube face) and a tri-axes magnetometer. QUEST or TRIAD algorithm together with Kalman filter will provide onboard attitude determination and estimation whereas attitude control will be based on a conventional PID, acting on the reaction wheels, and three magnetic coils necessary for wheel's de-saturation. Onboard software reliability is assured by minimizing the number of operating modes. Besides the nominal and stand-by modes (for Earth pointing and station keeping, respectively), the attitude acquisition mode and the safe mode for attitude de-tumbling shall be accomplish by means exclusively of the magnetometer (Bdot algorithm), course solar sensors and the torque coils. Since there is no complete attitude determination on the shadowed part of the orbit, the nominal mode is achieved only after Kalman filter convergence. This work will present the attitude control modes for CONASAT, as well as the transition conditions between modes. The results from the simulated attitude determination, estimation and control will be addressed, with focus on the attitude performance for both nominal and safe modes. This work shall constitute a base line that will guide the on-board control software development, integration, and qualification tests.

Acta Astronautica, 1983

Attitude reorientation maneuvers were conducted three times on the transfer orbit to obtain the apogee kick motor firing attitude of the Medium Capacity Geostationary Communication Satellite for Experimental Purposes (CS) on the third apogee. After two attitude and five orbit maneuvers on the drift orbit, the CS attained geostationary orbit with station keeping accuracy of +0.1 ° seven days after launch.

Transactions of the Japan Society for Aeronautical and Space Sciences, Space Technology Japan

Annual Reviews in Control, 2005

Several new space missions are under development within ESA's Earth Observation (EO) programmes. By 2009 the following satellites will be launched: Cryosat (ice altimetry); GOCE (Gravity field and steady-state Ocean Circulation Explorer); SMOS (Soil Moisture and Ocean Salinity); Aeolus (atmospheric winds); Swarm (magnetic field). Other prepared projects include the SPECTRA (Surface Processes and Ecosystem Changes Through Response Analysis) mission. These missions are briefly reviewed, emphasizing control/navigation aspects when instrumental to the novel EO data. Two representative examples, GOCE and SPECTRA, are described in more detail. Relevant sensor and actuator technology aspects are also outlined. #

Journal of Physics: Conference Series

The aim of this paper is to present an analytical solution for the spin motion equations of spin-stabilized satellite considering only the influence of solar radiation torque. The theory uses a cylindrical satellite on a circular orbit and considers that the satellite is always illuminated. The average components of this torque were determined over an orbital period. These components are substituted in the spin motion equations in order to get an analytical solution for the right ascension and declination of the satellite spin axis. The time evolution for the pointing deviation of the spin axis was also analyzed. These solutions were numerically implemented and compared with real data of the Brazilian Satellite of Data Collection-SCD1 an SCD2. The results show that the theory has consistency and can be applied to predict the spin motion of spin-stabilized artificial satellites.

2008

The Formation Autonomy Spacecraft with Thrust, Relnav, Attitude, and Crosslink (FASTRAC) project from the University of Texas at Austin has developed two nanosatellites as the winner of the University Nanosat-3 Competition. Both satellites have been manifested for a launch provided by the Space Test Program (STP) in December of 2009. The FASTRAC satellites will demonstrate the following enabling technologies for nanosatellites: (1) on-orbit real-time GPS relative navigation via real-time crosslink data exchange; (2) on-orbit real-time attitude determination using a single frequency, C/A-code, reprogrammable GPS receiver; (3) a micro-discharge plasma thruster; and (4) a distributed ground station network. In this paper, the design and testing of the FASTRAC command and data handling system (C&DH) is described. The C&DH system is divided into four subsystems, each controlled by one Atmel Atmega128 microcontroller: communications, electrical power, GPS, and thruster or IMU (depending o...

1993

Proc. 13th Annual AIAA/USU Conference on …, 1999

UoSAT-12 is a low-cost minisatellite built by Surrey Satellite Technology Ltd. (SSTL), it is amongst other objectives also a technology demonstrator for high performance attitude control and orbit maintenance on a future constellation of earth observation satellites. The satellite uses a 3-axis reaction wheel configuration and a cold gas propulsion system to enable precise and fast control of its attitude, for example, during orbit manoeuvres. Magnetorquer coils assist the wheels mainly for momentum dumping. This paper describes the various attitude control modes required to support: 1) the initial attitude acquisition phase, 2) a high resolution imager payload during pointing and tracking of targets, 3) the propulsion system during orbit manoeuvres. The specific attitude controllers and estimators used during these control modes are explained. Various simulation and in-orbit test results are presented to evaluate the performance and design objectives. To improve the control and estimation accuracy, on-board calibration and alignment procedures for the sensors and actuators are utilised. Some calibration results and the resulting improvement in accuracy from these procedures are shown.

Journal of physics, 2015

The goal of this paper is the study of the influence of the environmental torques in the angle between the spin axis and the Sun direction (solar aspect angle) for spin stabilized satellite. The theory uses a cylindrical satellite in an illumined orbit, considering the gravity gradient, aerodynamic, solar radiation, residual magnetic and eddy current torques. The mathematic model for each torque is shown. The dynamic equations are represented in a reference system fixed in the satellite and described by spin velocity and the right ascension and declination angles of the spin axis. An analytical solution for the spin velocity and the attitude angles is used to study the behavior of the solar aspect angle. The theory is applied for the real data of the Brazilian Satellite of Data Collection-SCD1 and SCD2. Two approaches are presented. The results agree with the real satellite behavior for specific time simulation. Then the theory has consistency and can be applied to predict the behavior of the solar aspect angle.

2003

An analytical approach for spin-stabilized satellites attitude propagation is presented, considering the influence of the residual magnetic torque and eddy currents torque. It is assumed the inclined dipole model for the Earth´s magnetic field and the method of averaging such torques, over each orbital period, is applied to obtain the components of the torques in the satellite body frame reference system. The inclusion of these torques on the rotational motion differential equations of spin stabilized satellites yields the conditions to derive an analytical solution. The solution shows that the eddy currents torques causes an exponential decay of the angular velocity magnitude and the coupled effect of both torques produces a precession on the spin axis. Numerical simulations performed with data of the Brazilian satellites (SCD1 and SCD2) show the agreement between the analytical solution and the actual satellite behaviour.

Computational and Applied Mathematics

This paper presents the comparison between the numerical and analytical results of a spacecraft attitude propagation for a spin-stabilized satellite. Some external torques are introduced in the equations of the motion and the comparisons are done considering that these torques are acting together, which are: gravity gradient, aerodynamic, solar radiation, magnetic residual and eddy current. In the numerical approach it is used the quaternion to represent the attitude. This numerical approach can be applied for any kind of satellite. The analytical approach is applied directly for a spin-stabilized satellite and the equations of motion are described in terms of the spin velocity, spin axis right ascension and declination angles. An analytical solution of these equations is presented and valid for one orbit period. Applications are developed considering the Brazilian spin-stabilized satellites SCD1 and SCD2. The comparisons are important to validate some simplifications that are required in

Computational and Applied Mathematics, 2018

SERPENS mission involves research and development of nanosatellites and is inserted in a set of activities carried on by Brazilian universities in the scope of strategies coordinated by AEB (Brazilian Space agency). The first satellite of a series, SERPENS-1, was put into orbit in September 2015, retiring in March 2016. SERPENS-2 mission is currently being designed. The experiments to be carried out in SERPENS-2 are: X and Gamma rays detection; South Atlantic magnetic anomaly detection and testing of a pulsed plasma thruster. Each experiment is related to the attitude. This paper is concerned with the Attitude Determination and Control System (ADCS) design of a 3U CubeSat. A proposal of

2017

MOVE-II (Munich Orbital Verification Experiment) will be the first CubeSat of the Technical University of Munich (TUM) utilizing a magnetorquer-based active attitude determination and control system (ADCS). The ADCS consists of six circuit boards (five satellite side panels and one central circuit board in satellite stack), each equipped with a microcontroller, sensors and an integrated coil. The design enables redundancy and therefore forms a fault-tolerant system with respect to sensors and actuators. The paper describes the hardware implementation, algorithms, software architecture, and first test results of the integrated ADCS on the engineering unit. A possibility to upgrade and extend our software after launch will enable further research on new and innovative attitude determination and control strategies and distributed computation on satellites. The MOVE-II flight unit is in the integration and test phase with an intended launch date in early 2018.

IFAC Proceedings Volumes, 2004

Several new miSSions are under development within ESA's Earth Observation (EO) programmes. In 2005-2009 the following satellites will be launched: Cryosat (ice altimetry); GOCE (Gravity field and steady-state Ocean Circulation Explorer); SMOS (Soil Moisture and Ocean Salinity); Aeolus (atmospheric winds); Swarm (magnetic field). Other projects under final preparations include: EarthCARE (Earth Cloud, Aerosol,and Radiation Explorer) and SPECTRA (Surface Processes and Ecosystem Changes Through Response Analysis). These missions are briefly reviewed, emphasizing controVnavigation aspects when instrumental to the novel EO data. Two representative examples (GOCE and SPECTRA) are described in more detail. Relevant sensor and actuator technology aspects are also outlined.

7TH EUROPEAN CONFERENCE FOR AERONAUTICS AND AEROSPACE SCIENCES (EUCASS), 2017

MOVE-II (Munich Orbital Verification Experiment) will be the first CubeSat of the Technical University of Munich (TUM) utilizing a magnetorquer-based active attitude determination and control system (ADCS). The ADCS consists of six circuit boards (five satellite side panels and one central circuit board in satellite stack), each equipped with a microcontroller, sensors and an integrated coil. The design enables redundancy and therefore forms a fault-tolerant system with respect to sensors and actuators. The paper describes the hardware implementation, algorithms, software architecture, and first test results of the integrated ADCS on the engineering unit. A possibility to upgrade and extend our software after launch will enable further research on new and innovative attitude determination and control strategies and distributed computation on satellites. The MOVE-II flight unit is in the integration and test phase with an intended launch date in early 2018.