It is important in the above application to point the antennas towards earth for beaming the cryptokey and receiving information from the ground.
For the above application it is proposed to use a satellite attitude control system design using low-cost hardware and software for a 3U CubeSat. For any satellite mission, the attitude control system architecture is a crucial subsystem for precise pointing, it is often required to meet mission objectives. It is often challenging for small satellites to obtain the accuracy and precision requirements where limited power, mass & volume is available for the attitude control system hardware. In this proposed 3U CubeSat embedded attitude control system design pointing is obtained through a two-stage approach involving coarse and fine control modes. Fine control is obtained through the use of three reaction wheels or three magnetorquers and one reaction wheel along the pitch axis. Already a significant design work has been conducted to realize the proposed architecture in various research papers. More information can be obtained from the link to the research paper below this gives a complete overview of the embedded attitude control system design; the verification results from numerical simulation studies to demonstrate the performance of a CubeSat-class nanosatellite; and a series of air-bearing verification tests on nanosatellite attitude control system hardware that compares the performance of the proposed nonlinear controller with a proportional-integral-derivative controller.
CubeSat ACS Hardware includes the following
1. Attitude Sensors
Honeywell HMC5883L three-axis MEMS magnetometer for magnetic field measurements.ngular rate information is obtained in three axes from three orthogonally mounted Analog Devices ADXRS614 MEMS gyroscopes. The attitude control system is managed by an AT91SAM9260 32-bit ARM9 microcontroller that runs embedded Linux, with 32 MB SRAM, and 256 MB NAND Flash attached for volatile and nonvolatile storage. All programming of control algorithms is accomplished in the C language using the GNU C compiler for the ARM processor. The power is provided by the solar panels.
2. Magnetorquer Design
Magnetic torque coils, also referred to as magnetorquers, in CubeSat-class nanosatellites provide baseline control in many small satellites. The rod configuration is often preferred because of its compactness and rigidity and the use of high-permeability, , materials for the core.
3.Reaction Wheel Design
For Maneuvering of satellites a rotating mass such as a reaction wheel and momentum wheel, which provide maneuvering torque and momentum storage is used . Reaction wheels can provide a high degree of attitude control accuracy with the limitation that the wheel may reach saturation after continued use, requiring an additional momentum control method such as magnetorquers to desaturate the wheel in a process known as momentum dumping.
4. Electronic Integration of ACS Components
To control the reaction wheel and magnetorquers hardware and house the attitude sensors and actuator drivers, a printed circuit board is required. The board makes a HMC5883 three-axis magnetometer, an ADXL345 3-axis accelerometer, and an ITG-3200 3-axis MEMS rate gyroscope available on the OBC I2C bus.
References:-
https://www.hindawi.com/journals/jcse/2013/657182/Design of Attitude Control Systems for CubeSat-Class Nanosatellite
Junquan Li, Mark Post, Thomas Wright, and Regina Lee
Department of Earth & Space Science and Engineering, York University, 4700 Keele Street, Toronto, ON, Canada M3J 1P3
