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Satellite General Description
The FloripaSat-I consists of a 1 U cubesat with seven boards stacked (OBDH, EPS, TT&C, battery board, interface board and two payloads).
The OBDH, EPS, TT&C, battery board and interface board were developed by FloripaSat team at UFSC. The antennas, solar panels and structure modules were acquired from ISIS nanosatellite supplier.
Payloads are modules that are not essential for the normal operation of the satellite. Usually they are scientific experiments, cameras and other equipaments that are part of the main objective of the mission.
The electrical power system main functions are to extract, store and manage electrical energy. It was designed to store the energy coming from solar panels in two lithium-ion batteries, and supply energy to all the modules of the FloripaSat. The batteries are monitored by a chip for charging and discharging them safely, and their temperatures are measured by an RTD and a chip to control a heater that keeps the batteries warmed. The EPS also has current sensors and performs voltage measurements to get information about solar panels performance. All information is managed and registered by a microcontroller. The batteries are allocated on a own board above EPS.
The On-Board Data Handling module is responsible for synchronizing actions, and also for the data flow between other modules (i.e. EPS, Payloads) and the ground stations. It packs the generated data into data frames and transmits telemetry back to Earth through the TT&C module, or stores it on a non-volatile memory, for later retrieval. Commands sent by the ground stations will be received by the TT&C and forwarded to OBDH, which takes the appropriate action, or forwards them to the responsible module, which allows direct communication from a ground station to specific Payloads.
The TT&C transmits telemetry and beacon signals. Also, it receives tele commands from ground stations which are processed by the OBDH module. It has two radios: one for transmitting beacon signals, at the VHF frequency; and the main one for telemetry transmission and commands reception at UHF frequency. This back and forth from the radios will be controlled by an RF switch. The main radio is controlled by the OBDH, and the beacon is controlled by the TT&C's microcontroller.
Our Attitude Determination and Control System (ADCS) is a Passive Attitude system, which uses Earth's magnetic field to rotate and stabilize the satellite. The system is composed of one magnet to create a force to align the magnet with the Earth's magnetic field and four hysteresis bars to damp the cube oscillations and stabilize. They are placed in positions to minimize the magnet effect on the bars. As a passive magnetic attitude control system is used, it is possible to stabilize only two axis, and so, the cubesat will still rotate around one of its axis, even after stabilized. A neodymium magnet N45 and 4 hysteresis bars of Permanorm 5000 H2 are used, courtesy of Vacuumschmelze, german company. The material of the hysteresis bar is shaped in order to maximize the stabilization, which is the most important part of the attitude control.
The Rush payload is a prototype developed by UNSW (Australia). Designed primarily to validate a new approach to reconfiguring single event upsets due to solar radiation in reconfigurable logic circuits. This payload takes as hardware reconfigurable an FPGA because of its ratio between logical density and power consumption.
The UFSC Campus Joinville developed a payload with the objective of generating energy from the temperature variations between the faces of the satellite. This payload is autonomous in matters of power, that is, the energy generated will be reverted to the power of the board itself.