Attitude determination and control LituanicaSAT-1 uses passive magnetic attitude control system consisting of permanent magnets that create a control torque and soft magnets that provide dampening torque using
hysteresis effect. Following attitude sensors are implemented for attitude determination: • PS-MPU-6000A MEMS
motion sensor • PS-MPU-9150A MEMS motion sensor • L3GD20 MEMS three-axis digital output gyroscope • HMC5883L three-axis digital magnetometer
Command and data management There are two on board computers in LituanicaSAT-1 due to redundancy requirements: the flight computer based on
ARM Cortex-M4F microcontroller and secondary (back-up) computer based on an
Atmel ATMega2560 microcontroller. The flight computer is the central control unit of the satellite responsible for maintaining the normal operating mode of the satellite, monitoring and control of energy resources, control of attitude determination sub-system and performance of telecommands received from the satellite ground station in
Vilnius University,
Lithuania. Secondary flight computer is based on
Arduino. It ensures limited but safe functionality of the satellite in case of the main CPU failure and will also take and record the first pictures made from space, as well as control the radio beacon of the satellite.
Payload The main payload is
amateur radio FM mode V/U voice repeater. It operates on 145.950 MHz uplink (PL 67 Hz CTCSS) and 435.180 MHz downlink. The FM repeater subsystem identifies itself with callsign LY5N. The first filter of repeaters receiver is 15 kHz wide, second is 12 kHz. The transmit filter is set to +/- 5 kHz, and bandwidth to 10 kHz, but this width depends highly on the incoming signal width, for example if the uplink signal is 15 kHz wide, it will be cut down with 12 kHz filter. The repeater payload was engineered and developed by
Žilvinas Atkočiūnas and
Žilvinas Batisa. Due to temperature changes, the downlink frequency may be shifted down by 5 kHz.
Power supply subsystem The power supply sub-system includes a
GomSpace Nanopower P31u power board with a lithium-ion battery and solar cells.
Communications subsystem Comm subsystem consists of
AX.25 transceiver and corresponding antennas.
He-100 COTS transceiver is used for establishing and maintaining radio communication with the ground station. The key technical specifications of the radio transceiver are as follows: • Operating frequencies: TX: 437 MHz / RX: 144 MHz • Sensitivity: -104.7 dBm @ BER 10-3 • Transmit power: 100 mW – 2 W • Receive power: < 200 mW • Data transfer rate: 9600 bit/s • Data protocol: AX.25 • Operating temperature: from -30 to +70 °C
Antennas There are 4 monopole antennas on LS-1: three UHF antennas and one VHF antenna. Each antenna is made of approx. 0.2 mm thick and 5 mm wide spring steel measurement tape. In deployed configuration, all UHF antennas are pointed towards the Z+ body axis direction and VHF antenna is pointed toward –Z body axis. ==Mission control==