The satellite LituanicaSAT-1 conforms to standard 1U size cubesat form factor as to the latest cubesat design specifications. The satellite does not have any active systems except the antenna deployment mechanism that is engaged 30 minutes after deployment sequence. Both attitude and thermal control sub-systems are implemented passively for simplicity and safety. The total mass of the body including the equipment within it is 1,090 kg.
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 axes 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 Arduino ATMega 2560 microcontroller. These 2 computers and their periphery are laid out on different sides of one shared PCB. 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 Lithuania.
The LituanicaSAT-1 team developed the secondary flight computer based on the open source hardware and software project named Arduino. This computer will ensure limited, however safe functionality of the satellite in case of failure of the main onboard computer and will also take and record the first pictures made by Lithuanians from space as well as control the radio beacon of the satellite.
Payload. The main payload is FM mode V/U voice repeater. Its key purpose is to extend the radio communication distance between the two correspondents from several to several thousand kilometers. In the course of the LituanicaSAT-1 mission, the stability, reliability and operation of the Lithuanian FM repeater will be verified in space. The repeater also provides an opportunity for alternative communication with the satellite in case of the disruption of the main communications transceiver or the functioning of the radio beacon.
Currently, the prototype of the FM repeater is already operating in the home of its author Žilvinas Batisa (LY3H) in Elektrėnai, Lithuania. Please visit his website here for more details.
The second payload is a 640X480 resolution VGA camera. The pictures will be downlinked to our mission control center and later used to analyze and verify correct satellite attitude.
Power supply sub-system. The power supply sub-system includes a GomSpace Nanopower P31u power board with a lithium-ion battery and solar cells. This sub-system is intended for ensuring continuous supply of electricity to all components of the satellite. When the satellite is in the sunlight, the electricity will be produced by solar cells developed in Lithuania and attached to all six outer walls of the satellite body. As the satellite enters the shadow of the Earth, electricity accumulated in the lithium-ion battery during sunlight will be used.
All sides of the cubesat are covered externally with body mounted (non-deployable) solar panels. Each solar panel is made of silicon solar cells laid on glassfiber-epoxy pad and covered by special transparent epoxy resin. Satellite’s external silicon monocrystaline based solar panels were specially built and donated by Lithuanian based R&D company „PrecizikaMET SC“.
Communications subsystem. This subsystem consists of transceiver and antennas. He-100 COTS transceiver is used on LituanicaSAT-1. This radio device performs a very important and complex function during the mission – to establish and maintain radio communication with the satellite ground station. This is one of the most complicated tasks in the mission, because the satellite will fly above Lithuania at a great speed for approximately 5 minutes. During that time we will have to download important telemetry data of the satellite while having very limited energy resources available and to transmit telecommands back to the satellite. The key technical specifications of the radio transceiver are as follows:
- Operating frequencies:
- Transmission: 437 MHz
- Reception: 144 MHz
- Sensitivity: -104.7 dBm @ BER 10-3
- Transmit power: 100 mW – 2 W
- Receive power: < 200 mW
- Data transfer rate: 9600 bps
- Data protocol: AX.25
- Operating temperature: from -30 to +70 °C
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.
Motherboard. Motherboard of the satellite has inbuilt important equipment for performing critical functions at the time of the satellite deployment, such as powering on the satellite and unfolding of radio communication antennas. Interfaces required for servicing the satellite on the ground are also connected to the motherboard.