CubeSat-UWE 2
If you want to be a part of our CubeSat-UWE 2project, we have following tasks to offer:
For further information contact:
Radu Barza, barza@informatik.uni-wuerzburg.de
- Integration of Solar Cells into the power system
- Finalize the power supply, without solar cells.
- Battery Testing
- Sensor system
- Communication System - Transceiver design
- Design of OBDH Board - Construction of new H8 CPU
- Investigate the attitude determination method
- Antenna deployment mechanism
- Design of the exoskeleton and mounting strategy
Define a test procedure and do preliminary tests with cheaper solar cells, which are already available (Si). Before starting the tests, the solar cells have to be connected to a rigid structure, a protection glass layer has to be mounted on top and electrical contacts have to be attached – this can be done by a specialized company which is to be looked for.
Acquire GaAs solar cells, mount them as described above and do some tests using a sun-simulator and a thermal chamber. Plot curves efficiency vs. temperature, voltage vs. incidence angle, maximum power vs. incidence angle. Determine the optimum layout for the solar cells in order to connect them with the power board.
Do a power budget in order to see how much power the solar cells can generate. Take into account the power losses in the protection diodes. Consider one, two or three faces illuminated by the sun, and albedo radiation.
Note: The solar cells have a p-n junction characteristic (diode). Make sure that under no circumstances some solar cells generate power while some other consume. Do not add unnecessary protection diodes, as they cause power losses and voltage drop.
Required skills: Electronic engineering, experience with solar cells design (preferable).
Duration: 3 months.
Look for and test different types of Li-polymer chargers with temperature control and select the one with the best efficiency. Design and test several under-voltage protection circuits and select the most reliable one.
Define an interface between the power board and the rest of the satellite and decide what kind of inputs (ex. Charge-enable pin) and outputs (ex. Current sensor outputs) are necessary. Implement the “remove-before-flight” pin. Design a board which integrates the charger and the under-voltage protection taking into consideration the interface specification.
Build the board and test it using a current limited power supply and a load simulating the other systems; determine the maximum power loss in the power system and the curve efficiency vs. power consumption.
Note: When the satellite is in the sun, the power board has to take the power delivered by the solar cells and divide it to charge the batteries and provide power to the other subsystems. When the satellite is in the shadow, the other subsystems have to be supplied with power from the batteries.
Required skills: Electronic engineering, layout design (Eagle), soldering skills.
Duration: 6 months.
Look for a vacuum chamber and ask for the costs to use it. Do tests with batteries using a vacuum chamber and determine whether the capacity has a significant variation under low pressure. Do complete and incomplete charge/discharge cycles and plot a curve capacity vs. recharge cycle for low pressure conditions. A relevant number of charge-discharge cycles have to be performed – suggestion: minimum 50. Do several incomplete charge-discharge cycles simulating the exact temperature variation in the satellite, under low pressure condition and see if the combination of low-pressure and temperature variation affects battery performance. A relevant number of charge-discharge cycles have to be performed – suggestion: minimum 25.
Required skills: Basic electronic knowledge, Excel, patience.
Duration: 2 months.
Decide what kinds of sensors (temperature, current, etc.) are mission-critical for CubeSat. Chose space proved sensors, build experimental boards and test them. Monitor the power consumption and accuracy variation vs. temperature for low pressure condition (if possible). Define an interface between the sensors and the on-board data handling system (A/D converter, digital interface, etc.). Build a board which integrates all sensors and which can be connected to the main microcontroller using the specified interface.
Required skills: Electronic engineering, experience in working with sensors, Layout design (Eagle), soldering skills.
Duration: 3 months.
Decide what kind of transceiver will be used for CubeSat.
Consider CubeSat specifications for mass, volume and power budget.
Build (or purchase) an experimental board. Decide what kind of antenna can be used on the satellite – transmission/reception in the 70[cm] band.
Purchase and install the antenna and perform transmission tests (measure gain, signal to noise ratio).
Connect the transceiver with the MSP430 processor and write software to control the data transmission.
Define an interface between the transceiver and the on-board data handling system (between the MSP430 and the H8 processor).
Do a power budget for the transceiver.
Note: Antenna design has to be made in close cooperation with the structural design, as an antenna deployment mechanism is needed.
The MSP430 and the H8 processor will be located on the same board.
The interface between them has to be defined before the design of this board starts.
Required skills: Electronic engineering, experience with HF modules required, Layout design (Eagle), soldering skills, C programming (MSP430).
Duration: 6 months.
Design a new board for the H8 and MSP430 processors. Implement external watchdog(s), internal one is not working.
Take into account the specifications for all interfaces related to this board – sensors, power system and communication module.
Check what types of memories and which amounts have to be installed in order that uLinux will run correctly on this board.
The microcontroller board must be laid out so that it fits into the CubeSat dimensions.
Ensure that the board is build according to EMI specification.
Build the board and test uLinux on it. Do a power budget for this board and check if the power consumption is within the specified limits.
Note: As the MSP430 and the H8 processor will be located on the same board, the interface between them has to be defined before the design of this board starts.
Required skills: Electronic engineering – in particular digital design, experience with EMI design required, Layout design (Eagle), soldering skills.
Duration: 6 months.
Recommended skills: Physics, mathematics
Duration: 3 months
Recommended skills: Basic mechanism, physics
Duration: 3 months
Recommended skills: 3D CAD, hand-drafting, strength of material
Duration: 3 months
