New steps of Lithuania towards space are being made by developing nanosatellites. Two working groups are working towards the development of concepts for the international project QB50. This time, we present a nanosatellite being designed by Space Science and Technology Institute (KMTI)
Over several years, Lithuanian Space Association (LKA) have managed to make a small however a clearly visible both political and social breakthrough in cosmic consciousness in Lithuania. The President of the Association Vidmantas Tomkus manages to be in several places at once wherever space trajectories meet: a number of visits abroad and four international space conferences in Lithuania gave the stimulus to our country to move towards cosmic orbit. Eventually, inspiration for nanosatellites emerged. In 2011, two working teams joined the international project QB50. Finally, we also design nanosatellites! Nanosatellites is a category of small artificial Earth satellites (weighting from 1 to 10 kg).
Objectives of the project
The objective of the project QB50 is to launch 50 nanosatellites to the low Earth orbit. The underlying scientific objective is to research low Earth thermosphere using the network of nanosatellites. The launch of the satellites is planned in the middle of the year 2015, however, related work has been already carried out. Orbital parameters: height 320 km, inclination – 79°, life cycle in the orbit – approx. 3 months. Launcher – Štil 2.1, modification of a ballistic missile R-29RM (Р-29РМ) to be launched from submarines of the type Delfin (project 667BDRM). It is planned to launch the missile from the submarine (non-immersed) in Barents Sea.
International project QB50 is being organized by the Von Karman institute in Belgium. QB50 is aimed at providing the possibility to world’s universities and organizations to get into space with their small satellites. Almost 100 universities and various organizations from all over the world are participating in this competition. In the project developed by the Lithuanian Space Science and Technology Institute, reaction sphere, a device that has not been used in the global practice will be implemented. One of the designers, the director of KMTI dr. Domantas Bručas gave more detailed information about the process of designing nanosatellite.
About the satellite
KMTI satellite of the type CubeSat is designed to be 200x100x100 mm in size with the weight up to 2 kg. There is a requirement imposed to use the supplied QB50 sensors (at the front of the satellite), integrated QB50 gauges, integrated operational equipment, and some load that would be interesting for the community of scientific engineering. The load may be selected at own discretion.
The designers of nanosatellites have chosen an experimental satellite 3-axis positioning device (3 degrees of freedom) as their load. This device operates on the principle of accumulating inertia momentum in a rotating mass (circle of reaction). It represents and innovative opportunity to shift the position of a satellite around three axes at once using the mass of a spherical shape (reaction sphere). The reaction sphere driven by piezo drives is being designed by Space Science and Technology Institute in cooperation with the Mechatronics Centre for Research, Studies and Information at Kaunas University of Technology.
For performing additional research, the following devices will be implemented into the satellite: Gammalink communication and GPS module from the company Tekever, which is still being tested; satellite communication modem STX-2 from GlobalStar; Space GPS Receiver MNP-6 (МНП-6); GomSpace NanoCam C1U Earth observation camera.
Unique reaction sphere
The equipment is unique and developed in Lithuania, it has not been used in the global practice. Rotary movement of the sphere is obtained by generating traveling wave in hemispherical converter. Rotating mass (sphere) is maintained pressed to the converter with the help of a rigid element or a magnet. The use of piezo drives allows reducing and simplifying the whole device. It has been determined that reliable navigation and stabilization of satellite (up to 8 degrees per second transversely, and 16 degrees/s longitudinally) requires a steel sphere 30 mm in diameter. A significant advantage of using piezo drives lays in its high angular acceleration that allows for prompt responses to satellite control (stabilization) commands. The problem with these drives is that rotation requires constant generation of vibrasions. This device will allow stabilizing the satellite in space at the required time thus ensuring a stable platform for various types of examinations (e.g., land surface photographing). Accumulation of inertia momentum in the sphere is compensated by magnetic coils integrated into solar cells.
Currently, the satellite is in the final stage of assembly with the systems being tested. In a short while, final testing of the satellite is planned (vibration and vacuum systems, radio equipment, etc.). Currently, the satellite is installed the following standard (commercial) parts: power supply unit, and data communication module, radio transponder. Parts that have been manufactured (modified) in Lithuania: housing (with antennas, etc..), silicon solar cells and the plate with light sensors; Gallium arsenide solar cells with the panel (the very cells are commercially available, however they were installed onto the plate in Lithuania) and light sensors; the main board with the ARM Cortex processor, GPS / GLONASS receiver (commercially available however not yet tested on small satellites), position sensors (gyroscopes, magnetometers , temperature sensors) radio transponder amplifier. The satellite will have a passive magnetic orientation in the orbit, i.e. it will be positioned according to the earth’s magnetic lines with the help of permanent magnet.
Some new tasks were performed that have not been planned in advance: additional heat sensors; light sensors on surface panels (for setting illumination level for the satellite); installation of transponder amplifier (which has not been planned before).
Additional functions of the satellite
The main task of the satellite is to test systems and equipment for subsequent scientific-exploratory missions, i.e. this is a pilot satellite that will give experience and provide knowledge on what equipment and systems should be used for future satellites (commercial equipment turned out to be not entirely well-functioning). Another mission is planned in 2013, and the satellite will be incorporated a completely new scientific-exploratory equipment.
The satellite under construction will have the following functions: turning on the systems, turning on radio beacon; establishing a two-way communication with the station on the ground (in Liepiškės); receiving data on the position of the satellite in space (rotation, position in magnetic field, illumination of the surface panels, inner temperature); obtaining data on the operation of the elements, general operation of the satellite; test the positioning with the help of GPS/GLONASS, obtain data; testing of radio transponder; broadcasting three Lithuanian words (with the help of transponder). Anyone with a radio receiver and a suitable antenna will be able to hear the words.
“Testing has revealed a substantial amount of defects of commercial equipment that cannot be removed (or takes too much time) due to the close software of the equipment. If such equipment would be designed on site (in Lithuania), these problems could be avoided thus significantly reducing the cost of equipment” – said Mr. Bručas.
The article prepared as a part of the project “Encouraging local and international scientific cooperation, and competence development” funded by the European Social Fund and the Ministry of Education and Science.
About the project: http://is.mokslasplius.lt/en/apie-projekta/