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THE MAGNETOMETER BOOM ASSEMBLY
The Magnetometer Boom Assembly (MBA) carries the heart and soul of the experiment: The bistable boom and the magnetometers. The boom is initially in a stowed position inside the MBA. When deployed, it extends to a length of 2 metres. The boom contains the magnetometers, accelerometers, gyros, etc. Deploying in about 2 seconds, the bistable boom is one of the most integral parts of our experiments. This self deployable boom consists of 4 bistable composite tape springs manufactured using a glass fibre composite with a vinylester matrix. The tape springs are bistable since they are stable in their coiled and deployed state. They also provide the required energy for boom deployment.
The boom assembly consists of three sections: The base plate, the middle plate and the tip plate. The base plate houses the boom in its coiled state and interfaces with the rest of the FFU. The other two plates- the middle and the tip- contain the two magnetometers and other attitude determination sensors. Previous Gravity offloading experiments with prototypes of the boom assembly show that the boom is deployed in about 2 seconds to a length of 2 meters. Since the assembly hasn't been tested in a low gravity environment, observing and determining the dynamics of boom deployment will be one of the major objectives of our project.
The Boom itself is comprised of 4 bi-stable composite tape springs. These tape springs are stable in their coiled and deployed state and provide the required energy for boom deployment. Bistable tape springs as self deployable booms are highly favorable in the space industry because of their high packing ratio, relatively low cost and their high stiffness to weight ratio. They are essentially ultra-thin composite beams which store strain energy when coiled up. When the deployment is triggered, the energy is released through a single kinematic path. The tape spring design and manufacturing method is similar to the one used in the 3U Cubesat SEAM. SEAM was a electromagnetically clean Cubesat designed and developed by KTH in collaboration with other universities and organizations.
Another major component of the Magnetometer boom assembly are the magnetometers themselves. The experiment uses two magnetometers, one each in the tip and mid plates of the deployed boom. The magnetometers to be used in this experiment are earth field digital fluxgate magnetometers developed by researchers at KTH. According to Forslund et.al. the aptly named SMILE- the Small Magnetometer In Low-Mass Experiment-design combines three dual rod cores in a Macor® cube occupying a volume of 8 cm^3. Since, the magnetic disturbances in the field due to auroras are in the order of 100-2000 nT at the target altitude, the sensors must be highly sensitive to detect disturbances. It has a relatively low power consumption, is compact, lightweight and suitable for deep space applications. Before using in our experiments, the magnetometers will be tested and calibrated in a labaratory at Uppsala University.
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