Wayne R. Keith
Fellowship Progress Report
Over the past year I have been involved in various aspects of bringing a space plasma instrument from design to flight, including hardware, calibration, computer modeling, and software development. This instrument, called the Miniaturized Electrostatic DUal-top-hat Spherical Analyzer, or MEDUSA, is the first in a series of such instruments that will be flying on various satellite missions in the coming years. Over the course of this project, I have had opportunities to work with numerous professionals at Southwest Research Institute on engineering, science, and software issues related to the instrument. From this I have gained valuable insight into the process of taking an idea from drawing board to science data, as well as collecting an abundance of material for my Master's Thesis.
The instrument is actually two in one, measuring the energies and directions of both ions and electrons in the 1eV to 20KeV energy range. Each side of the instrument is a spherical "top-hat" energy analyzer with a 360deg field of view divided into 16 sectors with a 10deg opening angle. The circuit boards and Data Processing Unit (DPU) for the instrument were fabricated at the Swedish Institute of Space Physics, with whom we are collaborating on this project. Its small size (18cm longest dimension) and light weight (1.7kg) make it suitable for even the smallest satellites. During this past year, we have completed the proto-flight model, which is currently in calibration. In addition, the engineering model which I initially assembled during the 96-97 academic year was refitted into the second flight unit, or MEDUSA-2. This instrument will be mated with it's Swedish components and tested during the first two weeks in August. I am currently in Sweden and will be aiding with the assembly and testing.
The satellite the first instrument will be on is the Swedish Space Corporation's Astrid-2 which is scheduled to launch from Russia in September of this year. Astrid-2 is a very small (35kg, < 1 cu. meter in volume) "microsatellite" which will orbit at an altitude of 1000m and an inclination from the equator of about 85 degrees. This high latitude orbit will take Astrid-2 over the auroral regions in the north and south, giving MEDUSA an excellent view of the precipitating particles that cause the phemomena. The data collected by this and other scientific instruments will contribute to our understanding of the space environment around the Earth and the interaction between Earth and it's surroundings.
The calibration of the instrument was performed at the Swedish Institute of Space Physics in Kiruna Sweden. I had the opportunity to go to Sweden on two separate occasions in order to perform the calibrations at their facilities. (In fact, I am in the Calibration Lab in Kiruna as I write this report.) Using electron and Argon ion sources, each side was characterized such that the data it will send down from space can be properly interpreted. Some of the calibration data include graphing the MCP bias voltage vs counts to determine the proper voltage setting, calculating the geometric factor and energy resolution from multiple elevation scans and varying energies, and confirming the variations in gain around the 16 sectors.
The calibration data can also be compared with the output of a 2.5D ray tracing model. This raytracing code, which I modified to allow for a more realistic instrument geometry, created simulated calibration data which can be used to better understand the data taken in Sweden. It was also used to test various changes in the collimator configuration in order to change the energy resolution for another upcoming mission. It was found that the best energy resolution without significant loss of geometric factor was produced by setting the opening angle of the collimator to 0 deg. This information will be helpful on future missions and improves our understanding of the instrument.
In addition to the work done on the instrument itself, I was also involved in writing the software that would convert the incoming telemetry into a standardized data format used at SwRI called the Southwest Data Display and Analysis System (SDDAS) and for viewing the data in various science units. Once the calibration data have been properly interpreted, the various tables needed to interpret the raw data will be added to this software "framework". A real-time web interface is also in the works, which would allow anyone to view the data from their Internet browser as it comes down.
This project has been very interesting and intellectually stimulating over the course of the past year. Additionally, I have had the opportunity to visit several foreign countries (Sweden, Norway, and Finland), and develop relationships with professionals in my field both in the US and Sweden that will be valuable assets in my future career. The knowledge and experienced I have gained during my time as a TSGC fellow has given me what I need to complete my Master's degree and move ahead towards my PhD in Space Physics.
Back to the 97-98 Fellowship Recipients
Saturday, 28-Aug-1999 12:55:01 CDT
CSR/TSGC Team Web