Innovative microsatellite could expand understanding of
storm systems

MIT Lincoln Laboratory and MIT’s Space Systems Laboratory
developed the prototype system

It's a quite ordinary occurrence for researchers at MIT Lincoln Laboratory to have systems they developed chosen to fly aboard U.S. government aircraft and satellites on scientific missions. For students in two classes in MIT's Department of Aeronautics and Astronautics, it is a special experience to have a microsatellite they conceived and built launched from a larger space vehicle NASA has scheduled for flight in 2014. The students developed the Micro-sized Microwave Atmospheric Satellite or MicroMAS, a three-unit miniaturized satellite designed for providing observations of hurricane dynamics and severe storms. 

CAD drawing of the MicroMASRendering of the Micro-sized Microwave Atmospheric Satellite (MicroMAS).

The MicroMAS project evolved from an idea Dr. William Blackwell, assistant leader of the Sensor Technology and System Applications Group at Lincoln Laboratory and Principal Investigator of the MicroMAS mission, had for an atmospheric satellite that would provide high-quality weather observations and take less time and cost to fabricate. "This was a picture perfect project for students interested in satellite design," says Blackwell about the conceptual problem of creating an innovative, high-tech satellite that can be adapted to the requirements for a 30 × 10 × 10 cm CubeSat with a mass of approximately 5 kg, a category of compact satellite for which commercial off-the-shelf components are typically used.

MicroMAS is composed of a three-axis stabilized CubeSat bus and a spinning interface assembly created by the students and an ultra-compact microwave radiometer payload that was developed by Lincoln Laboratory and that incorporates receiver front-end electronics developed by Neal Erickson, a research professor in the Department of Astronomy at the University of Massachusetts–Amherst.

A major hurdle in understanding and forecasting severe weather systems such as hurricanes is accurately measuring temperature and water-vapor profiles at low altitudes. Passive microwave observations near an oxygen absorption line at 118.75 GHz are used to measure scattering from cloud ice particles, the abundance and size of which give an indication of storm intensity. Lincoln Laboratory algorithms developed for the National Oceanic and Atmospheric Administration (NOAA) and NASA over the last ten years will be used by the MicroMAS for calibration and data exploitation during the observations.

The spacecraft folds up into the size of a quart milk carton, and after ejection from a host satellite, this free-flying microsatellite spins and its solar panels open out like petals of a flower. The panels provide power to the MicroMAS for about half its orbit about Earth and charges batteries that are used for the other half of the orbit.

"There were multiple facets of the project for students to work on," says Blackwell. Students could address structural questions for the development model, design of the spinner assembly, or other systems engineering. One of the more difficult facets of the project was the design of the attitude determination and control subsystem (ADCS), says Evan Wise, a graduate student in the Satellite Engineering course. "Since the payload, a sizable mass, has to rotate relative to the fixed bus, the ADCS must compensate for the angular momentum of the payload while still retaining enough control authority to counter disturbance torques." Wise added that keeping the MicroMAS flying level relative to the Earth's surface was a complementary challenge.

Prof. Cahoy and students work on the MicroMASProf. Kerri Cahoy (3rd from left) works with students (left to right) Eric Peters, Annie Marinan, and Evan Wise on the development of the MicroMas.

Benefits of the project

Blackwell notes one bonus in enlisting students to design the mechanism that will carry the payload. "They are full of ideas. They bring a fresh perspective, unencumbered by conventional wisdom." MicroMAS's dual-spinner, the first known usage of such a structure on a CubeSat, is one of those fresh ideas.

The project also provided a secondary benefit to both students and the Laboratory. "Several students have been inspired to look toward MIT Lincoln Laboratory for internships and after graduation," observes Dr. Kerri Cahoy, an assistant professor who has been leading the development of the MicroMAS spacecraft bus.

NASA too may profit from this capstone project. When deployed in space in early 2014, MicroMAS will collect multispectral, millimeter-wave, radiometric images of tropical storms, hurricanes, and cyclones. It will collect high-resolution data over a wide expanse to improve monitoring of a storm's development. In addition, the students designed a system that is relatively inexpensive to build and test. "Future versions of MicroMAS could potentially replace a $100 million unit with one that costs several million," says Blackwell, "and our analysis shows that the deployment of a constellation of such microsatellites would provide unprecedented performance and reliability at relatively low cost."

The project also introduced students to the demands they would face if they were working in the aerospace industry. According to Cahoy, "Many students haven't had the chance yet to see how a 'real' flight project paces itself from design through test and delivery."

Gwen Gettliffe, a graduate student who not only worked on MicroMAS as part of the Satellite Engineering course taught by Prof. David Miller, but also stayed on for another semester as lead systems engineer, agrees, "This was a realistic experience in presenting program reviews to stakeholders, collaborators, and experts in the field all at once." Anne Marinan, another graduate student also appreciated "the feedback and interaction with collaborators."

Working as part of a team, and one whose composition shifted, was another real-world lesson. Because the project spanned three semesters and a summer period, the roster of students changed during the development process. "The biggest challenge for the students is getting up to speed on a new (for some) project, in fields potentially new to them (especially the undergrads) all in a very short time period," says Rebecca Masterson, a post-doctoral researcher who served as a teaching assistant to the project in the spring 2011 semester. "Also, the MicroMAS team was small, and the biggest teamwork issue was that some members made a very large time commitment compared to others. Finding balance when there is so much work to go around and few experienced students is difficult. By the end of the semester, the students came together as a team and produced a detailed design document for MicroMAS."

To help with the various design tasks, the MicroMAS project drew on a network of engineering talent. Cahoy commends Dr. Idahosa Osaretin of Lincoln Laboratory's Sensor Technology and System Applications Group for his review of the students' design. "He really goes above and beyond." Funded by the Lincoln Laboratory New Technology Initiatives Board, Drs. Timothy Hancock and Christopher Galbraith of the Laboratory's Analog Device Technology Group designed back-end, intermediate-frequency electronics for the unit. Jose Martinez, an assistant professor at Northeastern University, designed the antenna for MicroMAS.

By the time MicroMAS flies, most of the students who worked on the original design will have moved on from MIT. But the experience on the project has been both valuable and memorable. "Having worked on five separate satellite projects during my academic career, this is the most exciting project I have worked on," says Eric Peters, who was involved in the project as an undergraduate student and is now a research specialist in MIT's Space Systems Laboratory, where the MicroMAS engineering design model was created.

"I'm more than a little sad that I've had to move on from MicroMAS . . . It was my first real introduction into the world of satellite engineering, and I'm thrilled that it is actually going to fly, even if it looks very different at launch from the last time I personally assembled it. It represents the efforts of dozens of students and has more than done its job as an educational mission," sums up Gettliffe.

The Space Systems Lab is currently developing the flight version of the spacecraft bus assembly that will accommodate the MicroMAS payload under development at Lincoln Laboratory.

Posted June 2012

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