Alice Liu’s Good Vibrations
One of the more challenging aspects of designing and building scientific spacecraft and instruments (as if there are EASY parts to that process!) is the ever increasing need from the science community for better and better instrumentation to provide higher quality data about the Earth and the universe. Telescopes need to be more powerful with higher resolution, tighter pointing requirements, and greater stability. As those space-based instruments become more sensitive, relatively small vibrations from solar arrays articulation, attitude control systems and other moving parts on a spacecraft can cause enough disturbances to degrade science observations. Characterizing that dynamic excitation, called “jitter,” and making sure that it doesn’t adversely impact a science mission is a specialized field of engineering requiring knowledge of both structural dynamics and control systems.
Alice Liu is one of the engineers at NASA Goddard Space Flight center who specializes in jitter analysis. I first met Alice back in 2006 when we were both working to develop the Solar Dynamics Observatory (SDO). Since then, Alice and I have worked on a few other projects together, but I hadn’t taken the time to get to know Alice much more beyond those professional interactions. It wasn’t until my interview with this remarkable engineer that I learned about her journey from a shy, teenage girl with little interest in a STEM career to becoming one of Goddard’s leading experts in jitter analysis.
Alice Liu and her family immigrated to the United States from Taipei, Taiwan when Alice was 14 years old. Her family settled in the Washington, DC suburb of Gaithersburg, Maryland and that was where Alice spent her Middle and High School years. After graduation from high school, Alice attended the University of Maryland in College Park, MD where she received her undergraduate degree in Aerospace Engineering and her Masters in controls. In 2003 she completed her PhD program at MIT with a major in controls and estimation, and a minor in structural dynamics.
It was her advisor at MIT who helped lead Alice to a career at NASA. As Alice said, “He (her advisor) was very much into controls work but also a lot of systems engineering work. He was very close to NASA and supported JWST (James Webb Space Telescope). He’s a telescope fan. That’s how we got into telescopes and doing structural dynamics and vibration work for NASA.”
That, In broad strokes, is how Alice got to where she is today. As we talked more, we discussed Alice’s decision to pursue engineering as a career, her experiences as a woman engineer both in school and the professional world, and advice she has for aspiring women engineers.
Q: How did you get interested in engineering and when did you know you wanted to be an engineer?
A: Unlike a lot of my peers, I didn’t know I wanted to be an engineer until much later in life. In fact I didn’t get excited about engineering until I took physics in high school. While I was growing up I preferred language and history more than math and science. However, when I first came to this country, I struggled with learning English and any literary focused classes, since I knew almost no English when my family moved here. I struggled with a lot in subjects that I used to like, like language and history, because there was too much reading involved. Also, in Taiwan we learned more advanced level math at an early age so when I came here math was really easy. I’d learned those types of problems before and knew how to solve them.
“All of the sudden I switched from someone who liked language and writing to someone who liked math and science”
So all of the sudden I switched from someone who liked language and writing to someone who liked math and science. Much less reading involved! I have to thank my high school physics teacher for inspiring me to become an engineer. He believed that the best jobs are either being an engineer or a teacher. So (when it was time to pick a college major) I literally opened up school catalogs to decide what kind of engineering field I wanted to go into. Aerospace was the one that popped out. It was the one that excited me the most. So that’s how I picked aerospace engineering.
Q: What was your experience like as a woman in a STEM degree program in college?
A: Going through college was probably one of the best times in my life in the sense that I went through this hardship of moving to a different country and learning a different language, so I was kind of shy in middle and high school because I didn’t know how to communicate well. By the time I got into college my communication skills had gotten a lot better and I could make friends and talk to people much better. So I really got involved in a lot of different things.
While there were only a few women in the Aerospace Engineering Department when I was in college, I got involved with the Society of Women Engineers (SWE) early on. I served as the treasurer, vice president, and membership coordinator for three consecutive years. I made a lot of friends and because I was in the SWE I met a lot of talented women. We worked well together and I never felt I was lonely in the engineering department because I had really good friends and support.
In addition (to SWE), I also got involved with American Institute of Aeronautics and Astronautics (AIAA) and was the vice president during my senior year in college. I had fun. Not just being a little nerdy person, I actually stepped out of my shell and did a lot of school related activities in science and engineering. One of the things I found out about myself is that I like to work with other people. I like to take a volunteer role and do more.
“I realized that I loved working with people and bringing people together to accomplish common goals.”
Through these voluntary and extracurricular activities, I was able to gain lasting friendships and support in my field of study. More importantly, I realized that I loved working with people and bringing people together to accomplish common goals.
One of the best decisions that I made was getting an undergraduate research assistantship at the Space Systems Lab (SSL) at UMCP. This was another turning point in my life. The SSL had many female graduate students and an extremely supportive faculty and research staff. If I hadn’t met those smart and strong women at the SSL, I may not have pushed myself as much as I did academically. I saw a different career path for myself. Before going to college it wasn’t my goal to get a Masters or PhD. Working at the SSL I had really good role models who made me want to do more than just doing undergraduate studies.
Q: How did you end up at Goddard?
A: Part of the reason was because my advisor had working relationships with NASA and JPL. I actually went out to JPL for a summer internship and I really loved my work out there. When I was about to graduate my family was still living in Maryland so part of me wanted to move back so that I could be close to my family. Also, my husband happened to be a tenured faculty member at Maryland so it made things a whole lot easier if I came to Goddard rather than stay at JPL! I was also lucky at the time because Goddard was hiring a lot of people around that time. I was kind of one of the last people get in the door!
Another reason (for winding up at Goddard) was that right around the time I was finishing my degree, space interferometry was a hot topic and my dissertation was on staged control systems for space based interferometers. When I first came to Goddard I worked with all kinds of different scientists who were doing interferometer work and writing proposals. I was supporting them on their proposals with the staged control system I’d come up with working on my PhD.
Q: How would you describe the work you do here at Goddard?
A: I’m in the Attitude Controls System engineering group and so a lot of my work involves designing and analyzing control systems. Because of my background in structural dynamics I’ve done a lot of work focusing around structural vibration issues. My work mainly focuses on developing control systems that can meet tight pointing requirements and addressing structural vibration issues (jitter) for multiple missions/instruments/payloads at Goddard.
Q: What was the first flight project you worked on at Goddard?
A: When I first came to Goddard I was doing a lot of proposal work. My branch head basically said, “We’re glad you’re working on these proposals but we want you to have some real-world experience, so you have to spend half of your time working on a flight project. Why don’t you work on SDO (Solar Dynamics Observatory)?”
When I joined SDO the team had already been formed. There were analysts for each control mode and they (the team) were thinking about what I could do. So I did anything that was not controls related. Eventually the team recognized that they needed someone to look at the effects of jitter on the observatory. And I said, “Well, I can do this jitter work because I’ve done it before when I was in school.” That was the start of my jitter career.
“I had a lot of fun with it (SDO) but it was a very humbling experience. Doing analysis and having that real-world experience are very different.”
I had a lot of fun with it but it was a very humbling experience. Doing analysis and having that real-world experience are very different. After CDR (Critical Design Review) we all panicked because we had some hardware data come in and when I compared that hardware data to my analysis models, my analysis models were under predicting by a factor of two! We formed a jitter analysis group and I had really great mentors to help me. I told my GNC system engineer at the time that I felt personally responsible because I didn’t predict these things correctly so I wanted to become the “jitter lead” so that I can make sure that we resolved all the issues with SDO. And so that’s how we coined the term “jitter lead.” I basically invented a job for myself! And ever since everyone comes to us if they have any jitter issues or want an analysis performed. It’s been a very fun road!
Q: What projects are you currently working on?
A: I’m currently finishing my work on the Neutron star Interior Composition Explorer (NICER) Project. NICER is an X-ray timing instrument devoted to the study of neutron stars, as well as a technology demonstration for celestial-based X-ray navigation that would enable NASA to navigate far outside of the GPS system. Since NICER will be an external payload on the International Space Station (ISS), a pointing system is required to track the neutron stars and slew to the next target, regardless of the ISS pointing direction.
I’ve led a small group of Goddard engineers to develop, analyze, and test the NICER Pointing System hardware and software. We also have various commercial vendors who have collaborated with us to build the flight hardware for the Pointing System. It’s been a really fun project because we don’t have a lot of people on the team so you have to do everything! I got to work on the hardware, the software, the ground system development, basically all aspects of the mission. That makes the job more interesting.
Q: Do you feel like you’ve experienced any unique challenges being a woman working in engineering? If so, what have they been?
A: I wouldn’t say that the challenges come from being a woman. To this day, even though I’m a lot more comfortable now, language is still my number one challenge. One of the reasons why I didn’t become a faculty member or look for an academic job after I finished my degree is because there’s a lot of pressure on publishing. Writing is something I’m not sure I’ll ever be comfortable with. I think that’s a bigger challenge than being a woman. There are days when I’m surprised at how few women are in a meeting, even in today’s time, but I think I’ve been very lucky so far. I went through school with very supportive faculty members. I have very supportive managers at work, so I haven’t had a lot of challenges about being a woman in engineering.
Q: What projects/work are you most proud of and why?
A: I’ve worked on a lot of them and for each project there are different things I like. For example with SDO I like the fact that that’s where my career kind of took off. I made some mistakes and corrected those mistakes and that made me better. I’ve helped to consult and support a lot of different missions. People keep saying “every mission I’ve worked on, you’ve worked on” which means I’ve worked too many missions! While I’m proud for all the work that I’ve done at Goddard, I’m most proud of the work performed on NICER. NICER’s pointing system posed unique challenges that I had not faced before. It’s a low cost mission which means that I’ve had a much greater level of responsibility than my previous projects. It’s also the first time that Goddard has built a large scientific instrument with pointing capability for the ISS. The NICER pointing work is different than developing typical control systems for a spacecraft, and it is especially challenging due to the cost constraints and ISS structural flexibility. I really enjoyed working on NICER and I think it’s going to be a fantastic instrument once we finally get up to the station.
Q: Where do you see your career going in the next 10 years or so?
A: I don’t really know. I think I’m someone who’s always looking for something different. One of the reasons jitter has been such an interesting and fun job for me is that the problem is different on every project. There isn’t a canned recipe that you can say these are the steps that you follow through to resolve all your jitter issues. And as we go forward we’re trying to build tighter and tighter pointing systems and more and more stringent jitter requirements. I really feel that I’d like to continue to develop my career along the path mitigating jitter issues. I’ve worked a lot on doing the analysis for jitter and want to move to resolving jitter issues.
For the next 10 years, I’m hoping to spend most of that time working on my next project — the Wide-Field Infrared Survey Telescope (WFIRST). It is NASA’s next flagship mission following Hubble and James Webb Space Telescope. It’s going to be a very challenging mission and has all the aspects of the problems I’m interested in: tight pointing and jitter. And because I’m part of the integrated modelling team and working the error budgets I get to work with people from all different disciplines. And I think that’s what I find interesting, to be able to understand what other people are doing, what they bring to the table and how we can all work together. I find that really fun, and that’s why I love working flight projects.
Q: What advice do you have for young women who want to pursue engineering as a profession?
A: I’m not sure I can give a lot of sound advice, but I do have some recommendations based on my own personal experience.
The first one would be to find a good mentor. That’s really key, finding someone who’s willing to support you not just technically and lead you on your way, but also someone to help you look out for your career. Those are very helpful things. I’ve had the opportunity to learn from quite a few really great mentors at Goddard and they really helped me get to where I am today and I’m very grateful.
The second one is to get involved. Going through engineering by yourself and just studying in your dorm room is probably not the best way. It’s just not very fun. When you’re really with your peers who are going through the same thing as you are and you can do things outside of your area of study, I find that very rewarding.
“The important thing to remember that you have to respect what you’re capable of and not worry too much about what you don’t know.”
And the last one is that you should demand respect. I’ve found that some women, including myself, at times tend to be less assertive and sure of themselves, even though we probably have more of a right to be confident and sure than some of our colleagues. The important thing to remember is that you have to respect what you’re capable of and not worry too much about what you don’t know. Not knowing something is something natural. But if you don’t know something and you’re shy and scared and intimidated and don’t want to ask questions, that’s where you’ll fail. Because you’ll never learn and you can never grow. So have enough self-respect to know that you deserve to be an engineer and it’s OK to ask questions.
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