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Chopo Ma - Mapper of the Stars
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In mapping the sky, Geophysicist Chopo Ma has spent the last 40 years studying the basic philosophical problem of measuring distances between objects in the sky.

Name: Chopo Ma
Title: Lead for Very Long Baseline Interferometry (VLBI)
Formal Job Classification: Geophysicist
Organization: Code 698, Planetary Geodynamics Laboratory, Science and Exploration Mission Directorate

What do you do and what is most interesting about your role here at Goddard? How do you help support Goddard’s mission?

I began at Goddard in 1971 as a graduate student. I worked throughout my entire career with the long-standing group that supports Very Long Baseline Interferometry (VLBI), a group which I now lead. VLBI is a technique that uses radio telescopes to measure positions on the Earth, changes to those positions, the orientation of the Earth in space, and the locations in the sky of extragalactic objects. Our data are used to determine movements and changes of the tectonic plates on Earth, which help show the impact of earthquakes, for satellite orbit tracking, which provides essential information to GPS systems, and for the celestial frame of reference that tells us where everything is in the sky.

VLBI is an international cooperative effort involving about twenty countries, so our community relies on other large radio telescopes throughout the U.S. and the world. We cover the whole sky as the Earth turns through our global network. We have two radio telescopes at Goddard, although they are smaller than most.
Photo of Chopo Ma› Larger image
Photo of Chopo Ma standing near a satellite dish at Goddard. Credit: NASA/W. Hrybyk

VLBI was developed by NASA to map changes in the Earth, but is now also used to map the sky. So, I’ve evolved into being a geophysicist who now looks at the sky. I am fascinated by VLBI because the problem of measuring distances between objects in the sky goes back to the first time man looked up at the sky. It is a basic philosophical problem. When VLBI was accepted as the means for measuring celestial positions, it was more than an order of magnitude better than what was previously done using stars. Somewhat surprisingly, the great precision possible from the celestial measurements allows geophysicists to make inferences about the Earth’s core. The influence of VLBI goes from far beneath our feet to the edge of the universe.

Certain types of data are so important that they need to be shared throughout the world, generally through a science service, which organizes the collection, analysis and distribution of the data. I am now the chair of the oldest geometric science service, the International Earth Rotation and Reference Systems Service, whose predecessors started measuring the motion of the North Pole at the beginning of the 20th century.

What makes Goddard a great place to work?

The interesting work and the people who do that work. Also, our work is always evolving, so it is always exciting.

Space geodesist Chopo Ma explains the science of Very Long Baseline Interferometry (VLBI): using radio emissions from distant galaxies to create a precise reference frame for the Earth. Credit: NASA's Goddard Space Flight Center

What is the coolest thing you’ve ever done as part of your job at Goddard?

In 2009, the General Assembly of the International Astronomical Union, the premier association of astronomers in the world, adopted an international celestial reference frame which was measured and created by VLBI. This act validated 38 years of work and made all our work worthwhile. It served as recognition of our international collaboration, including Goddard, and of our technique.

What lessons or words of wisdom would you pass along to somebody just starting their career at Goddard?

Volunteer for activities outside your area because that is the best way to get to know the rest of Goddard. I worked for several years on the Asian Pacific American Advisory Committee including serving as its chair.

Do you have a favorite book, magazine, movie, or TV show?

I enjoy reading “The Economist,” which helps me keep up with world events in economics, politics, science and culture. I also like reading “Natural History” because I grew up in Manhattan and loved visiting the Museum of Natural History.

Is there someplace in the world that you want to visit or someplace you have been and want to go back?

I am Asian American of Chinese descent. I was born in Shanghai. My parents left China in 1949 right before the People’s Republic emerged. I have taken my immediate family back to visit our relatives in China. I have been all over China, but especially enjoy returning to Shanghai, which is undergoing dramatic changes.

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Elizabeth M. Jarrell
NASA's Goddard Space Flight Center, Greenbelt, MD