man pointing at large screen
Image credit: NASA/JPL-Caltech


Brownsville High School, Brownsville, TX
Texas A&M University, College Station, TX
B.S., Education Curriculum and Instruction
Princeton University, Princeton, NJ
Ph.D. Geophysical Fluid Dynamics

What first sparked your interest in space and science?

The race to the Moon in the 1960s caught my imagination. Space was clearly the new frontier, and I wanted to get involved. I was fascinated by astronomy and learned everything I could in my math and science classes.

Where are you from?

Just about everywhere in the U.S., but mostly the Lower Rio Grande Valley in Texas.

How did you end up working in the space program?

It was a long, strange trip. While taking an astronomy course as an undergraduate education major, I became intrigued by the apparent “super-rotation” of Venus’ atmosphere. While writing a term paper on the topic, I made a discovery that my professors encouraged me to submit to the journal Icarus. I returned to graduate school to continue my studies of Venus’ atmosphere as I pursued a Ph.D. in Geophysical Fluid Dynamics.

I was then offered a postdoctoral position at the Caltech, where I participated in the Soviet/French/U.S. Vega mission to deploy a pair of weather balloons within the clouds of Venus. At the end of that successful effort, I moved to the Jet Propulsion Laboratory to join the Science Team of the Hubble Space Telescope Wide Field Planetary Camera-2 (WFPC-2) project. I have been at JPL ever since, participating in a broad range of Earth science, planetary science and astrophysics projects.

Tell us about your job. What do you do?

I have spent most of my career developing and using mathematical models for studying the interactions of solar and thermal radiation with the atmospheres and surfaces of Earth, Venus, Mars and, more recently, a few exoplanets. These tools are being used to retrieve information about the thermal structures and compositions of these planetary atmospheres and to study their climates. I have also contributed to the design, development and analysis of data from several space-based instruments, including WFPC-2 on Hubble, the Mars Pathfinder Lander and ESA’s Venus Express Mission.

For the past 20 years, I have spent most of my time leading the development and implementation of NASA’s Orbiting Carbon Observatories: OCO, OCO-2 and OCO-3. These are the first satellites whose instruments can return the data needed to estimate atmospheric carbon dioxide concentrations with the accuracy, precision, resolution and coverage needed to identify the sources emitting the gas into the atmosphere and the natural processes that absorb it at the surface.

Now that both OCO-2 and OCO-3 are in orbit, I coordinate the efforts of about 100 graduate students, postdocs, professors, research scientists and engineers to learn the most we can from the OCO-2 and OCO-3 observations. I am also helping to coordinate ongoing and future efforts to collect space-based atmospheric carbon dioxide and methane observations by the 34 space agencies that constitute the Committee on Earth Observation Satellites.

man speaking near large screen with map of earth
Image credit: NASA/JPL-Calteach

What’s one piece of advice you would give others interested in a similar career?

Select a field you love, sharpen your technical skills and apply these skills to solve the most important problems in your field. While collaboration and teamwork are essential for large efforts, you should initially try to produce high-impact first-author papers so that the community understands your interests and capabilities. This will encourage your colleagues to include you in their efforts. Also, learn how to effectively communicate your results, both in refereed publications and in presentations at meetings and conferences. Finally, learn how to write effective, interesting proposals to fund your scientific research. Your success as a scientist will depend on your proficiency in these areas.

What has been your biggest challenge, professional or personal, and how did you overcome it?

I have spent my entire career on “soft money” — all of my funding comes from competitively selected research proposals that are evaluated through a rigorous peer-review process. As a young researcher, I spent at least 30 to 50 percent of my time writing proposals for that funding. Unfortunately, there is almost never enough funding to support more than 10 to 30 percent of the very best proposals. I often found that the peer-review process tended to select low-risk projects rather than innovative, but riskier, efforts from new researchers.

To overcome this challenge, I continued to refine my ability to communicate my objectives, approach and expected products. I also learned to better understand what the funding program was trying to achieve and position my proposed effort as a solution to those needs. I finally broke through.

Who inspires you?

Many of my scientific colleagues inspire me with their insights, technical capabilities and persistence in studying difficult, but important, problems.

What have been some of your favorite projects to work on?

I have had an opportunity to work on a fascinating array of projects since I received my Ph.D. When I was a postdoc at Caltech, I got to fly a pair of weather balloons in Venus’ atmosphere as a member of the Soviet/French/U.S. Vega Venus balloon science team. I was then invited to move to JPL to contribute to the development of the primary camera on the Hubble Space Telescope, the Wide Field Planetary Camera-2 (WFPC-2), as a member of the camera’s science team.

While building that instrument, I continued my studies of Venus’ atmosphere as a ground-based astronomer. I traveled to astronomical observatories in Australia and Hawaii at 18-month intervals to gather observations of the night side of Venus. I analyzed these observations to study the thermal structure, composition and cloud structure at altitudes that were previously accessible only by entry probes.

In the early 1990s, I became interested in the weather and climate near Mars’ surface, because I realized this would be the working environment of our landers, rovers and, eventually, human explorers. I started a small program to develop compact, low-power weather stations that could collect measurements of atmospheric pressure, temperature, humidity and wind velocity on the Martian surface. This small program gave me an opportunity to contribute to the weather station on the Mars Pathfinder Lander.

As we approached the turn of the century, I became increasingly concerned about the rapid increases in the concentration of atmospheric carbon dioxide and its potential impact on Earth’s climate.

As we approached the turn of the century, I became increasingly concerned about the rapid increases in the concentration of atmospheric carbon dioxide and its potential impact on Earth’s climate. By that time, human activities, including fossil fuel combustion, cement production, heavy industry and deforestation, were emitting over 25 billion tons of carbon dioxide into the atmosphere every year. This was enough to increase the atmospheric concentration of this dangerous greenhouse gas from pre-industrial values near 280 parts per million (ppm) to over 370 ppm, and it was growing at over 2 ppm each year. I decided to try to design a satellite-based instrument to monitor these emissions because I knew that we can manage only what we can measure.

I combined everything I had learned about radiative transfer in planetary atmospheres and space-based instruments to develop a sensor with the accuracy, precision, resolution and coverage needed to identify the sources emitting carbon dioxide into the atmosphere and the natural processes (like photosynthesis) absorbing it at the surface. This research resulted in a preliminary design for a spectrometer that measured reflected sunlight at wavelengths where molecular oxygen and carbon dioxide absorb in the near-infrared and shortwave infrared parts of the spectrum.

I assembled a fantastic team of scientists and engineers and proposed this idea to the NASA Earth System Science Pathfinder Program (ESSP) as the Orbiting Carbon Observatory (OCO). In late 2001, our team won the competition over more than 30 competing proposals. The OCO project was repeatedly delayed by funding issues and technical problems, but the spacecraft was finally delivered to the launch pad in February of 2009.

Unfortunately, the launch vehicle malfunctioned shortly after liftoff, destroying the OCO spacecraft. We immediately started trying to get a re-flight. After 10 months of effort, we were given an opportunity to rebuild and re-fly the OCO mission. It took another four-and-a-half years to rebuild and launch the Orbiting Carbon Obseratory-2 (OCO-2) mission in July of 2014. By that time, the atmospheric carbon dioxide concentration had grown to about 400 parts per million. Since September of 2014, OCO-2 has been collecting a carbon dioxide dataset with unprecedented precision, resolution and coverage. Our colleagues around the world have been using these measurements to provide new insights into the processes emitting carbon dioxide into the atmosphere and those absorbing this gas at the surface.

As part of the OCO-2 program, we built a spare carbon dioxide spectrometer just in case there was another launch failure. Once OCO-2 was successfully launched, we were given an opportunity to install the spare spectrometer on the International Space Station as OCO-3. It was successfully launched on May 4, 2019, and installed on the ISS on May 10, 2019. Our team has started the in-orbit checkout of the OCO-3 instrument and will be delivering carbon dioxide data later this year. The adventure continues.

What are some fun facts about yourself?

Earlier in my career, I built and raced cars and motorcycles. These days, I drive very fast electric cars, charged by the solar panels on the roof of my house. My other hobbies include working out, tending bar and taking photographs as I travel across the planet.

What is your favorite space image and why?

Earthrise. On December 24, 1968, as Apollo 8 circled the Moon for the first time in human history, astronaut William Anders picked up a camera and photographed Earth rising above the Moon’s horizon. When this picture was returned to Earth, it had a profound effect on us. We realized that every human being who ever lived, besides Anders and his crew mates Frank Borman and Jim Lovell, were in that picture. The small disk of Earth against the vacuum of space also helped us realize that we are all in this together. There is no Plan(et) B.

earth over barren lunar horizon
This iconic image speaks volumes. To many it underscores the vastness of space, the loneliness of the cosmos and how fragile our home planet really is. Entitled “Earthrise,” it was taken by astronaut William Anders during an orbit of the moon as part of the Apollo 8 mission. Image credit: NASA