How We Became CORAL Scientists

Scientists on a boat
Coral Reef Airborne Laboratory (CORAL) scientists Michelle Gierach and Eric Hochberg identify reef locations for study at Kaneohe Bay on Oahu, Hawaii. Credit: NASA/James Round

Where most coral reef studies take the close-up view of a diver, Coral Reef Airborne Laboratory (CORAL) will get the wide-angle view that comes with remote sensing instruments. CORAL scientists Eric Hochberg, Bermuda Institute of Ocean Sciences, and Michelle Gierach, NASA Jet Propulsion Laboratory, talked about how their backgrounds and training prepared them for this ground-breaking mission.

Eric Hochberg (center) and CORAL scientists preparing for boat operations at Kaneohe Bay on Oahu, Hawaii.

Eric Hochberg, CORAL principal investigator

Did you grow up near the ocean?

I was born and raised in Tampa, Florida. Every year my father took us down to the Florida Keys to catch lobsters — “to try to catch lobsters” would be a better phrase. The whole family would spend a week on a boat, and I just loved it. Because of these experiences I started diving off the Florida Keys when I was 13 years old.

When I got to college [Brown University], I thought maybe I’d be an engineer because I liked high school physics. Then I took college physics and said “No thank you.” In my junior year, I took a class in invertebrate biology and, from that moment, I wanted to be marine biologist.

After college I lived in Taipei, Taiwan, for three years. I kept applying to grad schools, and on my third try I applied to the Department of Oceanography at the University of Hawaii. In the oceanography program my focus shifted away from “look at the pretty things” on a reef to trying to understanding reefs as an ecosystem.

When did you get involved with remote sensing?

I knew I wanted to do something with coral reefs in grad school, but I didn’t know exactly what it would be. My advisor, Marlin Atkinson, told me about a new technology program where they put a hyperspectral imager on an airplane and flew it over a reef. He thought it would fit me. It turned out to be a career-defining decision.

I’m very fortunate that I got in at the beginning of the program. No one else [in the department] was doing spectroscopy of coral reefs. My committee included renowned planetary scientists and biogeochemists, and I was able to learn from these diverse people, but I was there on my own. That was a challenge because collaborations help you get new ideas. At the same time, it was a benefit because I had to learn everything myself. That made me a lot more self-reliant than I would have been if I’d been in a big lab with 10 other grad students.

With remote sensing I see reefs as systems, not organisms. That’s a perspective that reef scientists often lack because of how they do their science. The science is very good, but it’s up close and personal. Remote sensing gives us a bird’s-eye view.

What do you hope to learn from the CORAL mission?

We’re worried about the future of coral reefs, and we have good reason to be. At the same time, I have seen reefs bounce back from major disturbances, and I have seen reefs that were not disturbed at all when we expected them to be. I have seen places where corals are growing and people say they shouldn’t even be there.

Reefs are vast and spread out over wide areas of ocean. There are a lot of fundamental questions that we can’t answer yet because we haven’t looked at enough reefs over a long enough time. CORAL will give us a better chance to answer some of those questions.

Scientist on a boat
Michelle Gierach scoping Kaneohe Bay on Oahu, Hawaii. Credit: NASA/James Round

Michelle Gierach, CORAL project scientist

Did you always want to be an oceanographer?

As a Floridian, I’ve always loved the water, but I actually started out as an aspiring TV meteorologist. Not just any meteorologist, but a Jim Cantore [from the Weather Channel] reporting live in the field during severe weather. Well, first I wanted to be Shamu’s trainer like most kids in Orlando, but by middle school I was determined to be a meteorologist.

I went to Florida State University for their renowned meteorology program. My freshman year I had an internship at [a TV station] in Orlando. It was a fantastic experience, but I realized TV was not for me. Rather, I wanted to be behind the scenes answering questions about atmospheric processes that would improve weather forecasts — a weather caped crusader of sorts.

My advisor at the time was a meteorologist and oceanographer, and he encouraged all his atmospheric science students to take oceanography classes and vice versa. The coupling between air and sea is so important that you really have to have an understanding of both. One particular class I took that got me thinking about oceanography as a career was satellite oceanography. It was intriguing to me that there was a suite of satellites informing us about different components of the Earth system. You could say this is where it all started. My master’s thesis used satellite observations to develop a technique to detect and monitor the early stages of tropical cyclone formation, and my Ph.D. dissertation [at the University of South Carolina’s Marine Science Program] used satellite observations and models to assess the ocean response to tropical cyclones.  I may not have known it at the time, but I was already destined for NASA and the Jet Propulsion Laboratory.

What is it you like so much about satellite observations?

I love the synergies, taking multiple observations to say something about a particular topic. If you look at an eddy, for example, from the Jason series [of satellites] you see it as elevated or depressed sea surface height. From a different satellite you get a chlorophyll-a response in its core or around its periphery, and from a third one you get a sea surface temperature response. Combining these observations tells a story about the transport of heat and carbon by eddies.

One of the great things about NASA is that all data are publicly available. This increases data visibility and usability to a larger community, increasing the opportunity for new measurements and science to be discovered, ultimately improving our understanding of the Earth system.

You’ve done quite a few field campaigns. How do you like field work?

When I got out of grad school I had only done remote sensing. I love it, but you always need some kind of validation to make sure that what you’re seeing is correct. For my postdoc [at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science] I wanted to witness firsthand what it takes to get those observations, as well as earn the right to call myself a seagoing oceanographer.

[Gierach’s first field experience was the 2010 Impact of Typhoons on the Ocean in the Pacific campaign off Taiwan. She helped place two buoys in the path of typhoons.]

They did withstand the typhoons and took observations. If you were to look at a global map with just those two [data points], they look like nothing, but seeing the work it took to get those two … it definitely took a village. I liked going to sea and was glad I had done it, but I realized that’s not the life for me. Remote sensing is my wheelhouse. I’m going to stick with it.

What are you most looking forward to in CORAL?

Seeing all the moving parts come together. There’s beauty to that. Also, seeing if the results confirm the held assumptions that coral reef cover decreases with increasing ocean temperature and increasing marine pollution, or if they tell us something entirely different.

The next steps beyond CORAL are also exciting. Is there additional information that can be extracted from the remote sensing data to further understand reef ecosystems and their environment? Can we take the next leap toward a dedicated, spaceborne mission to provide monitoring of coral reef ecosystems with greater spatial and temporal coverage? The CORAL mission, and the steps to follow, will take us to new heights in understanding.

Looking for a Few Cloudless Hours

Leafy valley
Kaaawa Valley, near Kaneohe Bay on the island of Oahu, on an overcast day. Credit: NASA/James Round

by Carol Rasmussen / OAHU, HAWAII /

Most offices in Honolulu were closed Friday, June 10, for King Kamehameha Day, but the National Weather Service (NWS) office was open. CORAL project scientist Michelle Gierach and project manager Bill Mateer from NASA’s Jet Propulsion Laboratory dropped in to learn about Hawaii weather from the pros.

That’s not to say that Gierach and Mateer are amateurs. Gierach has bachelor’s and master’s degrees in meteorology, and as JPL’s airborne science program manager, Mateer has an advanced degree and a good working knowledge of weather maps and forecasts. But Hawaii’s tropical climate and mountain terrain offer special weather challenges. “We’re just coming into the region, and they have the expert knowledge,” Gierach said.

Scientists talking
After giving a weather map briefing, NWS Senior Meteorologist Jon Jelsema discussed Hawaii weather with Michelle Gierach. Credit: NASA/James Round

Weatherwise, the biggest concern for CORAL’s airborne instrument is clouds. On a sunny day, the Portable Remote Imaging SpectroMeter (PRISM) can see the light reflecting off the bottom of the ocean to discriminate benthic cover — the ratio of coral, sand and algae. But the light from the seafloor is only about 1 percent of the total reflected light that reaches the instrument from the atmosphere and ocean below. If cloudy skies obscure or even dim that signal, PRISM can’t produce good measurements of coral reefs.

At the Honolulu NWS office, Science and Operations Officer Robert Ballard briefed the JPL scientists on what cloud cover they’re likely to see both this week and when the campaign returns in February 2017 to survey reefs in the entire island chain.

“Climatologically, you’re fighting a battle here,” Ballard said. “But you only need clear skies for an hour or two, and there are weather patterns where you get that.” The most common such pattern is light winds with a ridge of atmospheric high pressure over or near the islands. Offshore winds at night blow clouds away from the island so that mornings are generally cloudless. This pattern is more common during winter because the trade winds don’t blow as persistently as they do the rest of the year, so even though winter is rainier, it also has more clear skies.

National Weather Service Science and Operations Officer Robert Ballard.
National Weather Service Science and Operations Officer Robert Ballard. Credit: NASA/James Round

This weather pattern, Ballard noted, can usually be spotted a few days before it reaches the islands. “Forecasting in the tropics can be tricky, but this is a large-scale pattern, which lowers the level of difficulty for us.” Small-scale events like showers are still hard to predict because even the state-of-the-art weather forecasting models that NWS uses “don’t see the island super well. Knowing the climatology is huge.”

So prospects for February are good, but the prospects for the coming weeks are not as promising, Ballard said. “The trade winds are going on for at least the next 10 days. If you get [a long period of] clear skies in the trades, I want a picture of it.”

Fortunately, science flights during the Hawaii operational readiness test will not be as demanding in terms of results as the flights during the actual field campaign, Mateer said. From his perspective as project manager, “Success for the operations readiness test is to make sure we can execute all the steps of a mission day — the airplane’s ready to go, we can communicate with the optics team in the boat, we can get the data off the plane and onto the server, and we can confirm that the quality of the data meets the requirements. It’s important to get the whole data collection machine, both remote and in situ instruments, working as one unit. Then we’ll have confidence we’re ready for full science operations when we get to Australia.”

In an Airborne Campaign, Why Boats?


Science instrument
As boat operations begin on Tuesday, June 7, Brandon Russell (University of Connecticut) drops the inherent optical properties “cage” into the water. Instruments in the cage measure how light is absorbed and scattered in the water. The measurements will help scientists “see through” the water and isolate the light reflected from the bottom. Credit: HIMB/Daniel Schar

by Carol Rasmussen / OAHU, HAWAII /

What makes the Coral Reef Airborne Laboratory (CORAL) a game-changer is its airborne instrument. NASA’s Portable Remote Imaging Spectrometer (PRISM) will fly at 28,000 feet, viewing entire coral reef ecosystems on a scale that no boat-based campaign can match. Yet CORAL is using three research boats and scuba divers in the same areas that PRISM will be flying above. With a state-of-the-art remote sensing instrument in action, what’s the point of getting wet?

“We have to go in the water to make sure the airborne data are accurate,” said CORAL principal investigator Eric Hochberg, of the Bermuda Institute of Ocean Sciences. The boat measurements are like independent witnesses in a trial. If they agree with the PRISM data, it confirms that the PRISM measurements are valid—which is why this step is called validation.

Scientist on a boat
Eric Hochberg talks about the next location for collecting data with Russell and Garcia.

As CORAL’s operational readiness test—its final dress rehearsal—continues on Oahu, the first boat team has been testing optical instruments in the waters of Kaneohe Bay. Researchers Brandon Russell, from the University of Connecticut, and Rodrigo Garcia, from the University of Massachusetts, Boston, are measuring light at the ocean surface and optical properties of the water around the 17-square-mile bay. A second boat team arrived Thursday to start assembling and testing equipment to measure reef metabolism, specifically  photosynthesis and calcification. A third boat team arriving Saturday will measure the composition (coral, algae, and sand) of the seafloor, scientifically known as benthic cover. The third team will also measure optical properties (reflectance) of the seafloor.

Hochberg noted that validation is especially important in CORAL because its science is ultimately based on the large-scale airborne measurements, and it will be collecting data in many locations where there are no supporting data available. “The airplane will be flying over remote regions where we can’t go diving and we don’t know what’s there,” he said. “Every pixel in the PRISM data will have to be identified. Some will have more coral or less coral, some will be deeper, some will be shallower. We need validation data to give us confidence in all these different conditions.”



CORAL Mission Starts Work in Hawaii

Eric Hochberg, principal investigator of the CORAL mission, steers the research boat in Kaneohe Bay. Credit: NASA/James Round

by  Carol Rasmussen / OAHU, HAWAII /

Even in dark glasses, Eric Hochberg is squinting a little in brilliant sunlight glinting from a green ocean. He is driving a research boat across Kaneohe Bay, Oahu, Hawaii, on June 7, the first day of the operations readiness test for NASA’s Coral Reef Airborne Laboratory (CORAL) mission. Hochberg, a scientist at the Bermuda Institute of Ocean Sciences and CORAL’s principal investigator, is overseeing tests of two instruments that measure water’s optical properties.

Kaneohe Bay is patchy in the sunlight, brighter and darker spots showing where the ocean floor is mostly sand and where there’s a coral reef. Warm, sheltered and spectacularly beautiful, the bay is a magnet for both locals and tourists. About a dozen tourist boats are moored on a large sandbar. Hochberg and his team appear to be the only people who are working anywhere in the vicinity, but in fact, a small island in the bay houses the researchers of the Hawaii Institute of Marine Biology (HIMB), CORAL’s base during this Hawaii test.

Moku O Lo'e, also known as Coconut Island, is CORAL's base of operations in Hawaii. Credit: NASA/James Round
Moku O Loe, also known as Coconut Island, is CORAL’s base of operations in Hawaii. Credit: NASA/James Round

Hochberg has been working for years to bring a program like CORAL into existence. “The coral reef data we have were mostly gathered by scuba divers with measuring tapes, so they’re local, inconsistent and patchy,” he says. “CORAL will give us the first large, uniform dataset on the condition of coral reefs across key regions of the Pacific. We have good reason to be concerned about the future of reefs, but there are a lot of fundamental things we just don’t understand about them. With the CORAL dataset, we can begin to better understand how reefs interact with their environments.”

What makes this possible is a new airborne instrument called PRISM, the Portable Remote Imaging Spectrometer. Michelle Gierach of NASA’s Jet Propulsion Laboratory is the CORAL project scientist. She says, “PRISM is the heart and soul of the CORAL mission. It came into being to address the challenge of coastal observations.”

Michelle Gierach, CORAL’s project scientist, at the Hawaii Institute of Marine Biology on Oahu. Credit: NASA/James Round

The abundant light on the water that makes the scientists squint creates similar problems for remote sensors trying to focus on dimly visible objects underwater. PRISM was designed specifically to handle these tough light conditions. From reflected light on the ocean, it can extract the spectral signatures of coral, sand and algae — important indicators of the condition of a reef. The PRISM instrument is able to survey entire reef ecosystems in about the same time it would take boat-based researchers to survey a few square yards or meters.

In Kaneohe Bay, the scientists pull their instrument out of the water one final time, and Hochberg points the boat back toward HIMB’s boat docks. Their agenda for today was to check the performance of the optical instruments, and they’ve collected enough data for a first test. Two other boat teams will also be checking out their instruments in the next few days. When the aircraft and PRISM arrive from the mainland, the boat teams and aircraft will make more or less simultaneous measurements on and over the bay. While that’s going on, the workers on Kaneohe Bay might actually outnumber the tourists.