NASA’s Ocean Melting Greenland, or OMG, campaign is back in the Arctic, and this month it’s dropping scientific probes out of a NASA aircraft into the water just off Greenland’s coastline. The probes are the fourth and final part of OMG’s observations this year documenting how seawater is melting the underside of the world’s second largest ice sheet.
Three things about Greenland: it’s huge, it’s remote, and it’s melting so fast that scientists use words like “falling apart” and “vanishing” to describe what they’re seeing. But the hugeness and remoteness mean that many parts of the island have gone completely unmeasured. There aren’t enough data for scientists to be confident that they understand how processes are interacting now, much less how the melting will progress in coming years.
“It’s hard to predict what’s going to happen to Greenland because we’ve never watched it melt before,” said Josh Willis, OMG’s principal investigator with NASA’s Jet Propulsion Laboratory, Pasadena, California. The measurements OMG is making this month, and over the next four Septembers, should reduce some of the uncertainty.
To collect data around Greenland’s entire coastline, the OMG team is using four bases. Slice two imaginary lines across the island, one north-south and the other east-west, and there’s a different OMG base for each quarter, more or less. The bases for measuring the west side of the island are on Greenland itself; for the east side, the bases are in Iceland and on the Norwegian island of Svalbard.
OMG isn’t moving methodically around the island. It’s spending a few days in one location and then another, sometimes doubling back to the first location, as logistics and weather dictate. An Earth Expeditions reporting team will catch up with the team in a few days from Iceland. For now, here are some images from the field, captured by the team members themselves.
Willis and the other OMG scientists timed this campaign to coincide with the Arctic sea ice minimum (conditionally announced on Sept. 10) so they would have the best chance of finding open water to drop probes into. But even at minimum, there’s still plenty of ice around Greenland. In loosely packed ice like this, dropping probes has been no problem. But in other locations, the water is almost completely covered with big plates of ice separated by narrow cracks, testing the team’s ability to hit their open-water targets. Some areas are completely ice-covered, with no possibility for dropping probes.
If you want to drop probes along the coast, you need to be able to see the coast. The weather doesn’t always cooperate. On this day, no data were successfully collected.
The probes are similar to those dropped by hurricane hunters to monitor the ocean during storms. There’s a parachute to waft the package safely to the ocean surface. When it hits the water, a float inflates to hold up a radio transmitter. A sensor, tethered to the transmitter by wire, sinks some 3,000 feet (if the water is that deep), measuring water temperature and salinity on the way down. The transmitter relays these data back to the aircraft. OMG will drop about 250 of these probes by the end of its deployment in early October. Combined with maps of the seafloor shape around the coast that OMG is also producing, the probe measurements will give a picture of where warm, deeper water can creep onto the continental shelf and eat away at the glaciers fringing the ice sheet.
by Alan Buis / OFF HERON ISLAND, QUEENSLAND, AUSTRALIA /
Bob Carpenter surveys the seafloor surrounding the research vessel Anthias as it glides over Blue Lagoon, the largest part of the reef that envelops Heron Island. He and his team, which is conducting the in-water validation of reef metabolism for NASA’s Coral Reef Airborne Laboratory (CORAL) mission, are searching for a good spot among the numerous small patch reefs in the lagoon to erect what he calls an “underwater construction project.”
The boat stops to look at an area more closely.
“It’s looking pretty algalicious here,” says Carpenter with a laugh, knowing he just made up a word. He asks skipper Sam Ginther, a research technician at California State University, Northridge, where Carpenter is a professor of biology, to continue to another location.
Carpenter has brought his three-person team to the Great Barrier Reef to make in-water measurements of the productivity and calcification of the community of living organisms found on the seafloor here at Heron Island and also at Lizard Island, on the northern Great Barrier Reef. Their data will help the CORAL team validate CORAL’s advanced Level 4 science products.
It’s mid-September and day two out in the field for the team at Heron. They’ll be here for another week, installing instruments at up to 10 sites around Heron Reef. Yesterday they deployed a float called a drogue to track the paths of currents below the water surface to help guide their placement of instruments. On today’s trip they’ll be deploying two types of instruments: samplers that collect water for later analysis in the lab, and gradient flux instruments that measure oxygen and water flow.
At this location they are deploying the “gradient flux” instruments. The instruments will measure two of the three key aspects of reef metabolism his team is studying: primary productivity and respiration (the third is calcification). Metabolism refers to the processes by which reef communities acquire energy for growth and build their limestone skeletons.
The team must work quickly, because the high and low tides here at this time of the month are extreme.
“I think the difference at this time of day is 7.2 feet, so we need to get out to the lagoon when it’s high tide so we’ll have deep enough water to navigate in when we’re entering the lagoon and going over the reef crest,” says Chiara Pisapia, a postdoctoral researcher from Italy who came to Australia six years ago and recently completed her postdoc at James Cook University. She’s now joining Bob’s group at CSUN. “If we’re still in the lagoon when the tide goes down, we’ll be stuck here until the next high tide.” The team will have a little more than two hours in the lagoon, which averages about 11 feet in depth, to accomplish today’s tasks. The instruments have to be placed where they won’t go dry when the tide goes out.
The gradient flux system—oxygen sensors and acoustic Doppler velocimeters—will be mounted at two heights above the seafloor. The bottom instruments are placed 4 inches above the flora and fauna on the seafloor, with the top instruments placed 43 inches above the seafloor. The method they’re using relies on the flow of water to carry water and oxygen (either produced by photosynthesis or taken up by respiration) past the instruments.
“The water here doesn’t always flow in the same direction, so we’re looking for a coral patch that’s fairly uniform where the water will carry data signals on the surrounding habitat past these sensors,” Carpenter says. “We’ll then place the sensors right in the center of that patch so they will integrate the metabolism from that point to a larger scale: anywhere from 108 square feet to perhaps 538 square feet , depending on the speed of the water flow. Since the pixel size for PRISM’s spectrometer on the Gulfstream IV aircraft is 86 square feet, we’re able to match its scale really well.”
The team locates a suitable spot in the lagoon and gets to work, donning scuba gear and taking the equipment they will need down to the seafloor below. The equipment includes a tall cylindrical stand with adjustable brackets and clamps that hold the four gradient flux instruments in place at fixed heights to eliminate any bias in the measurements.
The sensors will continuously measure oxygen and water flow across the layer of water directly above the organism-covered seafloor, providing measurements of the area’s net productivity during the day and its respiration at night. Upon completing the installation, the divers release a special yellowish-green, reef-safe dye, which allows them to verify that water is flowing across the instruments. A member of the team notes the location of the installation using a portable GPS receiver. The team will repeat the process tomorrow, moving the instruments to a new location on the reef every 24 hours.
Earlier in the day, the team used GPS coordinates to locate instruments they installed in the lagoon yesterday that are used to measure reef metabolism, and placed two CSUN-built integrated water samplers at the same locations. The water samplers were placed about 1,312 feet apart, one downstream from the other, moored to the seafloor. They remain in place for five consecutive days.
“The water samplers take tiny little sips of water—only about 3 or 4 milliliters a minute—and they do that for six hours, so you get this long-term water sample, and we do that at both ends of the transect, and then we can come out tomorrow and collect the samples from the sample bags,” Carpenter says.
The team swaps the sample bags out and takes them back to the lab to analyze for total alkalinity. Changes in total alkalinity can be used to estimate reef calcification, a key element of reef metabolism.
Calcification is the secretion of calcium carbonate—what we think of as limestone. Coral skeletons and other calcifying organisms such as calcified algae build the reef framework, allowing reef systems to grow vertically over time to create the largest biogenic structures on Earth. The process of calcification is fundamental to the growth of corals and reefs in general. As climate changes and sea surface temperature and ocean acidification increase, calcification is predicted to decrease. In fact, experiments are showing that calcification decreases with simulated increases in ocean acidification and temperature.
Carpenter says the team wants to sample as many different habitats as they can so that CORAL’s benthic cover in-water validation team will know exactly what the metabolism is for these different habitat patches. “We install the instruments in a location, leave them for about 24 hours, and mark them with a float,” he says. “Then the benthic cover team comes the next day and creates their photo mosaic of the area. So we end up knowing exactly what’s there and exactly what the rates of metabolism were in those same patches. We can then match those different habitats with PRISM data to hopefully extrapolate what the reef is doing on a larger scale.”
Their work for the day complete, Pisapia takes the helm and carefully navigates the boat through the shallow corals out of the lagoon and back to the harbor. Tomorrow they’ll go out again and move another set of instruments. Their work here on Heron Island will be followed by several months of data processing and analysis.
As they head for shore, a large humpback whale and her calf breach out of the water a short distance away. They stop for a minute to watch in awe. Life is good.
by Alan Buis / OFF HERON ISLAND, QUEENSLAND, AUSTRALIA /
It’s a warm and sunny morning in mid-September as Stacy Peltier and her colleagues on NASA’s Coral Reef Airborne Laboratory (CORAL) mission survey team prepare for their first day in the water at Heron Island, a 42-acre coral cay about 45 miles off the coast of Queensland, Australia. As she places a Nikon D5500 camera into an underwater housing, several sharks swim nearby in the aquamarine waters of the island’s small harbor dredged out of the reef.
“I’ve never jumped in the water with tons of sharks before,” she quips with nervous laughter. Fortunately for her and her team, the sharks found around Heron Island aren’t particularly dangerous to humans.
The research technician from the Bermuda Institute of Ocean Sciences (BIOS) and her three teammates have come to Heron Island as one of three independent, but coordinated, in-water validation teams that are collecting data on reef condition at Australia’s Heron and Lizard Islands during CORAL’s two-month Great Barrier Reef study. This “ground truth” data will be compared with data collected from the air by NASA’s Portable Remote Imaging Spectrometer (PRISM) instrument to validate the accuracy of the PRISM data and map products. Three fundamental types of data are being gathered: water optics, reef benthic cover and reef metabolism.
Benthic cover is what grows on the seafloor. Reef benthic communities typically consist of a combination of coral, algae and sand. Over the next week, the benthic cover team is collecting a series of high-resolution photomosaics that will depict the composition of the various seafloor communities at multiple spots around the Heron Island reef.
Surveys of reef benthic cover are needed to validate some of CORAL’s more advanced data products. The CORAL mission is collecting benthic cover data for 160 to 250 separate sites across each reef validation location in the global mission. The team will analyze the mosaics to make a highly accurate determination of the percentages of various types of benthic cover in each photo.
By 9 a.m., the boat is loaded with the team’s research equipment and scuba gear. Peltier, co-skipper on today’s trip, slowly guides the Heron Island Research Station research vessel Chromis out of the harbor. As they head out, the ghostly, rusted wreck of the HMCS, Australia’s first official naval vessel, sits on its side on the reef crest at the entrance to the harbor.
On board with Peltier are teammates Yvonne Sawall, a postdoctoral scientist at BIOS; research technician Andrea Millan and team leader Steven Dollar, both of the University of Hawaii; and NASA CORAL project scientist Michelle Gierach, who’s come along to observe and assist from the boat.
Peltier radios the research station to report that there are seven passengers on board and that we are expected back to harbor at 4 p.m.
“Research, Research, Research, this is Chromis,” she says.
The station confirms, and informs us that the Gulfstream IV aircraft carrying NASA’s PRISM instrument is on its way to fly over the Heron Island region and is expected soon.
Our first dive point is an area called Blue Pools. The team attaches the boat to a mooring buoy. The water depth is about 20 feet.
The team quickly gets to work, donning scuba gear and plopping backward into the 72-degree Fahrenheit water. The skipper does not get in the water; she must remain with the boat at all times for safety purposes. The divers are handed one of the three cameras on board and they submerge.
It’s painstaking work. One team member first lays 1.6-foot-long poles across the seafloor to delineate 33-by-33 foot square plots, a size that correlates to the spatial resolution of CORAL’s PRISM instrument from 28,000 feet above sea level.
The other team members use their cameras to photograph the entire plot, with one diver scanning east to west and the other scanning north to south, swimming about 6 feet above the seafloor. A snorkeler at the water’s surface carries a handheld GPS unit to precisely mark the location of the plots to correlate with the plane data.
The team takes up to 1,000 pictures per plot, a process that takes 15-20 minutes. On a typical day the team will do two to three locations, collecting measurements from three to four sites at each location. They start in the deepest water, then move up the slope of the reef toward shore. If the water becomes too shallow they snorkel instead of scuba.
Later, back on land, a special software tool called Agisoft PhotoScan will stitch all the photographs together into a mosaic, which scientists can then use to characterize what the community structure of the coral reef is at the given spot.
“This is a new way of assessing reef structure and function using this mosaic, and we’ll follow it with analysis of these pictures to be able to see things you can’t see any other way but by jumping in the water and putting your eyes on it,” says Dollar, a coral reef biologist and environmental consultant. “This is the equivalent of going from a Model T to a Tesla compared to the way previous reef studies have been done. And the biggest thing that allowed this to happen is digital photography. Here, each time we come out of the water, we’ve taken up to a thousand pictures. This was not possible before the advent of digital photography.”
“We want to get as many different benthic community types as possible, and then match up the mosaics with the pictures we get from the airplane,” says Sawall, a postdoc with CORAL Principal Investigator Eric Hochberg at BIOS, where she specializes in coral metabolism.
A native of the south of Germany, Sawall was first inspired to study coral reefs when she dived the Great Barrier Reef at age 19. “It was my first experience in the ocean; I loved it so much,” she says. “The interplay between the organisms fascinated me. Yet at the same time I could see the impacts that humans were having on reefs, and that drove me to want to protect them.”
Sawall views the team’s work as a vital stepping-stone in our understanding of the health and status of coral reef ecosystems worldwide. “The goal of CORAL is to eventually assess reefs around the world and their status and health and monitor that over time,” she says. “What we are doing here is a little puzzle piece toward achieving that goal.”
The team finishes its work at the first dive location, which is primarily rubble (rocks, sand and dead coral), then they move closer to the reef, which consists of a variety of living corals occurring in a multitude of growth forms. The highest coral cover is typically found on the outside and slope of a reef, while inside the reef lagoon, algae and sand dominate the bottom.
Their first dive location completed, the team stops briefly to munch on some Tim Tams, Australian chocolate-covered biscuits; these have a distinct coconut taste. As they break, schools of little black fish swim next to and below the boat, attracted by our presence. One of the team spots a green sea turtle swimming nearby. The seas are calm.
I ask Peltier to describe what she’s seeing below the surface.
“The reefs at Heron Island are beautiful,” she says. “We were recently at Lizard Island on the northern Great Barrier Reef and you could see a lot of damage from both cyclones and the big bleaching event that happened this summer. But Heron Island farther south has been relatively untouched. We visited a few rubble sites, which are natural. The parts that were covered in coral were just incredible — we saw corals growing on top of corals, which I haven’t seen before. This is my first time diving in an area that has gigantic plate corals.”
Next it’s off to our second survey location, a place called Tenements 2. The team repeats the process of photographing plots of seafloor. As they work, the tide continues to go out, exposing coral heads, which rise like a modern-day Atlantis from the seafloor. Waves begin cresting as they hit the top of the reef. Flocks of birds circle above, looking for lunch.
Their second site completed, the team is ready for lunch themselves. I ask Millan, a native of Troy, Michigan, with the University of Hawaii about her impressions of the second dive site.
“I was surprised by the large diversity of coral, including fire coral,” she says. “There was a big school of unicorn fish. I wanted to go take a look at some things, but I had to keep telling myself, ‘Just keep swimming, stay on the square,’” she says with a laugh.
After lunch, it’s off to the final site: Libby’s Lair. Millan first does a quick snorkel trip to survey the location. It looks suitable, so the team suits up and goes back in the water. They report lots of varieties of coral and big fish.
As the day wraps up, the team is joined by another boat carrying two CORAL Australian collaborators from the University of Queensland: Stuart Phinn and Chris Roelfsema. They are doing separate in-water validation work in conjunction with the other CORAL validation teams. Chris joins us in the water, taking photos and video.
It’s now a little after 3 p.m., and our team has completed its surveys for the day. It’s time to head back to the harbor, unload the boat and clean the equipment.
Today the team photographed seven sites, while PRISM aboard the Gulfstream IV collected 17 lines of data on a nearly 6-hour flight. Today’s activities, combined with the CORAL team’s previous flights up and down the Great Barrier Reef and in-water validation activities at Lizard Island, mean that CORAL is well on its way to achieving its Level 1 science objectives in Australia. All in all, a good day by air and sea.
Heron Island: Like Nowhere Else on Earth
Heron Island is a 42-acre coral cay located within the World Heritage-listed Great Barrier Reef Marine Park, 45 miles (72 kilometers) off the coast of Queensland, Australia. It is surrounded by a 5-mile-long (8-kilometer-long) platform reef that drains at low tide to form a large lagoon around the island.
First discovered in 1843, Heron Island housed a turtle canning factory in the 1920s, but today it is best known as a popular destination for tourists and researchers alike. It was declared a national park in 1943. The island includes a resort and the Heron Island Research Station, Australia’s largest university marine research facility, which is operated by the University of Queensland. The station is involved in research and education on marine sciences and the marine environment.
Heron Island and its surrounding reef teem with life, including sea turtles, whales, sharks, rays, sea cucumbers, sea stars, Christmas tree worms, sea hares, algae, many other varieties of fish, crabs, shrimp, and of course many different species of coral. Named after the reef herons seen feeding on the reef flats, the island is a bird haven: In the summer its bird population is estimated at around 200,000. Flora include grasses, herbs and trees.
My heart races as I sit snugly buckled in the leather seat of our modified Tempus Applied Solutions Gulfstream IV aircraft on the runway at Australia’s Cairns Airport. For NASA’s COral Reef Airborne Laboratory (CORAL) team, the anticipation is palpable – after days of weather delays, would this be the day we get airborne again? Soon I hear the engines roar to life, and we bolt down the runway, faster than any plane I’ve ever flown in before. We go airborne and climb sharply through mostly cloudy skies, then bank left and head south over the Coral Sea. It’s 8:54 a.m. Australian Eastern Standard Time on Sept. 15.
Within minutes the Great Barrier Reef comes into view, in all its stunningly beautiful majesty. A shimmering, luminescent spectacle in shades of aquamarine, turquoise, cyan, white and more, the sight of the massive reef is enough to move one to tears. First a long crescent appeared, fringed by whitecaps, then a wispy auradescent amoeba. As we head farther from the coast, more reef structures appear in an array of sizes and shapes, their sight obscured at times by pockets of clouds. Above us, the sky shines blue and bright; below, clouds dot the seascape. We’re on our way.
It’s hard to imagine that less than three hours ago, as the team assembled for a 6 a.m. weather briefing, the odds of flying seemed uncertain at best due to clouds looming off the coast. Clouds are the enemy of CORAL’s Portable Remote Imaging Spectrometer (PRISM), developed by NASA’s Jet Propulsion Laboratory in Pasadena, California. CORAL will investigate the condition of the Great Barrier Reef and representative reef systems worldwide from its airborne perch 28,000 feet (8,500 meters) above sea level. For the past several days, clouds had grounded the CORAL team.
Hovering above a laptop computer in an office at the plane’s hangar, CORAL project system engineer and mission campaign manager Ernesto Diaz and NASA CORAL project scientist Michelle Gierach, both of JPL, reviewed an animated sequence of satellite cloud imagery. Other members of the team watched or listened in by phone. To the south, the images revealed pockets of clearing over some of CORAL’s target areas. But would the clearing hold for the several-hour duration of a flight?
On the phone Stuart Phinn, professor of geography at the University of Queensland, recommended flying, as the forecast for the next few days was only going to get worse. After further discussion, Diaz recommended the team reconvene at 8 a.m. to make a final go/no-go decision and instructed pilots Josh Meyer and Curt Olds to tow the plane to the tarmac. He also asked the PRISM team to begin preparing for flight. The five-member JPL team aboard the flight – Diaz, optical engineer Holly Bender, lead technician Scott Nolte, JPL videographer Jim Round and I – boarded the aircraft.
As the clock ticked, conditions remained marginal. Finally, it was 8 a.m., and the team convened again by phone. The clear patches to the south had remained. After a few more minutes of discussion, Diaz said, “We are a go.” The target area for today was a region of the Great Barrier Reef near Mackay.
Returning to present time, we head south along the Queensland coastline. It will take about an hour to reach Mackay, located on the south central portion of the reef. The team has targeted up to 20 flight lines to survey with PRISM today out of the CORAL campaign’s planned 151 flight lines over the reef. Our total flight time is expected to be up to five hours (two hours if the weather doesn’t hold when en route).
Diaz and Bender spend the early part of the flight ensuring that PRISM’s flight tracker is set up and jotting down flight lines, while Nolte monitor’s PRISM’s performance. The crew all wear headsets to facilitate communication between themselves and the pilots. PRISM’s focal plane temperature slowly begins to stabilize and eventually reaches its nominal 0 degrees Celsius (32 degrees Fahrenheit). Nolte also monitors the temperature inside the PRISM telescope and the pressure between the vacuum vessel. Thus far, everything looks normal.
We continue heading south, paralleling the Queensland coast, toward our destination about 375 miles (604 kilometers) south of Cairns, a bit more than the distance between Los Angeles and San Francisco.
I ask Diaz and Bender what’s going through their minds at this point in the flight.
“I’m hoping we have no clouds,” says Diaz. “I’m anxious to see how our forecast go/no go decision pans out.”
“I’m really excited,” says Bender, a 10-year JPL employee whose previous NASA airborne flights were in an unpressurized Twin Otter plane. “This is the fourth JPL imaging spectrometer I’ve flown with, but my first day operating PRISM for CORAL. Back at JPL, I work on the optical design and alignment for many of our imaging spectrometers, but to follow an instrument start to finish—from concept to seeing it out in the field—is an incredible feeling. I’m excited to see the data we’re going to get.”
This is essentially a training flight for Bender—the job of collecting PRISM CORAL data is normally a two-person job. The CORAL team members work in two-week stints.
Heading farther down the coast, the city of Townsville appears below along an irregular coastline. To the west, Australia’s vast interior is largely hidden beneath cloud cover. To the left, a large, mostly cloud-free area opens up, with scattered islands piercing the sea surface.
As the team reaches the first target region, they find a mix of cloud cover but it is within acceptable limits. They decide to begin collecting data along their first flight line. A beeping sound from the flight planning tool that sounds something like a percolating coffee pot begins signaling that PRISM is collecting data, in a ground swath measuring 3 miles (4.75 kilometers). They complete the data collection, then maneuver the plane to its next target line, then a third. As they assess the three lines collected, portions of the lines appear cloud-free, while others have 100 percent cloud cover. The team makes a real-time decision about whether to proceed to the next nearest flight line or skip it in favor of one with less cloud cover.
The aerial survey “mows the lawn,” so to speak, as the plane flies back and forth across target regions that have about a 15 percent overlap. Adjacent target flight lines may be in a completely different direction—CORAL scientists target representative reefs across a transsect of the reef from the coastline to the outer reef.
In the meantime, Nolte continues to monitor PRISM. His computer screen shows various data, including the plane’s pitch and roll and its heading, along with a visual of what PRISM sees and a more human-friendly view of the ocean below.
As they continue collecting data, the decision to change the flight plan pans out as flight lines appear to be mostly cloud-free. The team decides to not collect data over some of the flight lines, either due to unfavorable cloud conditions or the sun’s angle above, which becomes increasingly unfavorable as the morning flight continues. “We have about three hours in the morning and three in the afternoon where there are ideal lighting conditions,” Bender says.
After the team completes its 13th line, they decide to return to base. A future flight may collect the other lines. CORAL’s level one science requirement is to image at least half of the mission’s targeted sites. The plane touches down back in Cairns at 1:16 p.m., a little more than 4 hours after takeoff.
“We started off with clouds in the first few lines, but we ended up getting some good weather,” Diaz says. “We collected a good cross section of data from the inner reef to the outer reef. Our decision to fly today was a good one, and PRISM performed like a champ.”
Following the flight, the team shut down the PRISM instrument, removed the nearly 500 gigabytes of data collected and transferred the data to a field server where data processing begins. Initial quick-look data providing a snapshot of what was mapped are typically available within a day—these can sometimes be used to plan the next day’s flight activities. Level one data products take an additional day. More advanced data products are processed off-site.
With the completion of the successful flight, the CORAL team has now collected about a fifth of the data planned for the Great Barrier Reef deployment. The team will remain in Australia through the end of October.
by Alan Buis / Cairns, North Queensland, Australia /
On a non-flight day this week, I had a chance to chat with some of the crew from NASA’s Jet Propulsion Laboratory who are here in Australia to support the Coral Reef Airborne Laboratory’s (CORAL) Great Barrier Reef deployment about their roles in the mission.
Ernesto Diaz is CORAL’s project system engineer and mission campaign manager. He joined JPL in 2010 and is currently in JPL’s imaging spectroscopy group, working on PRISM and other spectrometer instrument programs that are pathfinders to develop technology for a planned NASA satellite called the Hyperspectral Infrared Imager.
Among Diaz’s responsibilities is to assess the weather each day to determine if a flight will be attempted. The team’s routine includes daily 6 a.m. weather assessment briefings. Diaz bases his assessments and recommendations on data from the Australian Bureau of Meteorology.
“I’m not a meteorologist,” he said. “But I’ve come to understand weather patterns well. A key is assessing how weather patterns are going to evolve over the course of a typical CORAL flight over the Great Barrier Reef, which can run from three to six hours.”
Because PRISM is a passive imaging system, meaning that it records the amount of light energy reflected back to it from Earth’s surface, it requires a cloud-free view to the ground below. CORAL’s science requirements state that cloud cover over a target area must be less than 20 percent, including clouds both below and above the plane. Winds must also be light, because strong winds create chop on the sea surface that interferes with PRISM’s performance.
Diaz said PRISM has two flight opportunities each day: one in the morning and one in the afternoon. On days when the initial 6 a.m. forecast looks favorable, the team is given a go to turn the PRISM instrument on. A second weather go/no-go call is then made at 8 a.m. prior to a takeoff at 8:30 a.m. Morning opportunities are typically better for winds.
The CORAL Great Barrier Reef deployment requires collecting data from 10 regions over the reef, and the PRISM aircraft is limited to a total of 48 flight hours. Because weather and technical delays are unpredictable, the CORAL mission has allotted a full two months to collect the necessary data. “There’s no reason to rush and get bad data,” he said. “We want to get the best possible data on flight days. When we don’t fly, it’s an opportunity to do routine maintenance.”
Diaz says CORAL is his favorite project since he’s been involved with it since its inception and he designed all the flight lines for the campaign. Imaging spectrometers have taken him not only to the Pacific, but to Chile and India as well. On the team’s day off this week, he and his wife went to Kuranda Koala Gardens, about 45 minutes north of Cairns, and got to hold and pet a koala. “It’s a perk of the job,” he said.
Technician Scott Nolte built hardware for PRISM’s high-powered UNIX-based electronics subsystem, which has the highest signal-to-noise ratio performance of all of JPL’s imaging spectrometers.
Nolte has worked at JPL for 33 years, 15 of them in the lab’s imaging spectroscopy group. He said he’s seen a lot of growth.
“For the first seven or eight years I was in the group, we only had the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) Classic instrument. Now we have multiple hyperspectral imager programs.”
For Nolte, a typical day in the field with PRISM consists of cooling the instrument’s camera down and stabilizing its temperature two hours before takeoff, as well as any required troubleshooting as necessary.
Nolte’s work has taken him to places like Hawaii; Norway; Punta Arenas, Chile; St. Croix; and Marathon in the Florida Keys. This is his first visit to Australia. “PRISM gets some pretty sweet deployments,” he said.
Justin Haag is PRISM’s optical engineer. His job is to make sure the PRISM instrument is working and ready. The Illinois native and graduate of Northern Illinois University and UC San Diego joined JPL two years ago.
When I caught up with Haag, he, Diaz and Nolte were making hardware adjustments to part of PRISM’s field health assessment kit. Unlike calibration tests, which are performed on PRISM both before and after its mission campaigns, the field health assessment kit is used to periodically assess PRISM’s performance between flights. It consists of a sphere attached to PRISM’s external camera port on the exterior of the Gulfstream IV aircraft. Two different types of lamps are shined into the sphere, which bounces the light around the sphere’s white, coated interior to create a uniform light input for PRISM to measure.
A previous health assessment test last week had detected some light leaking into the sphere through exterior gaps in the kit fixture’s hardware. The team’s solution? They covered the gaps with black tape. Think of it as an adult version of the arts and crafts we all did in elementary school.
Not every problem requires a high-tech solution. Just a little old-fashioned ingenuity.
by Alan Buis / CAIRNS, NORTH QUEENSLAND, AUSTRALIA /
G’day from Australia!
With the successful June campaign readiness tests in Hawaii behind them, NASA’s Coral Reef Airborne Laboratory (CORAL) team has rolled up their sleeves and are now hard at work shedding new light on our understanding of Earth’s coral reef ecosystems. The team’s first stop: Australia’s majestic Great Barrier Reef, the world’s largest reef ecosystem.
For this NASA Earth Expeditions reporter, the first thing I learned is that getting to Oz isn’t as easy as clicking your heels. I quickly grasped a new appreciation for just how vast the Pacific Ocean is: a 15-hour flight from LA, literally heading into the future, 17 hours ahead of when I left. After arriving in Sydney, it was another almost three-hour flight up the coast of Queensland to Cairns (pronounced “Cans”).
Yet as long as my travel odyssey was, it was even longer for some others on the CORAL team. For example, the crew of the Tempus Applied Solutions Gulfstream IV plane carrying CORAL’s NASA Jet Propulsion Laboratory-built Portable Remote Imaging Spectrometer (PRISM) instrument began its journey in Maine; CORAL Principal Investigator Eric Hochberg and his wife traveled from the Bermuda Institute of Ocean Sciences.
Cairns is a city of 160,000, located in tropical North Queensland. It is popularly known as the Gateway to the Great Barrier Reef. Overlooking a bay and surrounded by green hills with exotic flora and fauna, Cairns is a major tourist destination, filled with hotels, restaurants and attractions. To my disappointment, I’ve yet to encounter a single kangaroo, wallaby, emu or koala, but I have met a lot of friendly people. The bay does contain crocodiles; the boardwalk on the esplanade has signs warning people not to swim there.
Through October, the Gulfstream IV plane and its support team will be based here, closely monitoring the weather daily in search of the optimal clear sky and light wind conditions required for CORAL to collect its data. The team will survey six discrete sections across the length of the Great Barrier Reef.
The in-water science team calibrating and validating the airborne measurements from PRISM from two locations on the reef arrived in Cairns Sept. 1 and transited to Lizard Island, its first location, on Sept. 3. The team successfully conducted its in-water science validation operations there from Sept. 4. to Sept. 12. Over the next few days, most of the science team will depart for Heron Island, the other calibration/validation location.
The plane and its team arrived in Cairns Sept. 2 and set up residence at the Hawker Pacific Fixed Base Operations facility at Cairns Airport. Following a hard down day (day off) on Sept. 3 for the plane and crew, the team unloaded the aircraft and ran through all the procedures required for flight, including loading all 121 flight data lines PRISM will acquire over the reef into the pilot’s flight planning system. The aircraft’s systems were checked and the PRISM instrument was powered on and thermally stabilized.
And then the flight team waited for the weather to cooperate. And waited. And waited.
Following several days of weather scrubs, on Sept. 9 weather conditions were favorable over Lizard Island, and the team was given the go to fly. In their four-hour flight, the first operational flight of the CORAL mission, the team collected 14 lines of data, which were subsequently removed from the plane and downloaded and processed on the field server. On Saturday, Sept. 10, flush with the success of the previous day’s flight and with a somewhat favorable weather forecast in one of the data collection areas, the team prepared to fly again. They took off, bound for the Townsville coast area, but cloudiness forced them to return to base. Since then, weather has continued to not cooperate and no more flights have been conducted.
Today at Cairns Airport, the CORAL team will hold an event for Australian media and dignitaries from a number of Australian science organizations, where they will discuss the CORAL Great Barrier Reef campaign and reveal some of their initial data from the successful flight on Sept. 9.
“The view is incredible. You can see 300 miles away,” he said from the cockpit of NASA’s high-altitude ER-2 research aircraft. “You can see the curvature of the Earth. If you look up, the sky is very dark blue.”
Of course, for the ORACLES mission now in Namibia studying low-level clouds and aerosols over the south-east Atlantic Ocean, the view of never-ending white is not going to be quite so exciting for the pilots, he added with a grin. There’s more to flying high than the view.
“I kind of like the solitude, too. It’s my happy place. No matter what’s going on in my life, when I close the canopy, and especially when I leave the ground, I know I’ve got 12 hours of alone time. Busy alone time,” Broce said.
A retired Navy pilot, Broce flew commercial for nearly a year before post-9/11 furloughs led him back to the military, this time the Air Force, where he learned to fly the high altitude aircraft. As luck would have it, around the time he was retiring, NASA was hiring, and Broce has been flying the ER-2, as well as other aircraft, for NASA for the last five years at Armstrong Flight Research Center in California. He’s one of two pilots flying the ER-2 for the ORACLES mission this month.
It’s a challenging aircraft to fly. Landing in particular. “It’s like landing a big 30,000 pound bicycle,” he said. The ER-2’s two main sets of wheels are under the body. The wheels that prop up the wings on the ground drop off during take-off and don’t fly.
The ER-2 is a small, lightweight airplane with a single occupant: the pilot. Its job is to get the long view of the clouds below. Tucked into its nose, body and a pod under each wing, the ER-2 carries four remote-sensing instruments to 65,000 feet, twice the altitude of commercial airliners.
“The only people higher than us are the astronauts in the space station,” said Broce. “We fly so high, we fly above Armstrong’s line at 60 to 62,000 feet, where if you took a cup of water at altitude outside the plane, the water would boil just because of the low pressure there, even though it’s super cold.”
People don’t do so well at those low pressures. The pilots wear space suits that will pressurize in case of a loss of cabin pressure. Part of their prep is to breathe pure oxygen for an hour before flight to purge the nitrogen from their bodies so they don’t get the bends when they ascend so quickly. Food and water for the eight plus hours in flight both come through a tube – applesauce, pear-sauce, and peach-sauce are among Broce’s favorites, which he said are actually pretty good.
The instruments, on the other hand, do great at 12 miles above the Earth. While they’re not as high as satellites, some of the instruments simulate satellite measurements. Aboard the ER-2 they both test out new technology and software and get the equivalent of satellite data right where the scientists want it.
The science team is trying to understand the interaction of clouds and tiny airborne particles – smoke from fires central Africa – and how they change the amount of energy absorbed or reflected from the clouds, a key component for assessing how clouds affect Earth’s climate.
Broce helps out with gathering the data. The instruments are as fully automated as can be, but he still needs to turn them on after take-off and sometimes during flight switch their modes.
“I like to count the number of button presses per hour. It’s ‘BPH’ — my term. If it’s above ten, I consider that busy because you have to read checklists and know when to hit the button and check miles and time and locations. We also have to navigate and fly the plane, sometimes to precise navigation or headings, and then push the buttons.”
At the end of the day, the goal is to return measurements to scientists waiting on the ground.
Brent Holben stands in the shade of his car’s hatchback door, squinting at his phone. He’s checking Google Maps. From the dirt parking lot at the Walvis Bay Airport, Namibia, he temporarily has free internet access to the NASA wifi hotspot set up for NASA’s ORACLES airborne science campaign here.
“I don’t want to make a wrong turn,” he says. “Of course out here, that’s pretty hard. There’s not many turns.”
With a trim gray beard and brimmed hat, Holben, a scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, is in charge of the ground sites that will measure aerosols to complement observations made by ORACLES’s two research aircraft.
Today, Holben is heading out on a road trip southeast of Walvis Bay to the Gobabeb Research and Training Centre, 40 miles as the crow flies from the coast. There, perched atop a short tower, is one of Holben’s aerosol measuring instruments, a sun photometer that is part of the Aerosol Robotic Network. AERONET, which began in 1992 with two sensors, now has 600 sensors worldwide, but not as many in Africa as Holben would like.
“Africa is a giant place, and it’s underrepresented compared to Europe and the United States.” Holben is the AERONET project scientist.
As ORACLES was being planned to make measurements of aerosols over the southeast Atlantic Ocean from aircraft, he originally drafted plans for two AERONET instruments in Namibia that would study aerosols from the ground. He ended up setting up ten.
A sun photometer has one job: to look at the sun to see how many aerosols are between it and the ground by measuring the light energy that reaches the instrument.
“If the set-up weren’t simple, I wouldn’t do it,” Holben said of the solar-powered instrument.
But simple doesn’t mean without complications. One reason Holben is visiting Gobabeb is because he’s concerned about the instrument shutting down unnecessarily due to the region’s characteristic fog.
The sky is overcast on our drive south, which is not uncommon along the Namibian coast. Early morning fog develops when warm air condenses over the cold ocean water, and then it rolls over the length of the coast and inland. It’s the main source of water for much of the vegetation that grows where it can across the plain.
Not far from the airport the asphalt disappears and we’re driving on a dirt road. To either side the rocky desert is white-beige and flat, textured with small rocks and dotted with occasional buildings that grow fewer and farther between.
On the horizon ahead, great sand dunes appear, first as bumps, then looking like orange mountains. Eventually, a green strip comes into view at the base of the dunes. Holben points out as the green strip resolves into trees. “That’s the river.”
The river is the Kuiseb (pronounced kwee-sib), and it’s dry for most of the year. During the rainy season from November to January or so, it may have water for a few months, replenishing the groundwater for the trees – and everything that eats their leaves – to live on for the rest of the year.
The road turns east and from here parallels the river into the Namib-Naukluft Park and to Gobabeb Centre where it dead-ends. Along the way are the farms of the local Topnaar community, which has lived along the Kuiseb for the past 600 years. Many have day jobs in Walvis Bay to supplement their living. Along the river they raise cattle and other livestock.
“It’s a harsh existence. You’ve got to admire people who eke out a living here,” said Gillian Maggs-Kölling, the Gobabeb Centre’s executive director. The centre is located next to three ecosystems: the rocky plain, the linear oasis of the river, and the 1,000-foot sand dunes that roll into the Sand Sea to the south.
Maggs-Kölling is a biologist, as are most of the 18 researchers and students who live and work there. It’s an international mix, with students from the Namibian University of Science and Technology joined currently by a group from the University of Basel in Switzerland, and a handful of others from various other European and American universities.
The main building with labs and offices is surrounded by a spread of low cottages and gardens of scientific instruments measuring temperature, moisture, and a dozen other things. Completely off-grid, the site is powered by solar panels with the occasional help of a generator.
This is Holben’s third trip to Gobabeb, one each year since setting up the AERONET sensor here.
“We came here because we didn’t have an instrument in this part of the world. The Namib Desert is quite unique because it is influenced by fog,” said Holben. He and the ORACLES team hope to learn how the aerosols they’re measuring affect the fog and the clouds over the ocean.
We meet Monja Gerber, a relatively new technician and Masters student in plant physiology from North West University in South Africa, who is taking care of the instrument this year.
Atop the two-story tower where the AERONET instrument sits, Holben shows Gerber a few maintenance tricks. The instruments tube is open and sometimes spiders or bees like to make homes in them, he points out. Holben shows her how to disconnect the wet sensor that triggers when fog collects on it.
As the day warms, morning fog that rolls in from the coast clears. Using its own GPS location and the time of day to find the sun, the AERONET photometer spins into action.
“We’re looking at two main aerosols in this region. Dust blown from the desert is one, which is actually a very small component. The big one is smoke from fires in central Africa. These are man-made agricultural fires as people clear their land at this time of year,” said Holben.
Westerly winds take the smoke from the Democratic Republic of Congo, Zambia, and Angola, and carry it out over the southeast Atlantic, where ORACLES’s two research aircraft measure it to see how the smoke changes sunlight absorption or reflection – important to know for understanding and predicting climate change. That smoke arcs back to Namibia on south-easterly winds.
“We’ve been watching the aerosols day by day for ORACLES,” Holben said of both the measurements here at Gobabeb and the six sensors that are set up in Henties Bay, an hour north of Swakopmund. “Over the last several days, the optical depth went from almost background conditions to – yesterday – moderately high.”
Light scattered by the smoke aerosols makes sunsets here red, Holben added.
The sunset is spectacular. Holben and his son Sam, who accompanied him on the trip, cross the river and climb to the top of the nearby dune to watch. They leave with barely enough time, and Sam, not wanting to miss it, runs ahead and picks the steepest ascent.
Climbing a dune of fine sand is not easy, and he slides down nearly as much as he climbs, but persistence gets him to the top. Holben takes a less-steep approach and settles in for the show.
From the top, the Namibian landscape stretches as far as the eye can see, changing colors as the sun sinks behind the dunes in the west. The stars slowly come out and the Southern Hemisphere constellations brilliantly shine beneath the sweep of the Milky Way.
The ORACLES science team is in southern Africa to fly.
The bulk of their work is done in the narrow confines of the stocky P-3 aircraft amid racks of customized instruments. In the coming weeks these instruments will be complemented by remote sensors on the high-altitude ER-2 aircraft. But while the ER-2 team waits for the arrival of their specialized fuel, the science flight on September 2 is all P-3.
For this 8:00 a.m. flight, wake up time is early but you wouldn’t know it for the palpable sense of excitement the scientists have as they board the plane. This is the first “flight of opportunity;” the theme: It’s Positively Radiant Research. The flight will focus on the energy balance of the clouds over the ocean: how much light are clouds reflecting or absorbing as they interact with the smoke aerosols that travel from agricultural fires in central Africa.
The inside of the P-3 looks like a laboratory with big boxy instruments in front of airline seats. Twenty-four scientists can fly at a time with more than a dozen instruments. Once everyone’s aboard, ears safely covered by noise-cancelling headphones, the turboprop engines fire up. The P-3 taxis down the runway and takes off.
This is a LOUD plane – deafening, in fact. The headsets have the dual role of hearing protection and allowing everyone on board to communicate, reporting real-time observations. Sebastian Schmidt of the University of Colorado, Boulder is the flight scientist today. Sitting up front, his is the single voice speaking to the pilots, relaying any requests for adjustments in the flight path that come from the instrument teams.
The pilots, Mike Singer and Mark Russell of NASA’s Wallops Flight Facility, have final say on the flight path. They are responsible for the safety of the plane and its occupants. With hundreds of science flight hours under their belts, they’re very familiar with how scientists like to fly. Today it’s in tight spirals from the top of the smoke layer and clouds to near the ocean surface to see what the air is doing along a vertical column.
On this eight-hour flight, though, the science team channel isn’t all business. “Who still needs a nickname?” Sam LeBlanc of NASA’s Ames Research Center in charge of the 4STAR instrument asked at one point.
A number of the flying scientists apparently still do. Among them, Sabrina Cochrane, a second-year grad student at the University of Colorado, Boulder, manning the Solar Spectral Flux Radiometer. This is her first research flight.
“I was really nervous,” she said after the flight. “I thought I was going to feel sick the whole time with all the spirals, but I didn’t. It was really smooth. It was a lot more fun than I expected.”
Flying between the spiral locations, the Airborne Precipitation Radar team was on the look-out for another high-flyer: the CloudSat satellite in space, which was scheduled to make a pass over the same region the P-3 was flying. This radar measures cloud droplet sizes and numbers, validating the same measurements taken from space by CloudSat’s radar.
The satellite overpass was not exactly over the flight path, but close enough, said Steve Durden of NASA’s Jet Propulsion Laboratory. “Even if they’re not perfectly aligned you’ll see the same structures in the clouds,” he said.
The final maneuvers of the day occur during the last hour of flight on the way back to Walvis Bay Airport. David Noone of Oregon State University explained that these maneuvers are for the instruments, to find out how different orientations of the aircraft affect the measurements.
“My measurements, the water vapor and the water vapor isotope measurements, are a good example of this. We’re bringing in air from outside through an inlet that must be pointing directly forward into the flow. If it’s slightly off, the number of cloud droplets that enter the inlet might vary,” he said.
To test out the orientations the pilots will wiggle the tail of the aircraft, roll side to side, and go up and down like they’re going over a hill.
“Now some of these are good fun,” said Noone, “but we’re sitting here in the back of the aircraft. We’re way out in the tail so we’re going to get a good ride.”
Planning a science flight does not appear to be most exciting part of a NASA airborne mission, even from an exotic location like the Namibian coast where we are now for the ORACLES mission. No planes. No high-altitude views. Just a group of people on computers sitting at long tables in a windowless conference room staring intently at a projector screen.
“I couldn’t disagree more that it’s unglamorous,” said ORACLES principal investigator Jens Redemann of NASA’s Ames Research Center. “I am so excited to be here planning the flights. It’s the promise of a great flight, like visualizing the greatest possible outcome. It’s the perfect flight that we’re on the hunt for every time. You don’t think about anything else while you’re flight planning.”
The work they’re doing at this 8:00 a.m. meeting literally drives the mission. The forecasting team shows videos of slow-moving model projections of the clouds and aerosols over central and southern Africa and the Atlantic Ocean all the way out to Ascension Island. Like fishermen discussing where to find the best catch, they discuss in excruciating detail where they think the best clouds and aerosol plumes will be.
Like any other prediction of the future, however, these models are not 100 percent correct all the time.
“We know that models aren’t perfect,” said Karla Longo of the Global Modeling and Assimilation Office at NASA’s Goddard Space Flight Center. The Goddard Earth Observing System or GEOS-5 model, for instance, tends to underestimate low-level clouds in this region.
“We have to use it here though so we understand when and why it’s wrong. People don’t always feel good about it, but it’s the only way to improve,” said Longo.
Part of the forecast briefing is devoted to looking back to the previous flight and comparing the forecast for it with what the plane actually found. Over the coming months and years, the ORACLES measurements will be used to update the physics that drive the model.
Meanwhile the science team is riveted because flawed or not, these are the images they need to plan the next flight.
On an airborne mission like this there’s not a preset plan of where and when they will fly. Planning is done day by day. It’s a balance between the need for aircraft crew rest and the potential for good clouds and aerosol plumes to measure.
“We’re always concerned about low-level clouds and the amount of smoke in the biomass burning plumes,” said Redemann. “The juggling act is that our science objectives are diverse enough that we look for different plume and cloud characteristics on different days.”
After the forecast briefing to plan the flight for Friday, Sept. 2, Redemann gathers around a whiteboard with a few of the instrument scientists to hash out the nitty-gritty details of the main science section of the flight. The focus of Friday’s flight is radiative balance. They will design the flight plan to maximize the measurements taken by the Solar Spectral Flux Radiometer, which gauges the brightness of the clouds to determine the energy – light – in the atmosphere coming from all directions – directly from the sun, filtered through clouds, and reflected by clouds.
“The aerosol plume has a different effect on the radiation balance depending on whether the plume is above smooth or broken clouds,” said Redemann. Aerosols can have either a cooling or a warming effect, depending on the brightness of the clouds below. “We’re trying to verify that experimentally in flight.”
The science planning conversation is long and involves a shorthand language, squiggles on the whiteboard and questions like “Do you want to spiral here?”
Once they figure out the science plan, the pilots come in and work with the team to write their flight plans, including when and where to fly the aircraft from the cloud tops down to a few hundred feet above the ocean surface in a corkscrew-like spiral.
By the end of the day it all comes together, and all that’s left is for the science teams to decide who gets to fly onboard with their instruments.