Anita Arnoldt is the electrical lead for PACE at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
Arnoldt working on pin retention on PACE. Image credit: Dennis Henry
What do you do for PACE?
I’m an electrical technician. I did all the harness wiring, routing, and thermal work, all the electrical work. I worked with Amy Huong, and together we did the wiring for both OCI and for the PACE spacecraft. We plugged it all in and tested it!
What are you most looking forward to once data starts coming in?
I’m looking forward to making sure everything works. If everyone is happy with the data they collect from all the spacecraft instruments, and everything is working well, then I’ll be happy.
What is your favorite color and why?
Blue, because that’s the color of the ocean and the sky. I just like looking at blue.
Arnoldt and her husband, Jim, in front of PACE for family day. Image credit: Dennis Henry
What’s a fun fact about yourself?
I used to play softball for the Air Force. My husband is retired Air Force, so we were stationed in Italy and so I got to play on the European women’s softball team. I played first base and shortstop. We actually won that year for the European championship!
What advice would you give to aspiring scientists or engineers or technicians who are looking to get where you are today?
Try to learn as much as you can from the people that are around you. Make sure you have a really good team like we did on PACE – I think we had an excellent team from the top down. Everybody contributed so much, we communicated well, and it was just really good working together. And we had a fun time.
What is one catch all statement that you would want the public to know about the importance of PACE?
It’s important to study the climate and climate change to make sure people can make the best decisions – and PACE and OCI are going to help with that.
Header image caption: Arnoldt working on PACE’s solar panels. Image credit: Dennis Henry
By Erica McNamee, Science Writer at NASA’s Goddard Space Flight Center
Bridget Seegers is an oceanographer at NASA’s Goddard Space Flight Center in Greenbelt, Maryland and a team member for NASA’s Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission.
Bridget captaining her sailboat, Blissfully. That’s the boat name and she is quite blissful while sailing. Image Credit: Azul Gutierrez
What is your favorite atmosphere or ocean related book or movie?
“Life Aquatic” definitely comes to mind. It’s amazingly accurate in how it depicts certain aspects of life on a research vessel. For a book, there’s one called “The Long Way” by Bernard Moitessier. It’s about him sailing solo in a race around the world, way back in the day (1968), which is very interesting.
What is your research about?
I focus on harmful algal blooms. There are a lot of little, teeny organisms called phytoplankton in the ocean and lakes, and sometimes they grow into huge numbers, and we call that a bloom. That can be good because it feeds the food web, but sometimes it can be toxic and cause problems. People monitor those harmful events to reduce human exposure to any of the harmful toxins. I use satellites to monitor for these harmful events and help water quality managers respond to them.
Bridget with PACE ready for launch on top of a Falcon 9 rocket. Image Credit: Bridget Seegers
What was your favorite part of watching the launch?
The PACE team, friends, and families being together sharing all the excitement, hugs, and emotions was my favorite part of launch. It was incredible watching the rocket light up the night as PACE began its journey to space! And, of course, fantastic to hear updates throughout launch and since that all is well with PACE and the instruments. All wonderful experiences!
What are you most looking forward to post-launch?
The data and exactly what we can do with it. There’s been a lot of talks and hopes of what this data will be like, but there’s never been a satellite like PACE. We can imagine all these products, but it’ll be great to see what we actually can do with the products. If we can tell one type of phytoplankton from another, we can hopefully tell some of the more harmful ones from ones that are just average members of the phytoplankton community that aren’t causing problems.
We know that OCI on PACE is going to be able to look at all the colors of the ocean, so what is your favorite color and why?
My favorite color is purple. Why? I don’t know, it just feels right.
Christmas Tree worms from a reef in Rangiora from when Bridget was sailing there. Image Credit: Rory Moore
Do you have a favorite type of phytoplankton or sea creature?
I think my favorite sea creature would be Christmas tree worms. They live on coral reefs and they like pop out and they look like an evergreen tree. They come in all these different colors. When you get close, they like pull themselves in, but then they pop back up. They’re really fun and colorful, and they’re kind of interactive. For phytoplankton, there are a variety of species that bioluminesce and I think that’s pretty magical when you see the ocean light up at night, either with breaking waves or running your hands through it.
Bridget on her surfboard named Purple Rain catching a little wave and waving to a friend on a gray July day along the Southern California coast. Image Credit: Matt Marbach
What is a fun fact about yourself?
I like to sail. I had a friend who solo circumnavigated the globe, so I met him to sail in a variety of places like around French Polynesia, around nearly half of South Africa, and north of the Arctic Circle in this chain of islands called the Lofoten Islands. I was also able to surf north of the Arctic Circle from the sailboat!
What advice would you give to aspiring scientists who are looking to get where you are today?
Bridget with Chloe and Luca at a San Diego elementary school. They are prepping a plankton sample to view on the microscope. Image Credit: Isa Tavera.
Stay curious and be motivated by asking questions. Follow what interests you and what you’re passionate about. It’s not always a direct path and science can be a little bit tedious, so it’s really important to trust yourself and to pursue things that are interesting to you. Ask questions and don’t be afraid to chat with other scientists. Sometimes people think scientists are intimidating, but we’re mostly pretty nice and slightly awkward, so I would have those conversations!
What is one catch-all statement describing the importance of PACE?
Knowledge is power. For both PACE and science in general, the more information we have the better we understand things, and the more able we are to respond to the changing planet in an effective and meaningful way that empowers us.
Header image caption: Bridget with the PACE observatory. Image Credit: Dennis Henry
By Erica McNamee, Science Writer at NASA’s Goddard Space Flight Center
Fred Huemmrich is a member of NASA’s Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) science and applications team and a research professor at the University of Maryland, Baltimore County.
What is your favorite atmosphere, land, or ocean related book or movie?
“Dune.” To be specific, I really liked the appendix of Dune which has the story of the imperial planetologists, and when I read that as a kid it was the first time I ever thought of the concept of looking at an entire planet’s ecosystem. So, my goal in life is always to become an imperial planetologist.
Fred on top of an instrument tower at the Smithsonian Environmental Research Center. Image Credit: Fred Huemmrich
How will PACE help your research?
One of the things that I’m really interested in is the dynamic of ecosystems on land, and how they change over time. PACE really excites me because it’s an opportunity to look – with new, hyperspectral data – at seasonal dynamics of these ecosystems, or even shorter-term effects like droughts or heat stress or cold snaps. With the hyperspectral data available from PACE and OCI we’ll be able to do things like look at changes in leaf level pigment contents and biochemistry. Plants are constantly altering themselves to adjust to the environment and that is something we can see from data on the light that reflects off them. I’m really excited about PACE giving us this data of time series for vegetation types all over the world.
What are you most looking forward to after launch?
I envision doing a study, looking at the indices of plant conditions globally, after the first month of data. I’m going to make a global map because we just don’t even know what it will look like. That’s going to be the first step after launch.
OCI on PACE is going to be able to look at all the colors of the rainbow. What is your favorite color and why?
My favorite color is one you can’t see! Almost all the light that hits plant leaves in the visible wavelengths gets absorbed, except there’s a little hump in the green that they don’t quite absorb as much, which is why we see them as green. But just beyond what we can see, in the near-infrared, leaves have almost no absorption. If we could see leaves in the near-infrared it would almost be like looking at like highway signs that like reflect light back on you really brightly. In green leaves the transition from the visible wavelengths to the near infrared wavelengths is called the red edge and measuring it gives you a lot of information about how much chlorophyll is in leaves.
Do you have a favorite plant?
Fred doing fieldwork in the arctic tundra dealing with the mosquitos. Image Credit: Fred Huemmrich
One that I’m fond of is black spruce. Over the years I’ve done a fair amount of work in the boreal forests. In fact, just last this past summer I was doing fieldwork in the boreal forests in Alaska. I’m really interested in seeing if we can use the PACE data to detect changes in the spruce needle biochemistry that we can’t do with the satellites we have now.
What is a fun fact about yourself?
I worked my way through college in a brewery!
What is some advice that you would give to aspiring scientists who are looking to be where you are today?
Fred presenting results of arctic tundra research at Grey Towers National Historic Site in Milford, PA. Courtesy: Fred Huemmrich
One of the pieces of advice I give to my undergraduate students is that when I was an undergraduate, not only did I not know what I was going to end up doing, I didn’t know that what I ended up doing even existed. Very often undergraduates don’t have a lot of experience in the range of jobs available in the world. And that’s, of course, changing all the time with technology. One of the things that’s important for them to do is to look around and try to get outside of a narrow thing that they’re focused on, and spread out a little bit to look at what might be available because they might be surprised at what they find.
What is one catch-all statement describing the importance of PACE?
PACE is going to give us a fundamentally new view of the way ecosystems work on the planet.
Header image caption: Fred measuring spectral reflectance and photosynthesis in a cornfield. These types of measurements are used to develop approaches for applying PACE data to determine crop productivity. Courtesy: Fred Huemmrich
By Erica McNamee, Science Writer at NASA’s Goddard Space Flight Center
After years of planning, building, and testing, 2024 is the PACE mission’s time to shine: Launch is slated for February and the team is eagerly awaiting a wealth of ocean- and atmosphere-related data to dig into soon after.
Several PACE scientists closed out 2023 by sharing this enthusiasm for the mission at the American Geophysical Union’s annual meeting December 11-15 in San Francisco, which drew more than 24,000 Earth and space scientists.
“This is such a profound quantum leap forward in terms of our ability to monitor our home planet,” Jeremy Werdell, PACE project scientist at NASA’s Goddard Space Flight Center, told a group gathered in front of NASA’s hyperwall screens.
PACE project scientist Jeremy Werdell outlines diverse areas of study that data from the mission could help answer questions for, at the NASA exhibit booth at the American Geophysical Union’s annual meeting in San Francisco, Dec. 12, 2023. Image credit: NASA/Kate Ramsayer
He showed a visualization highlighting Earth’s pulsing phytoplankton blooms, masses of aerosols drifting across oceans, ice sheets retreating, and more. It’s 20 years of our home planet breathing, Werdell said. Insights like these about Earth are one of NASA’s key accomplishments, he said, right up there with landing on the Moon.
In the conference’s poster hall, researchers presented their work to get ready for using the data. Amir Ibrahim, an ocean scientist with NASA Goddard, talked to colleagues about a tool he is using to simulate the data that the team will receive once PACE’s Ocean Color Instrument is up and running in orbit.
“We’re here to interact with the community who will use the data, and share with them the great capabilities OCI will offer across various disciplines,” Ibrahim said, standing in front of a poster filled with data visualizations and charts.
Data from PACE will touch on many aspects of the interconnected Earth system, including air quality and water quality, Natasha Sadoff, PACE applications deputy coordinator, told the audience at a presentation later that day. With aerosol products from the mission, people can help improve health advisories for wildfire smoke. Other data products will help notify resource managers of harmful algal blooms, wetland health indicators, or even oil spills and seeps.
Natasha Sadoff, PACE applications deputy coordinator, speaks before a crowd of Earth and space scientists at the American Geophysical Union’s annual meeting in San Francisco, on Dec. 11, 2023. Image credit: NASA/Kate Ramsayer
She showed a global map of the locations of mission Early Adopters, people who are working with the mission ahead of launch to figure out how to use the satellite data to help address different questions across a wide range of disciplines. PACE will generate a new world of data, Sadoff said, and the mission welcomes others interested in exploring it.
“We’re always looking for new community members,” she said.
Header image caption: At a December 2023 conference, scientists presented findings about what the PACE mission and its instruments could accomplish after launch, scheduled for Feb. 6, 2023. Image credit: NASA/Kate Ramsayer
By Kate Ramsayer, Strategic Communications Lead for Earth Science Missions at NASA’s Goddard Space Flight Center
Gary Davis is the mission systems engineer for PACE at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
What is your favorite ocean or atmospheric related book or movie?
I don’t know if it’s classified as a book, but I do like the Edgar Allan Poe story “A Descent Into the Maelstrom.” My favorite ocean movie? I really liked the movie “Master and Commander.” It’s not really an ocean movie, but a lot of it takes place on sailing ships, and they do have a naturalist in that movie who researches plants, insects, and other creatures.
What is your background?
I went to engineering school at the University of Virginia, got a bachelor’s degree in aerospace there, and then went to Princeton and got a master’s in mechanical and aerospace engineering. Essentially right out of school, I came to Goddard. I started off in the propulsion branch, and I worked on the TRMM mission – Tropical Rainfall Measuring Mission – and then the MAP mission – Microwave Anisotropy Probe. That’s a mouthful. Then I worked on the Solar Dynamics Observatory, I worked on the MMS mission – Magnetospheric Multiscale, another mouthful – and then OSIRIS-REx and now PACE.
Gary with PACE Observatory in SCA Cleanroom. Image Credit: Dennis Henry
What is your role in PACE?
For PACE, I’m the mission systems engineer, so I’m the chief engineer on the project. I have a great team working with me to hopefully make sure it all works.
What are you most looking forward to during launch?
I am most looking forward to the moment when we get the telemetry that the spacecraft is alive and is stable and pointing the solar arrays at the sun. That’s the most critical part for us, is to make sure that the spacecraft has survived the rigors of launch, and that it knows what to do and is pointed in the right direction. So that’s a huge first step for us.
And once that’s all clear, what are you most looking forward to post-launch?
I want to see that first picture. The instrument folks call it first light, and I’m just really excited to see what PACE’s instruments can do. We’ve been testing them on the ground for all these years, but they’re not looking at anything really, just the laser light that we shine in or the ceiling of the cleanroom. When the Ocean Color Instrument is able to see the ocean and the polarimeters see the aerosols in the atmosphere, it will be amazing to get that first image.
Since OCI will be looking at all these different colors of the ocean, what is your favorite color and why?
That’s an easy one. My favorite color is British Racing Green and the reason why is I’m a Formula One fan and my favorite team (though they don’t race anymore) is Lotus. Way back in the day, most of their cars were painted British Racing Green, so I’ve always loved that color. It’s a dark green, and it’s very fast.
Gary with U.S. Marine Band Trombone Section. Learn more here. Image Credit: U.S. Marine Band
What advice would you give to aspiring engineers who want to someday work on NASA satellites?
The obvious answer that a lot of people give is “study this science or study that math or take that engineering class” and I kind of go in the opposite direction. For folks who want to work on NASA projects in science or engineering, they’re probably already very strong in science and engineering, so they don’t need any more of that. My advice would be to study and be trained as much as possible in human skills, leadership, team-building, and how to work as part of a team. Especially in today’s world, with so many virtual ways to communicate, your team might not be co-located with you. The better communication skills you have and the better you can get an entire team to work efficiently with you, that means a lot. For any big project, you need multiple people, and even with great people, nobody can do it by themselves – you need a whole team.
What’s a fun fact about yourself, something that a lot of people might not know?
Gary with other double bell friends at Tubachristmas Kennedy Center. Image Credit: A nice Tuba Player
I’m a trombone player, amateur. I did buy a euphonium so I can play it once a year in Tubachristmas, which is super fun because we get to play the melody which you don’t usually get as a low brass player. So, for one night a year, I’m like a quasi-tuba player and it’s really fun.
What’s one catch-all statement describing the importance of PACE?
PACE is going to teach us answers about the ocean that we haven’t even been able to ask the questions for yet. It’s going to show us stuff that we don’t even know that we don’t know yet.
Header image caption: Gary with PACE Observatory during PACE Family Day. Image Credit: Dennis Henry
By Erica McNamee, Science Writer at NASA’s Goddard Space Flight Center
With the towering structure of the spacecraft just behind clear plastic curtains, engineers, scientists, and others who worked on the Plankton, Aerosol, Cloud, ocean Ecosystem mission recently had the chance to see the result of their hard work.
“Your dad does amazing stuff for us. He goes and puts out fires all the time,” Juli Lander, the PACE deputy project manager, said to a teenager waiting with his family to take a picture in front of the satellite.
The spacecraft and its instruments are the culmination of more than eight years of hard work, late nights, and early mornings, she said, and this was their chance to see the finished product right before it traveled to Florida to prep for launch.
“It’s really important for us to let everyone see the great work that their family members have been doing,” Lander said. “Everybody who’s coming through is very excited, even if they’ve been here before.”
At one of the stops on the PACE Friends and Family Day tour at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, guests saw the thermal vacuum chamber where the spacecraft was tested to ensure it could survive in the harsh environment of space. Image Credit: NASA/Kate Ramsayer
More than 550 people came to the PACE Friends and Family day Oct. 28, 2023, at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, where the spacecraft and its Ocean Color Instrument (OCI) were built. They toured the cleanroom where PACE was assembled and tested, including the giant thermal vacuum chamber where it was subjected to the temperature and pressure extremes of space.
They heard from scientists about what insights the satellite will provide about the ocean, atmosphere, and climate, and got to peer through a microscope to see some of the tiny phytoplankton that PACE will study from space.
“We’re showing off the science that we’re doing with PACE,” said Carina Poulin, a scientist and outreach specialist who was helping with hands-on activities during the event. There were puzzles of colorful ocean waters, a PACE-themed card matching game, cultures of green and yellow and pink phytoplankton and more.
The visitors were asking lots of great questions, Poulin said. “They all know someone who works with PACE, so they’re excited.”
Sabrina Sharmin, who started with the PACE team almost seven years ago and is now a systems engineer with OCI, introduced her enthusiastic guests to coworkers, and pointed out highlights of the cleanroom facility.
“This remarkable spacecraft is a result of countless hours of collaborative effort by the entire team, and I am so proud of all of us,” Sharmin said. “It’s a momentous occasion, being able to showcase the project to friends and family.
Header image caption: PACE engineer Sabrina Sharmin, in center in brown shirt, brought friends and family to see the spacecraft at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “The anticipation and excitement within our team for launch is unparalleled,” she said. Image Credit: NASA/Kate Ramsayer
Kate Ramsayer, Strategic Communications Lead for Earth Science Missions at NASA’s Goddard Space Flight Center
Whether in plants or animals, greenhouse gases or smoke, carbon atoms exist in various compounds as they move through a multitude of pathways within Earth’s system. That’s why NASA’s Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission – scheduled to launch in January 2024 – was designed to peer down at Earth from space to see those many forms of carbon in a way no other satellite has done before by measuring colors not yet seen from the vantage point of space.
“PACE is standing on the shoulders of some giants, but previous and current satellites are limited in how many colors of the rainbow they can actually see,” said Jeremy Werdell, project scientist for the PACE mission at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
Although one of the primary goals of the mission is to measure the colors on the ocean surface, in the 420 miles (676.5 kilometers) between PACE in orbit and sea level are parts of the complex carbon web that the satellite will also be able to monitor.
The connection between major wildfires and the subsequent explosion of phytoplankton production is an example of the events NASA’s upcoming Plankton, Aerosols, Clouds, and ocean Ecosystem (PACE) mission will help investigate. PACE’s suite of instruments will allow scientists to get a clearer picture of carbon as it links land use and fires, atmospheric aerosols and marine communities. Credit: NASA’s Goddard Space Flight Center
Atmosphere
From PACE’s location in space, one of the nearest forms of carbon to detect could be the wispy plumes of smoke and ash rising into the atmosphere from fires. Carbon is a key building block of much life on Earth, including plant life. When burned, the vegetation’s carbon-based molecules transform into other compounds, some of which end up as ash in these plumes.
The instruments on PACE will be able to monitor these smoky clouds, as well as other atmospheric aerosol particles, measuring their characteristics including the relative amount of smoke in different places. Combinations of these measurements made by PACE’s two companion polarimeter instruments, SPEXone and the Hyper-Angular Rainbow Polarimeter-2 (HARP2), and the detailed color measurements of the smoke made by the Ocean Color Instrument (OCI) will also help scientists identify what was burnt.
“Each instrument brings something different,” said Andy Sayer, PACE’s project science lead for atmospheres at NASA Goddard. “Putting them all together though, you’re getting the most information.” Sayer is also a senior research scientist for the University of Maryland Baltimore County.
These measurements help scientists understand more about the balance between the incoming energy from the Sun, the outgoing energy from Earth, and where it may be absorbed in between by things in the atmosphere like these smoke plumes. Even at a local level, PACE can provide information about how smoke affects air quality, impacting communities that may be near fires.
Land
Peering through the smoke particles and other aerosols, PACE can also tell us about the health of terrestrial plants and trees. Even after a devastating wildfire, fresh green plant life begins to grow and thrive. With more spectral bands and colors to see from the upcoming satellite, scientists will be able to understand what kinds of plants are recovering from fires over the years.
“In a time where we’re experiencing unprecedented climate change, we need to be able to understand how global vegetation responds to its environment,” said Fred Huemmrich, research associate professor at the University of Maryland, Baltimore County, and a member of the PACE science and applications team.
PACE will be able to monitor the different shades of colors in vegetation, and plant color can be an indicator of health. Just as house plants begin to fade to yellow if they haven’t been watered enough, plant life around the globe changes color as it experiences stress. Healthy plants take up carbon in the form of carbon dioxide as part of photosynthesis, while unhealthy plants that can’t complete photosynthesis leave the carbon dioxide roaming around the atmosphere. Given that carbon dioxide is a greenhouse gas, these measurements also play a significant role in understanding climate change in greater detail.
By measuring a full spectrum of color, PACE will view tiny changes in pigment to detect how plants are responding to stressors, helping scientists learn whether they are utilizing the surrounding carbon or not. Previously, these colors were primarily viewed in field studies of specific areas. Stressors like droughts were inferred using weather data, but covering large expanses was difficult.
“For the first time, we’ll really be able to look at changes in the health of plants over the globe,” Huemmrich said. “It will dramatically improve our understanding of how ecosystems function and how they respond to stress.”
Ocean
From plants on land to organisms in the ocean, PACE will view the expanses of water on Earth to measure phytoplankton – the P in its name. With its ability to measure a wide spectrum of colors, PACE will now not only be able to see more across the surface of the ocean but will also help scientists differentiate between phytoplankton species.
“It’s like you were making a painting with really coarse brushes, and now you have thin, fine brushes that help explain so much more in greater detail,” said Ivona Cetinić, an oceanographer in the Ocean Ecology Lab at NASA Goddard.
Phytoplankton, small organisms that live on the surface of the ocean, play a critical role in the food chain and the global carbon cycle. Each type of phytoplankton provides a different pathway in that expansive web of routes that carbon can take, all depending on the characteristics of the plankton. One pathway may lead to the carbon becoming food for a larger species, while another may lead to carbon becoming waste, sinking deeper into the ocean.
Scientists conducting field work have found that types of phytoplankton vary slightly in color and have identified these phytoplankton on small scales. PACE’s ability to measure a full spectrum of color will help scientists tell the difference between phytoplankton on a global scale by seeing more of these colors, deepening the understanding of carbon pathways and quantities.
Though one of PACE’s key goals is to view the ocean, its line of sight looks over the atmosphere and land as well. With these expansive observations, and the massive quantities of data collected, PACE provides the ability to see in what ways the atmosphere, land, and ocean are connected, including with the complex web of carbon pathways.
“I’m energized for this opportunity for discovery that this observatory is offering,” Werdell said. “I have every expectation the world is going to do great things with these data.”
By Erica McNamee, Science Writer at NASA’s Goddard Space Flight Center
The Ocean Color Instrument (OCI) is integrated onto the PACE spacecraft in the cleanroom at Goddard Space Flight Center. Credit: NASA’s Goddard Space Flight Center.
The PACE satellite now has all three of its scientific instruments attached to the spacecraft, as the integration crew bolted the Ocean Color Instrument into place with its two polarimeter neighbors.
With the assembly completed Nov. 21 at NASA’s Goddard Space Flight Center, the team will now be working on the electronic and other connections between the different components of the satellite, then putting the complete observatory through tests to make sure it can work in the harsh environment of space.
By Kate Ramsayer, Science Writer at NASA’s Goddard Space Flight Center
NASA’s PACE mission, which will provide a major boost to scientists studying Earth’s atmosphere and ocean health, completed a milestone test in October at the agency’s Goddard Space Flight Center in Greenbelt, Maryland.
The Ocean Color Instrument (OCI) on the Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission passed thermal vacuum tests to ensure it can withstand the harsh space environments.
As we prepare the Plankton, Aerosol, and cloud Ecosystem satellite for launch, we’re gathering all the ingredients, um…instruments, and baking ourselves a fresh new satellite. Credit: NASA’s Goddard Space Flight Center/Scientific Visualization Studio. Video descriptions available.
PACE will view the atmosphere and ocean surface from space. While highly useful for studying atmospheric aerosols, OCI is specifically designed to look for small aquatic organisms called phytoplankton that can be so numerous they influence the colors of the ocean. Phytoplankton play a large role in the ocean ecosystem — not only are they food sources for larger species, but they also convert carbon dioxide into organic matter through photosynthesis, playing an active role in moving carbon from the atmosphere into the ocean.
The PACE mission will help scientists learn more about the relationships between phytoplankton and the surrounding environment by measuring how light reflects off the ocean and through the atmosphere. Scientists can see these organisms in the ocean using satellites, but currently can’t differentiate the phytoplankton by type easily. Identifying types of phytoplankton help scientists to detangle some of the complex ecological systems in the oceans.
“When you look down at the ocean, you can see phytoplankton there and for the first time, with PACE, the scientists will be able to see what type of phytoplankton there are from space,” said Gary Davis, mission systems engineer at Goddard for the PACE mission. “Hopefully this mission will be able to communicate the importance of ocean health and the health of plankton to the whole world.”
To ensure the satellite is ready to gather this data, engineers put the satellite through, well, its paces. The thermal vacuum test that was just completed reduces atmospheric pressure as close to the vacuum of space as possible and then cycles through a wide range of temperatures. During the sunlit part of a spacecraft’s orbit, it can get very hot, up to approximately 50 degrees Celsius (122 degrees Fahrenheit); at other parts of the orbit, zero solar exposure means extremely low temperatures, as low as -90 degrees Celsius (-130 degrees Fahrenheit).
OCI, which was built at Goddard, can measure light in a multitude of colors, far more than previous satellites that share its frequent global coverage. Light variation by wavelength, the character of light by which it is defined, provides the color we see. OCI can detect a continuous spectrum of different wavelengths of light, and can even see colors beyond what the human eye can detect. By detecting more wavelengths, the instrument will allow scientists to tell the difference between types of phytoplankton from space. This is helpful in understanding the pathways of the carbon cycle in the atmosphere, land, and ocean, and characterizing the phytoplankton as harmful or helpful.
“OCI is really a stretch of the state of the art of what we can do right now,” said Davis. “It’s probably the most advanced thing we have on the observatory.”
Former ocean-observing satellites had the ability to measure light at a small set of wavelengths through the development of multi-spectral instruments. OCI has the ability to measure color continuosly at many ultraviolet, visible, and near infrared wavelengths, also known as hyperspectral imaging.
The previous missions can be imagined as a regular 8-color box of crayons, said Jeremy Werdell, project scientist for the PACE mission. Though still highly valuable for creating a complete picture, there are gaps in between the shades of colors. For PACE, OCI can be imagined as a 128-color box of crayons, filling in those gaps using smaller and continuous intervals of wavelengths.
“With all of the colors of the rainbow here, most of us don’t know what we’re going to discover, because we’ve never had that chance on global scales,” Werdell said. “It’s the only mission planned at NASA or elsewhere that provide global hyperspectral, full colors of the rainbow everywhere, everyday.”
When light from the sun reflects off the ocean, that light has already traveled from the sun, through the atmosphere – clouds and aerosols that compose Earth’s atmosphere – and water before it reaches the plankton in the ocean. The light then bounces off the plankton and travels back through the water and atmosphere again. The light that makes its way through all those stages can tell a story through color but still needs to be analyzed and accounted for any atmospheric effects, which is where the polarimeters on PACE come into play.
The Hyper-Angular Rainbow Polarimeter 2 (HARP2) also recently completed TVAC testing, earlier in September. The instrument is one of two multi-angle polarimeters on PACE, which act as polarized sunglasses for the spacecraft, measuring how light bends as it travels through the water droplets, clouds, and aerosols in Earth’s atmosphere, informing scientists more about their physical properties, as well as providing another source of color measurements. HARP2 was built at the University of Maryland, Baltimore County.
SPEXone, the other multi-angle polarimeter, was built in the Netherlands by engineers from SRON Netherlands Institute for Space Research, Airbus Netherlands and NASA. Each of the three instruments will be integrated into the spacecraft as they complete their individual tests – and in fact, OCI was just lifted onto the spacecraft on November 21.
“We have an observatory!” said Werdell.
As the timeline of events for PACE ticks on, the days are being counted down, all leading to the launch scheduled for early 2024.
