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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
What Would It Take to Say We Found Life?
We call this the podium test. What would it take for you personally to confidently stand up in front of an international audience and make that claim? When you put it in that way, I think for a lot of scientists, the bar is really high.
So of course, there would be obvious things, you know, a very clear signature of technology or a skeleton or something like that. But we think that a lot of the evidence that we might encounter first will be much more subtle. For example, chemical signs of life that have to be detected above a background of abiotic chemistry. And really, what we see might depend a lot on where we look.
On Mars, for example, the long history of exploration there gives us a lot of context for what we might find. But we’re potentially talking about samples that are billions of years old in those cases, and on Earth, those kinds of samples, the evidence of life is often degraded and difficult to detect.
On the ocean worlds of our outer solar system, so places like Jupiter’s moon Europa and Saturn’s moon Enceladus, there’s the tantalizing possibility of extant life, meaning life that’s still alive. But potentially we’re talking about exceedingly small amounts of samples that would have to be analyzed with a relatively limited amount of instrumentation that can be carried from Earth billions of miles away.
And then for exoplanets, these are planets beyond our own solar system. Really, what we’re looking for there are very large magnitude signs of life that can be detectable through a telescope from many light-years away. So changes like the oxygenation of Earth’s atmosphere or changes in surface color.
So any one of those things, if they rose to the suspicion of being evidence of life, would be really heavily scrutinized in a very sort of specific and custom way to that particular observation. But I think there are also some general principles that we can follow. And the first is just: Are we sure we’re seeing what we think we’re seeing? Many of these environments are not very well known to us, and so we need to convince ourselves that we’re actually seeing a clear signal that represents what we think it represents.
Carl Sagan once said, “Life is the hypothesis of last resort,” meaning that we ought to work hard for such a claim to rule out alternative possibilities. So what are those possibilities? One is contamination. The spacecraft and the instruments that we use to look for evidence of life are built in an environment, Earth, that is full of life. And so we need to convince ourselves that what we’re seeing is not evidence of our own life, but evidence of indigenous life.
If that’s the case, we should ask, should life of the type we’re seeing live there? And finally, we need to ask, is there any other way than life to make that thing, any of the possible abiotic processes that we know and even the ones that we don’t know? And as you can imagine, that will be quite a challenge.
Once we have a piece of evidence in hand that we really do think represents evidence of life, now we can begin to develop hypotheses. For example, do we have separate independent lines of evidence that corroborate what we’ve seen and increase our confidence of life?
Ultimately, all of this has to be looked at hard by the entire scientific community, and in that sense, I think the really operative word in our question is we. What does it take to say we found evidence of life? Because really, the answer, I think, depends on the full scientific community scrutinizing and skepticizing this observation to finally say that we scientists, we as a community and we as humanity found life.
[END VIDEO TRANSCRIPT]
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Last Updated Sep 10, 2025 Related Terms
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By NASA
Space changes you. It strengthens some muscles, weakens others, shifts fluids within your body, and realigns your sense of balance. NASA’s Human Research Program works to understand—and sometimes even counter—those changes so astronauts can thrive on future deep space missions.
NASA astronaut Loral O’Hara pedals on the Cycle Ergometer Vibration Isolation System (CEVIS) inside the International Space Station’s Destiny laboratory module.NASA Astronauts aboard the International Space Station work out roughly two hours a day to protect bone density, muscle strength and the cardiovascular system, but the longer they are in microgravity, the harder it can be for the brain and body to readapt to gravity’s pull. After months in orbit, returning astronauts often describe Earth as heavy, loud, and strangely still. Some reacclimate within days, while other astronauts take longer to fully recover.
Adjusting to Gravity
NASA’s SpaceX Crew-7 astronaut Jasmin Moghbeli after landing in the Gulf of America on March 12, 2024, completing 197 days in space.NASA/Joel Kowsky The crew of NASA’s SpaceX Crew-7 mission— NASA astronaut Jasmin Moghbeli, ESA (European Space Agency) astronaut Andreas Mogensen, JAXA (Japan Aerospace Exploration Agency) astronaut Satoshi Furukawa, and Roscosmos cosmonaut Konstantin Borisov—landed in March 2024 after nearly 200 days in space. One of the first tests volunteer crew members completed was walking with their eyes open and then closed.
“With eyes closed, it was almost impossible to walk in a straight line,” Mogensen said. In space, vision is the primary way astronauts orient themselves, but back on Earth, the brain must relearn how to use inner-ear balance signals. Moghbeli joked her first attempt at the exercise looked like “a nice tap dance.”
“I felt very wobbly for the first two days,” Moghbeli said. “My neck was very tired from holding up my head.” She added that, overall, her body readapted to gravity quickly.
Astronauts each recover on their own timetable and may encounter different challenges. Mogensen said his coordination took time to return. Furukawa noted that he could not look down without feeling nauseated. “Day by day, I recovered and got more stable,” he said.
NASA astronaut Loral O’Hara after landing in a remote area near the town of Zhezkazgan, Kazakhstan, on April 6, 2024.NASA/Bill Ingalls NASA astronaut Loral O’Hara returned in April 2024 after 204 days in space. She said she felt almost completely back to normal a week after returning to Earth. O’Hara added that her prior experience as an ocean engineer gave her insight into space missions. “Having those small teams in the field working with a team somewhere else back on shore with more resources is a good analog for the space station and all the missions we’re hoping to do in the future,” she said.
NASA astronaut Nichole Ayers, who flew her first space mission with NASA’s SpaceX Crew-10, noted that the brain quickly adapts to weightlessness by tuning out the vestibular system, which controls balance. “Then, within days of being back on Earth, it remembers again—it’s amazing how fast the body readjusts,” she said.
Expedition 69 NASA astronaut Frank Rubio outside the Soyuz MS-23 spacecraft after landing near the town of Zhezkazgan, Kazakhstan, on Sept. 27, 2023. NASA/Bill Ingalls When NASA astronaut Frank Rubio landed in Kazakhstan in September 2023, he had just completed a record 371-day mission—the longest single U.S. spaceflight.
Rubio said his body adjusted to gravity right away, though his feet and lower back were sore after more than a year without weight on them. Thanks to consistent workouts, Rubio said he felt mostly recovered within a couple of weeks.
Mentally, extending his mission from six months to a year was a challenge. “It was a mixed emotional roller coaster,” he said, but regular video calls with family kept him grounded. “It was almost overwhelming how much love and support we received.”
Crew-8 astronauts Matt Dominick, Jeanette Epps, Michael Barratt, and cosmonaut Alexander Grebenkin splashed down in October 2024 after 235 days on station. Dominick found sitting on hard surfaces uncomfortable at first. Epps felt the heaviness of Earth immediately. “You have to move and exercise every day, regardless of how exhausted you feel,” she said.
Barratt, veteran astronaut and board certified in internal and aerospace medicine, explained that recovery differs for each crew member, and that every return teaches NASA something new.
Still a Challenge, Even for Space Veterans
NASA astronaut Suni Williams is helped out of a SpaceX Dragon spacecraft aboard the SpaceX recovery ship after splashing down off the coast of Tallahassee, Florida, March 18, 2025. NASA/Keegan Barber Veteran NASA astronauts Suni Williams and Butch Wilmore returned from a nine-month mission with Crew-9 in early 2025. Despite her extensive spaceflight experience, Williams said re-adapting to gravity can still be tough. “The weight and heaviness of things is surprising,” she said. Like others, she pushed herself to move daily to regain strength and balance.
NASA astronaut Don Pettit arrives at Ellington Field in Houston on April 20, 2025, after returning to Earth aboard the Soyuz MS-25 spacecraft. NASA/Robert Markowitz NASA astronaut Don Pettit, also a veteran flyer, came home in April 2025 after 220 days on the space station. At 70 years old, he is NASA’s oldest active astronaut—but experience did not make gravity gentler. During landing, he says he was kept busy, “emptying the contents of my stomach onto the steppes of Kazakhstan.” Microgravity had eased the aches in his joints and muscles, but Earth’s pull brought them back all at once.
Pettit said his recovery felt similar to earlier missions. “I still feel like a little kid inside,” he said. The hardest part, he explained, isn’t regaining strength in big muscle groups, but retraining the small, often-overlooked muscles unused in space. “It’s a learning process to get used to gravity again.”
Recovery happens day by day—with help from exercise, support systems, and a little humor. No matter how long an astronaut is in space, every journey back to Earth is unique.
The Human Research Program help scientists understand how spaceflight environments affect astronaut health and performance and informs strategies to keep crews healthy for future missions to the Moon, Mars, and beyond. The program studies astronauts before, during, and after spaceflight to learn how the human body adapts to living and working in space. It also collects data through Earth-based analog missions that can help keep astronauts safer for future space exploration.
To learn more about how microgravity affects the human body and develop new ways to help astronauts stay healthy, for example, its scientists conduct bedrest studies – asking dozens of volunteers to spend 60 days in bed with their heads tilted down at a specific angle. Lying in this position tricks the body into responding as it would if the body was in space which allows scientists to trial interventions to hopefully counter some of microgravity’s effects. Such studies, through led by NASA, occur at the German Aerospace Center’s Cologne campus at a facility called :envihab – a combination of “environment” and “habitat.”
Additional Earth-based insights come from the Crew Health and Performance Exploration Analog (CHAPEA) and the Human Exploration Research Analog (HERA) at NASA’s Johnson Space Center in Houston. Both analogs recreate the remote conditions and scenarios of deep space exploration here on Earth with volunteer crews who agree to live and work in the isolation of ground-based habitats and endure challenges like delayed communication that simulates the type of interactions that will occur during deep space journeys to and from Mars. Findings from these ground-based missions and others will help NASA refine its future interventions, strategies, and protocols for astronauts in space.
NASA and its partners have supported humans continuously living and working in space since November 2000. After nearly 25 years of continuous human presence, the space station remains the sole space-based proving ground for training and research for deep space missions, enabling NASA’s Artemis campaign, lunar exploration, and future Mars missions.
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By NASA
Advancing Single-Photon Sensing Image Sensors to Enable the Search for Life Beyond Earth
A NASA-sponsored team is advancing single-photon sensing Complementary Metal-Oxide-Semiconductor (CMOS) detector technology that will enable future NASA astrophysics space missions to search for life on other planets. As part of their detector maturation program, the team is characterizing sensors before, during, and after high-energy radiation exposure; developing novel readout modes to mitigate radiation-induced damage; and simulating a near-infrared CMOS pixel prototype capable of detecting individual photons.
Single-photon sensing and photon-number resolving CMOS image sensors: a 9.4 Mpixel sensor (left) and a 16.7 Mpixel sensor (right). Credit: CfD, RIT Are we alone in the universe? This age-old question has inspired scientific exploration for centuries. If life on other planets evolves similarly to life on Earth, it can imprint its presence in atmospheric spectral features known asbiosignatures. They include absorption and emission lines in the spectrum produced by oxygen, carbon dioxide, methane, and other molecules that could indicate conditions which can support life. A future NASA astrophysics mission, the Habitable Worlds Observatory (HWO), will seek to find biosignatures in the ultraviolet, optical, and near-infrared (NIR) spectra of exoplanet atmospheres to look for evidence that life may exist elsewhere in the universe.
HWO will need highly sensitive detector technology to detect these faint biosignatures on distant exoplanets. The Single-Photon Sensing Complementary Metal-Oxide-Semiconductor (SPSCMOS) image sensor is a promising technology for this application. These silicon-based sensors can detect and resolve individual optical-wavelength photons using a low-capacitance, high-gain floating diffusion sense node. They operate effectively over a broad temperature range, including at room temperature. They have near-zero read noise, are tolerant to radiation, and generate very little unwanted signal—such as dark current. When cooled to 250 K, the dark current drops to just one electron every half-hour. If either the read noise or dark current is too high, the sensor will fail to detect the faint signals that biosignatures produce.
A research team at the Rochester Institute of Technology (RIT) Center for Detectors (CfD) is accelerating the readiness of these SPSCMOS sensors for use in space missions through detector technology maturation programs funded by NASA’s Strategic Astrophysics Technology and Early Stage Innovations solicitations. These development programs include several key goals:
Characterize critical detector performance metrics like dark current, quantum efficiency, and read noise before, during, and after exposure to high-energy radiation Develop new readout modes for these sensors to mitigate effects from short-term and long-term radiation damage Design a new NIR version of the sensor using Technology Computer-Aided Design (TCAD) software SPSCMOS sensors operate similarly to traditional CMOS image sensors but are optimized to detect individual photons—an essential capability for ultra-sensitive space-based observations, such as measuring the gases in the atmospheres of exoplanets. Incoming photons enter the sensor and generate free charges (electrons) in the sensor material. These charges collect in a pixel’s storage well and eventually transfer to a low-capacitance component called the floating diffusion (FD) sense node where each free charge causes a large and resolved voltage shift. This voltage shift is then digitized to read the signal.
Experiments that measure sensor performance in a space relevant environment use a vacuum Dewar and a thermally-controlled mount to allow precise tuning of the sensors temperature. The Dewar enables testing at conditions that match the expected thermal environment of the HWO instrument, and can even cool the sensor and its on-chip circuits to temperatures colder than any prior testing reported for this detector family. These tests are critical for revealing performance limitations with respect to detector metrics like dark current, quantum efficiency, and read noise. As temperatures change, the electrical properties of on-chip circuits can also change, which affects the read out of charge in a pixel.
The two figures show results for SPSCMOS devices. The figure on the left shows a photon counting histogram with peaks that correspond to photon number. The figure on the right shows the dark current for a SPSCMOS device before and after exposure to 50 krad of 60 MeV protons. Credit: CfD, RIT The radiation-rich environment for HWO will cause temporary and permanent effects in the sensor. These effects can corrupt the signal measured in a pixel, interrupt sensor clocking and digital logic, and can cause cumulative damage that gradually degrades sensor performance. To mitigate the loss of detector sensitivity throughout a mission lifetime, the RIT team is developing new readout modes that are not available in commercial CMOS sensors. These custom modes sample the signal over time (a “ramp” acquisition) to enable the detection and removal of cosmic ray artifacts. In one mode, when the system identifies an artifact, it segments the signal ramp and selectively averages the segments to reconstruct the original signal—preserving scientific data that would otherwise be lost. In addition, a real-time data acquisition system monitors the detector’s power consumption, which may change from the accumulation of damage throughout a mission. The acquisition system records these shifts and communicates with the detector electronics to adjust voltages and maintain nominal operation. These radiation damage mitigation strategies will be evaluated during a number of test programs at ground-based radiation facilities. The tests will help identify unique failure mechanisms that impact SPSCMOS technology when it is exposed to radiation equivalent to the dose expected for HWO.
Custom acquisition electronics (left) that will control the sensors during radiation tests, and an image captured using this system (right). Credit: CfD, RIT While existing SPSCMOS sensors are limited to detecting visible light due to their silicon-based design, the RIT team is developing the world’s first NIR single-photon photodiode based on the architecture used in the optical sensors. The photodiode design starts as a simulation in TCAD software to model the optical and electrical properties of the low-capacitance CMOS architecture. The model simulates light-sensitive circuits using both silicon and Mercury Cadmium Telluride (HgCdTe or MCT) material to determine how well the pixel would measure photo-generated charge if a semiconductor foundry physically fabricated it. It has 2D and 3D device structures that convert light into electrical charge, and circuits to control charge transfer and signal readout with virtual probes that can measure current flow and electric potential. These simulations help to evaluate the key mechanisms like the conversion of light into electrons, storing and transferring the electrons, and the output voltage of the photodiode sampling circuit.
In addition to laboratory testing, the project includes performance evaluations at a ground-based telescope. These tests allow the sensor to observe astronomical targets that cannot be fully replicated in lab. Star fields and diffuse nebulae challenge the detector’s full signal chain under real sky backgrounds with faint flux levels, field-dependent aberrations, and varying seeing conditions. These observations help identify performance limitations that may not be apparent in controlled laboratory measurements.
In January 2025, a team of researchers led by PhD student Edwin Alexani used an SPSCMOS-based camera at the C.E.K. Mees Observatory in Ontario County, New York. They observed star cluster M36 to evaluate the sensor’s photometric precision, and the Bubble Nebula in a narrow-band H-alpha filter. The measured dark current and read noise were consistent with laboratory results.
The team observed photometric reference stars to estimate the quantum efficiency (QE) or the ability for the detector to convert photons into signal. The calculated QE agreed with laboratory measurements, despite differences in calibration methods.
The team also observed the satellite STARLINK-32727 as it passed through the telescope’s field of view and measured negligible persistent charge—residual signal that can remain in detector pixels after exposure to a bright source. Although the satellite briefly produced a bright streak across several pixels due to reflected sunlight, the average latent charge in affected pixels was only 0.03 e–/pix – well below both the sky-background and sensor’s read noise.
Images captured at the C.E.K. Mees Observatory. Left: The color image shows M36 in the Johnson color filters B (blue), V (green), and R (red) bands (left). Right: Edwin Alexani and the SPSCMOS camera (right). Credit: : CfD, RIT As NASA advances and matures the HWO mission, SPSCMOS technology promises to be a game-changer for exoplanet and general astrophysics research. These sensors will enhance our ability to detect and analyze distant worlds, bringing us one step closer to answering one of humanity’s most profound questions: are we alone?
For additional details, see the entry for this project on NASA TechPort.
Project Lead(s): Dr. Donald F. Figer, Future Photon Initiative and Center for Detectors, Rochester Institute of Technology (RIT), supported by engineer Justin Gallagher and a team of students.
Sponsoring Organization(s): NASA Astrophysics Division, Strategic Astrophysics Technology (SAT) Program and NASA Space Technology Mission Directorate (STMD), Early Stage Innovations (ESI) Program
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Last Updated Sep 02, 2025 Related Terms
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By NASA
Dr. Steven “Steve” Platnick took the NASA agency Deferred Resignation Program (DRP). His last work day was August 8, 2025. Steve spent more than three decades at, or associated with, NASA. While he began his civil servant career at the NASA’s Goddard Space Flight Center (GSFC) in 2002, his Goddard association went back to 1993, first as a contractor and then as one of the earliest employees of the Joint Center for Earth Systems Technology (JCET), a cooperative agreement between the University of Maryland, Baltimore County (UMBC) and GSFC’s Earth Science Division. At JCET Steve helped lead the development of the Atmosphere Physics Track curricula. Previously, he had held an NRC post-doctoral fellow at the NASA’s Ames Research Center. Along with his research work on cloud remote sensing from satellite and airborne sensors, Steve served as the Deputy Director for Atmospheres in GSFC’s Earth Sciences Division from January 2015–July 2024.
Dr. Steve Platnick Image credit: NASA During his time at NASA, Steve played an integral role in the sustainability and advancement of NASA’s Earth Observing System platforms and data. In 2008, he took over as the Earth Observing System (EOS) Senior Project Scientist from Michael King. In this role, he led the EOS Project Science Office, which included support for related EOS facility airborne sensors, ground networks, and calibration labs. The office also supported The Earth Observer newsletter, the NASA Earth Observatory, and other outreach and exhibit activities on behalf of NASA Headquarter’s Earth Science Division and Science Mission Directorate (further details below). From January 2003 – February 2010, Steve served as the Aqua Deputy Project Scientist.
Improving Imager Cloud Algorithms
Steve was actively involved in the Moderate Resolution Imaging Spectroradiometer (MODIS) Science Team serving as the Lead for the MODIS Atmosphere Discipline Team (cloud, aerosol and clear sky products) since 2008 and as the NASA Suomi National Polar-orbiting Partnership (Suomi NPP)/JPSS Atmosphere Discipline Lead/co-Lead from 2012–2020. His research team enhanced, maintained, and evaluated MODIS and Visible Infrared Imaging Radiometer Suite (VIIRS) cloud algorithms that included Level-2 (L2) Cloud Optical/Microphysical Properties components (MOD06 and MYD06 for MODIS on Terra and Aqua, respectively) and the Atmosphere Discipline Team Level-3 (L3) spatial/temporal products (MOD08, MYD08). The L2 cloud algorithms were developed to retrieve thermodynamic phase, optical thickness, effective particle radius, and derived water path for liquid and ice clouds, among other associated datasets. Working closely with longtime University of Wisconsin-Madison colleagues, the team also developed the CLDPROP continuity products designed to bridge the MODIS and VIIRS cloud data records by addressing differences in the spectral coverage between the two sensors; this product is currently in production for VIIRS on Suomi NPP and NOAA-20, as well as MODIS Aqua. The team also ported their CLDPROP code to Geostationary Operational Environmental Satellites (GOES) R-series Advanced Baseline Imager (ABI) and sister sensors as a research demonstration effort.
Steve’s working group participation included the Global Energy and Water Exchanges (GEWEX) Cloud Assessment Working Group (2008–present); the International Cloud Working Group (ICWG), which is part of the Coordination Group for Meteorological Satellites (CGMS), and its original incarnation, the Cloud Retrieval Evaluation Working (CREW) since 2009; and the NASA Observations for Modeling Intercomparison Studies (obs4MIPs) Working Group (2011–2013). Other notable roles included Deputy Chair of the Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) Science Definition Team (2011–2012) and membership in the Advanced Composition Explorer (ACE) Science Definition Team (2009–2011), the ABI Cloud Team (2005–2009), and the Climate Absolute Radiance and Refractivity Observatory (CLARREO) Mission Concept Team (2010-2011).
Steve has participated in numerous major airborne field campaigns over his career. His key ER-2 flight scientist and/or science team management roles included the Monterey Area Ship Track experiment (MAST,1994), First (International Satellite Cloud Climatology Project (ISCCP) Regional Experiment – Arctic Cloud Experiment [FIRE-ACE, 1998], Southern Africa Fire-Atmosphere Research Initiative (SAFARI-2000), Cirrus Regional Study of Tropical Anvils and Cirrus Layers – Florida Area Cirrus Experiment (CRYSTAL-FACE, 2002), and Tropical Composition, Cloud and Climate Coupling (TC4, 2007).
Supporting Earth Science Communications
Through his EOS Project Science Office role, Steve has been supportive of the activities of NASA’s Science Support Office (SSO) and personally participated in many NASA Science exhibits at both national and international scientific conferences, including serving as a Hyperwall presenter numerous times.
For The Earth Observer newsletter publication team in particular, Steve replaced Michael King as Acting EOS Senior Project Scientist in June 2008, taking over the authorship of “The Editor’s Corner” beginning with the May–June 2008 issue [Volume 20, Issue 3]. The Acting label was removed beginning with the January–February 2010 issue [Volume 22, Issue 1]. Steve has been a champion of continuing to retain a historical record of NASA science team meetings to maintain a chronology of advances made by different groups within the NASA Earth Science community. He was supportive of the Executive Editor’s efforts to create a series called “Perspectives on EOS,” which ran from 2008–2011 and told the stories of the early years of the EOS Program from the point of view of those who lived them. He also supported the development of articles to commemorate the 25th and 30th anniversary of The Earth Observer. Later, Steve helped guide the transition of the newsletter from a print publication – the November–December 2022 issue was the last printed issue – to fully online by July 2024, a few months after the publication’s 35th anniversary. The Earth Observer team will miss Steve’s keen insight, historical perspective, and encouragement that he has shown through his leadership for the past 85 issues of print and online publications.
A Career Recognized through Awards and Honors
Throughout his career, Steve has amassed numerous honors, including the Goddard William Nordberg Memorial Award for Earth Science in 2023 and the Verner E. Suomi Award from the American Meteorological Society (AMS) in 2016. He was named an AMS Fellow that same year. He received two NASA Agency Honor Awards – the Exceptional Achievement Medal in 2008 and the Exceptional Service Medal in 2015.
Steve received his bachelor’s degree and master’s degree in electrical engineering from Duke University and the University of California, Berkeley, respectively. He earned a Ph.D. in atmospheric sciences from the University of Arizona.
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By NASA
Dr. Steven “Steve” Platnick stepped down from his role at NASA on August 8, 2025, after more than three decades of public service. Steve began his career at NASA as a physical scientist at Goddard Space Flight Center in 2002. He moved to the Earth Science Division in 2009, where he has served in various senior management roles, including as the Earth Observing System (EOS) Senior Project Scientist. In this role, he led the EOS Project Science Office and continued periodic meetings of the EOS Project Scientists, initiated by Michael King during his tenure. Steve expanded these meetings to include representatives of non-EOS Earth observing missions and representatives from Earth Science Mission Operations (ESMO). In addition, Steve was named Deputy Director for Atmospheres in the Earth Science Division in January 2015 and served in this position until July 2024.
Dr. Steve Platnick Image credit: NASA During his time at NASA, Steve played an integral role in the development, sustainability, and advancement of NASA’s Earth Observing System platforms. From January 2003 – February 2010, Steve served as Deputy Project Scientist for Aqua. In this role, he applied his expertise in theoretical and experimental studies of satellite, aircraft, and ground-based cloud remote sensing to improve algorithms to benefit the data gathered from remote observing systems.
Taking the Lead to Improve Algorithms
Steve was actively involved in the Moderate Resolution Imaging Spectroradiometer (MODIS) Science Team, serving as the MODIS Atmosphere Team Lead. Steve helped advance several key components of the MODIS instrument, which flies on NASA’s Terra and Aqua platforms. He led a team that enhanced, maintained, and evaluated MODIS algorithms that support the Level-2 (L2) Cloud Optical/Microphysical Properties components (e.g., COD06 and MYD06) for MODIS on Terra and Aqua. The algorithms were designed to retrieve thermodynamic phase, optical thickness, effective particle radius, and water path for liquid and ice clouds. The team’s work also contributes to L3 products that address cloud mask, aerosols, clouds, and clear sky radiance for data within 1° grids over one-day, eight-day, and one-month repeat cycles. Under Steve’s leadership, the team also developed L2 products (e.g., MODATML2 and MYDATML2) that include essential atmosphere datasets of samples collected at 5–10 km (3–6 mi) that is consistent with L3 products to ease storage requirements of core atmospheric data.
Steve is also a member of the Suomi-National Polar-orbiting Partnership (Suomi NPP) Atmosphere Team, working on operational cloud optical and microphysical products. In this role, he contributed to algorithm development and refinement for the Cloud Product. In particular, he helped address a critical gap in the Visible Infrared Imaging Radiometer Suite (VIIRS) spectral channel, which was not designed to collect information for carbon dioxide (CO2) slicing and water vapor data in the same way as MODIS. Steve and his colleagues developed a suite of L2 algorithms for the spectral channels that were common to both MODIS and VIIRS to address cloud mask and cloud optical/microphysical properties. Through these efforts, the project has established a continuous cloud data record gathered from both instruments from 2017 to the present.
Steve also participated in numerous other working groups during the past 30 years. He participated in the Global Energy and Water Exchanges (GEWEX) Cloud Assessment Working Group (2008–present), Arctic Radiation-Cloud-Aerosol-Surface Interaction Experiment (ARCSIX) Science Team (2023–present), ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) Earth–Venture Suborbital (EVS)-2 Science Team (2014–2023), Deep Space Climate Observatory (DSCOVR) Science Team (2014–present), Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) Science Team (2014–2023), PACE Science Definition Team, Deputy Chair (2011–2012), Glory Science Team (2010–2014) NASA Observations for Modeling Intercomparison Studies (obs4MIPs) Working Group (2011), Advanced Composition Explorer (ACE) Science Definition Team (2009–2011), and Geostationary Operational Environmental Satellites (GOES) R-series Advanced Baseline Imager (ABI) Cloud Team (2005–2009).
Steve has also participated in numerous major airborne field campaigns in various roles, including: GSFC Lidar Observation and Validation Experiment (GLOVE, 2025), PACE Postlaunch Airborne eXperiment (PAX, 2024), the Westcoast & Heartland Hyperspectral Microwave Sensor Intensive Experiment (WH2yMSIE, 2024), ORACLES Science Team (2015–2019), Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) Science Team (2011–2015), Tropical Composition, Cloud and Climate Coupling (TC4) Management Team (2007), Cirrus Regional Study of Tropical Anvils and Cirrus Layers – Florida Area Cirrus Experiment (CRYSTAL-FACE) Science Management Team (2002), Southern Africa Fire-Atmosphere Research Initiative (SAFARI, 2000), First ISCCP Regional Experiment (FIRE) Arctic Cloud Experiment (ACE) (1998), Mikulski Archive for Space Telescopes (MAST, 1994), and ACE (1992).
Supporting Earth Science Communications
Through his senior leadership roles within ESD Steve has been supportive of the activities of NASA’s Science Support Office (SSO). He has participated in many NASA Science exhibits at both national and international scientific conferences, including serving as a Hyperwall presenter numerous times. He has met with task leaders frequently and has advocated on behalf of the SSO to management at NASA Headquarters, GSFC, and Global Sciences & Technology Inc.
For The Earth Observer newsletter publication team in particular, Steve replaced Michael King as Acting EOS Senior Project Scientist in June 2008, taking over the authorship of “The Editor’s Corner” beginning with the May–June 2008 issue [Volume 20, Issue 3]. The Acting label was removed beginning with the January–February 2010 issue [Volume 22, Issue 1]. Steve has been a champion of continuing to retain a historical record of NASA meetings to maintain a chronology of advances made by different groups within the NASA Earth Science community. He was supportive of the Executive Editor’s efforts to create a series called “Perspectives on EOS,” which ran from 2008–2011 and told the stories of the early years of the EOS Program from the point of view of those who lived them. He also supported the development of articles to commemorate the 25th and 30th anniversary of The Earth Observer. Later, Steve helped guide the transition of the newsletterfrom a print publication – the November–December 2022 issue was the last printed issue – to fully online by July 2024, a few months after the publication’s 35th anniversary. The Earth Observer team will miss Steve’s keen insight, historical perspective, and encouragement that he has shown through his leadership for the past 85 issues of print and online publications.
A Career Recognized through Awards and Honors
Throughout his career, Steve has amassed numerous honors, including the Robert H. Goddard Award for Science: MODIS/VIIRS Cloud Products Science Team (2024) and the William Nordberg Memorial Award for Earth Science in 2023. He received the Verner E. Suomi Award from the American Meteorological Society (AMS) in 2016 and was named an AMS Fellow that same year.
Steve has received numerous NASA Group Achievement Awards, including for the Cloud, Aerosol and Monsoon Processes Philippines Experiment (CAMP2Ex) Field Campaign Team (2020), Fire Influence of Regional to Global Environments and Air Quality (FIREX-AQ) Field Campaign Team (2020), ORACLES Field Campaign Team (2019), obs4MIPs Working Group (2015), SEAC4RS Field Campaign Team (2015), Advanced Microwave Scanning Radiometer for EOS (AMSR-E) Instrument Recovery Team (2013), Climate Absolute Radiance and Refractivity Observatory (CLARREO) Mission Concept Team (2012), Earth Science Constellation Red Team (2011), Science Mission Directorate ARRA Team (2011), TC4 Team (2009), MODIS Science Data Support Team (2007), Aqua Mission Team (2003), CRYSTAL-FACE Science Team (2003), and SAFARI 2000 International Leadership Team (2002).
Steve received two NASA Agency Honor Awards – the Exceptional Service Medal in 2015 and the Exceptional Achievement Medal in 2008. He was also part of the NASA Agency Team Excellence Award in 2017 for his work with the Satellite Needs Assessment Team. The Laboratory for Atmospheres honored him with the Best Senior Author Publication Award in 2001 and the Scientific Research Peer Award in 2005.
Steve received his bachelor’s degree and master’s degree in electrical engineering from Duke University and the University of California, Berkeley, respectively. He earned a Ph.D. in atmospheric sciences from the University of Arizona. He began his career at the Joint Center for Earth Systems Technology (JCET) at University of Maryland Baltimore County in 1996 as a research associate professor. He held this appointment until 2002. Steve has published more than 150 scholarly articles.
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