Dr. William J. Blackwell, Fellow, Massachusetts Institute of Technology Lincoln Laboratory
Research Interests: Atmospheric remote sensing from airborne and spaceborne platforms, including the development and calibration of airborne and space-borne microwave sensors; the retrieval of geophysical products from remote radiance measurements; and the application of electromagnetic, signal processing, and estimation theory.
Research Highlights: There is no question that NASA satellite missions, such as those of the Earth Observing System (EOS) have enhanced our understanding of the total Earth system and the effects of natural and human-induced changes on the environment. At the same time, there’s no denying that NASA’s flagship Earth-observing satellites, such as Terra and Aqua, or the spacecraft of the Geostationary Operational Environmental Satellite (GOES) and Joint Polar-Orbiting Satellite System (JPSS) missions require significant investments of time and resources to design, build, and launch. For example, the JPSS program, which began in the 2010s and will continue well into the 2030s, has a budget of more than $11 billion.
As an alternative to these larger and more budget- and time-intensive programs, some scientists are turning to small satellites, such as SmallSats and CubeSats, which offer more cost-effective platforms for conducting space-based scientific investigations and testing advanced mission concepts, such as using constellations or swarms of satellites to boost observational frequency. The term “SmallSat” refers to spacecraft that have a mass of 180 kilograms or less and are about the size of a large kitchen refrigerator. CubeSats are even smaller and range in size from one to 12 units (one unit or "1U" measures 10x10x10 centimeters).
These smaller, less-resource intensive satellites are playing a central role in NASA’s Time-Resolved Observations of Precipitation structure and storm Intensity with a Constellation of SmallSats (TROPICS) mission. TROPICS was created to study tropical cyclones via a constellation of CubeSats equipped with high-performance microwave sounders. Although existing polar-orbiting weather satellites can generally observe the characteristics of tropical storms and hurricanes once every few hours, this observational frequency still leaves coverage gaps during which storms may quickly strengthen. When its entire constellation is in orbit, TROPICS will help fill these gaps by providing near-hourly observations of a storm’s precipitation, temperature, and humidity, allowing scientists to better understand what drives storm intensification.
“Data from this mission will be available with unprecedented revisit rates for this kind of observation—one hour vs every four to six hours with present state-of-the-art technology,” said Dr. William Blackwell, Fellow at the Massachusetts Institute of Technology’s Lincoln Laboratory, and Principal Investigator of the TROPICS mission. “This new data will capture storm dynamics that we hope will lead to better characterization and understanding of the interaction of the storms with their environment, ultimately leading, we hope, to improved forecasting of tropical cyclone track and intensity.”
The Massachusetts Institute of Technology’s Lincoln Laboratory is a federally funded research center that develops sensors, information, communications, and decision support technologies, and it is there that Blackwell and his colleagues developed a miniaturized microwave radiometer. Roughly the size of a cup of coffee, this small instrument will travel aboard each of the mission’s CubeSats and measure storm strength by detecting thermal radiation in the atmosphere.
According to the mission’s website, the TROPICS constellation of CubeSats will provide rapid-refresh microwave measurements over the tropics that can be used to observe the thermodynamics of the troposphere and precipitation structure for storm systems throughout their lifecycles. Flying in three low-Earth orbital planes, each CubeSat’s radiometer will scan across the entire satellite track at 30 revolutions per minute, providing atmospheric profiles of temperature and water vapor, atmospheric imagery, and precipitation and cloud ice measurements.
“This observing system offers an unprecedented combination of horizontal and temporal resolution to measure environmental and inner-core conditions for tropical cyclones on a nearly global scale,” Blackwell said. “[It] is a profound leap forward in the temporal resolution of several key parameters needed for detailed study of high-impact meteorological events.”
The goal of the TROPICS mission is to demonstrate that a constellation approach to Earth science can provide improved resolution, configurable coverage, flexibility, reliability, and launch access at extremely low cost, thereby serving as a model for future missions. To date, one TROPICS CubeSat is in orbit and Blackwell expects four others will be in orbit in time for the 2023 Atlantic hurricane season, which begins June 1.
“We launched our qualification unit, which we now call the Pathfinder, in June 2021 and it is still working great and producing spectacular data,” he said. “We tried to launch the first two (of six) TROPICS constellation satellites this June, but the launch vehicle did not reach orbit. NASA’s Launch Service Program (LSP) is trying to get the remaining four launched by July 2023, in time for the 2023 Atlantic hurricane season.”
In addition to his work at the Lincoln Laboratory, Blackwell is a member of the NASA Goddard Earth Sciences Data and Information Services Center’s (GES DISC) User Working Group (UWG), which helps identify and coordinate scientific data needs from a range of sectors and contributes to the evolution and development of GES DISC’s data management services.
Located at NASA's Goddard Space Flight Center in Greenbelt, Maryland, GES DISC—one of 12 Distributed Active Archive Centers (DAACs) in NASA’s Earth Observing System Data and Information System (EOSDIS)—manages, archives, and distributes data, tools, and resources pertaining to the areas of atmospheric composition, atmospheric dynamics, global precipitation, and solar irradiance.
Blackwell said he “routinely uses” data from GES DISC and other sources to compare against and evaluate data from the TROPICS Pathfinder satellite. Among the datasets he uses are temperature profiles of the upper and lower atmosphere from the Atmospheric Infrared Sounder (AIRS) and Advanced Microwave Sounding Unit (AMSU-A) instruments aboard Aqua, and measurements of brightness temperature from the Global Precipitation Measurement (GPM) mission’s GPM Microwave Imager (GMI).
“The TROPICS Pathfinder satellite has a new observing band near 205 GHz that provides very detailed imagery of storm structure, due to its sensitivity to precipitation-sized ice particles in the storm clouds,” Blackwell said. “This channel has improved the retrieval of water vapor and water path products.”
It’s also provided Blackwell and his team with an opportunity to checkout and optimize elements of the TROPICS mission prior to the launch of the primary constellation next year.
“The Pathfinder satellite has made hundreds of passes over active tropical cyclones during its 1+ year lifetime. The image quality has been exceptional, surpassing state-of-the-art sensors in many instances,” Blackwell and his coauthors write in a 2022 paper published in Remote Sensing. “We expect the new, high-revisit capabilities of TROPICS with performance demonstrated by Pathfinder will provide invaluable information to better understand and predict severe storms.”
These expectations are not out of place, for as Blackwell, lead author Hui W. Christopherson of the Naval Research Laboratory, and others noted in a 2021 paper published in the American Meteorological Society’s Monthly Weather Review, experiments to determine the potential benefits of incorporating TROPICS data into tropical cyclone forecasts have yielded positive results.
“TROPICS all-sky radiances can have positive impacts on TC [tropical cyclone] track and intensity forecasts . . .. The largest impact on the model analyses is seen in the humidity fields, regardless of whether or not there are radiances assimilated from other satellites,” the researchers write. “The assimilation of the all-sky TROPICS radiances without default radiances leads to a consistent improvement in the low- and mid-tropospheric temperature and wind forecasts throughout the 5-day forecasts, but only up to 36-h lead time in the humidity forecasts at all pressure levels.”
In addition, the TROPICS Pathfinder satellite demonstrates the utility of small satellite missions as a way to complement or enhance current and long-term operational satellite systems.
“Small satellites built using standardized and commoditized parts and launched on rideshare missions have potential to add great value to operational Earth observing satellites systems,” writes Blackwell in a 2021 paper published as part of the 2021 Institute of Electrical and Electronics Engineers International Geoscience and Remote Sensing Symposium. “The TROPICS experience, both the build-and-test phase and the operational phase, will offer important lessons for future systems, both in how they are built and tested and how they are used optimally and synergistically with more traditional observing systems.”
He may be right, for as Earth's climate continues to change and those changes lead to more rapidly intensifying storms, cost-effective but powerful satellites like those of the TROPICS mission will likely play an important role in helping meteorologists and other scientists understand the mechanisms driving rapid change in extreme weather, and better predict—and prepare—for the next big storm.
“TROPICS represents a potentially game-changing mission that will allow for revisit times of identical sensors that are approximately 60 minutes,” Blackwell said. “This rapid-refresh rate will allow for better measurement of quickly evolving changes within tropical cyclones over their entire lifecycles.”
Yet, the TROPICS mission won’t be able to make this kind of impact without data from other instruments currently in orbit on other satellites. Fortunately, GES DISC’s archive of atmospheric composition, atmospheric dynamics, and global precipitation data from these sensors is available to ensure the observations from the TROPICS mission’s CubeSats are valid and accurate.
Representative Data Products Used or Created:
Available through GES DISC:
- AIRS/Aqua L1B Visible/Near Infrared (VIS/NIR) geolocated and calibrated radiances (V005)
- AIRS/Aqua L1B Near Real Time (NRT) AMSU (A1/A2) geolocated and calibrated brightness temperatures V005 (no doi)
- GPM GMI Brightness Temperatures L1B 1.5 hours 13 km (V07)
- GEOS-5 FP-IT Assimilation Geo-collocated to OMI/Aura VIS 1-Orbit L2 Support Swath 13x24km (V3)
- GPM IMERG Final Precipitation L3 1 day 0.1-degree x 0.1-degree (V06)
Other data products used:
- Advanced Technology Microwave Sounder Level 1B radiances (NOAA)
- Community Radiative Transfer Model (Joint Center for Satellite Data Assimilation)
- Hurricane Weather and Research Forecasting Model (Version 3.6 NOAA)
- Observing System Simulation Experiments (OSSEs, University of Miami)
- International Best Track Archive for Climate Stewardship (IBTrACS)
Read about the Research
Kidd, C., Matsui, T., Blackwell, W.J., Braun, S., Leslie, R., & Griffith, Z. (2022). Precipitation Estimation from the NASA TROPICS Mission: Initial Retrievals and Validation. Remote Sensing, (14): 2992. doi:10.3390/rs14132992
Blackwell, W.J. (2021). NASA Tropics Pathfinder and Constellation Mission Preparations for Launches in 2021 and 2022. 2021 IEEE International Geoscience and Remote Sensing Symposium, 1511-1513. doi:10.1109/IGARSS47720.2021.9553432
Blackwell, W.J. (2021). New microwave radiometer technologies featured in the upcoming NASA TROPICS Pathfinder and Constellation Missions in 2021/2022. Proceedings of the Society of Photo-Optical Instrumentation Engineers: Sensors, Systems, and Next-Generation Satellites, 25(118580J). doi:10.1117/12.2600441
Christophersen, H.W., Dahl, B.A., Dunion, J.P., Rogers, R.F., Marks, F.D., Atlas, R., & Blackwell, W.J. (2021). Impact of TROPICS Radiances on Tropical Cyclone Prediction in an OSSE. Monthly Weather Review, 149(7): 2279-2298. doi:10.1175/MWR-D-20-0339.1
Blackwell, W.J., Braun, S., Bennartz, R., et al. (2018). An overview of the TROPICS NASA Earth Venture Mission. Quarterly Journal of the Royal Meteorological Society, 144 (Supplement 1): 16-26. doi:10.1002/qj.3290