Saji Abraham
(PRINCIPAL TECHNICAL DATA SCIEN)
| Email: | saji.abraham-1@nasa.gov |
| Phone: | 301.286.8917 |
| Org Code: | |
| Address: |
NASA/GSFC Mail Code 617 Greenbelt, MD 20771 |
| Employer: | KBRwyle |
Brief Bio
Saji Abraham received a Ph.D. in Space Physics from the University of Delhi, Delhi, India; an M.Sc. in Space Physics from Andhra University, Waltair, India; an M.S. in Electrical and Computer Engineering with a major in Photonics from The Johns Hopkins University, Baltimore, Maryland, USA; and a B.Sc. in Physics from Kerala University, Trivandrum, India.
Dr. Abraham has been supporting NASA projects since 1997 and currently works with KBR at NASA's Goddard Space Flight Center in Greenbelt, MD. His research interests include the development of forward and retrieval algorithms for spaceborne radiometric applications, as well as the calibration of microwave radiometers at the instrument, observatory, and post-launch orbit levels.
Currently, Dr. Abraham is supporting the calibration of the Advanced Technology Microwave Sounder (ATMS) on the Joint Polar Satellite System (JPSS) and QuickSounder. The JPSS is the nation's new-generation polar-orbiting operational environmental satellite system for measuring atmospheric temperature, water vapor, and other geophysical parameters to support weather forecasting models, operating with a frequency range of 22 to 183 GHz.
Additionally, this technical support extends to NASA/NOAA’s Sounder for Microwave-Based Applications (SMBA) instruments in the Near-Earth Orbit Network (NEON) Program under Low Earth Orbit (LEO) missions, which will supplement and eventually replace the JPSS space missions. QuickSounder is the first space mission under the NEON program. Currently, Dr. Abraham is pursuing simulation efforts for the SMBA instrument by incorporating an instrument noise model, radio frequency interference (RFI), and the channelization of a hyperspectral microwave radiometer using the Community Radiative Transfer Model (CRTM). Furthermore, Dr. Abraham utilizes Artificial Intelligence and Machine Learning (AI/ML) techniques to optimize physical retrievals of atmospheric temperature and water vapor profiles from microwave sounding data.
Dr. Abraham has supported NASA’s Aquarius and SMAP (Soil Moisture Active Passive) space missions. These spaceborne prototypes were designed to measure sea surface salinity and soil moisture in the L-band, centered at 1.4 GHz.
Dr. Abraham performed data analysis of soil freeze/thaw states through microwave remote sensing using data from SMAP, SLAPEx (Scanning L-band Active Passive Experiment), GREX (Goddard RF Explorer), and in-situ measurements. He also used MODIS IGBP land cover data to classify radiometric brightness temperatures from AMSR-E and AMSR2 measurements, addressing the impact of forests and topography on the retrieval of physical parameters from microwave radiometry from space.
His expertise in interdisciplinary research activities includes the basic theory of electromagnetic interaction with matter, radiative transfer theory, land/sea/ice thermal emission models, surface roughness, atmospheric and ionospheric emissions, Faraday rotation and polarization mixing, and the celestial sky background, which consists of solar, lunar, cosmic, and galactic emissions. He has worked across wide areas of ionospheric radio wave propagation techniques and has published scientific articles on lower ionosphere dynamics and its coupling with the lower atmosphere through planetary waves and Quasi-Biennial Oscillations.
Dr. Abraham is a senior member of the IEEE Geoscience and Remote Sensing Society and a member of the American Geophysical Union.
Current Projects
Sounder for Microwave-Based Applications (SMBA)
Remote Sensing
- Engineer SMBA instrument simulations (forward algorithm) incorporating an instrument noise model, radio frequency interference (RFI), and hyperspectral microwave radiometer channelization using the Community Radiative Transfer Model (CRTM).
- Apply Artificial Intelligence and Machine Learning (AI/ML) techniques to optimize physical retrievals of atmospheric temperature and water vapor profiles from microwave sounding data (retrieval algorithm).
Advanced Technology Microwave Sounder (ATMS)
Remote Sensing
- Support ATMS Thermal Vacuum Calibration (TVAC) testing for the JPSS-1 through JPSS-4 and QuickSounder missions.
- Assist with pre-launch (component, instrument, and observatory-level testing) and post-launch (on-orbit calibration) activities for ATMS.
- Evaluate instrument performance against the Performance Requirements Document (PRD) and document performance trends of ATMS instruments across SNPP, the JPSS series, and QuickSounder.
- Perform data analysis of the measured Spectral Response Function (SRF) for all channels and builds of ATMS at the component and instrument levels, make noise floor corrections to the SRF, and release the data to the public.
- Develop a data pipeline to download daily Science Data Record (SDR) and Raw Data Record (RDR) files from NOAA CLASS, and process the data to evaluate Noise Equivalent Delta Temperature (NEDT) and Internal Calibration Target (ICT) temperatures. Verify NEDT at 300 K against project science requirements and generate the annual report on JPSS-2 ATMS performance.
Education
Master of Science (M.Sc.), Space Physics, Andhra University, Waltair, India.
Master of Science (M.S.), Photonics, The Johns Hopkins University, Baltimore, Maryland.
Bachelor of Science (B.Sc.), Physics, University of Kerala, Trivandrum, India.
Awards
The Office of Low Earth Orbit (LEO) Observations for outstanding team work on SMBA science support (2026).
NASA HBG (Hydrosphere, Biosphere and Geophysics) award for scientific achievement on SMBA support (2026).
NASA HBG (Hydrosphere, Biosphere and Geophysics) award for science support on SLAP radiometer (2022).
NASA Robert H. Goddard award on customer support on JPSS-2 Instrument (2022).
NASA Group Achievement award (2013).
NASA peer award for outstanding publication (2008).
NASA peer award for outstanding support (2004 and 2007).
Other Professional Information
Certified Associate in Project Management (CAPM)
Selected Publications
Refereed
2026. "Characterization of QuickSounder ATMS at Instrument Level TVAC.", IGARSS-2026 Proceedings, [Proceedings]
2025. "Remote Sensing of Live Fuel Moisture for Wildfires Using SMAP Satellite Observations.", Geophysical Research Letters, 52 (20): e2025GL117025 [10.1029/2025gl117025] [Journal Article/Letter]
2025. "On the Characterization and Mitigation of Noise in Space-Borne Microwave Sounding Instruments.", IEEE Transactions on Geoscience and Remote Sensing, 63 1-12 [10.1109/tgrs.2025.3616644] [Journal Article/Letter]
2025. "Validation of the Calibrated Microwave Lunar Radiative Transfer Model With the ATMS 2-D Moon Observations at Different Moon Phase Angles.", IEEE Geoscience and Remote Sensing Letters, 22 1-5 [10.1109/lgrs.2025.3582666] [Journal Article/Letter]
2023. "High-Resolution Soil Moisture—a European Airborne Campaign Using NASA Goddard’s Scanning L-Band Active Passive (SLAP).", Remote Sensing in Earth Systems Sciences, 6 (3-4): 309-321 [10.1007/s41976-023-00099-4] [Journal Article/Letter]
2022. "An Evaluation of NOAA-20 ATMS Instrument Pre-Launch and On-Orbit Performance Characterization.", IEEE Transactions on Geoscience and Remote Sensing, 60 1-13 [10.1109/tgrs.2022.3148663] [Journal Article/Letter]
2022. "ATMS Radiance Data Products’ Calibration and Evaluation.", IEEE Transactions on Geoscience and Remote Sensing, 60 1-11 [10.1109/tgrs.2021.3123576] [Journal Article/Letter]
2018. "Faraday Rotation Correction for SMAP and Soil Moisture Retrieval.", IEEE Transactions on Geoscience and Remote Sensing, 56 (2): 655-668 [10.1109/tgrs.2017.2752642] [Journal Article/Letter]
2016. "Faraday Rotation Correction for the SMAP Radiometer.", IEEE Transactions on Geoscience and Remote Sensing, 54 (4): 2070-2081 [10.1109/tgrs.2015.2495168] [Journal Article/Letter]
2014. "Aquarius: Status and recent results.", Radio Science, 49 (9): 709-720 [10.1002/2014rs005505] [Journal Article/Letter]
2014. "Aquarius: Status and recent results.", Radio Science, 49 (9): 709–720 [10.1002/2014RS005505] [Journal Article/Letter]
2013. "Aquarius Third Stokes Parameter Measurements: Initial Results.", IEEE Geosci. Remote Sensing Lett., 10 (3): 520-524 [10.1109/LGRS.2012.2211994] [Journal Article/Letter]
2011. "Impact of Antenna Pattern on Measurement of the Third Stokes Parameter From Space at L-Band.", IEEE Trans. Geoscience and Remote Sensing, 49 (1): 406-414 [10.1109/TGRS.2010.2051953] [Journal Article/Letter]
2011. "The Aquarius Simulator and Cold-Sky Calibration.", IEEE Trans. Geosci. Remote Sensing, 49 (9): 3198-3210 [10.1109/TGRS.2011.2161481] [Journal Article/Letter]
2009. "Effect of Emission From the Moon on Remote Sensing of Sea Surface Salinity: An Example With the Aquarius Radiometer.", IEEE Geosci. Remote Sensing Lett., 6 (2): 239-243 [10.1109/LGRS.2008.2008822] [Journal Article/Letter]
2007. "The influence of antenna pattern on Faraday rotation in remote sensing at L-band.", IEEE Transactions on Geoscience and Remote Sensing, 45 (9): 2737–2746 [Journal Article/Letter]
2004. "Use of IRI to model the effect of ionosphere emission on earth remote sensing at L-band.", Adv Space Res, 34 (9): 2059-2066 [10.1016/j.asr.2004.06.015] [Journal Article/Letter]
2004. "Galactic Noise and Passive Microwave Remote Sensing From Space at L-Band.", IEEE Trans Geosci Remote Sens, 42 (1): 119-129 [Journal Article/Letter]
2002. "The Effect of the Ionosphere on Remote Sensing of Sea Surface Salinity from Space: Absorption and Emission at L Band.", IEEE Trans Geosci Remote Sens, 40 (4): 771-782 [Journal Article/Letter]
2001. "Evaluation of IRI-95 to correct errors caused by Faraday rotation in passive microwave remote sensing from space.", Advances in Space Research, 27 (1): 153-156 [Journal Article/Letter]
2000. "Faraday rotation and passive microwave remote sensing of soil moisture from space.", Microwave Radiometry and Remote Sensing of the Earth's Surface and Atmosphere, 89-96 [Article in Book]
Non-Refereed
2014. "Aquarius radiometer status.", Microwave Radiometry and Remote Sensing of the Environment (MicroRad), 2014 13th Specialist Meeting on, 226 - 227 [10.1109/MicroRad.2014.6878945] [Proceedings]
2014. "Aquarius overview and update.", General Assembly and Scientific Symposium (URSI GASS), 2014 XXXIth URSI, [10.1109/URSIGASS.2014.6929699] [Proceedings]
2012. "Comparison of Aquarius Measurements and Radiative Transfer Models at L-band.", 2012 12th Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment (MicroRad), 1-4 [10.1109/MicroRad.2012.6185231] [Proceedings]
2008. "Simulation of the AQUARIUS Radar Scatterometer.", Proceedings of the XXIXth URSI General Assembly, 4 pp. [Proceedings]
2008. "L-band radiometry and reflection of the galaxy by a rough ocean surface .", Microwave Radiometry and Remote Sensing of the Environment (MICRORAD) 2008, 1-4 [10.1109/MICRAD.2008.4579494] [Proceedings]
2007. "The influence of antenna pattern on Faraday rotation in remote sensing at L-band.", IEEE International Geoscience and Remote Sensing Symposium (IGARSS) 2007, 239 - 242 [10.1109/IGARSS.2007.4422774] [Proceedings]