About

Srinivas V. Bettadpur is a Professor holding the FSX Professorship in Space Applications and Exploration in the Department of Aerospace Engineering and Engineering Mechanics at The University of Texas at Austin. His research focuses on space systems and astrodynamics, with particular interests in orbital mechanics, perturbations, and orbit determination, as well as space geodesy involving Earth's shape, orientation, and gravity field. Dr. Bettadpur's work involves modeling, determination, and interpretation of the Earth's gravity field, studying the Earth's dynamical processes driven by physical phenomena in the ocean, atmosphere, ice, and solid Earth, which can be analyzed through space-based radiometric, laser, and quantum sensing measurements. He specializes in the design and architecture of space missions aimed at studying Earth's physical processes, analyzing space geodetic data, and interpreting the results. Dr. Bettadpur holds additional appointments in the Department of Geological Sciences within the Jackson School of Geosciences and is an affiliate of the UT Applied Research Laboratory. He is recognized as a Fellow of the American Geophysical Union (AGU) and the International Association of Geodesy (IAG), and as an Associate Fellow of the American Institute of Aeronautics and Astronautics (AIAA). He serves as President of Commission-2 (Gravity Field) of the IAG for the 2023-2027 term, representing international interests from adherent nations to the IUGG/ICSU. His contributions have been honored with awards such as the Charles A. Whitten Medal from the AGU in 2024, the NASA Exceptional Public Achievement Medal in 2018, the Vening-Meinesz Medal from the European Geosciences Union in 2016, and the William T. Pecora Team Award in 2007 for his work with the GRACE team.

Research topics

• Computer Science
• Environmental science
• Geodesy
• Geology
• Artificial Intelligence
• Climatology
• Engineering
• Physics
• Aerospace engineering
• Remote sensing
• Mathematics
• Oceanography
• Statistics
• Optics
• Meteorology
• Algorithm

Selected publications

• Recent Ocean Tide Models Comparison From the GRACE Perspective

  Journal of Geophysical Research Solid Earth · 2026-05-01

  articleOpen access

  Abstract A model of ocean tides is generally used to remove the dynamic tidal signal in satellite gravimetric observations, such as GRACE(‐FO). Model imperfections can cause stripes and long period aliasing errors in monthly gravity solutions. Recent developments in ocean tide modeling have substantially improved accuracy at high latitudes and in shallow water regions. In this study, we compared the 8 major tidal constituents from three recent ocean tide models, namely EOT20, FES22 and GOT5.6, as well as GOT4.8, using 13‐year long GRACE ranging observations. The improvements of the three recent models are significant, showing more than 2 postfit variance reduction. Among them, GOT5.6 generally performs the best in terms of postfit variance reduction (11% vs. GOT4.8) and residual ocean tide fitting, particularly near West Antarctica. The residual ocean mass RMS, computed from monthly gravity solutions using GOT5.6, is on average 1 mm (GOT4.8), 0.3 mm (EOT20) and 0.1 mm (FES22) smaller. These results make it our preferred model for the upcoming GRACE(‐FO) Release 07 (RL07) re‐processing. Regarding implementation, utilizing the minor tides in GOT5.6 and long period tides in FES22 as well as considering geographically varying seawater density can further enhance model performance (denoted GOT5.6p3), which on average reduces the residual ocean mass RMS by an additional 7%. Notably, using lateral varying seawater density largely reduces the anomalous M 2 residuals in the North Atlantic Ocean. We anticipate that GOT5.6p3 will substantially reduce stripes and aliasing errors in forthcoming RL07 monthly solutions. The improvements will also benefit GOCE reprocessing and GRACE(‐FO) sub‐monthly solutions.

  PublisherDOI

• A unified model of feed rotation in radio telescopes and GNSS antennas

  ArXiv.org · 2025-02-12

  preprintOpen accessSenior author

  We describe a model that accounts for the phase rotation that occurs when a receiver or transmitter changes orientation while observing or emitting circularly polarized electromagnetic waves. This model extends work detailing Global Navigation Satellite Systems (GNSS) carrier phase wind-up to allow us to describe the interaction of changing satellite orientation with phase rotation in observing radio telescopes. This development is motivated by, and a critical requirement of, unifying GNSS and Very Long Baseline Interferometry (VLBI) measurements at the observation level. The model can be used for either stationary choke ring antennas or steerable radio telescopes observing either natural radio sources or satellites. Simulations and experimental data are used to validate the model and to illustrate its importance. In addition, we rigorously lay out the feed rotation correction for radio telescopes with beam waveguide and full Nasmyth focuses and validate the correction by observing the effect with dual polarization observations. Using this feed rotation model for beam waveguide telescopes, we produce the first phase delay solution for the VLBI baseline WARK30M-WARK12M. We provide a practical guide to using the feed rotation model in Appendix D.

  PublisherOA PDFDOI

• Precise Orbit Determination for Sentinel-6A using Galileo and GPS observations

  2025-03-15

  preprintOpen access

  The Sentinel-6A satellite, launched on November 21, 2020, is equipped with a dual-constellation (Galileo and GPS) onboard receiver for precise orbit determination (POD). Since launch, there have been significant improvements in the force models and data processing strategies. This has resulted in significant improvements to orbit accuracy. The Gravity Recovery and Climate Experiment-Continuity (GRACE-C) mission, which will be launched in 2028, will carry on a similar onboard receiver to Sentinel-6A. The main purposes of this study are to extend our software to process both Galileo and GPS data for preparing GRACE-C and to investigate how well the orbits of the Sentinal-6A satellite can be currently determined using Galileo or/and GPS data based on the current models and approaches. In this study, we present the results of Sentinel-6a POD solutions. The orbit accuracy is assessed using several tests, which include analysis of orbit fits, Satellite Laser Ranging (SLR) residuals, internal and external orbit comparisons. We show that less than one-cm radial orbit accuracy for the Sentinel-6A satellite has likely been achieved through different orbit accuracy evaluations. The precise Sentonel-6A orbits determined based on Galileo and GPS observations can meet the stringent requirement on radial orbit accuracy (1.5 cm).

  PublisherDOI

• Quantum gravity gradiometry for future mass change science

  EPJ Quantum Technology · 2025-03-14 · 3 citations

  articleOpen access

  Abstract A quantum gravity gradiometer in a low Earth orbit, operating in a cross-track configuration, could be a viable single-spacecraft measurement instrument to provide mass change data for Earth observation, at comparable or better resolutions to existing maps generated by GRACE-FO. To reach the sensitivity for these science-grade measurements, many parts of the cold-atom interferometer need to be operating at, or beyond, state-of-the-art performance. In order to raise the maturity of the technology of the cold-atom gradiometer and determine the feasibility of a science-grade instrument, a pathfinder technology demonstration platform is funded. The requirements and a notional design for such a pathfinder and the outstanding challenges for science-grade instruments are presented.

  PublisherOA PDFDOI

• A unified model of feed rotation in radio telescopes and GNSS antennas

  Journal of Geodesy · 2025-08-21

  articleOpen accessSenior author

  Abstract We describe a model that accounts for the phase rotation that occurs when a receiver or transmitter changes orientation while observing or emitting circularly polarized electromagnetic waves. This model extends work detailing Global Navigation Satellite Systems (GNSS) carrier phase wind-up to allow us to describe the interaction of changing satellite orientation with phase rotation in observing radio telescopes. This development is motivated by, and a critical requirement of, unifying GNSS and Very Long Baseline Interferometry (VLBI) measurements at the observation level. The model can be used for either stationary choke ring antennas or steerable radio telescopes observing either natural radio sources or satellites. Simulations and experimental data are used to validate the model and to illustrate its importance. In addition, we rigorously lay out the feed rotation correction for radio telescopes with beam waveguide and full Nasmyth focuses and validate the correction by observing the effect with dual polarization observations. Using this feed rotation model for beam waveguide telescopes, we produce the first phase delay solution for the VLBI baseline WARK30M–WARK12M. We provide a practical guide to using the feed rotation model in Appendix D.

  PublisherOA PDFDOI

• Verifiable Mission Planning For Space Operations

  ArXiv.org · 2025-04-15

  preprintOpen access

  Spacecraft must operate under environmental and actuator uncertainties while meeting strict safety requirements. Traditional approaches rely on scenario-based heuristics that fail to account for stochastic influences, leading to suboptimal or unsafe plans. We propose a finite-horizon, chance-constrained Markov decision process for mission planning, where states represent mission and vehicle parameters, actions correspond to operational adjustments, and temporal logic specifications encode operational reach-avoid constraints. We synthesize policies that optimize mission objectives while ensuring constraints are met with high probability. Applied to the GRACE-FO mission, the approach accounts for stochastic solar activity and uncertain thrust performance, yielding maneuver schedules that maximize scientific return and provably satisfy safety requirements. We demonstrate how Markov decision processes can be applied to space missions, enabling autonomous operation with formal guarantees.

  PublisherOA PDFDOI

• Quantum Pathways Institute contributions to a roadmap for technical implementation and scientific interpretation of a spaceborne quantum gravity gradiometer.

  2025-03-15

  preprintOpen access1st author

  The Quantum Pathways Institute (QPI), sponsored by NASA/STMD, is a collaborative effort between UT Austin, CU Boulder, Caltech, UC Santa Barbara, and NIST. The QPI is focused on advancing quantum sensing technology for next-generation Earth science applications, and its vision targets 1 micro-Eotvos precision gravity gradient measurements in orbit, requiring femto-meter/s^2 inertial sensing. Such a gravity gradiometer system could target ice-mass loss measurements within 10 Gt/year, ocean heat uptake inference within 0.1 W/m^2, and better than 0.1 mm/year sea-level rise inference.This paper reports progress on two fronts. First a short summary status of QPI team’s work is presented, on quantum sensing research, conceptual development, and experimental results targeted towards a gravity gradiometer system. Second, we present progress in developing a roadmap to science mission implementation, including progress in addressing some key technical spaceflight and data analysis challenges.

  PublisherDOI

• Leveraging Gated Recurrent Units for Iterative Online Precise Attitude Control for Geodetic Missions

  2025-01-03 · 1 citations

  article

  In this paper, we consider the problem of precise attitude control for geodetic missions, such as the GRACE Follow-on (GRACE-FO) mission. Traditional and well-established control methods, such as Proportional-Integral-Derivative (PID) controllers, have been the standard in attitude control for most space missions, including the GRACE-FO mission. Instead of significantly modifying (or replacing) the original PID controllers that are being used for these missions, we introduce an iterative modification to the PID controller that ensures improved attitude control precision (i.e., reduction in attitude error). The proposed modification leverages Gated Recurrent Units (GRU) to learn and predict external disturbance trends derived from incoming attitude measurements from the GRACE satellites. Our analysis has revealed a distinct trend in the external disturbance time-series data, suggesting the potential utility of GRU's to predict future disturbances acting on the system. The learned GRU model compensates for these disturbances within the standard PID control loop in real time via an additive correction term which is updated at regular time intervals. The simulation results verify the significant reduction in attitude error, verifying the efficacy of our proposed approach.

  PublisherDOI

• Towards 30-years of mass change observations: GRACE Follow-On extended mission phase, and GRACE-Continuity developments 

  2025-03-14

  preprintOpen access

  The GRACE Follow-On (GRACE-FO) satellite mission, a partnership between NASA (US) and GFZ (Germany), successfully completed its nominal five-year prime mission phase in May 2023, and is currently in its extended mission phase. GRACE-FO continues the unique essential climate data record of mass change in the Earth system initiated in 2002 by the GRACE mission (2002-2017). The combined GRACE & GRACE-FO data records now span 23 years and provide foundational observations of monthly to decadal global mass changes and transports in the Earth system derived from temporal variations in the Earth’s gravity field.  In parallel, as part of NASA’s Earth System Observatory (ESO), a continuity mission called GRACE-Continuity (GRACE-C) scheduled for launch end of 2028 is being developed in partnership between NASA (US) and DLR (Germany), leveraging heritage elements considerably in the design.  One departure from heritage, is that the primary ranging instrument on GRACE-C will be a higher precision laser interferometer, capitalizing on the successful demonstration of this technology on GRACE-FO.  In this presentation, we will present updates on GRACE-FO in the context of satellite operations, data processing, and science/applications highlights, along with updates on the development of GRACE-C, which is meanwhile in Phase C and approaching the Critical Design Review in May 2025.  Prospects for achieving gap-free continuity between GRACE-FO and GRACE-C will be presented.

  PublisherDOI

• Measuring 1-mm-accurate local survey ties over kilometer baselines at McDonald Geodetic Observatory

  Journal of Geodesy · 2024-05-27 · 2 citations

  articleOpen access

  Abstract The goal for the next generation of terrestrial reference frames (TRF) is to achieve a 1-mm- and 0.1-mm/yr-accurate frame realization through the combination of reference station solutions by multi-technique geodetic observatories. A potentially significant source of error in TRF realizations is the inter-system ties between the instruments at multi-technique stations, usually independently determined through ground-based local surveying. The quality of local tie surveys is varied and inconsistent, largely due to differences in measurement techniques, surveying instruments, site conditions/geometries, and processing methods. The Global Geodetic Observing System (GGOS) has tried to address these problems by issuing guidelines for the construction and layout of future multi-technique observatories, promoting uniformity and quality while minimizing existing problems with local surveying that are exacerbated over longer baseline distances. However, not every observatory is going to be able to completely satisfy these guidelines, and in this work, a successful endeavor to satisfy the accuracy goals while exceeding the GGOS baseline guideline is detailed for the McDonald Geodetic Observatory (MGO) in the Davis Mountains of Texas, USA. MGO consists of a VLBI Geodetic Observing System (VGOS), infrastructure in place for a Space Geodesy Satellite Laser Ranging (SGSLR) telescope, and several Global Navigation Satellite Systems (GNSS) stations spanning a 900 m baseline and a 120 m elevation change. The results of the local ties between the GNSS stations across the near-kilometer baseline, as measured from their antenna reference points, show sub-mm precision and 1 mm accuracy validated through repeatability across several surveys conducted in 2021as well as 1 mm consistency with the monthly averaged daily solutions of the GNSS-based positioning. In this paper, we report these results as well as the framework of the surveys with sufficient detail and rigor in order to give confidence to the quality claims and to present the novel design and techniques employed in the procedure, processing, and error-budget analysis, which were determined through iterative research methods across repeated survey campaigns.

  PublisherOA PDFDOI

Frequent coauthors

• B. D. Tapley

  The University of Texas at Austin

  84 shared

• Himanshu Save

  78 shared

• John Ries

  The University of Texas at Austin

  45 shared

• Z. Kang

  38 shared

• Peter Nagel

  Karlsruhe Institute of Technology

  37 shared

• Frank Flechtner

  Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

  37 shared

• M. M. Watkins

  Jet Propulsion Laboratory

  24 shared

• Nadège Pie

  24 shared

Education

• Ph.D.

  The University of Texas at Austin

Awards & honors

• Charles A. Whitten Medal (2024)
• NASA Exceptional Public Achievement Medal (2018)
• European Geosciences Union Vening-Meinesz Medal (2016)
• William T. Pecora Team Award (2007)