About

Dan A Erwin is a Professor of Astronautics and Aerospace and Mechanical Engineering at the University of Southern California. He holds a doctoral degree in Electrical Engineering from USC, earned in 1986, along with a master's degree in Electrical Engineering from USC obtained in 1983, and a bachelor's degree in Physics from the California Institute of Technology completed in 1981. His research focuses on spacecraft propulsion, optics and optical instruments, and the kinetics of gases and plasmas. Throughout his career, he has received several awards including the Engineers' Council Distinguished Engineering Project Achievement Award in 2017, the Engineers' Council Distinguished Engineering Educator Award in 2016, and multiple teaching awards from USC and TRW, Inc. Erwin has served as the Department Chair of Astronautical Engineering within the USC Viterbi School of Engineering and is actively involved in teaching and research in aerospace engineering disciplines.

Research topics

• Computer Science
• Engineering
• Systems engineering
• Computer Security
• Computer vision
• Physics
• Structural engineering
• Optics
• World Wide Web
• Real-time computing
• Acoustics
• Telecommunications
• Software engineering

Selected publications

• Sensing Lunar Dust Density Using Radio Science Signals of Opportunity

  Remote Sensing · 2025-06-04

  articleOpen accessSenior author

  Previous lunar missions, such as Surveyor, Apollo, and the Lunar Atmosphere and Dust Environment Explorer (LADEE), have played a pivotal role in advancing our understanding of the lunar exosphere’s dynamics and its relationship with solar wind flux. The insights gained from these missions have laid a strong foundation for our current knowledge. However, due to insufficient near-surface observations, the scientific community has faced challenges in interpreting the phenomena of lunar dust lofting and levitation. This paper introduces the concept of signals of opportunity (SoOP), which utilizes radio occultation (RO) to retrieve the near-surface dust density profile on the Moon. Gravity Recovery and Interior Laboratory (GRAIL) radio science beacon (RSB) signals are used to demonstrate this method. By mapping the concentration of lunar near-surface dust using RO, we aim to enhance our understanding of how charged lunar dust interacts with surrounding plasma, thereby contributing to future research in this field and supporting human exploration of the Moon. Additionally, the introduced SoOP will be able to provide observational constraints to physical model development related to lunar surface particle sputtering and the reactions of near-surface dust in the presence of solar wind and electrostatically charged dust grains.

  PublisherOA PDFDOI

• How GRAIL Radio Occultations Could Enable Future Lunar Missions for Mapping the Near-Surface Dust

  2025-03-01

  article

  Past NASA's Lunar missions, including Surveyor, Apollo, and Lunar Atmosphere and Dust Environment Explorer (LADEE), have provided valuable insights into the dynamics of the lunar exosphere and its relationship with solar wind flux. However, it has been a challenge for the scientific community to interpret the dust lofting and levitation on the moon. This research aims to utilize NASA's Gravity Recovery and Interior Laboratory (GRAIL) radio science as Signals of Opportunity (SoOP) to evaluate the Radio Science Measurements for the future Radio Occultation (RO) mission to investigate the lunar dust and surrounding plasma interactions. This paper will provide an assessment of new science observations derived using GRAIL RO data as a reference for the scientific community to design the future Lunar Radio Occultation Missions to improve understanding of the dense dust formation and evolution near the moon surfaces. Furthermore, the observations of the lunar dust with GRAIL's radio science signals of opportunity will provide a clean reference without lander impacts since the Apollo era as a comparison and a reference for future investigations of moon dust dynamics, especially in the south pole region where future Artemis human mission will land.

  PublisherDOI

• Multimode Propulsion: Cislunar Rideshare Mission Concept Trade Space Analysis for Small Spacecraft

  2025-03-01

  article

  Multimode propulsion offers the promise of space-craft equipped with a high-thrust chemical maneuver mode and a solar electric low-thrust maneuver mode. As national and commercial activity in cislunar space increases, new low-cost pathways for small spacecraft to access multi-body orbits can be explored. One pathway of key interest is the available excess payload capacity on launch systems and transfer stages designed to deliver landers to the lunar surface, such as those on the Commercial Lunar Payload Services (CLPS) missions [1]. To allow for flexibility in mission Concept of Operations (CONOPS), enable rapid-response mission timelines, and provide an examination of the design trade space for low-cost rideshare missions to cislunar space, this paper proposes a set of new preliminary mission concepts that utilize current CubeSat technology enhanced with multimode propulsion. The proposed mission concepts are designed around deployment from future rideshare opportunities to the lunar surface, aiming to deliver a 16U CubeSat to an Earth-Moon L2 Near Rectilinear Halo Orbit (NRHO). This study and resulting analysis find that the mul-timode system shows promising characteristics for enhancing flexibility in mission CONOPS. These include reduced transfer time, increased robustness to schedule changes and mission anomalies, and the ability to target powered lunar flybys. This work culminates in an overview of the low-cost cislunar mission concept trade space for small spacecraft utilizing future mul-timode propulsion systems. The principal results of this study consist of an analysis that trades time of flight (TOF) against the amount of propellant consumed across different families of multimode transfers. These families represent different sets of possible mission CONOPS with desirable attributes such as reduced time of flight or reduced propellant cost compared to baseline chemical-only missions. These results are presented to inform future mission formulation studies on low-cost cislunar missions and showcase the ability of multimode propulsion to enhance future mission concepts.

  PublisherDOI

• Radio Occultation Observations of the Lunar Ionosphere Variations Over GRAIL Mission Period

  2025-03-15

  preprintOpen access

  The Signal of Opportunity using NASA’s Gravity Recovery and Interior Laboratory (GRAIL) radio signals to remotely sense the Lunar ionosphere has been successfully demonstrated. The GRAIL mission consisted of an identical pair of spacecraft approximately 100 km apart in a circular polar orbit around the Moon; during the science mission period, the GRAIL’s X-band Radio Science beacon (RSB) data provide applicability for the radio occultation of the lunar electron density profiles with the uncertainty of frequency residual measurement ~ 1 mHz corresponding to ~ 2 x 108 m-3 electron density uncertainties. We will present our observation updates of the Lunar ionosphere in terms of the near-surface electron profiles versus altitude retrieved from the RSB data to understand its spatial and temporal variations during the GRAIL science mission period. The nature of the lunar ionosphere is a long-standing mystery; GRAIL’s observations of the near-surface electron density profiles and its responses to solar winds and storms impact the near-surface plasma environment.

  PublisherDOI

• Diffusion Models for Generating Ballistic Spacecraft Trajectories

  arXiv (Cornell University) · 2024-05-20

  preprintOpen access

  Generative modeling has drawn much attention in creative and scientific data generation tasks. Score-based Diffusion Models, a type of generative model that iteratively learns to denoise data, have shown state-of-the-art results on tasks such as image generation, multivariate time series forecasting, and robotic trajectory planning. Using score-based diffusion models, this work implements a novel generative framework to generate ballistic transfers from Earth to Mars. We further analyze the model's ability to learn the characteristics of the original dataset and its ability to produce transfers that follow the underlying dynamics. Ablation studies were conducted to determine how model performance varies with model size and trajectory temporal resolution. In addition, a performance benchmark is designed to assess the generative model's usefulness for trajectory design, conduct model performance comparisons, and lay the groundwork for evaluating different generative models for trajectory design beyond diffusion. The results of this analysis showcase several useful properties of diffusion models that, when taken together, can enable a future system for generative trajectory design powered by diffusion models.

  PublisherOA PDFDOI

• Investigating Lunar Ionosphere Using GRAIL Radio Science Signals

  2024-03-08 · 1 citations

  preprintOpen access

  The nature of the dense lunar ionosphere is controversial; the maximum electron density values in observed vertical profiles obtained from previous Lunar missions vary by two orders of magnitude. NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission consisted of an identical pair of spacecraft approximately 100 km apart in a circular polar orbit around the Moon at a mean altitude of 55 km during the science phase in 2012. The two GRAIL spacecraft conducted various radio science observations to determine the lunar gravity field. As a serendipitous consequence of these primary observations, the one-way spacecraft - Earth radio occultation observations of the lunar ionosphere were acquired using a carrier-only X-band radio signal from the Radio Science Beacon referenced to an onboard ultrastable oscillator (USO). GRAIL’s X-band Radio Science beacon (RSB) data provide applicability for the radio occultation of the lunar electron density profiles with the uncertainty of frequency residual measurement ~ 1 mHz corresponding to ~  2x108 m-3 electron density uncertainties. We will present our analysis of the electron density profiles retrieved from GRAIL Radio Science Beacon data to understand the formation and variations of the moon ionosphere. The findings of GRAIL results will improve our understanding of how those variations are spatial (e.g., latitude, longitude, solar zenith angle) or temporal (e.g., responses to external factors, such as meteor impacts and solar winds) during the GRAIL mission period.

  PublisherDOI

• Feasibility of Retrieving Lunar Near-Surface Dust Density Using Radio Occultation Measurements 

  2024-03-09

  preprintOpen access

  Lunar charged-dust dynamics (levitation and transportation) could be one of the primary sources to dominate the near-surface plasma environment on the Moon. Charged dust grains could reached up to a few kilometers above the moon surfaces and forming a complex dusty plasma environment. The findings of NASA’s LADEE Lunar Dust Experiment confirms the dust density variations at different altitudes above the surface. Additionally, previous research has reported the detection of the Moon’s electron density profiles using radio occultation measurements; these radio signals were made from Lunar missions, including Chandrayaan, Luna-19, Luna-22, LRO, GRAIL, and SELENE, providing accurate phase measurements with Allan deviations between 10-12 – 10-13. In this research, we will present a feasibility assessment of using the lunar radio occultation measurements to estimate the near-surface dust concentrations. Understanding the nature of near-surface dust density and dynamics is essential to assessing the dusty plasma environment impacts on future human and lander missions on the Moon.

  PublisherDOI

• MBSE Testbed for Unmanned Vehicles

  Springer eBooks · 2023 · 2 citations

  Senior authorCorresponding
  • Computer Science
  • Computer Science
  • Systems engineering
  PublisherDOI

• Recent Trends and Advances in Model Based Systems Engineering

  Springer eBooks · 2022 · 17 citations

  • Computer Science
  • Computer Science
  • Systems engineering
  PublisherDOI

• Laser Doppler imaging vibrometer for real-time health monitoring of civil infrastructures

  2022 · 2 citations

  Senior authorCorresponding
  • Computer Science
  • Computer Science
  • Real-time computing

  Active vibration monitoring of civil structures provides a basis for the assessment of their actual health status and advanced warning of potential structural deficiency. This paper discusses the wirelessly networked beam-array Laser Doppler Imaging Vibrometer (LDIV) for non-contact evaluation of civil infrastructures. The measured time domain data on structure spatial displacement and velocity serves as an input for various operational modal analysis algorithms and eventually for detection and localization of the potentially defected area. Essential for LDIV system effectiveness in structural health monitoring is the capability of its operational software in real time processing of the collected data.

  PublisherDOI

Frequent coauthors

• Joseph A. Kunc

  University of Southern California

  18 shared

• E. P. Muntz

  University of Southern California

  16 shared

• G. Pham-Van-Diep

  12 shared

• J. A. Kunc

  University of Chemistry and Technology, Prague

  10 shared

• Azad M. Madni

  8 shared

• M. Gruntman

  8 shared

• R. F. Brodsky

  7 shared

• Gajendra D. Savant

  Physical Optics Corporation

  6 shared

Education

• Ph.D., Aerospace Engineering

  University of Southern California

  1994

• M.S., Aerospace Engineering

  University of Southern California

  1991

• B.S., Aerospace Engineering

  University of Southern California

  1989

Awards & honors

• 2017 Engineers' Council Distinguished Engineering Project Ac…
• 2016 Engineers' Council Distinguished Engineering Educator A…
• 2006 USC-LDS Student Association Outstanding Teaching Award
• 1995 USC School of Engineering Outstanding Teaching Award
• 1993 TRW, Inc. TRW Excellence in Teaching Award