Aerospace Seminar Series

An Introduction to Guidance, Navigation, and Control

Speakers:

• Siddarth Kaki, Ph.D. – Navigation Discipline Engineer, EG6 / GN&C Autonomous Flight Systems Branch, NASA Johnson Space Center
• Jacob Sullivan – EG6 / GN&C Autonomous Flight Systems Branch, NASA Johnson Space Center

Radionavigation

Speaker:

• Dr. Greg Holt - GN&C Autonomous Flight Systems Branch, NASA Johnson Space Center

Speaker Bio:
Dr. Greg Holt is the Navigation Technical Discipline lead and System Manager for the Orion Multi-Purpose Crew Vehicle at NASA Johnson Space Center, having earned a Ph.D. from the University of Texas at Austin and with over 15 years of NASA service.  He has enjoyed many opportunities to be active in technical leadership and is a veteran Mission Control navigator of 8 Space Shuttle missions, the Orion Exploration Flight Test 1, and the Artemis I lunar mission.

Abstract:
Explore the principles and evolution of RadioNavigation, a cornerstone of modern aerospace engineering. We’ll trace the historical progression from early celestial navigation to advanced systems like the Global Positioning System (GPS), Global Navigation Satellite Systems (GNSS), NASA’s Deep Space Network (DSN), and emerging lunar relay satellite architectures for Artemis missions.  Through technical insights, practical examples, and discussions of triangulation, signal processing, and deep-space communication challenges, this talk will illuminate the critical role of radio navigation in enabling precise positioning for terrestrial and extraterrestrial exploration.

Entry, Descent, and Landing

Speaker:

• Dr. Sergio Sandoval - Guidance Engineer, NASA Johnson Space Center

Speaker Bio: 
Sergio Sandoval is a guidance engineer at NASA’s Johnson Space Center. He received a bachelor’s degree in Aerospace Engineering at the Georgia Institute of Technology in December 2017. During his undergraduate studies, he collaborated with the Space Systems Design Lab as part of Prox-1, the first satellite ever made by Georgia Tech students and with the Aerospace Systems Design Lab doing Systems Engineering for NASA projects such as the Europa Clipper and the TransHab Structure. His participation in these projects led to a Pathways Internship offer at the Johnson Space Center starting in August 2016, and an internship with the Jet Propulsion Lab during the summer of 2016. He completed his PhD in Aerospace Engineering at San Diego State University and the University of California San Diego in 2023. During his time at NASA, he has held different positions such as Systems Engineer for the Europa Clipper mission, Trajectory Operations and Planning Engineer for the International Space Station, Structural Engineer for experiments going to the International Space Station, and more recently he started as a Guidance Engineer for human and robotic exploration missions to the Moon, Mars, and beyond. He currently applies his expertise of Entry, Descent, and Landing to support the Orion Re-entry analysis for the Artemis Program.

Abstract:
Safety, precision, and efficiency are the key ingredients for successful human-scale entry, descent, and landing (EDL) in missions to the Moon, Mars and beyond. As one of the most dynamic and challenging phases of any interplanetary mission, it is very important to understand the different techniques, the conditions in which we apply these techniques, and for what reason. In this seminar, we will explore a complete overview of entry and powered descent guidance, from its origin to the state of the art. We will investigate successful examples that have flown to space before, as well as dive into the requirements of a mission in the future.

Optical Navigation

Speaker:

• Dr. Paul McKee

Speaker Bio:
Paul McKee was born and raised in Averill Park, NY. He studied mechanical and aerospace engineering at Rensselaer Polytechnic Institute (RPI), getting his B.S. in 2017, his M.S. in 2018, and his Ph.D. in 2022. His research was on autonomous spacecraft navigation. He now works at NASA Johnson Space Center in the Aeroscience and Flight Mechanics Division. His projects include Optical Navigation hardware and software analysis for the Orion spacecraft, lunar surface navigation algorithm development for the Artemis program, and he is Assistant to the Project Manager for Project TRON -- a next-gen optical navigation early-career project. Paul is also involved in numerous outreach efforts to grade school STEM students, and is a (remote) adjunct professor at RPI, teaching a graduate-level course in spacecraft navigation. 

Abstract:
A spacecraft can determine its position and attitude (orientation) using information in digital images taken with an onboard camera. This is referred to as Optical Navigation (OpNav). This begins with an understanding of cameras as navigation instruments, and how useful data can be extracted from images. Well-established methods of OpNav for attitude determination and localization are discussed, and then time is spent on some of the newer and more exotic problems in OpNav. Audience participation is highly encouraged and imagination will be a requirement.

Spacecraft Controls

Speaker:

• Dr. Omkar Mulekar

Speaker Bio:
Omkar Mulekar joined NASA Johnson Space Center in July 2024 as a navigation analyst for the Orion Relative Navigation system and as a controls engineer for the Gateway Controls system. He holds a PhD and a master’s degree from the University of Florida as well as a bachelor’s degree from Auburn University. His graduate research includes the use of neural networks to perform feedback-optimal control of nonlinear systems.

Abstract:
In this presentation, we will discuss the “Control” element of a spacecraft’s Guidance, Navigation, and Control system. From its overarching purpose on a spacecraft to specific examples of how we apply control logic to command actuators onboard autonomous spacecraft, we will explore the modern challenges of maintaining control in complex, harsh environments.

How Do You Throw a Refrigerator Away in Space – The story about jettisoning a large piece of equipment from the ISS without killing anyone in a illustration of what rocket science is all about.

Speaker:

• Dr. Robert Dempsey, aka “Dr. Bob”

Speaker Bio:
Dr. Robert Dempsey, aka “Dr. Bob”, received his PhD in astrophysics from the University of Toledo in 1984.  He worked on the Hubble Space Telescope for 5 years, both as an operator and a researcher. In his astronomy career, he published over 30 peer-reviewed articles. After programming his job away, and because he wanted to get involved in human space exploration, Dr. Bob literally got on a plane and cold-called United Space Alliance in Houston.  He joined the ISS program in 1997 as a Command & Data Handling front room controller (“ODIN”) due to said programming skills, before transitioning to Communications & Tracking (“CATO”) in 2003.  After supporting numerous International Space Station assembly missions, in 2005, he was selected as a Flight Director (call sign “Galileo”). Over his 17+ years as Flight, he led numerous Shuttle assembly missions, crewed and uncrewed dockings/undockings,  and spacewalks, including one where the Russians removed a live pyro bolt from the Soyuz. He helped lead the NASA Mission Operations team that operated Boeing’s Starliner spacecraft, including on the ill-fated Orbital Flight Test in 2019.  In 2022, he retired from the ISS program office and joined Blue Origin. While at Blue Origin, he has led mission operations for the Orbital Reef, the crewed space vehicle, and the New Shepard suborbital program, while also contributing to the New Glenn project.  Since July, he has been working part-time at Blue Origin while also working on a book about the Commercial Crew Program, a novel about time travel, and consulting when not baking bread or cookies.

Machine Learning and Artificial Intelligence for Space Applications

Speaker:

• Dr. Julia Briden

Speaker Bio:
Julia Briden works as an Advanced Mission Design and GN&C Engineer at NASA Johnson Space Center on the Amentum JETS-II Contract. She has received her PhD in Aeronautics and Astronautics, with a major in Autonomy, from MIT in 2024 and her Master’s and Bachelor’s, with a minor in Artificial Intelligence, from the Illinois Institute of Technology in 2021. Her research focuses on using deep learning for efficient spacecraft guidance.

Abstract:
This talk introduces the field of artificial intelligence (AI) and its sub-field, machine learning (ML), through the lens of space exploration. We begin by outlining the major categories of AI and ML and how they enable perception, reasoning, and decision-making in autonomous systems. The discussion then distinguishes between offline applications, where AI supports mission design and planning on the ground, and onboard implementations, where algorithms must operate in real time under strict computational and reliability constraints. The talk concludes with an overview of current research advancing ML for online guidance and control, highlighting efforts to improve efficiency, adaptability, and trustworthiness in future autonomous spacecraft.

Spacecraft Trajectory & Mission Design

Speaker:

• Dr. Stephen Scheuerle

Speaker Bio:
Stephen Scheuerle is a mission design engineer for NASA’s Gateway Program. He received his M.S. and Ph.D. in Aeronautical and Astronautical Engineering from Purdue University, and his B.S. in aerospace engineering from NC State University in 2018. Stephen’s graduate research focused on spacecraft trajectory design in multi-body systems, specifically exploring propellant efficient pathways for spacecraft in the three-body and four-body problems.

Abstract: 
This talk introduces orbital mechanics, and the role it plays in spaceflight. The presentation discusses the history of trajectory design, sharing the discoveries astronomers and mathematicians that shape modern-day trajectory design. The presentation then covers an overview of the types of trajectories spacecraft follow, and what it means to work in trajectory design. Finally, the presentation will focus on the role trajectory design and orbital mechanics play in end-to-end mission design. Looking at how constraints and objectives drive mission planning. 

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