Intercept and Engagement of the PDC 2019 Comet with Solar Sailcraft

An AIAA Distinguished Speaker Lecture, via Zoom

presented by

Dr. Nahum Melamed

 Project Leader in the Embedded Control Systems Department of the Guidance and Control Subdivision at The Aerospace Corporation

Friday, November 7th, 12:00-1:00 PM PST

Planetary defense for comets has not been given much attention to date because their estimated collision frequency with Earth is two orders of magnitude lower than that of asteroids. However, a comet entering the inner solar system is generally larger and faster than an asteroid thus has a greater potential for damage. Moreover, since comets originate from the outer regions of the solar system, they are discovered about a year or two before their potential impact, and they can approach Earth on highly inclined orbits with respect to the ecliptic plane. Accordingly, assessments made at recent Planetary Defense Conferences (PDC) place the risk from comets on par with that from asteroids.

To help understand possibilities and limitations in addressing the comet threat, NASA Jet Propulsion Laboratory (JPL) has constructed a fictitious comet threat that puts a comet on a collision course with Earth. This new threat has been added to those available on the NEO Deflection App (NDA, https://cneos.jpl.nasa.gov/nda/) developed jointly by The Aerospace Corporation and JPL. Chemical rockets are shown to be incapable of intercepting NEOs approaching Earth from such high declinations with respect to the ecliptic plane until a few weeks before impact. Aerospace has shown that the EXCALIBRS (Expeditionary Comet/Asteroid Lander Interceptor BDA and Reconnaissance Sail) solar sail concept can intercept the comet three to six months before impact when it is at a distance of several astronomical units from Earth.

Nahum Melamed is a project leader in the Embedded Control Systems Department in the Guidance and Control Subdivision at The Aerospace Corporation. He joined Aerospace in 2003. As a technical lead in Launch Vehicle Software, Dr. Melamed coordinates and guides a team of interdepartmental technical experts, and supports validation and mission readiness certification of the flight software and mission parameters for NASA’s Artemis missions. He conducts planetary defense technical and policy studies, co-chairs planetary defense conferences, serves on organizing committees, and speaks at these venues. He earned a Ph.D. in Aerospace Engineering from Georgia Tech. 

The presentation will be on Friday, November 7th, 2025 from 12:00 PM to 1:00 PM PST via Zoom. The Zoom link for the meeting is below.