1,1,1,1,1,1,1,1- 1Johns Hopkins University Applied Physics Laboratory, Laurel, MD, 20723, USA (ronald.ballouz@jhuapl.edu)
- 2Cornell University, 124 Hoy Rd, Ithaca, NY, 14850, USA
- 3NASA/GSFC, Greenbelt, MD, 20771, USA
- 4B612 Foundation, Mill Valley, CA, 94941, USA
- 5University of Maryland, College Park, College Park, MD, 20742, USA
There are a number of possible mitigation strategies that have been identified in the event a hazardous asteroid is discovered. NASA’s DART mission recently demonstrated the kinetic impactor technique [1]. The gravity tractor (GT) is attractive as the next technology for demonstration since other techniques may be prohibited by cost and legality [2]. A GT demonstration mission would align with NASA’s goal to "develop preliminary mission designs for future NEO deflection mission campaigns” [3]. Here, we present the design of a mission that would demonstrate a GT by changing the orbit of the secondary in an asteroid binary system.
The GT concept for deflecting asteroids involves bringing a spacecraft near an asteroid and controlling the spacecraft so that the asteroid’s orbit is altered by the spacecraft’s gravity [4]. This slow-pull mitigation strategy can achieve greater precision in an asteroid’s post-deflection orbit than impulsive mitigation techniques. GT also has the benefits of being agnostic to the material properties of the asteroid and not requiring contact between the spacecraft and asteroid. A GT may be used as the “primary” mitigation technique for hazardous asteroids that are found sufficiently far in advance of their Earth impact dates, or as a “secondary” mitigation technique applied after a “primary” impulsive technique to ensure the avoidance of gravitational keyholes. Inspired by the success of the DART mission, we are studying whether GTs will be more easily tested in a binary asteroid system in the same way that kinetic impactors are: a small velocity change on the order of what would be necessary in a real emergency is more easily detected and measured on an asteroid satellite's orbit than it is on a single asteroid’s heliocentric orbit [5].
We report on the design of a GT demonstration mission to a binary asteroid system. We identify three main goals that a GT mission to a binary asteroid should achieve: (1) guide and navigate the spacecraft to the vicinity of the secondary and precisely control its relative position (within a few body radii), (2) measure the change in the secondary’s orbit due to the GT, (3) demonstrate long-duration tractoring operations in close proximity to the asteroid. We present mission requirements needed to achieve these mission goals. These requirements are used to define a concept of operations for a binary asteroid system “characterization phase” and “tractor phase,” which would lead to a measurable deflection of the secondary within a 12-month timeframe for asteroid proximity operations. We present the mission design and baseline payload that would meet these investigation requirements. In sum, this report outlines a demonstration mission of a GT at reasonable cost that will accomplish NASA’s goal of demonstrating a slow-pull asteroid deflection technique.
References
[1] Chabot, N., et al. (2024). Planet. Sci. J. 5 49
[2] Abell, P. and Frazier (2021). Planetary Defense Missions: Rapid Mission Architecture Study. Planetary Science Decadal Survey: Mission Concept Study Report.
[3] NASA Planetary Defense Strategy and Action Plan (2023). NASA. https://go.nasa.gov/3UO2mmt
[4] Lu, E. T. and Love, S. G. (2005). Nature, 438, 177–178.
[5] Merrill, C., et al., Planetary Defense Conference 2025.
How to cite: Ballouz, R., Rivkin, A., Merrill, C., Bull, R., Barnouin, O., Hatten, N., Fletcher, Z., Rodovskiy, L., Bushman, S., Atchison, J., Barbee, B., Chabot, N., Cheng, A., Daly, T., Ernst, C., Graninger, D., Lu, E., Richardson, D., Savransky, D., and Stickle, A.: A Gravity Tractor Mission Concept to a Binary Asteroid, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–12 Sep 2025, EPSC-DPS2025-645, https://doi.org/10.5194/epsc-dps2025-645, 2025.
