Operational Mass Measurement for Flyby Reconnaissance Missions of Potentially Hazardous Asteroid

TL;DR

The paper tackles the challenge of in-situ mass measurement for potentially hazardous asteroids during rapid reconnaissance flybys, where Earth-based RF tracking is insufficient for 50–500 m objects. It proposes a dual-spacecraft approach: a host vehicle executes a close low-altitude encounter while a CubeSat test-mass trails at ~10 km, enabling precise intersatellite tracking; enhancements with laser ranging (LRI) or high-precision Doppler (HPD) further improve mass sensitivity. Across three planetary-defense scenarios (2023 PDC, 2024 PDC25, and 2024 YR$_4$), the study shows that RF intersatellite measurements alone fail for small bodies, but LRI or HPD can enable mass determinations down to ~50–100 m diameters, contingent on B-plane targeting accuracy and timing of the final maneuver. The findings highlight the operational tension between achieving tight encounter geometry and processing lead times, and they point to practical pathways—improved OpNav, onboard processing, an OpNav scout, multiple small satellites, or future radar—to realize precise mass measurements for rapid defense decisions. $\Delta v$ observations and $GM$-related dynamics underpin the methodology, offering a concrete route to meaningful planetary-defense mass characterization with near-term tech if targeting and data-processing challenges can be managed.

Abstract

This study evaluates a technique for determining the mass of a potentially hazardous asteroid from a high-speed flyby in the context of a rapid reconnaissance planetary defense scenario. We consider a host spacecraft that dispenses a small CubeSat, which acts as a test-mass. Both spacecraft perform approach maneuvers to target their flyby locations, with the host targeting a close proximity flyby and the CubeSat targeting a distant flyby. By incorporating short-range intersatellite measurements between the host and the CubeSat, the mass measurement sensitivity is substantially improved. We evaluate a set of proposed host and CubeSat hardware options against the 2023 and 2025 Planetary Defense Conference hypothetical threats, as well as a hypothetical flyby of 2024 YR4. These scenarios differ predominantly in their flyby speeds, which span from 1.7 to 22 km/s. Based on these scenarios, we demonstrate that a typical radio-frequency intersatellite measurement is ineffective for asteroids with diameters relevant to planetary defense (i.e., 50 - 500 m). However, we find that augmenting the system with a laser-based intersatellite ranging system or a high-precision Doppler system can enable mass measurements of asteroids as small as 100 m across all cases, and as small as 50 m for the slower (< 8 km/s) cases. The results are very sensitive to the timing of the final maneuver, which is used to target the low-altitude flyby point. This presents an operational challenge for the smallest objects, where optical detection times are comparatively late and the optical navigation targeting knowledge converges too slowly.

Figures (18)

• Figure 1: Illustration of flyby intersatellite mass measurement concept, where host spacecraft passes close to the asteroid and cubesat test-mass passes is distant
• Figure 2: Probability distribution functions for the mass of a 140 m diameter asteroid, including the PAIR model Mathias2017 and the metrics used in this study
• Figure 3: The velocity change imparted for the three scenarios in this study, parameterized over asteroid diameter. The reference diameter for each case is indicated with a black marker
• Figure 4: Nominal B-plane targets for a 0.3 km diameter asteroid. The velocity vectors of the two spacecraft are perpendicular to the plane show (i.e., into the page).
• Figure 5: Case 1. (a) Flyby trajectory to 2023 PDC. (b) Temporal evolution of the apparent magnitude of 2023 PDC from the spacecraft for varying asteroid diameters. The vertical line indicates the time of closest approach (TCA). (c) Measurement schedule for the encounter with 2023 PDC. The vertical dashed lines indicate the times of host (H) and test-mass (TM) maneuvers.