Improved measurement of radar meteor shower mass indices

Measurements of meteor radar-derived mass indices are known to be contaminated by sporadic meteoroids (Pokorný and Brown 2016). This leads to overestimated values for the mass index and typically inflates associated meteoroid fluxes. Here we apply a novel mixing model approach to retroactively remove sporadic contamination. This technique, previously applied to the Daytime Sextantid meteor shower (Kipreos et al. 2022), is adapted to a wider suite of meteor showers.

Applying this mixing model to the strongest meteor shower detected by the Canadian Meteor Orbit Radar (CMOR), namely the Geminids, we calculate an uncontaminated differential mass index of 1.51 at a CMOR limiting mass of 10⁻⁷ kg for the stream at its maximum activity. Additionally, we extend this method to eighteen radar-detected showers in total (ARI, BTA, DRA, DSX, ETA, GEM, NIA, NOC, NOO, OCE, ORI, OSE, PCA, QUA, SDA, TCB, XCB, ZPE) and find mass index values ranging from 1.45–1.79, lower than previous estimates.

Meteor showers can pose a substantial meteoroid impact risk to spacecraft and astronauts, with mitigation procedures sometimes being required. A shower’s meteoroid risk assessment uses the mass index of that shower, so more accurate shower mass indices, calculated using the mixing model, lead to more accurate meteoroid risk assessments. By utilizing the uncontaminated mass indices of the eighteen most significant meteor showers for satellite impact risk, we re-assess the risk level posed by each, based on the framework from Moorhead et al. (2024a). As a result, the impact risk levels of six showers have been revised downward. Since mitigation procedures require resources such as fuel, time, and operational opportunities, improving impact risk accuracy allows for more efficient mission planning and execution.