Insights on Radiation Belt Precipitation and Losses using Low-Altitude Measurements in Conjunction with NASA’s Radiation Belt Storm Probes

The FIREBIRD-II CubeSats (FU3 and FU4) have been successfully operating in a high-inclination, low-earth-orbit since January 31st, 2015. FIREBIRD was primarily designed to observe relativistic electron microbursts, specifically improving the understanding of spatial dimensions, energy spectra at moderately relativistic energies and time evolution of the microburst precipitation region. Microbursts are sharp increases (often greater than an order of magnitude) in precipitating electron flux lasting ~100 ms. Microbursts have been simultaneously observed when the CubeSats were separated by as little as ~15 km. Protracted observations from the long-duration FIREBIRD-II mission utilize synergistic measurements from other CubeSats, stratospheric balloons, and magnetic conjunctions with NASA’s Radiation Belt Storm Probes mission to reveal new insights on radiation belt electron losses. Each FIREBIRD-II CubeSat contains two solid-state detectors with complementary geometric factors measuring electrons from 200 keV to ~1 MeV. FIREBIRD observations are gathered in multi-week duration campaigns producing two data products, Context and HiRes. Context is an electron count rate from two energy channels at a 6 s cadence, and HiRes is at a cadence as fast as 12.5 ms. Context data is downlinked for the entirety of the campaign, but telemetry constraints allow only a selected subset of HiRes data to be downlinked. Microbursts, and precipitation in this energy range, can strongly affect the dynamic balance of radiation belt electron flux as well as influence atmospheric chemistry at a range of altitudes. This paper will present science highlights from the FIREBIRD CubeSats including spatial scale observations, energy spectra, and conjunctions with other missions.