PADRE

PADRE [University of California]

PADRE (solar PolArization and Directivity X-Ray Experiment) is NASA cubesat mission to study the Sun. The mission is a collaboration between the Space Sciences Laboratory – University of California Berkeley (SSL/UCB), Goddard Space Flight Center (GSFC), SouthWest Research Institute (SWRI), University of Applied Sciences and Arts Northwestern Switzerland (FHNW), the Saclay Nuclear Research Centre of the Commissariat à l’énergie atomique (CEA-Saclay).

As a 12U solar spinner CubeSat, PADRE focuses on measuring the polarization and directivity of hard X-rays (HXRs) emitted during flares, unraveling the behaviors and distributions of high-energy electrons in the Sun’s atmosphere. Developed on a EnduroSat CubeSat platform, PADRE combines advanced instrumentation with a robust, cost-effective design.

Solar flares are the most powerful explosions in the solar system, yet there are many parts of their mechanisms that scientists don’t fully understand. During a flare, the Sun releases magnetic energy violently and rapidly enough to accelerate charged particles to relativistic speeds. The details of the energy conversion process and particle propagation during this acceleration are largely unknown. PADRE’s mission will revolutionize our understanding of solar flare physics by determining the angular distribution of flare-accelerated electrons through the observation of two hard X-ray (HXR) characteristics:

• X-ray Polarization Measurements: The SHARP (Solar Hard X-ray Polarimeter) instrument measures the degree of polarization of HXRs, revealing whether the flare-accelerated electrons are strongly beamed or isotropic.
• X-ray Directivity Studies: The MeDDEA (Measuring Directivity to Determine Electron Anisotropy) system quantifies the anisotropy of HXRs by cross-calibrating detectors observing the same solar flare from multiple perspectives.

HXRs are emitted by energetic electrons via bremsstrahlung collisions with ambient ions, making them the most direct available characteristic of solar flare electron acceleration. These observations will provide more thorough diagnostics for constraining different flare particle acceleration scenarios.