The Solar Polarization and Directivity X-Ray Experiment (PADRE) is a groundbreaking NASA CubeSat mission dedicated to exploring the mysteries of the Sun. As a 12U solar spinner CubeSat, PADRE will investigate the polarization and directivity of hard X-rays (HXRs) emitted during solar flares. Built on a cutting-edge spacecraft provided by EnduroSat, PADRE aims to provide critical insight into the behavior and distribution of high-energy electrons in the solar atmosphere.
Our Teams
PADRE is a global collaboration between institutions leading in solar and space science, including the Space Sciences Laboratory (SSL) at UC Berkeley, NASA Goddard Space Flight Center (GSFC), Southwest Research Institute (SWRI), University of Applied Sciences and Arts Northwestern Switzerland (FHNW), CEA-Saclay, and EnduroSat, the spacecraft provider. SSL leads the project, integrating contributions from each partner to deliver groundbreaking solar science.
Science Goals
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.
Innovative Design
PADRE’s compact 12U CubeSat design incorporates:
- EnduroSat’s solar-spinning spacecraft configuration for stable and continuous Sun-facing observations.
- The SHARP polarimeter to measure hard X-ray polarization with high precision.
- The MeDDEA detector system to perform directivity measurements.
- Advanced high-voltage systems supplied by SWRI to power state-of-the-art photon-counting detectors.
Global Impact
PADRE is the result of an international collaboration that will provide information about acceleration and transport mechanisms present in solar eruptive events. This knowledge is key to understanding solar energetic particles (SEP), which are a major component of space weather. The mission will answer fundamental questions about solar flare dynamics while showcasing the capability of CubeSat technology for high-impact space science.