India’s ASPEX Instruments on Aditya-L1 Illuminate Solar Wind Mysteries
India’s space agency, the Indian Space Research Organisation (ISRO), announced on Saturday that the Aditya Solar wind Particle Experiment (ASPEX) payload onboard the Aditya-L1 satellite has commenced operations and is performing normally. The Aditya-L1 spacecraft, launched on September 2, 2023, is India’s first space-based observatory designed to study the Sun from a halo orbit around the first Sun-Earth Lagrangian point (L1), situated approximately 1.5 million km from Earth.
The ASPEX payload includes two cutting-edge instruments: the Solar Wind Ion Spectrometer (SWIS) and the SupraThermal and Energetic Particle Spectrometer (STEPS). The STEPS instrument began its operations on September 10, 2023, while the SWIS instrument was activated on November 2, 2023, demonstrating optimal performance, according to ISRO.
SWIS, equipped with two sensor units offering a remarkable 360° field of view each, operates in planes perpendicular to one another, as stated in the ISRO statement. The instrument has successfully measured solar wind ions, including protons and alpha particles. ISRO shared a sample energy histogram acquired from one of the sensors over two days in November 2023, illustrating variations in proton and alpha particle counts.
The directional capabilities of SWIS allow precise measurements of solar wind protons and alphas, contributing significantly to addressing longstanding questions about solar wind properties, underlying processes, and their impact on Earth. ISRO explained that the change in the proton and alpha particle number ratio observed by SWIS holds the potential to provide indirect information about the arrival of Coronal Mass Ejections (CMEs) at the Sun-Earth Lagrange Point L1.
An enhanced alpha-to-proton ratio is considered a sensitive marker of the passage of interplanetary coronal mass ejections (ICMEs) at the L1 point and is crucial for space weather studies. The observations from ASPEX contribute valuable data to space scientists and researchers studying the dynamics of solar wind and its effects on Earth’s space environment.
The successful activation and performance of ASPEX mark a significant milestone for India’s space exploration efforts, showcasing the country’s capabilities in space-based solar observations and contributing to the global understanding of solar-terrestrial interactions.