Plasma-Analyzer Package for Aditya (PAPA) on Board the Indian Aditya-L1 Mission

Abstract

Aditya-L1 is the first space-based solar observatory from India, which is studying the Sun and solar wind from the first Lagrangian point (L1) in a halo orbit. Among the seven payloads, four of them are remote sensing and three are in situ ones. The Plasma-Analyzer Package for Aditya (PAPA) is one among the in situ payloads for exploring the composition of the solar wind and its energy distribution (in the range from 0.01 to 3 keV for electrons and 0.01 to 25 keV for ions) continuously throughout the lifetime of the mission. PAPA has two sensors: the Solar-Wind Electron Energy Probe (SWEEP) indented to measure the solar-wind electron flux and the Solar-Wind Ion Composition AnalyzeR (SWICAR) indented to measure the ion flux and composition as a function of direction and energy as well as electrons. Thus, SWEEP measures only electron parameters, whereas SWICAR has two modes of operation – ion mode in which ion parameters are measured and electron mode in which electron parameters are measured. These two modes in SWICAR are mutually exclusive. The payload is unique and the technologies like the high-voltage (± 5 kV DC) programmable power supply and the dual-mode (electrons and ions) detection of particles using a single sensor (SWICAR) are notable first-time developments. Data from PAPA will provide detailed knowledge of the solar-wind conditions with high time resolution. SWICAR will also provide: (1) the elemental composition of solar-wind ions in the mass range of 1 – 60 amu, and (2) the differential energy flux and abundances of dominant ion species. The key parameters such as bulk speed, density, and kinetic temperature of the solar-wind electrons and dominant ion species can be regularly derived. From these, inferences can be made on the coronal temperatures, plasma sources of suprathermal ion populations, and the nature and dynamics of the solar-wind plasma, with the support of models. In this article, the scientific objectives as well as the design aspects of PAPA payload are discussed in detail along with the calibration and first on board observational results.