R. Thampi, Space Physics Laboratory, Vikram Sarabhai Space Centre, satheesh_thampi@vssc.gov.in
  A. Bhardwaj, SPL, VSSC, anil_bhardwaj@vssc.gov.in
  G. Nampoothiri, SPL, VSSC, govind_g@vssc.gov.in
  V. P, AVN, VSSC, vinod_p@vssc.gov.in
  M. SV, SPL, VSSC, sv_mohankumar@vssc.gov.in

Solar wind is a stream of magnetized plasma from the Sun, which carries the solar magnetic field along with it, called the interplanetary magnetic field (IMF). The solar wind particles gyrate around the magnetic field with their thermal velocity (proton thermal velocity ~50 km/s and electron thermal velocity ~1000 km/s); whereas the bulk velocity of flow is on an average ~400 km/s. The composition of the solar wind contains an imprint of the composition of solar corona, modified by solar wind processes. Accurate measurements of its composition aids in separating the effects of different processes from the original makeup of the corona. Plasma Analyser Package for Aditya (PAPA) is one of the seven payloads for the upcoming Aditya-L1 Mission for exploring the Sun. It aims at studying the composition of solar wind and its energy distribution. PAPA contains two sensors: Solar Wind Electron Energy Probe (SWEEP) and Solar Wind Ion Composition AnalyseR (SWICAR), which would measure, respectively, the solar wind electron and ion fluxes and composition as a function of direction and energy. SWICAR
also provides: (1) the elemental composition of solar wind low energy ions, and (2) the differential energy spectra, abundances of dominant ion species in the mass range 1-30 amu with energies between 0.01 and 25 keV/q. From the differential energy spectra the bulk speed, density and kinetic temperature of the dominant solar wind ion species can be derived routinely, and which can be used to identify sources of low energy ion populations as well as the nature and dynamics of solar wind plasma. Major subsystems of the PAPA payload are the Front End Electronics (FEE), Papa Processing Unit (PPU) and the programmable High Voltage Power Supply (HVPS). The FEE translates the incident charged particles into impulses. These impulses are processed by the subsequent electronics. PPU is the central control for the payload, and acts as the interface between sensors and the spacecraft. It also provides the tele-command interface, decoding and execution, interface to spacecraft telemetry for science data and HK data transfer, generate Sensor ON/OFF commands, ramp HVPS based on ground commands, and time stamp all data with respect to universal time. The HVPS caters to all biasing requirements of the analyser, guiding plates and detectors of both SWEEP and SWICAR sensors. Various design aspects and few test results of the PAPA payload are presented and discussed in detail in this paper.