Visible Emission Line Coronagraph (VELC) on-board Aditya-L1 space mission, is an internally occulted solar coronagraph to carry out simultaneous imaging, spectroscopic and spectro-polarimetric observations of the solar corona from close to the solar limb. Some of the primary science goals for the payload are: (i) to understand heating of the solar corona; (ii) observations of the origin and development of coronal mass ejections near the Sun; (iii) observations of coronal magnetic field topology and measurement of their strength over active regions; (iv) coronal loop oscillations. To realize the above, VELC has been designed to image the solar corona at 500 nm wavelength with a pixel resolution of 2.5’’ over a field of view (FOV) of 1.05 – 3 solar radii. In addition, the payload can carry out simultaneous multi-slit spectroscopic observations at three emission lines, viz. Fe XIV (530.3 nm), Fe XI (789.2 nm) and Fe XIII (1074.7 nm) with a spectral resolution of 28, 31 and 202 mÅ/pixel respectively, over a FOV of 1.05 – 1.5 solar radii. There is also dual-beam spectro-polarimetry channel for coronal magnetic field observations at 1074.7 nm over a FOV of 1.05 – 1.5 solar radii. The spectroscopic and spectro-polarimetric observations can be either in sit and stare (or) raster scan mode. There is also option to choose spectral line(s) of interest. There are four slits in total. Each slit has a width of ~50um and they are separated by 0.75 solar radii. The continuum channel is capable of producing one image of the solar corona every 15 sec. The exposure time for the spectroscopic observations are in the range of ~148 msec – 100 sec and for spectro-polarimetric observations are in the range of ~53 msec – 603 msec. Observations are also possible in different spatial and temporal binning modes for all the channels. Feasibility to observe in window mode where only the east or west or north or south halves in the FOV is also there.

Description of the VELC FOV: The background is the white light picture of the solar corona obtained from Maharastra, INDIA during the total solar eclipse that occured on 22 January 1898. The inner most filled black circle is the solar photosphere. The radii of the yellow, red and white open circles are ~1.05 R, ~1.5 R and ~3.0 R (where R is the solar radius = 0.696 million km). The vertical lines in red indicate the home positions of the 4 slits used for spectroscopic and spectro-polarimetric observations. The width of each slit ~0.01R and they are separated by ~0.75 R.
For more details, visit: https://velc.iiap.res.in

The Solar Ultraviolet Imaging Telescope (SUIT), aboard ISRO’s Aditya-L1 mission, is a cutting-edge instrument designed to observe the Sun in the near-ultraviolet (UV) wavelength range between 200–400 nm. Positioned at the first Lagrange point (L1), SUIT offers continuous, high-resolution images with a good cadence in eleven spectral bands that cover the photosphere and chromosphere of the Sun. The telescope features an off-axis Ritchey-Chr´etien design, with a field of view of 1.5 R⊙ and a plate scale of 0.7 arcsec per pixel. The cadence of SUIT’s observations can range from 4 to 40 seconds, depending on the mode of operation, allowing for flexible monitoring of solar events from rapid flares to slower, evolving features.
The filters enable SUIT to examine various solar layers, providing insights into phenomena like solar flares, jets, filament evolution, and eruptions. By mapping the Sun’s atmospheric dynamics, SUIT helps scientists investigate the transfer of mass and energy between different layers of the solar atmosphere. Additionally, for the first time, SUIT enables the measurement and monitoring of spatially resolved solar spectral irradiance in the near-UV range, which is crucial for Sun-Earth connection climate studies.
For more details, visit: https://suit.iucaa.in

Solar Low Energy X-ray Spectrometer (SoLEXS), one of the payloads on Aditya-L1, is a sun-as-a-star spectrometer in the energy range of 2 keV to 22 keV. The instrument is developed by U.R. Rao Satellite Centre, Bangalore. The primary science objectives of SoLEXS payload are: (1) Flares and Coronal Heating (2) Coronal Abundances and FIP (3) Flare – CME studies. The instrument employs Silicon Drift Detector (SDD) as sensor element to detect energy. To cover an extensive dynamic range from A class to X class flares, the payload has two apertures with areas of 7.1 and 0.1 mm2. The on-board processing unit histograms the recorded energies of the x-ray events to build a spectrum every second to capture the impulsive solar activity.

High Energy L1 Orbiting X-ray Spectrometer (HEL1OS) is the hard X-ray spectrometer on Aditya-L1 Solar Mission by ISRO. It operates in the wide X-ray energy band of 10 – 150 keV for solar flare studies. The primary objectives of the HEL1OS payload are: (a) Study of explosive energy release, acceleration and transport of electrons during Solar flares using fast timing measurements and high resolution spectra; (b) Quasi-periodic Pulsations (QPPs) of hard X-rays during Solar flares to understand its connection with particle acceleration mechanisms. HEL1OS is designed with two different types of detectors – (a) Cadmium Telluride (CdTe) operating in 10 – 40 keV band and, (b) Cadmium Zinc Telluride (CZT) operating in 20 – 150 keV band. HEL1OS was commissioned on Oct 27, 2023 and it has been monitoring the Sun for hard X-ray activities ever since. The main data products of HEL1OS include Type-II Spectra and light curves in 10 – 150 keV X-ray band.
HEL1OS has been developed by the Space Astronomy Group of the U. R. Rao Satellite Centre, ISRO, Bengaluru, in collaboration with different entities of the centre.
For more details, visit: https://www.ursc.gov.in/hel1os.jsp

The Aditya Solar wind Particle EXperiment (ASPEX) is a scientific payload onboard the Aditya-L1 mission, designed to study solar wind, suprathermal, and energetic particles in the interplanetary medium. Its primary objective is to investigate the composition, origin, and acceleration and anisotropy mechanisms of these particles as well as their space weather impact. ASPEX covers a broad energy range, from 100 eV to 6 MeV/n, and observes particles arriving from multiple directions. Since the full energy range cannot be measured by a single device, ASPEX is divided into two subsystems: the Solar Wind Ion Spectrometer (SWIS) and the Supra-Thermal and Energetic Particle Spectrometer (STEPS), each having distinct design philosophies and measurement techniques. For more details, visit: https://www.prl.res.in/ASPEX/

The SWIS subsystem uses an electrostatic analyzer with a large area microchannel plate (MCP) imaging detector to analyze ion energy along with its arrival directions in the energy range of 100 eV – 20 keV. SWIS has two Top Hat Analyzers, (THA-1 and THA-2). Of these two, THA-1 has a mass analyzer. THA-1 has a field of view of nearly 360° in the plane of the ecliptic, while THA-2 has a field of view of nearly 360° perpendicular to the ecliptic plane.

The STEPS subsystem uses a custom designed Si-PIN detector to measure the spectrum of proton and alpha particles in the energy range of 20 keV/n to 6 MeV/n. It consists of six detector units, each oriented in different directions to sample particles from various regions: Sun Radial (SR), Parker Spiral (PS), Earth Pointing (EP), Intermediate (IM) between SR and PS, North of the Ecliptic plane (NP), and South of the Ecliptic plane (SP). Each of the six detector units has a magnetic assembly (MA), comprising SmCo permanent magnets to avoid electrons from reaching the detector and hence to avoid possible detector saturation.

Plasma Analyser Package for Aditya (PAPA) is one among the seven payloads onboard Aditya-L1 spacecraft, meant for exploring the composition of 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) from the first Lagrangian point (L1) of the Sun-Earth system. PAPA has two sensors; Solar Wind Electron Energy Probe (SWEEP) and Solar Wind Ion Composition AnalyseR (SWICAR). SWEEP is intended to measure the solar wind electrons (energy and directional flux). SWICAR is capable to measure the solar wind ions (energy, directional flux and composition) as well as the electrons (energy and directional flux). Thus, basically, SWICAR operates in two modes - ion mode where ion parameters are measured and electron mode where electron parameters are measured, whereas SWEEP operates only in electron mode. The two modes in SWICAR are mutually exclusive. Data from PAPA would provide detailed knowledge of the solar wind conditions with high time resolution. The key parameters such as bulk speed, density and kinetic temperature of the solar wind electrons and dominant ion species can be derived.

Magnetometer onboard Aditya-L1 provides continuous measurements of local, interplanetary magnetic field (IMF) at the location of the spacecraft. The payload consists of two identical tri-axial fluxgate magnetometers placed on a boom at 3m and 6m from the spacecraft. The sensor located at 6m is named as MAG1, while the sensor at 3m is labelled MAG2. The magnetometer dataset has a highest cadence of 128ms.The magnetometer captures the IMF as well as a slow varying component of spacecraft field. Dataset from both the sensors is used to identify spacecraft-induced component and separate it from the measurements to obtain IMF. The Level2 dataset is provided at a minimum cadence of 10 seconds in different standard frames like GSE, GSM. These measurements are useful in studying the dynamics of solar-driven IMF and its effect on the Earth’s magnetosphere.