The Aditya-L1 mission, India’s first dedicated solar observatory at the first Lagrange point of the Sun-Earth system, carries the Solar Wind Ion Spectrometer (SWIS) as part of the Aditya Solar Wind Particle Experiment (ASPEX) payload suite. Even before settling down at the Halo orbit, AL1-ASPEX-SWIS has been delivering nearly continuous in situ measurements of solar wind ion spectra. Moments of the velocity distribution function (VDFs) have been calculated to derive the solar wind bulk parameters like density, bulk speed, temperature etc. Through this work, we evaluate the performance of AL1-ASPEX-SWIS through comparisons with contemporaneous measurements from the Wind and DSCOVR spacecrafts. A detailed case study of the 07 August 2024 interplanetary coronal mass ejection (ICME) is presented where sharp transitions in bulk speed, thermal speed, and number density were well-aligned with independent observations, confirming the instrument’s capability in capturing dynamic solar wind features. Spectral analysis of kinetic fluctuations revealed a well-defined inertial range with a spectral slope consistent with magnetohydrodynamic (MHD) turbulence. Additionally, a 17-month statistical comparison (January 2024–May 2025) shows strong agreement in bulk velocity ( R^2 ≈ 0.94 with Wind), with expected variability in thermal speed and density due to inter-instrument differences. These results confirm the scientific utility of AL1-ASPEX-SWIS in monitoring both transient events and long-term solar wind conditions.

The interaction between interplanetary coronal mass ejection (ICME) structures can alter the geoeffectiveness of the ICME events in myriad ways. Many aspects of these interaction processes are not well understood. Using the energy spectra measured in two mutually orthogonal top-hat analyzers (THA-1 and 2), which are part of the Solar Wind Ion Spectrometer subsystem of the Aditya Solar Wind Particle EXperiment (ASPEX) on board India’s Aditya-L1 mission, we gain insights into intricate features of ICME–ICME interactions during the 2024 May solar event. We report here an unprecedented two-orthogonal-plane perspective of ICME–ICME interactions for the first time from the L1 point. The investigation reveals a special interaction region formed by the propagation of the forward shock driven by complex ejecta in the preceding ICME. The interaction causes the formation of a downstream region spanning over 13 hr, which propagates in the interplanetary medium. The observations reveal that this region serves as a site for proton and alpha particle energization, and the particles within this region get distributed from one plane to the other. The presence of forward shock and particle energization is confirmed by the energetic particle flux measurements by the SupraThermal and Energetic Particle Spectrometer of ASPEX. These observations provide an unprecedented perspective on how solar wind ions become energized and distributed in an ICME–ICME interaction region.

Aditya–L1, the first dedicated Indian solar mission, was launched on 02 September 2023 and has been placed in a halo orbit around the first Lagrange point (L1) of the Sun-Earth system on 06 January 2024. Aditya Solar wind Particle EXperiment (ASPEX) is one of the three in situ science experiments on board the Aditya–L1 mission that provides measurements of primarily protons and alpha particles in the solar wind, suprathermal, and energetic particles in the energy range from 100 eV to 6 MeV/nucleon. ASPEX consists of two independent spectrometers: the Solar Wind Ion Spectrometer (SWIS: 100 eV – 20 keV) and Supra Thermal and the Energetic Particle Spectrometer (STEPS: 20 keV/nucleon – 6 MeV/nucleon). In this article, we provide the details of the STEPS configuration, ground calibration, and in–flight performance. After the launch of Aditya–L1, two STEPS units were switched–on during the Earth-bound phase on 10 September 2023. STEPS has carried out measurements in the Earth-bound orbit for altitudes ≳ 8 RE, and also in the cruise phase from the Earth to the halo orbit, and has been continuously operational after insertion to the L1 orbit. The performance of STEPS is as expected during all the phases of the mission so far and all its observations are found to be consistent with similar measurements from other contemporary instruments at the L1 point.

The origin, acceleration, and anisotropy of suprathermal ions in the interplanetary medium during quiet time have remained poorly understood issues in solar wind physics. Using measurements (in the energy range of 0.12−1.33 MeV n ^−1 ) by the four detectors that are part of the Supra-Thermal and Energetic Particle Spectrometer (STEPS) of Aditya Solar Wind Particle Experiment (ASPEX) on board the Aditya L1 spacecraft, we address the variations in spectral indices with directions in shorter durations during 2024 January–November, which coincides with the maximum phase of Solar Cycle 25. Three out of four detectors on STEPS—Parker Spiral, Intermediate, Earth Pointing—are in one plane, while the fourth detector—North Pointing—is in a mutually orthogonal plane. The derived spectral indices are found to be −1.99 ± 0.06 regardless of directions, suggesting directionally near isotropic behavior during quiet times. It is also shown that the influence of the Compton–Getting effect is negligible in this assessment of directional isotropy. This result has important ramifications as directional isotropy is assumed while solving the Parker transport equation to explain the acceleration of energetic particles. Further analysis of elemental abundance ratios ( ^3 He/ ^4 He, Fe/O, and C/O) during the same quiet times obtained from the Ultra Low Energy Isotope Spectrometer on board the Advanced Composition Explorer spacecraft suggests possible contributions from the leftover ions from the previous solar energetic particle events in the quiet time suprathermal ion pool.

The Solar Wind Ion Spectrometer (SWIS) instrument is a part of the Aditya Solar Wind Particle Experiment (ASPEX), one of the three in situ observation instruments on board India’s Aditya-L1 spacecraft. SWIS comprises two Top-Hat analysers (THA-1 and THA-2), which have a 360∘ angular coverage in the ecliptic plane and in the plane perpendicular to the ecliptic plane, respectively, with opening angles of ± 1.5^∘ . Both are electrostatic scanning instruments designed to measure the flux, the energy distribution and the angular distribution of the solar wind particles, covering the energy range of 0.1 – 20.0 keV with a 5 s cadence and 8

During its earth-bound phase of the Aditya-L1 spacecraft of India, the Supra-Thermal and Energetic Particle Spectrometer (STEPS) of the Aditya Solar wind Particle EXperiment (ASPEX) was operated whenever the orbit was above 52000 km during 11 - 19 September 2023. This phase of operation provided measurements of energetic ions (with energies 0.1–2 MeV) in the magnetosphere, magnetosheath, and interplanetary medium. Three interplanetary coronal mass ejections (ICME) hit the magnetosphere during this period. This provided opportunity to examine the relative roles of ICME-generated solar energetic particles (SEPs) and substorm generated energetic ions on the magnetosphere. We approach this objective by detailed spectral analyses of energetic ion fluxes measured by two units of ASPEX-STEPS. We identify three distinctly different conditions of the north-south component of the interplanetary magnetic field (IMF B_z = 0, > 0, and < 0) and use the derived spectral indices to understand this relative role. By combining these with the simultaneous energetic ion flux variations from the Advanced Composition Explorer (ACE) around the Sun-Earth first Lagrangian (L1) point and the Geostationary Operational Environmental Satellite (GOES) in the Earth's magnetosphere, we show that the polarity of IMF B_z influences the energetic ion spectra in the magnetosphere by modulating the interplay of the ICME-generated SEP with the energetic particles generated inside the magnetosphere by substorms. Interestingly, ASPEX-STEPS observations also indicate towards directional anisotropy based on spectral indices. This suggests spatially inhomogeneous mixing of energetic ions coming from different source processes.

We present Daksha, a proposed high energy transients mission for the study of electromagnetic counterparts of gravitational wave sources, and gamma ray bursts. Daksha will comprise of two satellites in low earth equatorial orbits, on opposite sides of earth. Each satellite will carry three types of detectors to cover the entire sky in an energy range from 1 keV to >1 MeV. Any transients detected on-board will be announced publicly within minutes of discovery. All photon data will be downloaded in ground station passes to obtain source positions, spectra, and light curves. In addition, Daksha will address a wide range of science cases including monitoring X-ray pulsars, studies of magnetars, solar flares, searches for fast radio burst counterparts, routine monitoring of bright persistent high energy sources, terrestrial gamma-ray flashes, and probing primordial black hole abundances through lensing. In this paper, we discuss the technical capabilities of Daksha, while the detailed science case is discussed in a separate paper.

We present the science case for the proposed Daksha high energy transients mission. Daksha will comprise of two satellites covering the entire sky from 1~keV to $>1$~MeV. The primary objectives of the mission are to discover and characterize electromagnetic counterparts to gravitational wave source; and to study Gamma Ray Bursts (GRBs). Daksha is a versatile all-sky monitor that can address a wide variety of science cases. With its broadband spectral response, high sensitivity, and continuous all-sky coverage, it will discover fainter and rarer sources than any other existing or proposed mission. Daksha can make key strides in GRB research with polarization studies, prompt soft spectroscopy, and fine time-resolved spectral studies. Daksha will provide continuous monitoring of X-ray pulsars. It will detect magnetar outbursts and high energy counterparts to Fast Radio Bursts. Using Earth occultation to measure source fluxes, the two satellites together will obtain daily flux measurements of bright hard X-ray sources including active galactic nuclei, X-ray binaries, and slow transients like Novae. Correlation studies between the two satellites can be used to probe primordial black holes through lensing. Daksha will have a set of detectors continuously pointing towards the Sun, providing excellent hard X-ray monitoring data. Closer to home, the high sensitivity and time resolution of Daksha can be leveraged for the characterization of Terrestrial Gamma-ray Flashes.

Interaction of X-rays with a scintillation detector produces optical photons in the visible range. The spectral and spatial information of the X-ray can be derived by detecting these output photons using a Silicon Photomultiplier (SiPM). Two types of detector modules: CeBr 3 and NaI (Tl), coupled with an array of SiPM are presented here, which are being developed for the future space exploration programs. The development of the front end electronics (FEE) for the charge readout from SiPM for X-ray spectrometer application is presented here which is characterized for SiPM's over -voltages and shaping amplifier's time constant. In this article, both the detector modules are subjected to a wide temperature range to establish a relationship of the SiPM's gain, energy resolution and scintillators' output photon yield with ambient temperature. The test results show that energy resolution improves with higher over -voltage of SiPM and also with lower operating temperature. The gain of the SiPM array shows negative temperature dependence of --0.81 %/degrees C for an over -voltage of 2.5 Volts. To derive the temperature dependency of scintillators' output photons, gain of the SiPM array was made constant by operating it at a fixed over -voltage for a wide temperature range. With the constant gain of SiPM, CeBr 3 scintillator shows negative temperature coefficient of --0.27 %/degrees C and NaI (Tl) shows positive temperature coefficient of -+0.5 %/degrees C for the light output in the temperature range of -31 degrees C to +26 degrees C. (c) 2024 COSPAR. Published by Elsevier B.V. All rights reserved.

Silicon Photomultipliers (SiPMs) are the devices, which along with scintillation detectors can be used for the radiation measurements. We are developing instruments using scintillation detector and SiPM arrays for the measurements of high-energy X-rays and charged particles. These instruments are being developed for the future space exploration programs. Here, we report the work carried out for the characterization of SiPM and its response in the hardened environments. Results from two different experiments are presented. In the first experiment: electrical characterizations of SiPMs from two manufacturers i.e. SensL (now Onsemi) and Ketek have been car-ried out. Three different pixel sizes 20 lm, 35 lm and 50 lm of MicroC series from SensL and 50 lm pixel size of PM3350 series of Ketek have been tested. In order to see 'device - to -device' variations, three SiPMs of each pixel size are used in the experiment i.e. total twelve SiPMs have been characterized for the breakdown voltage, quenching resistor and their temperature dependences. Variations in the gain and microcell recovery time due to temperature are also estimated. In the second experiment: one of the SiPM models (SensL make 35 lm pixel size) has been subjected to various environmental tests mimicking the space conditions. Matching of pre and post I-V mea-surements for each tests confirms that performance of the device is not degraded and hence selected model of SiPM can be explored for the future space instrumentation.(c) 2022 COSPAR. Published by Elsevier B.V. All rights reserved.

Paper mill bamboo sludge (PMBS) and Paper mill lime waste (PMLW) are extensively produced as solid wastes in paper mills. Untreated PMBS and PMLW contain substantial amount of heavy metals (Zn, Pb, Ni, Cd, Cr) in soluble forms. Efficiency of vermiconversion and aerobic composting with these wastes is reported here. Adopted bioconversion systems enhanced the availability of some essential nutrients (N, P, K and Zn) in various combinations of cow dung (CD) with PMBS and PMLW. Colonization of nitrogen fixing bacteria and phosphate solubilizing bacteria considerably intensified under the vermiconversion system. Moreover, significant metal detoxification occurred due to vermiconversion. Various combinations of bioconverted PMBS and PMLW were applied to tissue cultured bamboo (Bambusa tulda) and chilli (Capsicum annum). Accelerated nutrient uptake coupled with improved soil quality resulted in significant production of chilli. Furthermore, vermiconverted PMBS+CD (1:1) and PMLW+CD (1:3) confirmed as potential enriching substrate for tissue cultured bamboo.

We report a detailed theoretical calculation of the electronic band structure of CeO2 in cubic and orthorhombic phases under pressure using a tight-binding linear muffin-tin orbital method (TB-LMTO) within local density approximation (LDA). The compressibility behavior of this compound was discussed in the light of the changes occurring in the electronic structure. Apart from the electronic band structure and structural stability calculations, the density of states (DOS) and Fermi energies (Ef) at various pressures are calculated. The calculated lattice parameter, transition pressure, bulk modulus and the pressure–volume relation are found out to be in good agreement with experimental results.