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Register a new userSolar X-ray Monitor (XSM) On-board Chandrayaan-2 Orbiter
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Solar X-ray Monitor (XSM) is one of the scientific instruments on-board Chandrayaan-2 orbiter. The XSM along with instrument CLASS (Chandras Large Area Soft x-ray Spectrometer) comprise the remote X-ray fluorescence spectroscopy experiment of Chandrayaan-2 mission with an objective to determine the elemental composition of the lunar surface on a global scale. XSM instrument will measure the solar X-rays in the energy range of 1-15 keV using state-of-the-art Silicon Drift Detector (SDD). The Flight Model (FM) of the XSM payload has been designed, realized and characterized for various operating parameters. XSM provides energy resolution of 180 eV at 5.9 keV with high time cadence of one second. The X-ray spectra of the Sun observed with XSM will also contribute to the study of solar corona. The detailed description and the performance characteristics of the XSM instrument are presented in this paper.
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Chandrayaan-2, the second Indian mission to the Moon, carries a spectrometer called the Solar X-ray Monitor (XSM) to perform soft X-ray spectral measurements of the Sun while a companion payload measures the fluorescence emission from the Moon. Together these two payloads will provide quantitative estimates of elemental abundances on the lunar surface. XSM is also expected to provide significant contributions to the solar X-ray studies with its highest time cadence and energy resolution spectral measurements. For this purpose, the XSM employs a Silicon Drift Detector and carries out energy measurements of incident photons in the 1 -- 15 keV range with a resolution of less than 180 eV at 5.9 keV, over a wide range of solar X-ray intensities. Extensive ground calibration experiments have been carried out with the XSM using laboratory X-ray sources as well as X-ray beam-line facilities to determine the instrument response matrix parameters required for quantitative spectral analysis. This includes measurements of gain, spectral redistribution function, and effective area, under various observing conditions. The capability of the XSM to maintain its spectral performance at high incident flux as well as the dead-time and pile-up characteristics have also been investigated. The results of these ground calibration experiments of the XSM payload are presented in this article.
The Solar X-ray Monitor (abbreviated as XSM) on board Indias Chandrayaan-2 mission is designed to carry out broadband spectroscopy of the Sun from lunar orbit. It observes the Sun as a star and measures the spectrum every second in the soft X-ray band of 1 - 15 keV with an energy resolution better than 180 eV at 5.9 keV. The primary objective of the XSM is to provide the incident solar spectrum for the X-ray fluorescence spectroscopy experiment on the Chandrayaan-2 orbiter, which aims to generate elemental abundance maps of the lunar surface. However, observations with the XSM can independently be used to study the Sun as well. The Chandrayaan-2 mission was launched on 22 July 2019, and the XSM began nominal operations, in lunar orbit, from September 2019. The in-flight observations, so far, have shown that its spectral performance has been identical to that on the ground. Measurements of the effective area from ground calibration were found to require some refinement, which has been carried out using solar observations at different incident angles. It also has been shown that the XSM is sensitive enough to detect solar activity well below A-class. This makes the investigations of microflares and the quiet solar corona feasible in addition to the study of the evolution of physical parameters during intense flares. This article presents the in-flight performance and calibration of the XSM instrument and discusses some specific science cases that can be addressed using observations with the XSM.
Solar X-ray Monitor (XSM) instrument of Indias Chandrayaan-2 lunar mission carries out broadband spectroscopy of the Sun in soft X-rays. XSM, with its unique features such as low background, high time cadence, and high spectral resolution, provides the opportunity to characterize transient and quiescent X-ray emission from the Sun even during low activity periods. It records the X-ray spectrum at one-second cadence, and the data recorded on-board are downloaded at regular intervals along with that of other payloads. During ground pre-processing, the XSM data is segregated, and the level-0 data is made available for higher levels of processing at the Payload Operations Center (POC). XSM Data Analysis Software (XSMDAS) is developed to carry out the processing of the level-0 data to higher levels and to generate calibrated light curves and spectra for user-defined binning parameters such that it is suitable for further scientific analysis. A front-end for the XSMDAS named XSM Quick Look Display (XSMQLD) is also developed to facilitate a first look at the data without applying calibration. XSM Data Management-Monitoring System (XSMDMS) is designed to carry out automated data processing at the POC and to maintain an SQLite database with relevant information on the data sets and an internal web application for monitoring data quality and instrument health. All XSM raw and calibrated data products are in FITS format, organized into day-wise files, and the data archive follows Planetary Data System-4 (PDS4) standards. The XSM data will be made available after a lock-in period along with the XSM Data Analysis Software from ISRO Science Data Archive (ISDA) at Indian Space Science Data Center(ISSDC). Here we discuss the design and implementation of all components of the software for the XSM data processing and the contents of the XSM data archive.
Alpha Particle X-ray Spectrometer (APXS) is one of the two scientific experiments on Chandrayaan-2 rover named as Pragyan. The primary scientific objective of APXS is to determine the elemental composition of the lunar surface in the surrounding regions of the landing site. This will be achieved by employing the technique of X-ray fluorescence spectroscopy using in-situ excitation source Cm-244 emitting both X-rays and alpha particles. These radiations excite characteristic X-rays of the elements by the processes of particle induced X-ray emission (PIXE) and X-ray fluorescence (XRF). The characteristic X-rays are detected by the state-of-the-art X-ray detector known as Silicon Drift Detector (SDD), which provides high energy resolution as well as high efficiency in the energy range of 1 to 25 keV. This enables APXS to detect all major rock forming elements such as, Na, Mg, Al, Si, Ca, Ti and Fe. The Flight Model (FM) of the APXS payload has been completed and tested for various instrument parameters. The APXS provides energy resolution of 135 eV at 5.9 keV for the detector operating temperature of about -35 deg C. The design details and the performance measurement of APXS are presented in this paper.
The Solar X-ray Spectrometer (XSM) payload onboard Chandrayaan-2 provides disk-integrated solar spectra in the 1-15 keV energy range with an energy resolution of 180 eV (at 5.9 keV) and a cadence of 1~second. During the period from September 2019 to May 2020, covering the minimum of Solar Cycle 24, it observed nine B-class flares ranging from B1.3 to B4.5. Using time-resolved spectroscopic analysis during these flares, we examined the evolution of temperature, emission measure, and absolute elemental abundances of four elements -- Mg, Al, Si, and S. These are the first measurements of absolute abundances during such small flares and this study offers a unique insight into the evolution of absolute abundances as the flares evolve. Our results demonstrate that the abundances of these four elements decrease towards their photospheric values during the peak phase of the flares. During the decay phase, the abundances are observed to quickly return to their pre-flare coronal values. The depletion of elemental abundances during the flares is consistent with the standard flare model, suggesting the injection of fresh material into coronal loops as a result of chromospheric evaporation. To explain the quick recovery of the so-called coronal First Ionization Potential (FIP) bias we propose two scenarios based on the Ponderomotive force model.
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