  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.
