Exploring the outer emission corona spectroscopically by using Visible Emission Line Coronagraph (VELC) on board ADITYA-L1 mission

Characterizing Spectral Channels of Visible Emission Line Coronagraph of Aditya-L1

“…It should be noted that increasing the slit width results in the broadening of the spectral lines and hence a reduction in the spectral resolution. Singh et al (2019) studied the effect of increasing the slit width for the three spectral channels of VELC. Their analysis also indicates that the slit width should be increased to enhance the SNR at the same time, optimizing the spectral resolution to meet the scientific requirements.…”

“…where "dispersion" corresponds to 28.4, 31, and 227.3 mÅ/pixel for the three channels, respectively (Singh et al, 2019). A pixel size of 6.5 μm for the visible spectral channels and 25 μm for the IR channel result in pixel scales of 1.25 arcsec pixel -1 and 4.8 arcsec pixel -1 , respectively.…”

“…The solid angle subtended is calculated using the slit scale and pixel scale along the horizontal and vertical dimensions, respectively. The efficiency of the spectral channels in the visible and IR wavelengths is taken to be ∼ 5 and ∼ 4%, respectively (Singh et al, 2019).…”

“…It was reported by Singh et al (2019) that the slit width of VELC needs to be increased for achieving the desired scientific goals. For obtaining an optimized value of slit width, we used the synthetic spectra for analysis.…”

“…Increasing the number of incident photons also imposes the challenge of attaining sufficient SNR without saturating the detector. The CMOS sensors used for the visible spectral channels have a full well capacity of ∼30,000 electrons in both high and low gain, whereas for INGAS (InGaS) used for the IR detector, it is ∼30,300 electrons in the high-gain mode (Singh et al, 2019). The IR channel is also equipped with a spectropolarimeter mode which will operate in the high-gain mode with a fixed exposure time of 500 ms.…”