Abstract:
Visible emission line coronagraph (VELC) is the prime payload on board India’s first
space solar observatory Aditya-L1. VELC is a unique payload with simultaneous
observational capabilities in imaging, spectroscopy, and spectro polarimetry modes.
VELC is capable of achieving high spatial, spectral, and temporal resolution closer to
the solar limb 1.05R⊙ compared to the existing space and ground-based solar coronagraphs.
VELC consists of a total of 44 optical elements in 18 groups, which are
custom designed and developed to meet the desired performance requirements.
In addition, it consists of four mechanisms out of which two are multioperational with
expected life cycle of million operations. Four detectors (three sCMOS and one
InGaAs) are used to record the data. The performance of the payload depends
on the performance of individual element, subsystems, and the system level performance
of all the elements (such as optics, mechanism, and detectors) together. To
ensure the desired performance levels are achieved, each element/subsystem
should be tested prior to integrating them together. Evaluation of performance of
the integrated system is essential to validate the payload capabilities to meet the
proposed science goals. This paper summarizes the calibration tests carried out on
the integrated system and compares the results obtained with respect to the design
requirements to meet the proposed science goals.
