Before the launch of the Jawaharlal Nehru National Solar Mission (JNNSM) in 2010, not much attention was paid to solar radiation assessment in India. The country had 45 meteorological stations managed by the Indian Meteorological Department to operate as weather observatories, which were not equipped to collect data on direct normal irradiance (DNI), a measure of solar radiation received per unit area, along with weather parameters at various locations.