The military department is authorized and empowered to procure and pay for group death and dismemberment insurance coverage to protect members of the National Guard and their estates, or their named beneficiaries, to the extent of twenty-five thousand dollars ($25,000.00) per person, if death or dismemberment occurs while performing authorized state military duty. The premiums on such insurance shall be calculated on a man-day basis and coverage shall be in effect only during such duty.