The weakness in the secondary market has failed to dampen activity in the primary market. Five mainboard IPOs, aiming to raise a total of Rs 24,328 crore, are set to hit the market this week. The much-awaited Rs 22,561.6-crore IPO of NSE will open for subscription on September 17. The price band has been fixed at Rs 1,700-1,785 per share. The issue will close on September 21.