engineer. The successful cold-fission test was supervised by Ishfaq Ahmad and witnessed by key high officials including PAEC chairman Munir Ahmad Khan; General Khalid Mahmud Arif, Chief of Army Staff; and Ghulam Ishaq Khan, then Chairman Senate. Results and aftermath The cold test of 1983 by PAEC was a major step in Pakistan's nuclear weapons program. However, it did not mean PAEC had produced Pakistan's nuclear bomb. As Houston Wood, Professor of Mechanical & Aerospace Engineering, University of Virginia, Charlottesville, USA, points out in his article on gas centrifuges, "The most difficult step in building a nuclear weapon is the production of fissile material", yet PAEC had not produced any fissile material by 1983. So, the most difficult step in building a nuclear weapon had yet to be taken by PAEC. The need to improve and perfect the design of the first nuclear device required constant testing. 24 different cold tests were conducted between 1983 and 1990 with the help of mobile diagnostic equipment. These tests were carried out in 24 horizontal-shaft designated weapon-testing laboratories measuring in length, which were bored inside the Kirana Hills. The United States Vela satellites began monitoring the region, leading to the testing program being moved to Kala Chitta Range. The test sites were abandoned and the Pakistani government opened the region for public tourism in 1990.It also has Radar Station for monitoring the airspace of Pakistan. Development and the test teams Pakistan Atomic Energy Commission Munir Ahmad Khan – Chairman, Pakistan Atomic Energy Commission (PAEC) Ishfaq Ahmad – Member (Technical) of PAEC. Samar Mubarakmand – Director-General of the Diagnostics Group of PAEC (DG) Hafeez Qureshi – Director-General of the Directorate of Technical Development (DTD) Zaman Sheikh -Directorate-General of the Wah Group of PAEC (WG). Naeem Ahmad Khan – Director-General of Radiation and Isotope Applications Division (RIAD). Hameed Ahmed Khan – Director-General of the Radiation Physics Division (RPD). Masud Ahmad – Director-General of Theoretical Physics Group (TPG). Special Works Development Major-General Michael John O'Brian, Pakistan Air Force — Director-General of the Special Works Development Brigadier-General Muhammad Sarfaraz, Pakistan Army — Deputy Director of Special Works Development Government observers General Khalid Mahmud Arif, Pakistani Army — Vice Chief of Army Staff Ghulam Ishaq Khan, (SP) – Chairman of the Senate of Pakistan Vice-Admiral Iftikhar Ahmed Sirohey, Pakistan Navy — Directorate-General Naval Weapon Engineering Branch (WEB). See also List of mountain ranges of Pakistan List of mountain