The Upstream No. 1 missile uses a capsule altimeter for altitude control, which has a large error; it uses a cone scanning radar, which has poor anti-electronic and wave interference performance. In October 1973, Nanchang Aircraft Factory first replaced the two-centimeter terminal guidance radar and radio altimeter in response to the above defects, and successfully conducted a flight test of the improved Upstream No. 1 craft bomb. In May 1974, the Navy requested approval from the Central Military Commission and the State Planning Commission for the development of the Upstream No. 1 improved missile. In July of the same year, the National Defense Industry Office officially assigned the task of modifying the Upstream No. 1 missile and named it the Upstream No. 1A missile. The modification work was carried out by Nanchang Aircraft Factory. The main improvements were the use of a small monopulse transistorized radar developed by Factory 781, a radio altimeter produced by Factory 782, and a simplified engine from Factory 111. During this period, under the leadership of Jiang Longtan, Factory 232 used integrated circuit operational amplifiers and first designed an analog computer control system to meet the control requirements for missile ultra-low altitude flight trajectories. In the third quarter of 1975, low-altitude simulation tests showed that the missile could track and capture targets normally while flying across the sea.
From 1977 to 1980, the Upstream No. 1A missile conducted three finalization tests. The missile sometimes hit the target and sometimes failed to fly. When analyzing the reasons, in addition to equipment failures such as the radar and pilot on the missile, technicians at the naval test base also found that the natural frequency of the missile was related to the hit situation, and believed that the vibration environment on the missile was also an important reason for the test failure. In order to clarify these problems, Nanchang Aircraft Factory conducted a comparative test between the Upstream No. 1 A missile and the Upstream No. 1 missile, and found that the frequency of the Upstream No. 1 A missile was low.
In February 1981, He Wenzhi, deputy director of the Three Machinery Department, presided over a fault analysis and coordination meeting to determine the technical measures to strictly ensure the quality of finished parts and carry out comprehensive management. Under the leadership of Peng Lisheng, director of the Design Institute of Nanchang Aircraft Factory, a large number of tests were conducted, and measures such as adding shock absorbers to the counterweight of the radar cabin and reducing the instantaneous impact of the ignition of the electric detonator on the radio altimeter were taken. Factory 781 has adopted shock-absorbing measures for self-frequency adjustment and selected "seven special" components to improve product reliability. In 1982, the missile conducted its fourth final test and was successful. In March 1984, the Conventional Military Products Finalization Committee of the State Council and the Central Military Commission approved the design and finalization of the Upstream No. 1 A missile. The successful development of the Upstream No. 1A missile has improved the anti-interference ability of the missile and has taken a gratifying step towards achieving ultra-low-altitude flight.
While developing the Upstream No. 1A missile, Nanchang Aircraft Factory began research on continuing to lower its altitude. After multiple flight tests at sea, the Upstream No. 1A missile achieved two altitude-lowering flights for the first time in November 1979, indicating that the matching problem between the radar system and the pilot system during the missile's sea-skimming flight has been basically solved. In particular, a special study was conducted on the "multi-finger" phenomenon that occurs when the flight altimeter is lowered and the "multi-path" effect that occurs on radar, and satisfactory results were achieved. In 1983, the Upstream No. 1 secondary altitude-lowering missile passed ministerial appraisal, indicating that the missile's ultra-low-altitude flight performance had reached a relatively advanced level.