The July 22, 1975 White House Memo signed by Henry A. Kissinger, approving the launch of the SNAP-19 radioisotope thermoelectric generators may not seem significant, however this document was a "Go No Go" for the mission. With the green light to launch, the mission could continue. Because of the hazards of the SNAP-19s, as well as the political climate, these approvals were not assumed. During the approval pending period there was a strong level of confidence, however with the cold war and and activities in Vietnam still very volatile, these decisions were carefully weighed. Fortunately, the progress of the Viking mission and the parallel efforts of the Soviet Union to reach Mars. resulted in some collaboration between scientists, and in fact in July of 1975, just before the launch of Viking, the Apollo–Soyuz Test Project (ASTP) was agreed upon forming the first joint Soviet and US space flight. This was significant, and marked the ending of the space race, and the beginning of public cooperation and formal collaboration between the nations.