The National Aeronautics and Space Administration and the German Ministry for Education and Science (BMBW) are planning to release a cloud of barium and strontium in space during the second half of 1970. In this experiment an 18-kg mixture of barium metal and copper oxide powder will be ignited and released at an altitude of approximately 5 earth radii in the general region of 10°N, 75°W. Launch windows for the release are: August 25 through September 8, 1970; September 23 through October 6, 1970; October 20 through November 3, 1970; and November 18 through December 1, 1970.
The release must be made at a time when the ground observing stations are in darkness, but the cloud must also be illuminated by the sun at this time. The exact time of release varies between launch windows. It is also governed by the final trajectory of the Scout launch vehicle. Consequently, the exact time of release cannot be specified at this time. It will, in general, be around 0300 UT, that is, pre-midnight local time.