P78-1 or Solwind was a United States satellite launched aboard an Atlas F rocket from Vandenberg Air Force Base in California on February 24, 1979.

[1] The satellite's mission was extended by several weeks, so that it operated until it was destroyed in orbit on September 13, 1985, to test the ASM-135 ASAT anti-satellite missile.

This caused more and more frequent "under-voltage cutoffs", a condition where the satellite detected a low main bus voltage and automatically shut down all non-vital systems.

Because of the additional burden on the Air Force Satellite Control Network (e.g., extra support and antenna time at the tracking stations), discussions were already underway to terminate the mission.

On September 13, 1985, the satellite was destroyed in orbit at 20:43 UTC at 35°N 126°W / 35°N 126°W / 35; -126 with an altitude of 525 kilometres (326 mi)[5] by an ASM-135 ASAT launched from a US Air Force F-15 Eagle fighter aircraft.