The Halley Armada is the name of space probes, five of which were successful, sent to examine Halley's Comet during its 1986 sojourn through the inner Solar System, connected with apparition "1P/1982 U1". The armada included one probe from the European Space Agency, two probes that were joint projects between the Soviet Union and France and two probes from the Institute of Space and Astronautical Science in Japan.
Probes involved (in order of closest approach):
Without the measurements from the other space probes, Giotto's closest distance would have been 4,000 km instead of the 596 km achieved.
Other space probes had their instruments examining Halley's Comet:
The Space Shuttle Challenger, on its launch on January 28th, 1986, was carrying SPARTAN-203 with the mission to make observations of Halley's Comet. STS-51L failed to reach orbit, resulting in the total loss of crew and vehicle. That launch failure resulted in the cancellation of dozens of subsequent shuttle missions, including the very next scheduled launch, STS-61-E, which had been slated for a March 6, 1986 launch, with its payload including the ASTRO-1 observatory, which was intended to make astronomical observations of Halley's Comet.