In addition to the major tests involving explosions, many subcritical minor trials were also carried out between June 1955 and April 1963. While the major tests had been carried out with some publicity, the minor tests were carried out in absolute secrecy. The "Kitten" tests tested bomb components, while "Tims" and "Rats" were early subcritical hydronuclear tests. The "Vixen" tests involved safety testing of nuclear weapons—assuring that the core would not accidentally undergo criticality in the event of a fire or crash. These minor tests left a legacy of radioactive contamination at Maralinga.