Explorer 3 (1958 Gamma 1) was launched in conjunction with the IGY by the U.S. Army (Ordinance) into an eccentric orbit. The objective of this spacecraft was a continuation of experiments started with Explorer 1. The payload consisted of a cosmic ray counter (a Geiger-Mueller tube), and a micrometeorite detector (erotion gauge). The Explorer 3 spacecraft was spin stabilized and had an on-board tape recorder to provide a complete radiation history for each orbit. It was discovered soon after launch that the satellite was in a tumbling motion with a period of about 7 s. Explorer 3 decayed from orbit on June 27, 1958, after 93 days of operation.