Vanguard 2 or Vanguard II is an Earth-orbiting satellite launched February 17, 1959, aboard a Vanguard SLV 4 rocket as part of the United States Navy's Project Vanguard. The success of this launch was an important part of the space race between the United States and the Soviet Union. Vanguard 2 was the first weather satellite. The satellite was designed to measure cloud-cover distribution over the daylight portion of its orbit, for a period of 19 days, and to provide information on the density of the atmosphere for the lifetime of its orbit (about 300 years).