Launch Vehicle: Scout
First Launch: September 1959 (Transit 1A)
Total Weight: 135 pounds (Transit 5A)
Diameter: 18 inches (without solar panels deployed)
Height: 12 inches (without antenna deployed)
Systems: Two ultrastable oscillators operating on 150 and 400 MHz plus a digital clock

The Transit spacecraft were the first US military navigational satellites. They were originally developed by the US Navy to help ballistic-missile submarines fix their locations to an accuracy of 1.1 miles. The Transit pulse-doppler navigational spacecraft, designed for the Navy by Johns Hopkins University beginning in 1958, were launched from Vandenberg AFB and were controlled by the Naval Astronautics Group at Point Mugu NAS in California. The Transit satellites were designed to have a useful lifespan of three months, and by 1968 three series of them had been put into service in 23 successful launches. The program was declassified and made available for civilian use in 1967. At about the same time, the Transit-type spacecraft were given numerical designations in the Navsat series, which ultimately included the Transit Improvement Program (TIP) and NOVA spacecraft.