Blazing a Trail Around the Sun

Blazing a Trail Around the Sun

First series of interplanetary Pioneers, extensions of the initial Pioneer program completed with Pioneer 5 in 1960, were seeking a better understanding of the Sun and its impact on the space environment. About 37 inches in diameter and 35 inches high, and weighing about 140 pounds, the Pioneer spacecraft allowed scientists to predict space “weather” with increasing accuracy.

The first of the new series, Pioneer 6, was launched in 1965 on an “inward” path. Its solar orbit oranges more than 20 million miles inside the Earth’s orbit. Pioneer 7, launched in 1966 and Pioneer 8, launched in 1967, both followed “outward” paths, ranging as far as 13 million and 9 million miles, respectively, beyond Earth’s orbit around the Sun. Pioneer 9 was launched in 1968 into another inward orbit like that of Pioneer 6.

Two Velas undergoing non-reflective testing of electronic systems in a plastic-spiked sound-proof chamber. Photo in public domain

Nuclear watchdogs patrol dual circular orbit

An intricate three-part launch and injection technique is used to position TRW’s Vela nuclear detection satellites in orbit. First, two satellites are tandem-launched into a wide-ranging elliptical transfer orbit. Next, as they reach the 60-70,000-mile apogee of the transfer orbit for the first time, an injection motor – mounted on each spacecraft – fires and sends one of the satellites into a circular orbit, leaving its twin in the transfer orbit. Then, with the second Vela completes one more revolution and returns to the original apogee, it too is injected into a circular orbit. By this time, the first Vela has traveled in its orbit to a point about 150 degrees away or almost to the other side of the Earth. The two spacecraft are then in the same orbit on nearly opposite sided of the planet.

Designed and manufactured by TRW for the Air Force, the 500-pound spacecraft carry delicate sensors which can detect nuclear weapons testing anywhere on Earth or in the atmosphere – or even as far away as Venus and Mars.