Barium Releases from Orbit

Those Alaskans and Canadians ambitious enough to stay up and watch the sky Saturday night, October 28, 1978, had the opportunity to see a new type of scientific experiment likely to be the forerunner of many to come. It was the first time that an earth-orbiting vehicle was used to inject visible chemicals into the high atmosphere.

At 2:07 a.m. Sunday morning (daylight saving time), a command was sent up from the NASA Gilmore satellite tracking station north of Fairbanks to a Delta rocket flying over the polar cap southward towards Alaska. This rocket had launched a Nimbus G weather satellite from Cape Vandenberg 5 days earlier and was following the satellite along in its orbit 600 miles above the earth. Upon receipt of the command, the Delta vehicle ejected four puffs of barium vapor, spaced 40 seconds apart.

Though it was dark at the ground, sunlight impinging upon the released barium atoms plucked off electrons and thereby left the barium atoms in the charged (ionized) state. In that condition, the barium atoms could move freely along the direction of the earth's magnetic field but not transverse to it.

Then the fact that the barium had been released from a fast-moving vehicle came into play. Carrying the orbiting release vehicle's forward speed of 8 km per sec (18,000 mph), the barium ions slammed against the steeply inclined geomagnetic field and scooted upward along the direction of the field. The ions moved so high up over Alaska that they could be seen well up in the northern sky of California and Hawaii. The clouds also were photographed by camera crews at Fairbanks, Fort Yukon, Barrow, Barter Island and Cape Parry, N.W.T.

The primary objective of the experiment was to measure electric fields in the polar cap, but the rapid upward motions of the barium ions proved equally interesting, especially since early results indicate that the barium moved upwards faster than anyone expected.