... Auroral Currents . 25H. Birkeland Currents . ... 25c. Space Tether . ... The space tether experiment, a joint venture of the US and Italy, called for a scientific payload--a large, spherical satellite--to be deployed from the US space shuttle at the end of a conducting cable (tether) 20 km (12.5 miles) long. ... One purpose of such a set-up might be to produce electric power, generating current to run equipment aboard the space shuttle. ... A Russian space tether experiment? ...