The Japanese Aerospace Exploration Agency will test an early space junk removal tether prototype using its HTV-6 robotic cargo ship, as seen in this artist's illustration. The cargo ship launched to the International Space Station in December 2016.http://www.space.com/35059-japan-space-junk-tether-tech.html
So my source, with high school and college Japanese, did some translating of the labels in the video.They discuss orbital debris, and talk about the KITE experiment being done after the HTV leaves the ISS.They call the device an electrical "taser".The tether is 700 meters long.There is a disclaimer that, for the purposes of easy explanation, the cable is not shown at full length.The "taser" end mass is ejected by a big spring.(Opinion: This seems way too simplistic and uncontrolled. Let's hope there are more cable guides than shown.)In the end mass there is a brake on the cable to effect a smooth stop. There are optical cameras and a lidar, which may be the same one used for rendezvous with the ISS. (It looks like about a 15-20 degree square field of view in the video.)The lidar tracks the end mass and the HTV Kounotori changes attitude to keep it pointed at the end mass as it swings around. There are boxes for data storage, and electrical power supply, and command and data handling.There is a diagnostic box with a large D connector.The electron emitter (literally "electric child launch type") couples to the plasma.There seem to be two of these of different sizes, one with a cover that opens.When the current flows up the wire, and the Earth's magnetic field lines cross the velocity direction, the Lorentz force acts as a drag.They plan to turn the current on and off and sense the creation and cessation of the Lorentz force.At the end of the experiment the cable is severed. Kounotori reenters the atmosphere, followed by the end mass a few months later.JAXA plans on using the KITE method to deorbit large space debris.
There's a quite detailed overview here too: http://spaceflight101.com/htv-6/htv-kite-experiment/
The Exposed Pallet (EP) of KOUNOTORI6 was reinstalled into KOUNOTORI6's Unpressurized Logistics Carrier (ULC) at 11:20 a.m., January 23.Meanwhile, station crew continues cargo and trash transfer between the Pressurized Logistics Carrier (PLC) and the ISS. KOUNOTORI6 will be unberthed from Harmony (Node 2) on January 27 and will be released by the Space Station Remote Manipulator System (SSRMS) on January 28, at 0:30 a.m.*All times are Japan Standard Time (JST. UTC + 9 hours)