Japan’s H-II Transfer Vehicle-4 (HTV-4) departed from the International Space Station at 12:20 p.m. EDT Wednesday after a one-month stay at the orbiting outpost. The 33-foot-long, 13-foot-diameter cargo vessel, also known by its Japanese name Kounotori-4 (“White Stork”), had delivered 3.6 tons of supplies and equipment to the orbiting laboratory.
Now loaded down with trash and unwanted gear, the HTV was unberthed from the space station’s Harmony module at 8:07 a.m. EDT. Working from the cupola robotics work station, Expedition 36 Flight Engineer Karen Nyberg then used the station’s 58-foot Canadarm2 to slowly maneuver the cargo ship to a position some 30 feet below the ISS.
Due to a problem that arose when the third HTV left the station in September 2012, astronauts were tasked with following a new plan for the release of HTV-4. On the previous occasion, the robot arm had slightly nudged the cargo vessel after releasing it. The extra motion was detected by HTV-3’s onboard computer which then triggered an abort sequence, causing the main engines of the unmanned vehicle to fire in close proximity to the station.
The revised procedure called for the arm to not to be pulled back immediately after release. The delay was to ensure the arm’s end effector would be free of the grapple fixture on the HTV before it was withdrawn.
HTV-4 arrived at the ISS six days after its screaming launch on Aug. 3 from the Tanegashima Space Center in southern Japan, making it the fourth H-II Transfer Vehicle (HTV-4) to journey to the International Space Station. The payload for this flight included equipment, supplies, food, water, clothes, experiments, and a talking robot to the incumbent Expedition 36 crew.
Japanese flight controllers will deorbit HTV-4 on Saturday, Sept. 7, and the spacecraft will burn up as it reenters the Earth’s atmosphere over the Pacific Ocean. Its departure frees the Harmony module’s docking port for the arrival of the Orbital Sciences Corporation’s Cygnus cargo craft in late September.
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