The fourth Japan Aerospace Exploration Agency H-II Transfer Vehicle, or HTV-4 was installed on its berthing port on the Earth-facing side of the International Space Station’s Harmony node at 11:38 a.m. EDT Friday, delivering 3.6 tons of science experiments, equipment and supplies to the orbiting complex.
Flight Engineer Karen Nyberg, with the assistance of Flight Engineer Chris Cassidy, initially grappled the HTV-4 with the Canadian Space Agency-provided arm at 7:22 a.m. as the Japanese space freighter flew within about 30 feet of the complex. Flight Engineer Luca Parmitano of the European Space Agency joined the two NASA astronauts in the cupola to monitor the systems of the Japanese space freighter during its approach.
At the time of capture, the station was orbiting 260 miles just to the south of South Africa.
With HTV-4 securely in the grasp of Canadarm2, the robotics team at the Johnson Space Center’s Mission Control Center remotely commanded the arm to guide HTV-4 to a ready-to-latch position on the Earth-facing port of the Harmony node. Nyberg and Cassidy then used a laptop computer to conduct the initial bolting and first stage capture of Harmony’s Active Common Berthing Mechanism (ACBM) with HTV-4’s Passive Common Berthing Mechanism (PCBM). Once that was done, the ground team completed the bolting process through second stage capture.
Also known as Kounotori – Japanese for “white stork” because it is emblematic of an important delivery – the HTV is a 33-foot-long, 13-foot-diameter unmanned cargo transfer spacecraft capable of delivering both internal and external supplies and hardware to the station. HTV-4 launched from the Tanegashima Space Center in southern Japan on Aug.3 at 3:48 p.m. (Aug. 4 at 4:48 a.m., Japan time).
After equalizing pressures between the cargo craft and the station, the crew is scheduled to open the hatches Saturday and begin the process of removing the supplies from the Kounotori’s pressurized logistics carrier.
Among the items within Kounotori’s pressurized section are test samples for research experiments inside the Kibo laboratory, a new freezer capable of preserving materials at temperatures below -90 F, four small CubeSat satellites to be deployed from Kibo’s airlock as well as food, water and other supplies for the station’s crew. The pressurized section also is delivering new hardware for the Robotic Refueling Mission to demonstrate robotic satellite-servicing tools, technologies and techniques.
The HTV-4’s unpressurized section is delivering two orbital replacement units (ORUs) – a spare Main Bus Switching Unit (MBSU) and a spare Utility Transfer Assembly (UTA) – to keep the space station’s electrical system operating smoothly. The UTA maintains electrical continuity through the Solar Alpha Rotary Joint, passing electrical power generated by the complex’s huge solar arrays to station elements and payloads, while the MBSU provides switching capabilities for the various power channels and sources. ORUs are modular station components designed to be replaced periodically.
Also inside HTV’s unpressurized cargo hold is the Space Test Program – Houston 4 (STP-H4) payload, which is a suite of seven experiments for investigating space communications, Earth monitoring and materials science.
The exposed pallet to which all the unpressurized cargo is mounted will be removed from Kounotori by Canadarm2, handed off to the Japanese Experiment Module robotic arm and attached to a platform on the Kibo module’s Exposed Facility over the weekend.
In early September, the cargo vehicle will be filled with trash, detached from the station and sent to burn up in Earth’s atmosphere.