The Japanese H-II Transfer Vehicle-4 (HTV-4) automated resupply spacecraft has arrived at the International Space Station (ISS) following its launch into space from the Tanegashima space center in Japan on August 3. HTV-4’s capture was at 7:22 AM EDT, ahead of berthing at 11:38 AM EDT, which marked a large delivery of critical supplies and research cargo to the orbital outpost.

HTV-4 rendezvous, capture and berthing operations:

HTV-4 was injected into a roughly 200km x 300km orbit by the H-IIB booster, ahead of a series of burns to bring itself in to the ISS just less than one week later.

The HTV-4 rendezvous burns began with Phasing Maneuver-1 (PM-1), followed by Height Adjustment Maneuver-1 (HAM-1), followed by PM-2, which led into Co-elliptic Maneuver-1 (CM-1) and CM-2, and then HAM-0, CM-3, HAM-2, following which HTV-4 was inside the Communication Zone (CZ) with the ISS, and ready for Approach Initiation (AI).

Once inside the CZ, HTV-4 began to use the Proximity Operations (PROX) system, located in the Japanese Experiment Module (JEM) on the ISS, to communicate with the station.

As shown via L2 documentation, the same system will also be used by Orbital Sciences’ Cygnus cargo vehicle to communicate with the ISS when it makes its debut trip to the orbital outpost next month. Orbital and JAXA have worked together on refining this procedure for Cygnus.

Using PROX, HTV-4 performed an AI burn and, and once it reached a desired point below the station, made an R-bar Injection (RI) burn.

The R-bar – a term commonly heard during Space Shuttle dockings to the ISS – stands for Radius bar, and is effectively an imaginary line drawn between the center of the ISS and the center of the Earth, thus ensuring that any vehicle which approaches “up” the R-bar is directly below the ISS.

Once HTV-4 performed the RI burn, it entered the ISS Keep Out Sphere (KOS), following which HTV-4 proceeded to a point 30m below the station, following which it then proceeded to the capture point, thus concluding the rendezvous phase of the mission, and beginning the capture phase.

Following HTV-4’s arrival at the capture point, the spacecraft was put into free drift, inhibiting any thruster activity from occurring during this time.

The free drift command was sent to HTV-4 via the Hardware Command Panel (HCP), which sends commands between the ISS and HTV via the PROX link, in the same way that the Crew Command Panel (CCP) sends commands between the ISS and Dragon spacecraft via the COTS UHF Communication Unit (CUCU).

The HCP previously stood for HTV Command Panel, but the “HTV” has since been replaced with “Hardware” since the Cygnus spacecraft will also use the HCP, as it will utilise the PROX link to communicate with the ISS, as the HTV does.

The HCP, located in the Cupola module on the ISS, allowing the crew to control the Space Station Remote Manipulator System (SSRMS) via the Cupola Robotics Workstation (RWS), with the RWS in the US Lab in “hot backup” standby mode.

The Cupola RWS offers increased situational awareness over the Lab RWS due to the its seven windows.

With their added situational awareness, the SSRMS was translated over the Flight Releasable Grapple Fixture (FRGF) on HTV-4, and “fired” the snares on the SSRMS to close over the grapple pin, following which rigidization of the SSRMS was completed, where the FRGF/HTV is “pulled tight” against the SSRMS, thus securing the HTV-4 firmly in the station’s grip.

Following HTV capture, the SSRMS translated the spacecraft to the Ready To Latch (RTL) position below the Node 2 Nadir Active Common Berthing Mechanism (ACBM) port – the same port used by SpaceX’s Dragon – and the process to attach the HTV to the ISS then began via the Node 2 Nadir ACBM extending hooks to pull the HTV’s Passive CBM (PCBM) into the ACBM.

Four sets of four bolts (16 in total) drove to secure the HTV to the ISS.

HTV-4 hatch opening – including pressurization of the CBM vestibule, opening of the Node 2 Nadir hatch, removal of the Center Disk Cover (CDC) and four Controller Panel Assemblies (CPAs), connection of vestibule jumpers including Inter-Module Ventilation (IMV) ducts, installation of the Vestibule Barrier Assembly (VBA), and finally opening of the HTV-4 hatch – is scheduled to be completed later today or tomorrow, depending on how fast the ISS crew can work.

The HTVs consist of two cargo-carrying sections: The Pressurized Logistics Carrier (PLC) to carry internal cargo, and the Unpressurized Logistics Carrier (ULC) to carry external cargo.

The PLC has space for eight ISS racks in total, however the four aft racks in the PLC are fixed and can only be of the HTV Resupply Rack (HRR) type, whereas the four forward racks can be either HRRs or any other type of International Standard Payload Rack (ISPR).

As such, the HTV the only vehicle capable of delivering racks to the ISS since the retirement of the Space Shuttle (neither the ATV, Dragon or Cygnus can deliver racks to the ISS).

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HTV-4’s eight rack bays, all of which are filled with HTV Resupply Racks (HRRs), are packed with food, water, hygiene items, clothing, spare parts, personal items, and scientific experiments for the ISS crew.

Gaining a lot of media attention ahead of launch has been HTV-4’s a small humanoid robot passenger, known as Kirobo (Kibo Robot Project), which, while much smaller than its bigger cousin Robonaut, has the ability to interact with humans via speech.

Kirobo will stay aboard the ISS until December 2014 to test human-robot voice interaction in space, prior to being returned to Earth.

In addition to its internal cargo located in the PLC, HTV-4 launched some external cargo, attached to the EP in its ULC. The external cargo consists of two spare parts – or “Orbital Replacement Units (ORUs)” – and one new experiment for the outside of the station.

HTV-4 has a mission length of around 35 days, ahead of being unberthed for a destructive re-entry.

(Images via L2, JAXA and NASA).

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