The Japanese H-II Transfer Vehicle-3 (HTV-3) automated resupply spacecraft has arrived at the International Space Station (ISS) following its launch into space from the Tanegashima space center in Japan last Friday (July 21). HTV-3’s capture was at 8:23 AM EDT, ahead of berthing at 10:34 AM EDT, which marked a large delivery of critical supplies and research cargo to the orbital outpost.
HTV-3 rendezvous, capture and berthing operations:
Following HTV-3’s injection into a roughly 200km x 300km orbit by the H-IIB booster last Friday, HTV-3 began a series of burns to bring itself in to the ISS just less than one week later. For this mission, the second stage of the H-IIB booster performed a de-orbit burn shortly following launch for a destructive re-entry, as part of a capability demonstration that JAXA have since confirmed was successful.
The HTV-3 rendezvous burns – performed using four newly designed Japanese engines, as the two previous HTVs used engines made by US company Aerojet – 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-3 was inside the Communication Zone (CZ) with the ISS, and ready for Approach Initiation (AI).
Once inside the CZ, HTV-3 began to use the Proximity Operations (PROX) system, located in the Japanese Experiment Module (JEM) on the ISS, to communicate with the station. The same system will also be used by Orbital Sciences’ Cygnus cargo vehicle to communicate with the ISS. Using PROX, HTV-3 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-3 performed the RI burn, it entered the ISS Keep Out Sphere (KOS), following which HTV-3 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-3s 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-3 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, allowed Expedition 32 Flight Engineers Joe Acaba and Aki Hoshide 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 Cupola’s seven windows – one of which (window 2) was damaged recently by a piece of Micro Meteoroid Orbital Debris (MMOD).
While the MMOD strike was only small, and with the Cupola windows being comprised of multiple, replaceable debris panes, pressure panes, and scratch panes to protect against such incidents, Mission Control Houston (MCC-H) requested the ISS crew to close the protective external shutter over Cupola window 2 until the damage could be analysed and cleared. As expected, the analysis showed that the damage was not of concern, and the window 2 shutter was cleared to be re-opened.
With their added situational awareness from the Cupola, Acaba and Hoshide maneuvered the SSRMS over the Flight Releasable Grapple Fixture (FRGF) on HTV-3, 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-3 firmly in the station’s grip.
This marked the first time that a Japanese astronaut, in the form of Aki Hoshide, assisted in the capture of a Japanese spacecraft – another badge of honour for Hoshide, who also helped to install the Japanese Pressurised Module (JPM) “Kibo” onto the ISS during the STS-124 Shuttle mission in May 2008.
Following HTV capture, the SSRMS maneuvered the spacecraft to the Ready To Latch (RTL) position below the Node 2 Nadir Active Common Berthing Mechanism (ACBM) port – the same one to which the SpaceX Dragon berthed to two months ago – 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-3 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-3 hatch – is scheduled to be completed later today or tomorrow, depending on how fast the ISS crew can work.
ISS preparations for HTV-3’s arrival:
Preparations for the HTV-3’s arrival at the ISS have been ongoing over the past week, as detailed in an exclusive set of ISS on-orbit status notes, available to view on L2 – LINK.
“Ground specialists successfully uploaded three configuration tables in preparation of the installation of the Space Communications and Navigation (SCaN) Testbed on ExPrESS Logistics Carrier-3 (ELC-3) following the HTV-3 berthing,” noted the information.
“Following each configuration, a flight software reboot of the ELC was performed for the new tables to be applied. No issues were reported during the upload and reboot process.”
Another set of notes added that ground controllers performed the Hot Backup powerup of the Mobile Servicing System (MSS) while the crew performed multiple offset grapple approaches.
“During the final approach, the crew reacted to ground-commanded safing by performing a transition to the hot backup string and backing away. The transition and backaway proceeded nominally.”
The notes also mentioned that the Node 2 Nadir CBM hatch mechanism was actuated from the latched position to the fully unlatched hard stop position. The hatch will remain in this configuration until HTV-3 berthing.
“The successful actuation of the hatch mechanism to the fully unlatched configuration meets Flight Rule F2-1, ISS Driven HTV Launch Commit Criteria”, continued the notes. CBM hatches are unlatched prior to vehicle launches in order to prevent a latch issue from precluding access to a vehicle and thus wasting its on-board supplies.
HTV-3 cargo overview:
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), making 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).
On the HTV-3 mission, the PLC is carrying eight HRRs, all of which are loaded with Cargo Transfer Bags (CTBs), and larger M0-1 and M0-2 bags via front-mounted cargo carrier panels attached to the HRRs. The PLC is also equipped with a standard ISS United States Operating Segment (USOS) Common Berthing Mechanism (CBM) hatch, to facilitate the transfer of large cargo items, such as racks.
The HTV-3 PLC is carrying many important cargo items, since it is the first vehicle to deliver a large load of cargo to the USOS since the retirement of the Space Shuttle, as the ATV docks to the Russian Segment (RS) with its smaller hatchways, and the SpaceX Dragon C2+ flight was a test flight, and thus did not include any valuable cargo.
One major cargo item inside the PLC is a new CubeSat deployment system for the ISS, consisting of the Multi Purpose Experiment Platform (MPEP), complete with two JEM-Small Satellite Orbital Deployers (J-SSODs), and five CubeSats. Once unpacked from the PLC, the two J-SSODs will be attached to the MPEP, and the five CubeSats will be installed into the J-SSODs, whereupon the MPEP will be installed onto the Japanese Airlock (A/L) slide table.
The Japanese A/L is located in the Japanese Pressurized Module (JPM), and is used to pass experiments (but not spacewalkers) between the interior and exterior of the ISS. It features a slide table that extends both inside and outside the ISS, allowing experiments to be loaded onto the slide table by the internal ISS crew, then following A/L depresurization, be retrieved by the Japanese Experiment Module Remote Manipulator System (JEM RMS) on the outside of the ISS.
This is the process that will be used for the MPEP, which, once extended outside the ISS on the JEM A/L slide table, will be grappled via its FRGF by the JEM RMS, and then maneuvered to an attitude to allow the J-SSODs to release the CubeSats in their desired direction. The MPEP with J-SSODs will then be brought back inside the ISS for future re-use.
The benefits of launching CubeSats to the ISS inside the PLC include lower vibration environments, which can damage small CubeSats, and the ability to have the CubeSats checked-out post-launch but pre-deployment by the ISS crew.
Another important cargo item inside the PLC is the ISS SERVIR Environmental Research and Visualization System (ISERV), a modified commercial telescope which will be mounted in the Window Observational Research Facility (WORF) rack and used for Earth observations, to provide disaster relief through the SERVIR program.
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The Aquatic Habitat (AQH) is also carried in the PLC, which, when installed in the Japanese Multipurpose Small Payload Rack (MSPR), will provide a habitat for Medaka fish aboard the ISS, aiding research into how fish born in space will react and adapt to the microgravity environment.
On the external side, the HTV-3 ULC carries one Exposed Pallet (EP), which is grappled by the Space Station Remote Manipulator System (SSRMS) via the EP’s Power & Data Grapple Fixture (PDGF) and extracted from the ULC once the HTV arrives at the ISS, and is then handed off to the JEM RMS via the EP’s FRGF, and attached to the Japanese Exposed Facility (JEF) via the Exposed Facility Unit (EFU)/Payload Interface Unit (PIU), which together form an Equipment Exchange Unit (EEU).
For the HTV-3 mission, a new type of EP is being flown, which, in addition to its visual differences from previous EPs, “eliminates an exposed pallet pull-in mechanism and replaces its hold-down mechanism with a position inspecting mechanism”.
Following its attachment to the JEF, the external payloads that are mounted to the EP are removed via Extra Vehicular Robotics (EVR) and installed onto their specific locations on the ISS.
The HTV-3 EP is carrying two external payloads – firstly, the Multi-mission Consolidated Equipment (MCE), which includes five small research payloads, which will be removed from the EP with the JEM RMS and installed onto JEF EFU #8.
The second EP payload, the NASA-developed Space Communications and Navigation (SCaN) Testbed, which will be used for research into Software Defined Radio (SDR), will be removed from the EP via the Special Purpose Dextrous Manipulator (SPDM) “Dextre” and installed onto ExPrESS Logistics Carrier-3 (ELC-3) via the Flight Releasable Attachment Mechanism (FRAM) interface.
Following removal of both payloads, the EP will be re-inserted into the HTV ULC for disposal when HTV-3 re-enters Earth’s atmosphere, which is currently scheduled for some time around HTV-3’s ISS unberthing date of 6 September.
(Images via L2, JAXA and NASA).
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