PMA-3 relocation to aid Harmony on Station

by Chris Bergin

The International Space Station (ISS) has a busy week ahead, with the process of relocating the PMA-3 (Pressurized Mating Adapter) beginning on Monday.

The docking port is moving from the Node 1 (Unity) portside CBM (Common Berthing Mechanism) to the Nadir port, making room for the installation of the Node 2 (Harmony) module, which will ride uphill with shuttle Discovery during October’s STS-120.

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The three member Expedition 15 crew have been given a comprehensive timeline of events, which start on Monday, carrying through the week, when the PMA will be moved by the Station’s robotic arm to its new position on Thursday.

The ISS holds a total of three PMAs – used to interconnect spacecraft and modules with different docking mechanisms. The first two PMAs arrived with the STS-88 mission, alongside the Unity module. The third was carried on shuttle Discovery during the 100th shuttle mission – STS-92.

Although PMA-3 is only a small part of the ISS, the relocation marks a major milestone, ahead of the arrival of an array of new modules that will be launched over the remainder of the shuttle program – starting with the addition of Node 2 ‘Harmony’.

The timeline of events on the ISS this week, classed as ‘detailed procedural materials for Robotics and CBM proficiency training,’ have been uplinked to the crew on the station. They included the following timeline:

‘Monday: Reconfigure Node 1 (stowage, UOP outlet for CBCS install), plus initial SSRMS (Space Station Remote Manipulator System) ops: double-walk from MBS PDGF-2 (Mobile Base System Power & Data Grapple Fixture 2) to MBS PDGF-3 and then to Lab PDGF),’ as listed in Saturday’s On Orbit Status report on L2, reports which will provide extensive coverage of the operations at the end of each ISS day next week.

‘Tuesday: Close Lab window shutter, do CBM and Robotic ops training, release SSRMS from MBS PDGF-3 and maneuver to Node nadir CBM survey position while remained based on Lab PDGF.

‘Wednesday: Prepare for PMA-3 depressurization, open Node nadir hatch latch (door being kept sealed by ~38,993 lbf), install CBCS (Centerline Berthing Camera System), ground check out both CBMs overnight.

‘Thursday: Power on CBCS, depressurize PMA-3, Clay grapple PMA-3, Fyodor unbolt PMA-3, SSRMS transfer PMA-3 to nadir CBM, SSRMS ungrapple after bolts secured, power down CBCS, re-latch Node hatch door.

‘Friday: Cleanup, reconfigure Node 1 stowage, get-ahead relocate stowage for Node 2 (Harmony) ingress during 10A (STS-120).’

STS-120, commanded by US Air Force Colonel Pam Melroy, will deliver launch package 10A, which consists of the US Node 2 ‘Harmony’ module (with four DC-to-DC Converter Unit (DDCU) racks and three Zero-g Stowage Racks (ZSR) installed), a Power and Data Grapple Fixture (PDGF) for the station’s robot arm, and a Shuttle Power Distribution Unit (SPDU).

Node 2 – which will also provide a docking port for future shuttle missions – will be the first pressurized habitable module delivered to the station since the Quest Airlock was installed in June, 2001. Also on this flight, the P6 solar arrays will be moved from the Z1 truss on top of the Unity module to its final position at the port end of the truss.

Once Discovery arrives at the ISS at the end of October, the station’s arm will transfer Harmony to the port dock of Unity. Three ISS EVA’s will be carried out after STS-120, relocating Harmony once again, this time to the forward dock of the Destiny laboratory.

Meanwhile, it’s already been a busy few days onboard the ISS, with various troubleshooting and testing being added to the daily schedule of experiments and housekeeping on board the orbital outpost.

Elements noted range from what is being described as a ‘GPS-1 Failure’ on the ISS, preparations for the belated maiden voyage of the European cargo transport, the ATV, next year, and the discovery of a Russian part that is out of spec.

‘GPS-1 Failure: Ground specialists at MCC-Houston are investigating yesterday’s failure of SIGI-1 (Space Integrated Global Positioning Satellite/Inertial Navigation Systems 1) resulting in loss of redundancy for vehicle state vector updates, but other sources of state determination (GPS-2 & Russian data) are available,’ added Saturday’s On Orbit Status report. ‘Failure signatures indicated a timing issue that has occurred before.

‘ASN Testing: On Monday, TsUP/Moscow will begin two-week testing of the Russian Satellite Navigation Equipment (ASN), with data download to Laptop 3 for ground access via RGS (Russian Ground Site) passes.

‘This is in preparation for the arrival of the European ATV-1 (Automated Transfer Vehicle 1), currently planned for early March 2008, which requires ASN for proximity operations and docking approach to the SM (Service Module) aft end.

‘VOA Maintenance Update: During yesterday’s (Friday) OMI (On-orbit Maintenance Item) change-out on the CHeCS VOA (Volatile Organics Analyzer), NASA’s Clay Anderson discovered that the new Progress 26P-delivered inlet nozzle filter has the wrong dimension for fitting on the inlet nozzle.

‘Following ground advice, Clay reinstalled the old filter (certified lifetime expired on 7/24/07 but still OK). The VOA Maintenance was erroneously reported yesterday as having proceeded without issues.’

L2 members: All documentation – from which the above article has quoted snippets – is available in full in the related L2 sections, updated live.


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