STS-134: Mission Timeline and Contingency Options Take Shape

by Chris Gebhardt

With just over one month to go before the scheduled No Earlier Than launch of Space Shuttle Endeavour on her 25th and final mission – and the penultimate flight of the Space Shuttle Program – NASA has defined the nominal mission timeline for Endeavour and her six-member Flight Crew, as well as determined OBSS contingency procedures, Minimum Duration Flight rules and timelines, and mission extension guidelines.

Launch Windows and Launch Times:

Currently targeting launch No Earlier Than 19 April 2011 at 19:48 EDT, Endeavour’s available launch window for the STS-134/ULF6 mission has been determined based on a complex ballet of schedules between Shuttle, Progress, Soyuz, and Solar Beta Angle cutouts.

Currently, the duration of Endeavour’s “available” launch window runs from April 19 – May 3. However, contained within that window is an April 23-29 cutout (or elimination of launch opportunities for Endeavour) due to the currently-scheduled rotation of Progress unmanned resupply vehicles at the International Space Station.

Thus, from a Progress standpoint, Endeavour’s launch window is actually April 19-22 and then April 30-May 3.

Beginning on May 4, Endeavour would be prevented from launching until mid-June based on two factors, the scheduled rotation of a three person subset of the International Space Station crew on the Soyuz 25S (deorbit) and Soyuz 27S (launch) vehicles and a Solar Beta Angle cutout.

For this crew rotation cutout, Soyuz 25S is scheduled to undock on May 16, thus preventing Endeavour from launching on or after May 4 as that would either put Endeavour’s undocking on the same day as the Soyuz 25S undocking or cause Endeavour to be docked to the ISS during the 25S undocking – something that is prohibited by Dual Docked Operation (DDO) constraints.

The next Soyuz, 27S, is then scheduled to launch from the Baikonur Cosmodrome in Kazakhstan on May 30, docking to the ISS on June 1.

For this, Endeavour would not be allowed, under current DDO and STS-134 mission flight rules, from launching in between the Soyuz rotations because of potential 27S docking overlaps (violation of DDO rules) and the hindrance of science/experiment operations on ISS with a reduced crew size (STS-134 is planned to utilized six ISS crewmembers, not three).

Thus, from a Soyuz standpoint, Endeavour’s earliest launch attempt, should she miss the late-April/early-May window, would be June 2 based on a Soyuz docking on June 1.

However, this would not be the case as a further complication to the STS-134 launch window arises in the form of a Solar Beta Angle cutout that begins on May 31 and runs through June 20.

Thus, should Endeavour miss the late-April/early-May window, NASA would have to wait until June 20 to send Endeavour off on her capstone mission unless the usual dance of launch schedules could be arranged to open up a few launch day opportunities in mid-May for Endeavour. This would mandate an adjustment to the ISS and Shuttle mission schedules to account for the fact that the ISS will have 3 less people than STS-134 has been planned and trained for.

Nonetheless, Endeavour’s launch window could become even more complicated in the coming days as Russia continues to evaluate a problem with the Soyuz 26S spacecraft that was scheduled to launch on March 29 but has since been delayed to an unspecified date to allow Russian teams time to troubleshooting and fix the Kvant-V communications systems on the spacecraft.

While no official launch date has been rescheduled for the Soyuz 26S, some indicators point to as much as a month-long delay to the launch – which would place liftoff around April 30th. In this month-long delay scenario and a late-April launch of Soyuz would then play into direct conflict with the April 19th opening of Endeavour’s launch window since this would place Endeavour at the ISS during the Soyuz docking – a violation of current DDO constraints.

Should this month-long Soyuz delay become a reality, it would be up to NASA and Roscosmos to decide which mission (Endeavour or Soyuz 26S) gets priority on the International launch schedule.

UPDATE:  Roscosmos are likely to announce an initial NET date of April 4 (22:18 UTC) on Friday.

Nominal Mission Timeline:

Based on an opening launch date of April 19, and a March 18 reboost of the ISS by Soyuz of 3.6 m/s, FD-3 (Flight Day 3) rendezvous capability will be available for Endeavour/STS-134 for the duration of the April 19-May 3 window, with FD-4 rendezvous capability available in conjunction with FD-3 rendezvous capability for launches on April 20, 27, 29, and May 1.

On April 20, the Flight Director’s Overview presentation to the MOD FRR (Mission Operations Directorate Flight Readiness Review) notes that “Flight Day 3 launch window times prior to the inplane time on Apr 20 may not be available due to small phase angle limitations.”

Likewise, the FD-3 launch window close times on April 26 and April 28 may be limited by large phase angle constraints.

(Should Endeavour launch on April 19 at 17:48 EDT, she would launch on her final mission 5-minutes before local sunset at the Kennedy Space Center.)

After arriving on orbit, Endeavour’s crew would spend the remainder of FD-1 conducting post-insertion activities, powering up and checking out the Alpha Magnetic Spectrometer (AMS), performing the NC-1 course correction burn, powering up the SRMS (Shuttle Remote Manipulator System), and downlinking/downloading all External Tank umbilical well photos, hand-held ET video (if applicable since a launch on April 19 and 20 would result in on orbit nighttime ET photography), and Wing Leading Edge Sensor system data.

FD-2 will then be spent conducting the standard OBSS (Orbiter Boom Sensor System) inspections of Endeavour’s Wing Leading Edges, nose cap, T0 umbilicals, and upper flight surfaces (including the OMS pods). The crew will also use the SRMS to grapple the ELC-3 pallet in Endeavour’s cargo bay. The SRMS will remain grappled to ELC-3 through docking on FD-3.

The crew will then perform both NC-2 and NC-3 course correction burns, perform EMU (Extravehicular Mobility Unit) checkouts, install the centerline camera for docking, perform rendezvous tool checkouts, and extend Endeavour’s Orbiter Docking Ring before heading to bed.

FD-3 will then be dominated by rendezvous and docking operations. 

STS-134 Specific Articles:

Following the Terminal Initiation burn, Endeavour will approach the International Space Station from “behind” and “underneath.” Once 600ft below the ISS on the R-bar, Commander Mark E. Kelly will guide the good ship Endeavour through a 360-degree backflip R-bar Pitch Maneuver (RPM) to allow the ISS crew to capture hundreds of Hi-RES digital images of Endeavour’s Thermal Protection System (TPS).

After the RPM, Commander Kelly will move Endeavour out in front of the ISS and then slow Endeavour’s orbital velocity by two-tenths of a foot per second at first (later down to only one-tenth of a foot per second) relative to ISS velocity, thereby allowing the ISS to catch up to dock to Endeavour.

Following docking, scheduled to occur at 16:38 EDT on April 21 (assuming an April 19th liftoff), Endeavour’s crew will downlink data collected during rendezvous and docking from STORRM, unberth ELC-3 from OV-105’s payload bay, handoff ELC-3 to the SSRMS (Space Station Remote Manipulator System), and then use the SSRMS to berth ELC-3 to its permanent location on the ISS’s P3 truss UCCAS-1 berthing location.

Meanwhile, the Station crew will downlink all RPM photography to the ground for analysis. N2 (Nitrogen) and O2 (Oxygen) transfer from Endeavour to ISS is also scheduled to take place post-docking on FD-3.

And then, on FD-4, the premiere scientific experiment for the International Space Station will be hoisted from Endeavour and affixed to its permanent home on the S3 truss of the Space Station.

The Alpha Magnetic Spectrometer (AMS) will then spend the rest of the decade, and possibility longer, in a constant quest to seek out evidence of and information on dark matter, dark energy, and anti-matter in the hopes of expanding humanity’s ever-changing knowledge on the functionality of the universe.

Delivery of the AMS to the International Space Station will mark the final European Space Agency experiment to fly on the Space Shuttle and will represent the final major scientific experiment to be delivered to Low Earth Orbit and the Space Station by the Space Shuttle.

On FD-5, Drew Feustel and Greg Chamitoff will venture outside the ISS for the first of four spacewalks for STS-134. During the 6.5 hour EVA, the MISSE 7A and 7B experiments will be retrieved from ELC-2 and returned to Endeavour’s payload bay, MISSE 8 will be installed on ELC-2, a CETA light will be installed on S3, Starboard SARJ cover #7 will be installed, NH3 (ammonia) vent prep will take place, and the Destiny lab EWC antenna will be installed.

Additional tasks on FD-5 will include completion of FGB Y-cable internal power jumper installation which began on FD-4, middeck transfers from Endeavour to ISS, and SSRMS walkoff to Node-2.

The crew will then spend FD-6 performing a Focused Inspection (if needed) of specific areas of Endeavour’s TPS. If no FI is needed, the OBSS will be removed from Endeavour’s payload by the SSRMS and handed off to the SRMS.

The crew will then enjoy some off duty time before moving into EVA-2 tool Config and campout ops.

The following day (FD-7), Feustel and Mike Fincke will exit the Space Station for EVA-2. During this EVA, the spacewalking duo will fill the NH3 P3 PVTCS, lube the port SARJ, install the S1 Radiator Grapple Bar Stowage Beam, install Dextre’s (the Special Purpose Dexterous Manipulator) base CLA cover, and lube Dextre’s LEE.

Middeck transfers will continue on this day as well, and the SSRMS will be walked off to the Mobile Base Station in the overnight hours.

FD-8 will then be a much-deserved day off for the crew. In preparation for EVA-3, NO campout in the Quest Airlock will be conducted; instead, Feustel and Fincke will use the new ISLE (In Suit Light Exercise) protocol on the morning of FD-9.

On FD-9, Feustel and Fincke will perform the ISLE pre-breathe protocol before egressing the ISS. During EVA-3, the two spacewalkers will install a Power Data Grapple Fixture (PDGF) to the FGB, install Y power feed cables (Y-jumpers) to the FGB, install a 1553 data cable to FGB, and take PDGF and FGB thruster photos.

Middeck transfers will resume on this day.

Then, on FD-10, Endeavour’s crew will perform a Docked Late Inspection (DLI) of Endeavour’s Wing Leading Edges and nose cap – a procedure that has been done on two previous Shuttle missions: STS-123 (Endeavour) and STS-131 (Discovery).

For this Docked Late Inspection, Endeavour’s STS-134 mission timeline has been set up to include a 26 hour buffer between the start of DLI and EVA-4 egress. For the two previous DLIs, STS-123 required 25.5 hours from DLI start to TPS clearance for reentry; STS-131 needed 30.25 hours from DLI start to TPS clearance for reentry.

As noted by the Mission Overview MOD FRR presentation, available for download on L2, “STS134 has 26H from DLI start to EVA4 egress. Will probably clear vehicle prior to nominal egress or be very close (high confidence no serious issues). Will egress as planned unless told otherwise by the Mission Management Team (same as STS-123 plan).”

Middeck transfers will continue on FD-10, CDRA (Carbon Dioxide Removal Assembly) bed R&R (Removal and Replacement) will also take place on this day, as will EVA-4 tools prep and Quest airlock overnight campout.

Then, on FD-11, the final spacewalk to be performed by a Space Shuttle crew will take place from the ISS’s Quest Airlock. During the 6.5 hour EVA, Fincke and Chamitoff will take the necessary steps to transfer Endeavour’s OBSS from her SRMS to the Integrated Truss Structure of the International Space Station – where it will remain for the duration of the International Space Station Program to aid in any contingency repair/maintenance EVAs once the Shuttle program ends later this year.

In all, this means that Endeavour will be the only Shuttle orbiter in the post-Columbia era to launch but not return with her OBSS – a distinction she holds for two separate missions: STS-123 being the first.

Perhaps, fitting enough, once back on the ground, Endeavour will also have her SRMS arm removed during T&R (Transition and Retirement) processing. Endeavour’s SRMS arm will be given back to the Canadian Space Agency in acknowledgment of Canada’s unwavering contribution to the Space Shuttle Program through, among other things, the fabrication of all five SRMS arms and all three OBSS arms for the Shuttle orbiters.

FD-12 will then follow on orbit with EMU reconfig and transfer back to Endeavour, O2 and N2 transfer teardown, completion of CDRA bed R&R, completion of middeck transfer tops, Rendezvous tools checkout, final farewells, and ISS/Endeavour hatch closure.

Endeavour will then undock from the International Space Station for the final time at 09:50 EDT on May 1 (assuming an on time launch on April 19). Following undocking, Endeavour will perform one last victory lap around the Station for which she began construction of during STS-88 in December 1998.

She will then perform a STORRM re-rendezvous to gather more data for that system before performing her final separation burns to move out in front of the ISS.

The following day, EOM-1 (End Of Mission -1), Endeavour’s crew will begin the process of converting Endeavour back into a plane for reentry, as well as conduct the necessary Flight Control System checkouts and Reaction Control System hot fire tests.

After these checks are complete, the final Flight Crew of Endeavour will take time to pay a special tribute to Endeavour and her career of excellence on her final day in Earth orbit.

Then, on FD-15 Endeavour will, weather permitting, perform the deorbit burn at 12:23 EDT May 3 (assuming an on time April 19 launch) to bring herself back to her home in Florida.

If all goes to plan, Endeavour will effortlessly glide down to Runway 15 at ~13:27 EDT for a final wheels stop at STS-134 Mission Elapsed Time 13 days 17 hours 39 minutes.

STS-134/ULF6 Minimum Duration Flight and Potential Mission Extension:

While it is highly unlikely the Endeavour would encounter a problem after launch that would prevent her from carrying out her fully-planned STS-134 mission, the possibility always exists that Endeavour’s mission will have to be cut short and a Minimum Duration Flight (MDF) ordered by the Mission Management Team.

In a MDF scenario, seven (7) flight days and all four (4) EVAs would be eliminated from the flight, and Endeavour would return to Earth with her OBSS instead of leaving it at the ISS since OBSS leave behind requires an EVA.

In all, under MDF flight rules for STS-134, FDs 1-3 would play out exactly as they are planned under the nominal mission timeline.

On FD-4, AMS would be removed from Endeavour and installed to the ISS. Only mandatory middeck transfers per Flight Rule ULF6_C2-16 would begin on FD-4.

FD-5 would be devoted to mandatory middeck transfers and a Focused Inspection if necessary.  If no FI is needed, the OBSS will remain berthed until after undocking.

This would be followed on FD-5 by hatch closures between Endeavour and the ISS followed by undocking, post-undocking late inspection, and OBSS berth on FD-6.

FD-7 would be EOM-1 with cabin stow for reentry, FCS checkout, and RCS hot fire.

Endeavour would then deorbit and land on FD-8.

However, the much more likely scenario is that Endeavour’s mission will be extended by at least one day once on orbit and docked to the ISS.

As noted by the Mission Overview presentation, “Endeavour is SSPTS (Station to Shuttle Power Transfer System) enabled. The +1 mission extension day may be used to accommodate docked contingencies such as additional docked Focused Inspection (FI) time if more FI time is required than pre-flight available (4 hours), additional time to accomplish CAT1 IVA objectives, and as a contingency EVA day.”

However, as seen with STS-133, it is also possible that the +1 mission day would be used to add more docked time to the mission to help out the ISS crew on various tasks.

It is also possible that the +1 day could be used to enable a Soyuz flyaround of the ISS/Shuttle complex since those discussions with the Russians are underway and under evaluation for STS-134.

(Numerous articles will follow. L2 members refer to STS-134 coverage sections for internal coverage, presentations, images and and updates from engineers and managers. Images used: Larry Sullivan MaxQ Entertainment – from a 1200mb database of photos and video (L2) of rollover, VAB and Pad ops for STS-134, and STS-134 FRR documentation on L2).

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