From: Johnson Space Center
Posted: Sunday, December 17, 2006
MSG 088A (14-0607A) - FD08 MMT SUMMARY
The objective of the FD 8 MMT was to understand the implications of a fourth EVA to assist with retraction of the P6 array with respect to the remainder of the STS-116 mission timeline. As a result of these discussions, the MMT decided to add EVA 4 on FD 10 to assist and troubleshoot retraction of the P6 solar array. Both the Shuttle and Station Programs felt it was important to understand the issues with P6 retract in order to increase the probability of success of STS-117/13A which retracts the other P6 array. While the team is confident of the crew's execution of the newly developed techniques on EVA 4, due to the inherent design of the solar array, it may not be possible to fully retract the array with the tools in place on this mission. Regardless of the outcome of EVA 4, the techniques developed and tested during this EVA will prove extremely beneficial to both Programs.
The timeline impact for adding EVA 4 resulted in a trade between Late Inspection and the EOM weather wave-off day since consumables constrain the mission to 12+2. The limiting consumable is cryo which only supports through EOM+2. The MMT decided to keep Late Inspection in the timeline due its ability to further mitigate MMOD risk. The MMT also concurred with the plan to activate all three CONUS landing sites on EOM in order to increase the probability of a safe landing and mitigate the risk of using the last day of consumables. The site priority would be the usual KSC/EDW/NOR. Summary timeline details for the new plan will be provided as soon as they are available.
At the MMT on your behalf, Steve Lindsey complemented the MCC, MER, Damage Assessment, and all other teams for the outstanding support that the ground teams have provided during all mission related activities including the three EVAs and the Solar Array troubleshooting. All of the teams very much appreciated the compliment!
EVA 4 Requirement - The ISS MMT met prior to the Shuttle MMT and decided that EVA 4 was required to be performed prior to undocking. This discussion centered on understanding why EVA 4 is required during this mission versus waiting to gather more data and develop procedures for implementation on STS-117/13A. In addition to retracting the array on STS-116, the team decided that the lessons learned on EVA 4 relative to techniques, tools, and array hardware access will help increase the probability of success for having both P6 arrays retracted during STS-117/13A. There was significant discussion on performing the solar array retract during a Stage EVA. The downside to the Stage EVA is fewer crew members available to perform the complex robotics, commanding, and IV tasks which are required for the solar array retraction. Additionally, reduced KU band coverage will significantly decrease the ability of MCC to assist with array issues and provide the SRMS and orbiter crew cabin views of the array. For all these reasons it became obvious that a shuttle docked EVA was a better option to assist with final array retraction.
EVA 4 P6 Array Retract Plan- The team 4 activities led by Flight Director/Dana Weigel were presented to the FD 08 MMT. Details of this plan will be discussed with you by the Flight Control Team, but the overall plan is to have one EV crewmember on the SSRMS and one crewmember free-float. The SSRMS will be positioned near the P6 IEA to perform a survey along the blanket boxes. The overall concept would be to iterate with the EV crewmember to attempt to manipulate the grommets with several tools to release snags and/or for less severe snags manipulate the guide wires. It was obvious to the team that there might be some learning curve to find techniques that will work to allow final retraction 8 of the array. As each blanket is free and placed in a good configuration to retract, the EV crewmembers would move out of the way such that the IV crew could send the retract commands one bay at a time. This would be very similar to the "array shake" followed by retract tasks performed during EVA 3 today.
P6 Loads Analysis - The ISS team has finalized analysis of the P6 solar array in the current configuration. The STS-116 shuttle undocking and STS-117 docking loads are not a concern. Progress docking loads are acceptable as is a Soyuz docking to the FGB nadir port. This basically means that there are no loads constraints through the STS-117/13A mission and the ISS can execute reboost maneuvers as required for debris avoidance and/or altitude adjustments.
At the current 56% deployed position, the loads are unacceptable for a reboost using a Progress docked at the FGB Nadir port or with the Service Module Main Engine. With the current visiting vehicle plan this means that debris avoidance maneuvers and altitude adjustments are unavailable from April 8, 2007 (23 Progress) to August 2007 (ATV Docking).
Transfer Status - As of the MMT approximately 61% of the Middeck and Spacehab transfer is complete. Based on our assessment transfer is slightly ahead of schedule.
ISS N2 Transfer - As of the end of FD 8 a total of 47 lbs of N2 has been transferred to the ISS.
DAIU Troubleshooting- The DAIU troubleshooting plan procedures are still being finalized. The procedure requires 2 crewmembers for 3.5 hours. Because of mission priorities and transfer being a higher priority task, it may not be possible to fit this troubleshooting into the timeline.
Cryo Margins- The cryo margins are approximately 4 hours O2 limited for a 12+2 day mission and 2 deorbit opportunities each day. The margins for 13+1 day mission with the addition of EVA 4 are being evaluated with the goal of protecting 3 deorbit opportunities each day.
Solar Activity - The good news is that the solar activity has subsided from the higher levels that were encountered during the last few days although levels continue to remain slightly elevated. The Space Radiation Analysis Group continues to closely monitor Solar Region 930 since that region continues to have a magnetic complexity that could be favorable for future solar activity.
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