HOUSTON — STS-134 Astronauts Drew Feustel, Greg Chamitoff and Mike Fincke will rotate through four two-man spacewalks outside the International Space Station during their mission, marking the last extravehicular excursions scheduled for the shuttle era.

“We will be traversing from one end of the station to the other on just about every extravehicular activity [EVA],” says Feustel, who leads the spacewalk team.

During the outings, the three men will retrieve and install science experiments, inject coolant into a slowly leaking thermal control system radiator, lubricate the station’s port side solar array rotary joint and establish a backup power connection between the station’s U.S. and Russian segments.

Mission extension

Following the scrub of an April 19 launch attempt, mission managers elected to extend Endeavour’s flight from 14 to 16 days to assist the station’s crew with a range of maintenance activities.

Prior to the spacewalks, on May 18 the astronauts will extract the Express Logistics Carrier 3 from the orbiter’s payload bay and place the rack securing a spare station ammonia coolant tank, S-band communications antennas and components for Canada’s Dextre robotic hand on the port side of the solar power truss.

On May 19, they will use similar robotic procedures to hoist the AMS from the cargo bay and secure the particle detector to the station’s starboard solar truss.

On May 23, Space Station Commander Dmitry Kondratyev, NASA’s Catherine Coleman and the European Space Agency’s Paolo Nespoli are scheduled to descend to Earth aboard the Soyuz TMA 20/25S, ending a 159-day tour of duty aboard the station and leaving three to staff the orbiting laboratory until replacements arrive on June 9.

The Soyuz crew’s departure may provide an opportunity for a “family portrait” of the station with a shuttle docked. The Russians vetoed an opportunity to take the image while Discovery was docked during the STS-133 mission in late February and early March. That image also would have included ESA’s ATV and JAXA’s now-departed HTV cargo craft. Mission managers will evaluate the prospect after Endeavour docks, according to Bill Gerstenmaier, NASA associate administrator for space operations.

Before returning to Earth, Kelly’s crew will demonstrate flash lidar and high-definition video camera sensors developed as part of the Orion capsule’s relative navigation system.

Sensor test

The Sensor Test for Orion Relative Navigation Risk Mitigation, or Storrm, will be initiated during Endeavour’s initial station rendezvous. The developmental sensors will shadow the traditional radar and trajectory control sensors (TCS) employed during shuttle/station manual docking operations.

Ground tests suggest the Storrm sensors will establish a lock with pre-positioned reflectors on the station’s docking port at 20,000 ft., a three-fold improvement in shuttle TCS acquisition.

The performance of the new sensors will be characterized by ground teams during the docked period. After undocking from the station late on May 29, Endeavour’s crew will carry out a 4-hr. re-rendezvous exercise to record the performance of the two Storrm sensors.

The shuttle crew will fly out to a distance of 29,000 ft. behind the station before initiating a nontraditional, Orion-style rendezvous approach that will conclude with Endeavour about 1,000 ft. below and 300 ft. behind the station.