ISS robotics assess AMS-02 health, potential EVA, five years into operations

by Chris Bergin

The International Space Station’s robotic assets paid a recent visit to AMS-02 (Alpha Magnetic Spectrometer -02) to survey the external health of the payload and gain imagery ahead of a potential servicing EVA. This week marked the fifth anniversary since AMS-02 was launched to the orbital outpost in the payload bay of Space Shuttle Endeavour, as it continues its investigation into cosmic rays.

AMS-02 – The Ride To Station:

The AMS-02 experiment is a state-of-the-art particle physics detector that uses the unique environment of space to advance our knowledge of the universe.

AMS-02 Oveview, via L2AMS was launched on Space Shuttle Endeavour on May 16, 2011 – her swansong mission named STS-134.

STS-134 came to life via the Flight Definition and Requirements Directive (FDRD) process as a mission for Discovery, based on strong political support to extend the life of the ISS and to facilitate a ride uphill for AMS-02.

Funding for the payload’s ride uphill came via the support of a NASA Authorization Bill in September of 2008, which directed NASA to “take all necessary steps” to add STS-134’s delivery of AMS to the Station into the schedule.

STS-134 coming to life via the FAWG Manifests, via L2STS-134 soon matured into a baselined mission – as seen in its progression in the planning manifest of the time – as it moved from a Launch On Need (LON) support mission, to an actual mission in its own right.

With a Change Request (CR) swapping the STS-134 mission from Discovery to Endeavour, the youngest orbiter in the fleet was baselined to carry to AMS-02), along with the Express Logistics Carrier 3 (ELC-3), Materials on International Space Station Experiment 8 (MISSE 8), an Orion Rendezvous Detailed Test Objective (DTO) kit and a GLACIER freezer module for one of the Station’s science laboratories.

Endeavour would also return the MISSE 7a and 7b experiments to Earth as well as perform four Department of Defense payloads of opportunity: MAUI, SEITI, RAMBO-2, and SIMPLEX.

Title Page for the STS-134 FDRD Presentation, via L2The STS-134 FDRD document (available in L2) provided an overview of Endeavour’s final – and rather hefty – payload upmass requirement, totaling 36,740lbs, including middeck payload and crew equipment weight.

The star of the show as the primary payload was AMS-02 – weighing in at 15,300lbs.

The particle physics detector, designed with a large, cryogenic super-fluid helium superconducting magnet, was constructed to “search for antimatter and the origin and structure of dark matter.”

Ironically, it was that magnet that became a problem ahead of the launch date – relating to a vastly reduced lifetime estimation that was observed during testing in Holland, as engineers worked on finding a solution that would allow AMS to enjoy a lifetime that would match the extension of ISS operations until at least 2020.

AMS-2 Magnet Change, via L2A decision was made to changeout the hardware for a permanent magnet, as noted by the STS-134 Mission Integration Manager (MIM) at the time, which in turn slipped the launch date deeper into 2011.

Getting AMS-02 uphill to the ISS was also a challenge, with mission documentation (L2) noting the need for four longeron payload latches and one active keel latch for its attachment to the payload bay sidewalls of Endeavour.

Additionally, once on orbit, Remotely Operated Electrical Umbilicals (ROEU) would provide AMS-02 with 124V of power for its heaters and avionics – required to keep it alive in the cold of space.

Prior to liftoff, this power was provided via the T-0 umbilicals on the launch pad. These T-0 umbilicals also allowed launch personnel to monitor the health of AMS-02 prior to liftoff and make sure that Launch Commit Criteria for the AMS-02 was not breached.

STS-134 LaunchEndeavour had an eventful final flow at the launch pad, with her first launch attempt scrubbed due to problems with heaters on her Auxiliary Power Units (APUs).

Launching on May 16, 2011 – Endeavour enjoyed a successful trip to the ISS, kicking off the docked phase with the transition of AMS-02 from the orbiter’s payload bay to its new home on the Station.

The robotic ballet involved the Shuttle Remote Manipulator System (SRMS) unberthing the AMS from the payload bay, before handing AMS to the SSRMS (Space Station Remote Manipulator System).

AMS-02 on ISSThe crew then ungrappled the SRMS from AMS, officially handing the experiment over to the ISS, before it was maneuvered to its attachment point on the Starboard 3 Upper Inboard Command Attach System (CAS).

This was followed by stage one installation/first stage capture. Stage two installation was completed, before the umbilical mates were then secured. The SSRMS then ungrappled AMS, marking the completion of its permanent installation on ISS.

STS-134 Animation via photo sequence on L2Endeavour completed her final mission and returned home on June 1, 2011.

(Animated image resized from hires/full-screen version and sequence photo dumps on L2’s STS-134 Flight Day image section – several hundred megabytes strong = L2 Link.)

She was then placed into a Transition & Retirement (T&R) flow – marked by her final powerdown in May, 2012.

Endeavour was then given an emotional farewell tour on the back of the Shuttle Carrier Aircraft, prior to her handover to her retirement home at the California Science Center (CSC). She is currently awaiting External Tank ET-94 to become part of a stacked Shuttle display at the exhibition.

AMS-02 – Five Years On:

STS-134’s final primary payload lives on, with AMS-02 now having measured over 80 billion cosmic rays at energies in the range of trillions of electron volts.

AMS-02 on ISSIts permanent magnet and array of precision particle detectors collect and identify charged cosmic rays passing through AMS from the far reaches of space.

The data continues to be transmitted to Earth for analysis by the AMS Collaboration.

Scientists have already said the results have provided evidence of the elusive “dark matter” – the mysterious element that accounts for most of the mass in the Universe – colliding with itself.


Ensuring AMS-02 will continue to provide valuable science is the responsibility of the ISS Program, which used the fifth anniversary to conduct an external health check on the payload.

2016-05-20-235226Utilizing the SSRMS and the Dextre robot (SPDM), the Canadian duo took a closer view of the condition of the thermal shield an associated hardware.

“Alpha Magnetic Spectrometer (AMS) Survey – The Space Station Remote Manipulator System (SSRMS) and Special Purpose Dexterous Manipulator (SPDM) were used to perform a video survey of the Alpha Magnetic Spectrometer (AMS) payload,” noted L2 ISS Status Information.

Such surveys also allow experts on the ground to check for potential MicroMeteoroid and Orbital Debris (MMOD) strikes, which are a constant threat to external payloads on the ISS.

2016-05-20-235346The notes also added that there is preliminary interest in “servicing” AMS-02 via a future spacewalk.

“The AMS survey (was) performed to understand the state of the payload and gain detailed views in preparation for a possible EVA to service the payload.”

However, good news was reported, based on the initial evaluations into the survey imagery, adding the experiment payload appears to be in a good condition, with the notes adding: “There were no issues reported during the survey.”

(Images: Via NASA and L2 content from L2’s Expansive STS-134 specific section, which includes vast amount of FRR/PRCB level presentations, photos, graphics, videos, flow and mission updates – complete coverage available on no other site.)

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