Space Acceleration Measurement System-II


Summary | Overview | Operations | Results | Publications | Imagery

Facility Summary

This content was provided by William Foster, and is maintained in a database by the ISS Program Science Office.

Brief Summary

Space Acceleration Measurement System-II (SAMS-II) is an ongoing study of the small forces (vibrations and accelerations) on the International Space Station (ISS) resulting from the operation of hardware, crew activities, dockings and maneuvering. Results generalize the types of vibrations affecting vibration-sensitive experiments. Investigators seek to better understand the vibration environment on the ISS.

Facility Manager(s)

  • William Foster, Glenn Research Center, Cleveland, OH, United States
  • Facility Representative(s)

    Information Pending


    ZIN Technologies Incorporated, Cleveland, OH, United States

    Sponsoring Space Agency

    National Aeronautics and Space Administration (NASA)

    Sponsoring Organization

    Human Exploration and Operations Mission Directorate (HEOMD)

    ISS Expedition Duration

    March 2001 - September 2014

    Expeditions Assigned


    Previous ISS Missions

    SAMS, the precursor to SAMS-II flew on numerous shuttle flights since STS-40, including STS-107 (Columbia) which was lost in 2003. SAMS-II has been operating on ISS since Expedition 2.


  • Onboard
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    Facility Overview

    • Space Acceleration Measurement System-II (SAMS-II) measures accelerations caused by vehicle, crew and equipment disturbances. These vibratory/transient accelerations occur in the frequency range 0.01 to 300 Hertz.

    • Vibrations exist on the space station for a variety of reasons: equipment operation, structural motion, crew movement, and thermal expansion are but a few.

    • Multiple sensors measure accelerations electromechanically at various locations in the US Lab.

    • SAMS-II measurements help investigators characterize accelerations that influence International Space Station (ISS) experiments. The acceleration data is available to researchers via the World Wide Web.

    Space Acceleration Measurement System-II (SAMS-II) measures vibrations from vehicle acceleration, systems operations, crew movements, and thermal expansion and contraction. Multiple Remote Triaxial Sensor (RTS) systems directly monitor individual experiments. Each RTS is capable of measuring between 0.01 Hz to beyond 300 Hz of vibration, also known as g-jitter. The RTSs consist of two components: the RTS sensor enclosure (SE) and the RTS electronics enclosure (EE). The RTS-SE, placed as close to the experiment as possible, translates the g-jitter into a digital signal. The RTS-EEs provide power and command signals for up to 2 RTS-SEs and receive the g-jitter data from the RTS-SEs. The RTSs are linked together by the Interim Control Unit (ICU), which coordinates the various RTS systems being used throughout the station. Eventually, the ICU will be replaced by a full-fledged Control Unit (CU), which will allow on board data analysis and direct feedback and will permit crew to control the measurement parameters. The main component of the ICU is a computer. Once the ICU receives the measurements from the RTS systems, it checks the data for completeness, and then sends the data to the SAMS-II Ground Operations Equipment in the TeleScience Center at Glenn Research Center in Cleveland, OH.

    The SAMS-II RTS is installed in Rack 1, drawers 1 and 2, away from the Active Rack Isolation System (ARIS) in Rack 2, which could cause disruptions to measurements. The ICU is in Rack 2, drawer 1 prior to Increment 3. At the end of Increment 3, the crew transfers it to EXPRESS Rack 4. Once installed and activated, SAMS-II operates automatically.

    SAMS-II measures subtle vibrations that affect only certain types of experiments and is not operational all the time. SAMS-II operates from the Glenn Research Center Telescience Support Center as needed. The ICU laptop has the capacity to save up to ten hours of data from five sensors working at maximum frequency range. This capacity is intended to act as a backup if downlink services are interrupted.

    SAMS-II provides environmental data for scientific experiments that are conducted on board the ISS. Any degree of acceleration disturbance can ruin their science. In fluid physics and crystal growth, SAMS-II detects the vibrational disturbances that cause the microstructures to form undefined and disfigured. The liquid - solid transition is difficult when the amount of disturbances is high.

    The residual acceleration environment of an orbiting spacecraft in low earth orbit is a complex phenomenon. Many factors, such as experiment operation, life-support systems, crew activities, aerodynamic drag, gravity gradient, rotational effects and the vehicle structural resonance frequencies (structural modes) contribute to form the overall reduced gravity environment. Weightlessness is an ideal state, which cannot be achieved in practice because of the various sources of acceleration present in an orbiting spacecraft. SAMS-II records acceleration disturbances caused by the ISS, its crew, and equipment. A complete understanding of the vibration environment will help researchers develop methods to minimize disturbances. It also allows other principal investigators to design their payloads with the vibration environment in mind.


    Facility Operations

    SAMS-II measures subtle vibrations that affect only certain types of experiments and is not operational all the time. SAMS-II operates from the Glenn Research Center Telescience Support Center as needed. The ICU laptop has the capacity to save up to ten hours of data from five sensors working at maximum frequency range. This capacity is intended to act as a backup if downlink services are interrupted.

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    Results/More Information

    One of the major goals of the ISS is to provide a quiescent low-gravity environment to perform fundamental scientific research. However, small disturbances aboard the ISS impact the overall environment in which experiments are being performed. Such small disturbances need to be measured in order to assess their potential impact on the experiments. The Space Acceleration Measurement System - II (SAMS-II) is used on board the ISS to do just that.

    SAMS-II measures accelerations caused by vehicle, crew, and experiment disturbances. SAMS-II measures the vibratory/transient accelerations, which occur in the frequency range of 0.01 - 400 Hz. The sensors measure the accelerations electronically and transmit the data to the Interim Control Unit (ICU) located in the EXPRESS Rack drawer. Data is collected from all the sensors and downlinked to the TeleScience Center at Glenn Research Center. The acceleration data is processed and made available to the microgravity scientific community at Principal Investigator Microgravity Services.

    SAMS-II measures vibratory acceleration disturbances in microgravity and non-microgravity modes of ISS operations. Current data indicate that ISS is not meeting its microgravity mode design requirement, and that there is no clear reduction in these disturbances during crew sleep periods (DeLombard et al. 2005).

    SAMS-II has collected over 3.4 terabytes of acceleration data, much of which have been processed and analyzed to characterize the reduced gravity environment on board the ISS in order to help science teams understand the ISS environment. SAMS-II, began to have some computer difficulties at the beginning of Expedition 12 (October 2005); the harddrive was replaced at the end of Expedition 14 (April 2007) and SAMS-II functions nominally on an as-needed basis.

    Results Publications

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    Ground Based Results Publications

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    ISS Patents

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    Related Publications

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    Related Websites
  • Space Acceleration Measurements System - II
  • Principal Investigator Microgravity Services
  • SpaceRef.com - End of an Era for SAMS
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    image NASA Image: ISS004E8406 - SAMS sensor head mounted near top of EXPRESS Rack 2 in U.S. Lab taken during Expedition 4.
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    image NASA Image: ISS008E11936 - SAMS-II in EXPRESS Rack 4 in U.S. Lab during Expedition 8.
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    image NASA Image: ISS007E06980 - Back-dropped by the blackness of space and Earth's horizon, an unmanned Progress supply vehicle approaches the ISS during Expedition 7. Inset image shows microgravity acceleration data provided by the SAMS-II hardware during a Progress docking with ISS.
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    image NASA Image: ISS027E009634 - Documentation of a Space Acceleration Measurement System (SAMS) sensor installed at location LAB1S1 in the Destiny U.S. Laboratory during Expedition 27.
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