Actiwatch Spectrum System (Actiwatch Spectrum) - 11.29.17

Summary | Overview | Operations | Results | Publications | Imagery

ISS Science for Everyone

Science Objectives for Everyone
The Actiwatch Spectrum is a waterproof, nonintrusive, sleep-wake monitor worn on the wrist of a crewmember. The device contains an accelerometer for measuring motion and color sensitive photodiodes (a photodetector capable of converting light into voltage) for monitoring ambient lighting. Together, these capabilities enable the Actiwatch Spectrum to be used to analyze circadian rhythms, sleep-wake patterns, and activity.
Science Results for Everyone
Information Pending

The following content was provided by Suzanne McCollum, and is maintained in a database by the ISS Program Science Office.
Facility Details

OpNom: Actiwatch Spectrum

Facility Manager(s)
Suzanne McCollum, Johnson Space Center, Houston, TX, United States

Facility Representative(s)
Information Pending

NASA Johnson Space Center, Human Research Program, Houston, TX, United States
Philips Respironics, Inc., Bend, OR

Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)

Sponsoring Organization
Human Exploration and Operations Mission Directorate (HEOMD)

ISS Expedition Duration
September 2010 - September 2015; April 2017 - February 2018; -

Expeditions Assigned

Previous Missions
Information Pending


  • Onboard
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    Facility Description

    Facility Overview

    • The Actiwatch Spectrum captures data on subject activity and the amount of ambient light to which the subject is exposed.
    • The Actiwatch Spectrum is a replacement for an older Actiwatch system and comes with the added capability to differentiate between multiple wavelengths or colors of ambient light across a broad spectrum (400-700 nm). The Actiwatch Spectrum also has the added capability to display time and function as a watch.
    • The Actiwatch Spectrum can be used to investigate a number of activities such as sleep quality, sleep onset, hyperactivity and other daily routines.
    The Actiwatch Spectrum System is a modified commercial-off-the-shelf (COTS) system consisting of the Actiwatch Spectrum Kit, Actiwatch Spectrum, Actiwatch Spectrum Dock, Actiwatch Spectrum Universal Serial Bus (USB) Cable, and Actiware Software (version 5.52 or later).  The Actiwatch Spectrum is a small, battery-powered, limb-worn device that simultaneously detects body movement and light intensity.  The unit can be used to investigate a number of activities such as sleep quality, sleep onset, hyperactivity and other daily routines.  The Actiwatch Spectrum System can be used by experiment teams for baseline data collection on the ground as well as onboard the International Space Station (ISS).  The Actiwatch Spectrum is designed for intravehicular activity (IVA) only and, although waterproof to a limited extent, should be removed prior to performing any activity that would put the hardware at risk of immersion in water. 
    The Actiwatch Spectrum can be programmed to collect data in a variety of modes including activity, photopic light, red-green-blue (RGB) light or any combination thereof.  Data is sampled by the Actiwatch sensors at a frequency of 32 Hz and may be recorded at a variety of epochs: 15 and 30 seconds and 1, 2 and 5 minutes.  Total recording time is limited by the data collection mode, epoch setting, and battery life.  For example, an Actiwatch configured for activity, RGB light and photopic light at a 15-second epoch is able to collect data for 9 days while an Actiwatch configured for activity only at a 1-minute epoch can collect data for 182 days.  When initialized, the Actiwatch Spectrum may be configured to begin recording data immediately or delay data acquisition to a specific time and date.  In addition, the Actiwatch can be configured to either collect data until the memory is full or halt data acquisition and go to sleep mode (a low-power, battery saving setting) after a user-specified length of time.  When collecting data until the memory is full, the Actiwatch will go to sleep mode once it can no longer continue recording data.  The Actiwatch Spectrum is also capable of detecting when the watch is worn against skin or a conductive surface (< 2mm separation) and recording event markers.
    The Actiware Software is used for data analysis, file management, configuring an Actiwatch Spectrum for data collection and retrieving data.  Data downloaded from an Actiwatch Spectrum is stored in a user-specified database file and organized by the subject ID used to configure the Actiwatch Spectrum.  The Actiware Software may be used to access subject information and view or analyze data for sleep parameters and rhythmicity.  Raw data or statistics may also be exported for external analysis or archival.  Battery life may be checked using the Actiware Software while communicating with an Actiwatch Spectrum.  While the Actiware Software supports older versions of the Actiwatch hardware, the Actiwatch Spectrum and Actiwatch Spectrum Dock cannot be used with older versions of Actiware, Actiwatch Readers or Actiwatches.
    The Actiwatch Spectrum System was first launched on STS-133/Flight ULF-5 in February 2011.  Replacement of internal batteries cannot be performed on-orbit.  Therefore, periodic resupply of fresh Actiwatches is planned.
    • Integrated Cardiovascular (NASA):  used in the ambulatory monitoring portion of the experiment beginning with Increment 28.  Activity data collected by the Actiwatch Spectrum was analyzed in conjunction with cardiovascular data from other devices to estimate the amount of work the crewmember’s heart performed on a daily basis. 
    • Circadian Rhythms (ESA):  used to monitor daily activity and sleep for some sessions aboard the ISS.
    • Biological Rhythms 48 Hrs (JAXA):  HRF Actiwatch Spectrum Dock used to configure JAXA-owned Actiwatch Spectrums for data collection and to download the data after completion.
    • Energy (ESA):  used as a contingency replacement to ESA’s activity-monitoring Armband hardware.
    • Sleep ISS-12 (NASA):  used to monitor daily activity, light exposure, and sleep patterns throughout the ISS mission for participating crewmembers.

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    Facility Operations

    • Use of the Actiwatch Spectrum involves a small number of basic operations: initialization, data collection, downloading data and downlinking data.
    • Initialization of the Actiwatch Spectrum involves configuring the hardware to start recording data at a specific sampling rate at a specific time.
    • The period over which the Actiwatch Spectrum may be used to collect data depends on the sampling rate and is limited by the internal storage capacity of the device and battery life.
    • Data collection using the Actiwatch Spectrum is very similar to wearing a standard wristwatch. Once the device has been initialized and begins collecting data, the user need merely wear it at the location specified by the experiment for which data is being collected.
    • Downloading the Actiwatch Spectrum involves connecting the device to a reader plugged into a computer and transmitting the data from the Actiwatch Spectrum to the computer.
    • Downlinking the data from the Actiwatch Spectrum is a matter of transmitting the data stored on the ISS servers to the science teams on the ground.


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    Decadal Survey Recommendations

    Information Pending

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    Results/More Information

    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

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    Figure 1:  The Actiwatch Spectrum is a waterproof, nonintrusive, sleep-wake monitor worn on the wrist of a crewmember.

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    Figure 2:  Actiwatch Spectrum installed in Actiwatch Dock for initialization and/or data download.

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