Space Acceleration Measurements System II (SAMS-II)

SAMS-II measures vibrations and transient acceleration disturbances resulting from ISS vehicle activities, ISS systems operations, experiment operations, crew movements, and ISS structure thermal expansion and contraction. SAMS Remote Triaxial Sensor (RTS) systems are used to monitor on-board ISS accelerations for individual experiments requiring direct acceleration measurement support. Each RTS is capable of measuring acceleration disturbances between 0.01 Hz and 400 Hz.  This aggregate set of acceleration disturbances is commonly referred to g-jitter. Each 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 provides power and command signals for up to 2 RTS-SEs and receives the g-jitter data from the RTS-SEs.

An additional sensor called the RTS Ethernet Standalone (RTS-ES) is available for acceleration measurement support.  The RTS-ES is just that, a sensor capable of making acceleration measurements in a standalone fashion; the RTS-ES does not require an RTS-EE to function.
 
All SAMS RTSs are linked together by the Interim Control Unit (ICU), which coordinates the command and telemetry data for the various RTS systems being used throughout the Station.  All acceleration data obtained by each SAMS RTS are routed to the ICU for downlink to the ground.  All command and control for each RTS is accomplished through the ICU. The main component of the ICU is a laptop computer. Once the ICU receives the measurements from the RTS systems, it checks the data for completeness, breaks the data into well-defined information packets, and sends the packets to the SAMS Ground Operations Equipment located at the Telescience Support Center (TSC) at Glenn Research Center.

The MAMS is a complimentary acceleration measurement system to SAMS.  While the SAMS system measures acceleration disturbances from 0.01 to 400 Hz, the MAMS measures accelerations from DC to a maximum of 0.01 Hz.  MAMS provides this complimentary function by measuring accelerations caused by the aerodynamic drag of the ISS as it orbits the earth.  In addition, MAMS measures accelerations caused by small ISS attitude adjustments and ISS gravity gradient effects. These quasi-steady accelerations are confined in the frequency range below 1 Hz. MAMS consists of a low-frequency triaxial accelerometer, the Miniature Electro-Static Accelerometer (MESA), and associated computer, power, and signal processing subsystems contained within a Double Middeck Locker enclosure.

The MAMS MESA consists of a hollow, cylindrical flanged proofmass, two X-axis forcing electrodes, an outer cylindrical proofmass carrier with Y- and Z-axis electrodes, and control electronics enclosed in a protective case. Static electricity forces the sensor proofmass to remain centered between the electrodes. The "sensed" acceleration is proportional to the voltage needed to keep the sensor centered.  The MAMS MESA is mounted on a Bias Calibration Table Assembly (BCTA) with a dual-gimbal rotation system.  The BCTA and dual-gimbal systems allow the MAMS MESA to perform on-orbit bias calibrations.  With the MAMS electronic bias measured, the extremely small quasi-steady accelerations can be accurately sensed and transmitted to the ground to the Glenn Research Center Telescience Support Center for analysis and archive.