MMA
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MMA fully assembled (top view)
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The Microgravity Measurement Assembly (MMA) is one of the Fluid Science Lab (FSL) in-orbit
replaceable units. FSL is one of the scientific facilities for the European Columbus module
on the International Space Station.
The MMA is a tri-axial accelerometer measuring the residual
acceleration levels in the frequency range between 0.01Hz and 300Hz.
The MMA design is based on high-performance high-reliability Honeywell QA3000 series acceleration
sensors.
(more pictures)
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The main MMA specifications are:
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| Parameter |
Value |
| Mode |
A |
B |
| Range |
-100mg..+100mg |
-3mg..+3mg |
| Resolution |
5µg |
0.2µg |
| Accuracy |
±30µg or ±10% |
±1µg or ±2% |
| Bandwidth |
0.01Hz..300Hz |
0.01Hz..11.2Hz |
| Data sampling rate |
1500 S/s |
| Mass |
2.5 kg |
| Volume |
150 x 145 x 100 mm³ |
| Power |
4.0 Watt |
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Typical features of the MMA design are:
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- Three single axis sensors are mounted orthogonal to each other. Each sensor carries a small
Printed Circuit Board (PCB), featuring a selectable gain amplifier (selection based on the MMA
Mode input).
- The main MMA electronics section consists of five PCBs connected by a rigid
backplane). The main functions of this electronics are:
- Temperature output filtering, conversion to voltage signals,
scaling and time-multiplexing.
- Acceleration signal anti-alias filtering (cut-off frequency selected based on MMA Mode input).
- The three filtered acceleration signals and the multiplexed temperature signal are
multiplexed and converted into digital signals using a single analog-digital converter.
- The digital output signals are available as 16-bit words at a data rate of 1500 samples
per second on a synchronous serial bus.
- Inrush current limiter implemented on all power input lines.
- Possibility to test accelerometer functionality and perform in-flight electronics
calibration using a test signal generator circuit.
- The MMA housing consists of a bottom module carrying the tri-axial sensor assembly and four
vertical modules (which are clamped to each-other using tie-bolts). The five main MMA PCBs are
mounted into the vertical modules. Access to the rigid backplane and to the tri-axial sensor
assembly interface/positioning bolts is possible by removing the two covers bolted to the bottom
of the bottom module.
The assembled MMA housing is essentially shaped as an aluminium rectangular box featuring Nickel
surface finish and the following interfaces:
- Mechanical interface consists of four captive bolts.
- Electrical interfaces consist of two sub-miniature D-type connectors (one data input/output
connector and one power input connector) and one bonding bolthole.
- Thermal interface consists of two cooling air inlet/outlet slits close to one of the side
walls. The cooling air circulation is restricted to the flow through the internal heatsink
(all internal MMA components are conduction cooled to this heatsink).
- Emission and susceptibility to electro-magnetic radiation is very low due to the
fully encapsulating metal housing.
- Due to the 10-year lifetime requirement only high-reliability components have been selected.
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FSL is developed for ESA by a European consortium headed by Alenia. Verhaert is building the
FSL core unit, which contains the MMA.
FSL is part of the European Columbus module, which was launched and attached to the International
Space Station (ISS) in February 2008.
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Related pages:
TAS3 project
ALSM project
RedShift reference projects
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