DIMAC study phase

 


DIMAC prototype mechanism assembly
(study phase status, 06/2005).

The acronym 'DIMAC' stands for 'direct measurement micro-accelerometer'. DIMAC is a development study proposed by RedShift in the frame of a call for innovative technology proposals by ESA. The proposed device is intended to supplement the existing range of low-cost micro-accelerometers by extending the measurement bandwidth down to steady-state accelerations (true DC).
 
Current low-cost measurement devices are restricted to vibratory acceleration measurement (frequency >0.01Hz). Existing quasi-steady micro-accelerometers (frequency >10-4Hz) are expensive and bulky. The proposed device is low-cost, low power and small. Therefore it would fit any space platform.
 
The DIMAC baseline design solution is to track the displacement of a small free-floating object. This object is confined to a small space (free float volume). Analysis of the trajectory reveals the quasi-steady acceleration level. An electro-mechanical device repositions the free-floating object at discrete time intervals. The absence of any feedback force during the free float period guarantees long term performance without recalibration.
 
The DIMAC target specifications are:
 
Parameter Value
Mode B A1 (nominal) A2 (high-res)
Range -1mg..+1mg -10g..+10g -1g..+1g
Resolution 5g 50ng 10ng
Bandwidth 0Hz..0.1Hz 0Hz..0.01Hz 0Hz..0.01Hz
DC Accuracy 10g 100ng 10ng
AC Accuracy 10g 100ng 100ng
Data sampling rate 1 S/s 0.1 S/s 0.1 S/s
Sensor head mass (System mass) <2.5kg (<4.5kg)
Sensor head volume (System volume) <1.5dm (<2.5dm)
Sensor head power (System power) <10W (<15W)
 
A market study in the European scientific community performing systematic research in microgravity shows a high level of interest in this product. The DIMAC mode A2 target specifications have been based on the feedback received from these scientists.
 
The target of the DIMAC study phase project is the development of a prototype which allows basic validation of the DIMAC operation principle using parabolic flight tests.
(see pictures)

RedShift participated to the 40th ESA parabolic flight campaign (June 2005) in order to test the DIMAC prototype. Additional tests have been performed during the 42nd and 43rd ESA parabolic flight campaigns (March 2006).
(see pictures and movie)
 
However, final DIMAC validation requires orbital flight tests.
Therefore RedShift was granted an extension of the TAS3 contract, in order to develop DIMAC flight hardware for the Foton M-3 flight (launch foreseen for fall 2007). The DIMAC sensor head will be controlled and monitored by the DIMAC data acquisition module, which re-uses the TAS3 hardware (supplemented by two DIMAC electronics modules).
The DIMAC sensor complements the TAS3 sensor (resulting in a frequency measurement range down to quasi-static acceleration measurements).
 
Related pages:
DIMAC FM project
RedShift reference projects