Physics
Scientific paper
Dec 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufmsm21a2004b&link_type=abstract
American Geophysical Union, Fall Meeting 2011, abstract #SM21A-2004
Physics
[2794] Magnetospheric Physics / Instruments And Techniques
Scientific paper
The Magnetospheric MultiScale (MMS) mission will enable the study of small-scale magnetic reconnection structures and their rapid motions from closely spaced platforms using instruments capable of high angular, energy, and time resolution measurements. To meet these requirements, the Fast Plasma Instrument (FPI) consists of eight (8) identical half top-hat electron sensors, eight (8) identical half top-hat ion sensors, and an Instrument Data Processing Unit (IDPU) on each of the four (4) MMS spacecraft. The sensors are packaged into pairs (DES & DIS) whose 90° x 180° (with electostatic deflection) fields-of-view (FOV) are placed at 90° intervals around the spacecraft periphery. Each sensor is equipped with electrostatic aperture steering to allow the sensor to scan a 45° x 180° fan about the its nominal viewing (0° deflection) direction. The combination of the eight electron/ion sensors, employing aperture steering, image the full-sky every 30ms (electrons) and 150ms (ions), respectively. To probe the diffusion regions of reconnection events, the highest temporal/spatial resolution mode of FPI results in the DES complement of each spacecraft generating 6.5-Mb s-1 of electron data while the DIS generates 1.1-Mb s-1 of ion data yielding an FPI total data rate of 7.6-Mb s-1 for each of the 4 MMS spacecraft. The FPI electron and ion data is collected by the IDPU and transmitted to the Central Data Instrument Processor (CIDP) on the spacecraft for science interest ranking. Owing to limitations in downlink band width, only data sequences that contain the greatest potential for reconnection science may be down-linked by the spacecraft. This requires a data ranking process implemented as part of a burst trigger system. The FPI burst trigger system uses count rate sums representing pseudo physical quantities to approximate the local plasma environments. As each pseudo quantity will have a different value, a set of two scaling factors is employed for each pseudo term. These pseudo quantities are then combined at the instrument, spacecraft, and observatory level leading to a final ranking of mission data based on expected scientific interest. Here, we present simulations of the fixed-point burst trigger system for the FPI. A variety of data sets based on previous mission data as well as analytical formulations are tested. Comparisons of floating point calculations versus the fixed-point hardware simulation are shown. Analysis of the potential sources of error from overflows, quantization, and other sources are examined and mitigation methods are presented. Finally, a series of calibration curves are presented, showing the expected error in pseudo quantities based solely on the scale parameters chosen and the expected data range. We conclude with a presentation of the current base-lined FPI burst trigger approach.
Adrian Mark L.
Barrie A.
Dorelli John
Paterson William R.
Pollock C. J.
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