2001 mars odyssey page 1 w o r k s h o p h e n d - 2003 institute for space research, june 9 - 11,...

2001 Mars Odysseypage 1

W o r k s h o p H E N D - 2003

Institute for Space Research, June 9 - 11, 2003

Robotic algorithm of Robotic algorithm of HENDHEND detection of GRBsdetection of GRBs

V. Grinkov, A. Sanin, S. Charyshnikov, A. Kozyrev, M. Litvak, I. Mitrofanov, V. Tret’yakovInstitute for Space Research

K. HurleySpace Sciences Laboratory, University of California, Berkeley

T. ClineNASA/Goddard Space Flight Center




Gamma-Ray Burst HEND SubsystemGamma-Ray Burst HEND Subsystem

Profile data are transmitted continuously by 60 s profiles

Time resolution: Outer 0.25 s Inner 1 s

Energy range: Outer 30 – 1000 keV Inner 60 – 2000 keV

Spectra of both detectorsconsist of 16 channels andhave time resolution of 20 s




t

GRBphase

Afterglowphase

1 second

1 minute 1 hour 1 day

1 month

0

This is the position where the GRB will be

registered




I. Background Model,to know the background variations

II. Search for Events, to find possible candidates to be GRBs

III. Correlation Analysis, to eliminate non-burst events

Three main steps of the algorithm are as follows:




I. Background modelI. Background model

1. Smoothing2. Weight determination3. Weighed smoothing4. Return to Step 2

The initial profile is smoothed with 70-bin window to derive a smoothed one






In future smoothingeach bin will have its weightwhich is determined by the weight function (upper left)according to the differencebetween smoothed and initialprofiles






Derived with the same window,new smoothed profilesubstitutes the old one






Steps 2-3-4 are repeated 20 times until the smoothed profilerepresents a goodbackground estimate(green line at the picture)




II. Search for eventsII. Search for events

1. Search for triggered bins and combine them into events2. Discard short events3. Stretch boundaries

All bins exceeding 6 std. dev. above the backgroundare treated as triggered.Neighboring triggered bins are combined into events.






Events shorter than 3 binsare discarded






35 bins are added to each side of the event.Some events will merge.




The GRB gives signals both in the outer and inner SC (left),

III. Correlation analysisIII. Correlation analysis

The blue lines represent flux in the outer, and the green lines in the inner, detector

while the anomalous signal is

reflected only in the outer (down).




Time period Known GRBs

GRBs found manually

GRBs found by the algorithm

Number of false events

Feb 02 - Oct 02

(quite)

92 41 6 0

Nov 02 - Jan 03

(noisy)

34 7 1 14

Mar 03 - Apr 03

(noisy)

30 9 1 10

Statistics of the registered events




The whole set of GRBs found by

the algorithm




ConclusionsConclusions

1. An algorithm to search for bursts in HEND data was built.

2. The algorithm triggered 8 real and 24 false events during both quite and noisy data.

3. As an improvement of the algorithm spectral data procession must be added.

2001 mars odyssey page 1 w o r k s h o p h e n d - 2003 institute for space research, june 9 - 11,...

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