1. 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, 2003 Robotic algorithm of HEND detection of GRBs V. Grinkov, A. Sanin, S. Charyshnikov, A. Kozyrev, M. Litvak, I. Mitrofanov, V. Tret’yakov Institute for Space Research K. Hurley Space Sciences Laboratory, University of California, Berkeley T. Cline NASA/Goddard Space Flight Center

2. 2001 Mars Odyssey page 2 W o r k s h o p H E N D - 2003 Institute for Space Research, June 9 - 11, 2003 Gamma-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 detectors consist of 16 channels and have time resolution of 20 s

3. 2001 Mars Odyssey page 3 W o r k s h o p H E N D - 2003 Institute for Space Research, June 9 - 11, 2003 t GRB phase Afterglow phase 1 second 1 minute 1 hour 1 day 1 month 0 This is the position where the GRB will be registered

4. 2001 Mars Odyssey page 4 W o r k s h o p H E N D - 2003 Institute for Space Research, June 9 - 11, 2003 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:

5. 2001 Mars Odyssey page 5 W o r k s h o p H E N D - 2003 Institute for Space Research, June 9 - 11, 2003 I. Background model 1.Smoothing 2.Weight determination 3.Weighed smoothing 4.Return to Step 2 The initial profile is smoothed with 70-bin window to derive a smoothed one

6. 2001 Mars Odyssey page 6 W o r k s h o p H E N D - 2003 Institute for Space Research, June 9 - 11, 2003 1.Smoothing 2.Weight determination 3.Weighed smoothing 4.Return to Step 2 I. Background model In future smoothing each bin will have its weight which is determined by the weight function (upper left) according to the difference between smoothed and initial profiles

7. 2001 Mars Odyssey page 7 W o r k s h o p H E N D - 2003 Institute for Space Research, June 9 - 11, 2003 1.Smoothing 2.Weight determination 3.Weighed smoothing 4.Return to Step 2 I. Background model Derived with the same window, new smoothed profile substitutes the old one

8. 2001 Mars Odyssey page 8 W o r k s h o p H E N D - 2003 Institute for Space Research, June 9 - 11, 2003 1.Smoothing 2.Weight determination 3.Weighed smoothing 4.Return to Step 2 I. Background model Steps 2-3-4 are repeated 20 times until the smoothed profile represents a good background estimate (green line at the picture)

9. 2001 Mars Odyssey page 9 W o r k s h o p H E N D - 2003 Institute for Space Research, June 9 - 11, 2003 II. Search for events 1. Search for triggered bins and combine them into events 2. Discard short events 3. Stretch boundaries All bins exceeding 6 std. dev. above the background are treated as triggered. Neighboring triggered bins are combined into events.

10. 2001 Mars Odyssey page 10 W o r k s h o p H E N D - 2003 Institute for Space Research, June 9 - 11, 2003 1. Search for triggered bins and combine them into events 2. Discard short events 3. Stretch boundaries II. Search for events Events shorter than 3 bins are discarded

11. 2001 Mars Odyssey page 11 W o r k s h o p H E N D - 2003 Institute for Space Research, June 9 - 11, 2003 1. Search for triggered bins and combine them into events 2. Discard short events 3. Stretch boundaries II. Search for events 35 bins are added to each side of the event. Some events will merge.

12. 2001 Mars Odyssey page 12 W o r k s h o p H E N D - 2003 Institute for Space Research, June 9 - 11, 2003 The GRB gives signals both in the outer and inner SC (left), III. 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).

13. 2001 Mars Odyssey page 13 W o r k s h o p H E N D - 2003 Institute for Space Research, June 9 - 11, 2003 Time periodKnown GRBs GRBs found manually GRBs found by the algorithm Number of false events Feb 02 - Oct 02 (quite) 924160 Nov 02 - Jan 03 (noisy) 347114 Mar 03 - Apr 03 (noisy) 309110 Statistics of the registered events

14. 2001 Mars Odyssey page 14 W o r k s h o p H E N D - 2003 Institute for Space Research, June 9 - 11, 2003 The whole set of GRBs found by the algorithm

15. 2001 Mars Odyssey page 15 W o r k s h o p H E N D - 2003 Institute for Space Research, June 9 - 11, 2003 Conclusions 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.