How to define a user GTI for SPI analysis

last update of this page: 28.02.2003

Here I describe how to create a good time interval, which is then used by the SPI analysis software. Using this, you can in- or exclude certain time periods in your analysis. This is particular interesting for short events, like GRBs.

create an empty GTI structure:
dal_create obj_name="usergti.fits" template="GNRL-USER-GTI.tpl"
Fill some keywords (ftools command; you can of course also set the keywords by hand using e.g. fv):
fparkey value=0.0 fitsfile=usergti.fits\[1] keyword=TSTART fparkey value=10000.0 fitsfile=usergti.fits\[1] keyword=TSTOP fparkey value=GOOD fitsfile=usergti.fits\[1] keyword=GTI_TYPE
TSTART and TSTOP define the start and end validity of your selection, not the selection itself.
The GTI_TYPE can be 'GOOD' (use the time specified in the user GTI file) or 'BAD' (exclude the time specified in the user GTI file)
open the fits file (e.g. with fv):
fv usergti.fits
click on 'Table'
click on 'Edit'
select 'Insert' and then 'row'
insert as many rows as you want to have good time intervals
fill in the row either the UTC or the IJD or the OBT columns corresponding to your good/bad time you want to define. It is only necessary to fill ONE time format.
'Save' the fits file
Now you can use the 'usergti.fits' file in your analysis; when you run spi_science_analysis, set the following parameters to activate your personal GTI (this example assumes that you defined the GTIs in UTC) :
spi_gti_creation_use_gtis,s,ql,"DATA_GAPS USER",,,"Input GTI names of all SPI GTIs (ATTITUDE DATA_GAPS USER)" spi_gti_creation_usergtiname,s,ql,"usergti.fits[GNRL-USER-GTI]",,,"User defined GTI table" spi_gti_creation_usergtiformat,s,ql,"UTC",IJD|UTC|OBT,,"Time format used from user defined GTI table (IJD, UTC, OBT)"

In case of questions and comments: contact me.