Quick start with the inversion software:


0)      download/unzip IDL inversion routines inversion.zip Place all IDL routine so that they are seen by IDL program.


1)    SPEX USERS:  do thermal plus+broken-power law thin-target fit (f_vth_thin )

(for details see http://hesperia.gsfc.nasa.gov/rhessidatacenter/spectroscopy.html)

 OSPEX USERS: start OSPEX defining OSPEX object name


or do thermal plus thin fit inside OSPEX  (vth+thin), Press Accept the results and Continue

Currently inversion works for one time interval only.

(How to use OSPEX see http://hesperia.gsfc.nasa.gov/~dennis/OSPEX/The_Basics/index.htm)


1)       run invesion program

       within SPEX: 

       SPEX> idl, inv_counts2electrons

       within OSPEX: 

       IDL> inv_counts2electrons,obj=o

       If you want to find a photon flux replace electrons with photons :

       within SPEX: 

       SPEX> idl, inv_counts2photons

       within OSPEX: 

       IDL> inv_counts2photons,obj=o



3)      Look at the residuals you have after the inversion. Do you like the regularised solutions and the residuals? If not adjust  reg_tweak   parameter. If the resulting regularised solution is still oscillating (and the residuals are too good (CHI2<1)) you need to increase the regularisation parameter, if the residuals are bad (CHI2 >1) the solution is likely to be over-regularised then reduce the parameter. It is wise to decrease/increase reg_tweak bit-by-bit changing by 20 % or so. The default value of  reg_tweak  is 1.

SPEX users:    SPEX> idl, inv_counts2electrons, reg_tweak=0.8

OSPEX users: IDL> inv_counts2electrons, obj=o, reg_tweak=0.8


4)      Make sure that the results are correct. Play with different energy ranges in SPEX/OSPEX and regularisation order. Try different parameters in the inversion software. The output of the inversion will be written into your working directory.  The code produces (model-independent (regularised) either electron flux  <VnF> [electrons/sec/keV/cm^2]) or photon flux [photons/sec/cm^2/keV] saved as IDL save file, plotted into ps files.



;  inversion,version=version,order=order,Npass=Npass,Guess=Guess,reg_tweak=reg_tweak




;   version   - string, version of the inversion code (currently only one version exist)

;   order     - integer, regularization order. Can be 0 (default), 1, or 2.

;   Npass     - integer, number of random noise realisations for the confidence strip.

;                 Default is 30.

;   Guess     - integer, 1 or 0 (default) – to use or NOT to use forward-fit solution in the constraint

;   reg_tweak - float,  parameter to adjust the regularization parameter (default is 1).


Last updated, 24-Oct-2005 by eduard (at) astro.gla.ac.uk