The response of the SXT to a thermal plasma has been computed using the thermal spectrum of Mewe et al. (1985, 1986), but with the abundances adjusted to coronal values (Meyer, 1985). The SXT thermal responses are shown in Fig. 4 for the various analysis filters. One can see from the curves that there are essentially two ``thick'' filters and three ``thin'' filters plus the open position. The open position has almost never been used during flight. This is because, prior to the entrance filter failure in November 1992, the aspect sensor door was left open almost continuously in order to take optical exposures. After the entrance filter failure in November 1992, the open position became unusable.
The SXT response functions are available through the IDL routine SXT_FLUX.
For example,
IDL> te = 5.5+findgen(51)*.05 ; Log10(te) vector between 5.5 and 8.0
IDL> plot_io,te,SXT_FLUX(te,1),yr=[.01,1000]
IDL> for i=2,6 do oplot,te,SXT_FLUX(te,i)
should reproduce Fig. 5. Note that the second argument is the normal
SXT filter-B number.
The units of the plot are DN/sec for an emission measure,
EM=
cm
. SXT_FLUX has an optional switch:
/photons; if specified, the routine
will return the equivalent photons s
detected by the SXT.
This will allow the user to determine the value of DN/photon as a
function of filter and electron temperature. For example, try the
following IDL commands to plot DN/photon for each filter as a function of
electron temperature.
IDL> plot,te,SXT_FLUX(te,4)/SXT_FLUX(te,4,/photons) ; plot DN/photons vs te
IDL> for i=1,6 do oplot,te,SXT_FLUX(te,i)/SXT_FLUX(te,i,/photons)
The partial entrance filter failure in November 1992 caused a small
change to the SXT response function. SXT_FLUX has a date=
option which will return the new response function if the date is given
as date='13-nov-92 17:01' or later (the date can be given in any
standard Yohkoh format, such as a roadmap or index structure). In this
case, the fractional open area of the entrance filter (the size of the
hole) is taken to be 0.0833.
For information about how to obtain temperature estimates from the intensity ratios through the various filters, see the User's Guide.