  A number of X-ray instruments have been active in observing the solar coronal
X-ray radiation this decade. We have compared XSM observations with
simultaneous GOES and RHESSI observations. We present flux calibrations for all
instruments, and compare XSM and GOES total emission measures (TEM) and
temperatures (T). The model-independent flux comparison with XSM and GOES data
at the 1 - 8 angstrom band shows that the fluxes agree with a ratio of 0.94 +/-
0.09 for the data up to April 2005. The Mewe model-dependent Ts and TEMs differ
as XSM observes 1.47 +/- 0.03 times higher Ts than GOES and 1.23 +/- 0.08 times
higher TEMs and 0.92 +/- 0.05 times lower fluxes. The comparison with RHESSI
data at the 6 - 8 keV band shows that the average XSM/RHESSI flux ratio is 2.63
+/- 0.23. The discrepancies revealed in this study were similar to
discrepancies observed in a number of other spaceborne cross-calibration
studies.
