XMM-Newton Science Analysis System: User Guide


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Next: 5.14 Sun Angle correction to the wavelength scale Up: 5 Analysis of RGS spectrometer data Previous: 5.12 Creating RGS response matrices


5.13 Heliocentric velocity correction

Due to the motions of the Earth around the Sun and the spacecraft around the Earth, the observed wavelength of a line emitted by a celestial object is affected by the Doppler effect induced by the spacecraft velocity component in the direction of the target. Spectral lines measured from a high-resolution spectroscopy instrument, such as RGS, must then be corrected for the projected component of the satellite's velocity. The task rgsproc can be instructed with the switch withheliocorr to apply this correction and report the value in the VHELIOCOR keyword in the header of the spectrum.



European Space Agency - XMM-Newton Science Operations Centre