High-resolution Doppler spectroscopy is a powerful tool for identifying molecular species in the atmospheres of both transiting and non-transiting exoplanets .
Currently , such data is analysed using cross-correlation techniques to detect the Doppler shifting signal from the orbiting planet .
In this paper we demonstrate that , compared to cross-correlation methods currently used , the technique of Doppler tomography has improved sensitivity in detecting the subtle signatures expected from exoplanet atmospheres .
This is partly due to the use of a regularizing statistic , which acts to suppress noise , coupled to the fact that all the data is fit simultaneously .
In addition , we show that the technique can also effectively suppress contanimating spectral features that may arise due to overlapping lines , repeating line patterns , or the use of incorrect linelists .
These issues can confuse conventional cross-correlation approaches , primarily due to aliasing issues inherent in such techniques , whereas Doppler tomography is less susceptible to such effects .
In particular , Doppler tomography shows exceptional promise for simultaneously detecting multiple line species ( e.g .
isotopologues ) , even when there are high contrasts between such species – and far outperforms current CCF analyses in this respect .
Finally , we demonstrate that Doppler tomography is capable of recovering molecular signals from exoplanets using real data , by confirming the strong detection of CO in the atmosphere of \tau Boo b .
We recover a signal with a planetary radial velocity semi-amplitude K _ { p } = 109.6 \pm 2.2 km s ^ { -1 } , in excellent agreement with the previously reported value of 110.0 \pm 3.2 km s ^ { -1 } .