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Published online by Cambridge University Press: 23 December 2005
With the COLLISA foil experiment onboard the Mir space station we have collected samples of interstellar helium, which have been returned to the Earth and investigated by mass spectrometric analysis. Recently, we have been able to reduce the experimental uncertainties as given earlier (Salerno et al. 2003). Our improved estimate of the helium isotopic ratio in the local interstellar medium is now ($^3$He/$^4$He)$_{LISM}$=(1.62 $\pm$ 0.29)$\,{\times}\,$10$^{-4}$ (Busemann et al. 2005).