Surveying the dark side

We examine the prospects for the next generation of surveys aimed at elucidating the nature of dark energy. We review the methods that can be used to determine the redshift evolution of the dark-energy equation-of-state parameter w, highlighting their respective strengths and potential weaknesses. All of the attractive methods require surveys covering more than 5 - 10 000 square degrees of the sky. We examine the accuracy that each method is likely to deliver within a decade, and discuss the difficulties arising from systematic uncertainties associated with the techniques. We conclude that the proposed photometric and redshift surveys have the potential to deliver measurements of w with percent accuracy at several redshifts out to z similar to 3. Of particular interest will be the combination of weak lensing and baryonic acoustic oscillations measurements. This exquisite precision is likely to have a fundamental impact on our understanding of the nature of dark energy, providing the necessary guidance for its theoretical explanation.