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The new release of data from Wilkinson Microwave Anisotropy Probe improvesthe observational status of relic gravitational waves. The 7-year resultsenhance the indications of relic gravitational waves in the existing data andchange to the better the prospects of confident detection of relicgravitational waves by the currently operating Planck satellite. We apply toWMAP7 data the same methods of analysis that we used earlier [W. Zhao, D.Baskaran, and L.P. Grishchuk, Phys. Rev. D 80, 083005 (2009)] with WMAP5 data.We also revised by the same methods our previous analysis of WMAP3 data. Itfollows from the examination of consecutive WMAP data releases that the maximumlikelihood value of the quadrupole ratio $R$, which characterizes the amount ofrelic gravitational waves, increases up to $R=0.264$, and the intervalseparating this value from the point $R=0$ (the hypothesis of no gravitationalwaves) increases up to a $2\sigma$ level. The primordial spectra of densityperturbations and gravitational waves remain blue in the relevant interval ofwavelengths, but the spectral indices increase up to $n_s =1.111$ and$n_t=0.111$. Assuming that the maximum likelihood estimates of the perturbationparameters that we found from WMAP7 data are the true values of the parameters,we find that the signal-to-noise ratio $S/N$ for the detection of relicgravitational waves by the Planck experiment increases up to $S/N=4.04$, evenunder pessimistic assumptions with regard to residual foreground contaminationand instrumental noises. We comment on theoretical frameworks that, in the caseof success, will be accepted or decisively rejected by the Planck observations.

Relic gravitational waves in the light of 7-year Wilkinson Microwave Anisotropy Probe data and improved prospects for the Planck mission