  We present the results of spectral analysis of the galactic black-hole binary
MAXI J1659--152 in the rising phase of the outburst that lasted for about 65
days starting on 2010 September 25. The presence of a broad Fe line, verified
by Monte-Carlo simulations, and coverage of a wide energy band by utilizing the
combined spectral capabilities of XMM-Newton/EPIC-pn and RXTE/PCA allowed us to
use a combination of reflection spectroscopy and continuum fitting methods to
estimate the spin of the black hole. We explored the entire parameter range
allowed by the present uncertainties on black-hole mass, inclination, and
distance as well as the accretion rate. We show that for about 95 percentage of
parameter space and very reasonable upper limits on mass accretion rate, the
spin of the black hole has to be negative. This is the first clear detection of
negative spin in a galactic black-hole binary.
