  We compute the Picard group $ Pic(A_q) $ of the noncommutative algebraic
2-torus $A_q$, describe its action on the space $ R(A_q) $ of isomorphism
classes of rk 1 projective modules and classify the algebras Morita equivalent
to $ A_q $. Our computations are based on a quantum version of the
Calogero-Moser correspondence relating projective $A_q$-modules to irreducible
representations of the double affine Hecke algebras (DAHA) $ H_{t,
q^{-1/2}}(S_n) $ at $ t = 1 $. We show that, under this correspondence, the
action of $ Pic(A_q) $ on $ R(A_q) $ agrees with the action of $ SL_2(Z) $ on $
H_{t, q^{-1/2}}(S_n) $ constructed by I.Cherednik. We compare our results with
smooth and analytic cases. In particular, when $ |q| \not= 1 $, we find that $
Pic(A_q) $ is isomorphic to the group of auto-equivalences $ Auteq(D^b(X))/Z $
of the bounded derived category of coherent sheaves on the elliptic curve $ X =
C*/Z $ modulo translations.
