  The radiative transitions between the $4d^{10}5p^2(^3P_{0,1,2})nl$ and
{$4d^{10}5s5p({}^3P_1^o)nl$ autoionizing} states of an indium atom that
represent dielectronic satellites of the $4d^{10}5p^2 {}^3P_0 \to 4d^{10}5s5p
{}^3P_1$ ($\lambda =171.7$ nm), $4d^{10}5p^2 {}^3P_1 \to 4d^{10}5s5p {}^3P_1$
($\lambda =166.7$ nm), and $4d^{10}5p^2 {}^3P_2 \to 4d^{10}5s5p {}^3P_1$
($\lambda =160.7$ nm) spectral lines of an In$^{+}$ ion have been observed for
the first time. The energy dependences of the effective excitation cross
sections of dielectronic satellites, as well as near-threshold regions of these
spectral lines, were investigated in the range of electron energies 9$\div $15
eV with the help of the spectroscopic method using crossed beams of electrons
and In$^{+}$ ions. The absolute excitation cross sections of dielectronic
satellites amount to $(0.7\div 2)\times 10^{-16}$ cm$^{2}$ and are of the same
order of magnitude as the effective excitation cross sections of the
corresponding ionic lines. It is found that a considerable increase of the
probability of radiation decay of the $4d^{10}5p^2(^3P_{0,1,2})nl$ autoionizing
states of the In atom is related to strong relativistic and correlation
effects, in particular to the configuration interaction of the $5p^2nl$ levels
both with one another and with the levels of the $5s5dnl$ and $4d^95s^25p^2$
configurations.
