$\DeclareMathOperator\GL{GL}\DeclareMathOperator\PSL{PSL}$Consider the group $\GL_+(3,\mathbb{R})$ acting on $\mathbb{R}^3$. It induces an action on the "sphere at infinity". Moreover, the group of Moebius transformations $\PSL(2,\mathbb{C})$ of the sphere at infinity is a $6$-dimensional subgroup of $\GL_+(3,\mathbb{R})$. Thus the $\GL_+(3,\mathbb{R})$-orbit of the standard conformal structure $c$ on the $2$-sphere at infinity is $3$-dimensional, and can be described as $$ \GL_+(3,\mathbb{R}) / \PSL(2,\mathbb{C}). $$

Could someone perhaps describe this homogeneous space more concretely? As a wild guess, is it perhaps diffeomorphic to $\mathbb{R}^3$?