Supersymmetric instantonic D1-branes in AdS${}_5\times$S${}^5$ background

According to the covariant open superstring description of 1/2-BPS D-branes in the AdS${}_5\times$S${}^5$ background, there are two kinds of purely instantonic D-branes. One is the well known D(-1)-brane or D-instanton, and another is the D1-brane spanning a two dimensional subspace inside S${}^5$. We identify the actual 1/2-BPS instantonic D1-brane configurations and their supersymmetry structures. From the results, it is concluded that any spherical D1-instanton with the radius equal to that of S${}^5$ is 1/2-BPS. After evaluating the 1/2-BPS D1-instanton action, we discuss the relation of D1-instanton with the $(p,q)$ string instanton. We also discuss the possible 1/2-BPS and 1/4-BPS multiple D1-instanton configurations.