Abstract
We classify trigonometric reflection matrices for vector representation of quasistandard quantum affine Kac-Moody pairs of classical Lie type. The coideal subalgebras involved are described by admissible pairs, which are in one-to-one correspondence with affine Satake diagrams. The reflection matrices are found by solving the associated boundary intertwining equation. Quasistandard coideal subalgebras are a generalization of standard coideal subalgebras as defined by Letzter and Kolb; the associated K-matrices in the vector representation have particularly elegant representation-theoretic properties. Additional characteristics such as minimal polynomials and affinization relations are also investigated.