$\mathit{A}$, ${\mathit{A}}_{11}$, ${\mathit{A}}_{12}$, ${\mathit{A}}_{21}$, ${\mathit{A}}_{22}$, ${\mathit{B}}_T$, ${\mathit{B}}_D$	state-space model matrices of active defense
${\mathit{A}}_i$, ${\mathit{b}}_i$, ${\mathit{C}}_i$, ${\mathit{d}}_i$	state-space model matrices of aircraft’s internal dynamics
$a_M$, $a_T$, $a_D$	acceleration of attacking missile, target, and defender
$a_{MN}$, $a_{TN}$, $a_{DN}$	acceleration component of attacking missile, target, and defender along the Y-axis
$k_1$, $k_2$, ${\mathit{k}}_M$, ${\mathit{k}}_T$, $k_{uT}$	guidance parameters of the attacking missile
$N_{PN}$, $N_{APN}$, $N_{OGL}$	navigation gains of PN, APN, and OGL
$n_M$, $n_T$, $n_D$	dimension of the internal state vector of the attacking missile, target, and defender
$q_M$, $q_T$, $q_D$	internal state vector of the attacking missile, target, and defender
${\mathit{R}}_k$	measurement noise covariance matrix at time instant k
$t_{f_{MD}}$, $t_{f_{MT}}$, $t_{g{o}_{MT}}$	D–M and M–T interception time, time-to-go of M–T engagement
$u_M$, $u_T$, $u_D$	guidance command of the attacking missile, target, and defender
$u_{MN}$, $u_{TN}$, $u_{DN}$	guidance command of the attacking missile, target, and defender along the Y-axis
$u_{TN}^A$, $u_{DN}^A$	adaptive guidance laws of the target and defender
$\mathit{X}$, ${\mathit{X}}_M$	state vector of active defense kinematic model and state vector of the attacking missile
${\widehat{\mathit{X}}}^j$	jth model-conditioned state estimate of active defense
${\widehat{\mathit{X}}}_M\left(k\right|k)$, $\mathit{P}\left(k\right|k)$	state estimate and error covariance of attacking missile
${\widehat{\mathit{X}}}_M^j\left(k\right|k)$, ${\mathit{P}}^j\left(k\right|k)$	jth model-conditioned state estimate and error covariance of the attacking missile
$y_{MD}$, $y_{MT}$, ${\dot{y}}_{MD}$, ${\dot{y}}_{MT}$	D–M and M–T relative displacements and relative velocity along the Y-axis
$Z_{MD}$, $Z_{MT}$	D–M and M–T zero-effort miss distances
$\mathit{z}\left(k\right)$, $z_{MD}\left(k\right)$, $z_{MT}\left(k\right)$	measurement vector, D–M and M–T angle measurement at time instant k
${\tilde{\mathit{z}}}^j\left(k\right|k)$, ${\mathit{P}}_{zz}^j\left(k\right|k-1)$	jth model-conditioned innovation and innovation covariance at time instant k
$\alpha$, $\beta$	penalty weights in the cost function
${\gamma }_M$, ${\gamma }_T$, ${\gamma }_D$	flight-path angle of the attacking missile, target, and defender
${\mathsf{\Lambda }}^j\left(k\right)$, ${\mu }^j\left(k\right)$	jth model-conditioned likelihood function and jth model probability
${\lambda }_{MD}$, ${\lambda }_{MT}$	D–M and M–T line-of-sight angle
$\mathit{\nu }$, ${\nu }_{MD}$, ${\nu }_{MT}$	white Gaussian noise vector, D–M and M–T angle measurement noise
$\rho$, $\mathsf{\Phi }$	expected evasion miss distance, transition matrix
${\tau }_M$, ${\tau }_T$, ${\tau }_D$	time constant of the attacking missile, target and defender