A New Approach for 4-D Exospheric Tomography Based on Optimal Interpolation and Gaussian Markov Random Fields. - Gonzalo Cucho-Padin; Humberto Godinez; Lara Waldrop; Igor Baliukin; Dolon Bhattacharyya; David Sibeck; Michael Henderson (IEEE Geosci. Remote. Sens. Lett., 2023)