Sunday Orthros (Morning Prayer) begins with Great Vespers the evening prior and both together are part of the Sunday worship. In the Russian tradition both these services are, in certain places, combined to form a Vigil service that take place on Saturday evening. Great Vespers begins with the setting of the sun and moves into and through the darkness of night into the light. Orthros, on Sunday morning, continues the theme of God’s revelation and light.
Orthros is like celebrating Pascha every single week. It is one of the most prayerful and powerful services of the Orthodox Church. It begins with a prayer asking the Holy Spirit to come and live in us and cleanse us from sin and save us.
O Heavenly King, O Comforter, the Spirit of Truth, Who art everywhere present and fillest all things, Treasury of blessings and Giver of Life, come and abide in us, and cleanse us of all impurity, and save our souls, O Good One.
But the main focus is on the Resurrection of our Lord Jesus Christ. The entire service has such an abundance of scripture (mostly Psalms and the Gospel accounts of the Resurrection read every single week) and theology one cannot help but be instructed and inspired.