Santa-rasa means appreciation of the greatness of the Lord, but there is no active service of the Lord. The land, the grass, the trees, the plants, fruits, or the cows in the transcendental world are supposed to be situated in the santa-rasa. As spiritual beings, they are all conscious of Krishna, but they prefer to appreciate Krishna's greatness remaining as they are.
The next development from santa-rasa is dasya-rasa, which means voluntary offering of some service. Next development is Sakhya rasa, or service in spirit of friendship and well-wisher. The next development is Vatsalya rasa, service as well wisher and affection. The next development is Madhura rasa, service, friendship, affection and conjugal love. So in the Madhura rasa, everything is complete; there is Santa rasa, Dasya rasa, Sakhya rasa, Vatsalya rasa, and Madhura rasa. But each and every one of the rasas is complete in itself. A person in Santa rasa or Sakhya rasa is as good as one in Madhura rasa because in the spiritual world everything is absolute. But from the platform of spiritual vision, where there is transcendental discrimination, one can appreciate Madhurya rasa as complete as anything.
In the spiritual world there is no such relationship as God as the father. In the material world such conception is appreciated very much. In the material world everyone wants to take from God because the conditioned soul wants to enjoy senses. And the concept of fatherhood is to drag resources from the Supreme. But in the spiritual world there is no question of drawing from the Supreme. Everything there is to serve the Lord, and service is rendered in 5 different rasas or transcendental humors as described above. In the transcendental world instead of taking the Lord as father, He is treated as son, because son derives service from the Father, whereas in the material world the father maintains the conditioned souls or sons of God.
Rupa Goswami's eternal rasa is conjugal love. He is one of the associates of Radharani, and he helps Radharani while engaged in the service of Krishna. He is known as Rupamanjari in the spiritual world.