The Andhra Christian Theological College, Hyderabad where Rajarathnam studied is affiliated to the Senate of Serampore College (University), India's first[5] {a University under Section 2 (f) of the University Grants Commission Act, 1956}[6] with degree-granting authority validated by a Danish Charter and ratified by the Government of West Bengal.
In 1996 when Bishop D. N. Samuel retired on attaining superannuation, the ensuing sede vacante was filled up by the Church of South India Synod by appointing Rajarathnam to the bishopric in 1997 who was principally consecrated by Vasanth P. Dandin, Moderator, Church of South India Synod and William Moses, Deputy Moderator, Church of South India Synod.
[2] In 1998,[1] Rajarathnam attended the thirteenth Lambeth Conference presided over by George Carey, Archbishop of Canterbury.
On 11 April 2006,[1] Rajarathnam stepped down as the Bishop-in-Dornakal due to superannuation causing the Diocese of Dornakal to be sede vacante.
The Ramanuja Scholar, B. S. Devamani succeeded Rajarathnam as Bishop-in-Dornakal.