He was consecrated as a deacon on 2 July 1966, and as priest on 28 January 1967 at St. Peter's Cathedral, Osnabrück, celebrating his first mass at St. Marien Immaculata Conceptio, Bückeburg [de].

[5] When the diocese became an archdiocese the following year, he was also Bischofsvikar [de] for the doctrine of faith, responsible for ecumenism in the fields of church, culture and media.

[7] Jaschke belonged to the Freitagsgesellschaft [de], a think tank of politicians, entrepreneurs, scientists, artists and theologians founded in 1985 by Helmut Schmidt.

[8] He was known nationwide by his presence in the media in many talk shows,[2][9] not avoiding difficult questions such as celibacy, homosexual priests and pomposity of dignitaries.

[4][5] He was buried at the Hamburg Cathedral on 15 July 2023 following a pontifical requiem mass held by Archbishop Stefan Heße, who said that Jaschke had given God's word his unmistakable voice in sound and thoughts, translating it into today's language.