Axially grooved heat pipes are widely used for thermal management of electronics in spacecraft. Considering the need of high heat flux electronics in future satellites of ISRO, single-channel axially grooved aluminium-ammonia miniature heat pipes were developed and tested at ISRO satellite centre. In order to gain on-orbit experience and to have flight heritage, a miniature heat pipe was flown on-board GSAT-19 and successfully tested. This paper presents the details of a miniature heat pipe developed in-house, its performance during integrated level satellite thermo-vacuum test on ground and the on-orbit test results.