The objective of mission C39 (the 41st mission for India’s PSLV XL launcher) was to place the IRNSS H navigation satellite (1,425kg) navigation satellite into geostationary transfer orbit.

Following launch from Sriharikota at 19:00 local time on 31^st August and nominal operation of the first three stages for 203 seconds, the payload fairing failed to separate and fourth stage ignition did not occur as planned.

Deployment of the Indian Regional Navigation Satellite System (IRNSS), redesignated NavIC in commercial operation, was completed in April 2016, with the launch of the seventh and final satellite, IRNSS G.

Three months later, however, the first satellite in the constellation, IRNSS A, had to be withdrawn from service, following problems with at least three of its rubidium atomic clocks. Since then, four other clocks on other system components have also malfunctioned, hence the decision to launch IRNSS H, one of the four back-up satellites ordered by ISRO in early 2016.

It is the first in-flight failure of India’s workhorse launcher since 29th September 1997, when the IRS D Earth observation satellite failed to reach its intended orbit, though the correct orbit was subsequently achieved. Since then, there had been a series of 36 successful missions, and the XL version, introduced in October 2008, had performed 17 problem-free launches.

The accident comes at a time when India — now the world’s fourth-ranked space power by number of launches per year (and even third from 2004 to 2016), was looking to increase the PSLV XL launch rate. It follows the maiden flight of the new GSLV Mark III launcher on 6^th June.