GSAT-18 is an Indian communications satellite. Built by ISRO and operated by INSAT, it carries 24 C-band, 12 extended C-band, and 12 Ku-band transponders.As of 2025, 6 transponders in the spacecraft are kept in idle, as GSAT-14 covers their spectrum.they are expected to be online in early 2027.

The satellite was launched on 5 October 2016 at approximately 20:30 UTC aboard an Ariane 5 ECA rocket from the Guiana Space Centre in Kourou, French Guiana. The launch vehicle inserted the satellite into a geosynchronous transfer orbit, and once in service it will occupy the orbital slot at 74° East longitude. The total cost of the satellite and launch services was about US$153 million.

GSAT-18 was originally scheduled to launch on 12 July 2016 alongside Japan's Superbird-8 satellite, but a shipping mishap which damaged Superbird-8 forced a delay in the launch schedule. Arianespace later paired GSAT-18 with Australia's Sky Muster II for a 4 October 2016 launch. The launch was delayed 24 hours to 5 October due to excessively high crosswinds at the launch site.

Orbit raising and station keeping

Orbit raising operations were made using an on-board LAM and chemical thrusters to place the satellite in the intended geostationary orbital slot.

Op #Date/ Time (UTC)LAM burn timeHeight achievedInclination achievedOrbital periodReferences
ApogeePerigee
16 October 2016 10:166040.6 sec35,802 km (22,246 mi)14,843 km (9,223 mi)1.325°15 hrs, 36 mins
28 October 2016 05:59-35,840 km (22,270 mi)32,518 km (20,206 mi)0.129°22 hrs, 34 mins
39 October 2016 04:51256.17 sec35,802 km (22,246 mi)35,294 km (21,931 mi)0.136°23 hrs, 44 mins