GSAT-18

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 K_u-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.^[5]

GSAT-18

Mission type	Communications
Operator	INSAT
COSPAR ID	2016-060A
SATCAT no.	41793
Website	GSAT-18
Mission duration	Planned: 15 years Elapsed: 8 years, 9 months, 23 days
Spacecraft properties
Bus	I-3K[1]
Manufacturer	ISRO Satellite Centre Space Applications Centre
Launch mass	3,404 kg (7,505 lb)[2]
Dry mass	1,480 kg (3,263 lb)[2]
Power	6,474 watts[2]
Start of mission
Launch date	5 October 2016 (2016-10-05), ≈20:30 UTC[3]
Rocket	Ariane 5 ECA, VA-231[1]
Launch site	Guiana Space Centre ELA-3[1]
Contractor	Arianespace[1]
Orbital parameters
Reference system	Geocentric
Regime	Geostationary
Longitude	74° E
Perigee altitude	35,750 km (22,214 mi)
Apogee altitude	35,822 km (22,259 mi)
Inclination	0.0616°
Epoch	11 June 2017 01:46:00 UTC[4]
Transponders
Band	24 × C band 12 × extended C band 12 × Ku band 2 × Ku beacon
GSAT ← GSAT-15 GSAT-9 →

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.^[3][6] 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.^[1][7] The total cost of the satellite and launch services was about US$153 million.^[8]

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.^[9][10] Arianespace later paired GSAT-18 with Australia's Sky Muster II for a 4 October 2016 launch.^[11] The launch was delayed 24 hours to 5 October due to excessively high crosswinds at the launch site.^[12]

Orbit raising and station keeping

Orbit raising operations were made using an on-board LAM and chemical thrusters^[2] to place the satellite in the intended geostationary orbital slot.

Op #	Date/ Time (UTC)	LAM burn time	Height achieved		Inclination achieved	Orbital period	References
			Apogee	Perigee
1	6 October 2016 10:16	6040.6 sec	35,802 km (22,246 mi)	14,843 km (9,223 mi)	1.325°	15 hrs, 36 mins	[13]
2	8 October 2016 05:59	-	35,840 km (22,270 mi)	32,518 km (20,206 mi)	0.129°	22 hrs, 34 mins	[14]
3	9 October 2016 04:51	256.17 sec	35,802 km (22,246 mi)	35,294 km (21,931 mi)	0.136°	23 hrs, 44 mins	[15][16]