TELKOM 3S

Telkom 3S is an Indonesian Geostationary communication satellite built as a replacement of Telkom 3 that was lost due to launch failure on 6 August 2012. It is fitted with 24 C-band transponders, 8 extended C-band transponders, and 10 Ku-band transponders with 6,4 kW of power, covering Indonesia and parts of Southeast Asia. This satellite was built by Thales Alenia Space to last for over 16 years on the platform of Spacebus 4000B2. It has the dimensions of 1,8 m x 2,95 m x 2,86 m, weighing 3550 kg at liftoff.

Image of Telkom-3S Satellite.
(https://www.broadbandtvnews.com/2017/02/14/ariane-5-ready-for-tonights-mission/)

The satellite is launched by Ariane 5-ECA launch vehicle on 14 February 2017. The rocket also carries another satellite owned by AT&T/DIRECTV called SKY Brasil-1.

Launch Vehicle Details.

Mission

This satellite is owned by PT. Telkom Indonesia to provide high-definition television services (HDTV), as well as mobile communications and internet applications. 

Positioned at 118° East, Telkom 3S will provide C-band coverage for Indonesia and Southeast Asia, while extended C-band beams will cover Indonesia and part of Malaysia. It also is fitted with Ku-band transponders dedicated to national coverage. 

Telkom-3S In Production.

Launch Process

Telkom 3S satellite is launched by Ariane 5-ECA flight VA235. The Ariane 5-ECA launch vehicle is primarily composed of one cryogenic main stage, which in France is called etage principal cryogénique (EPC), with one Vulcain 2 engine; 2 solid rocket boosters, which in France is called étages d'accélération à poudre (EAP); upper cryogenic stage, which in France is called étage supérieur cryotechnique (ESC-A), with one HM-7B engine; vehicle equipment bay (VEB); and payload. 

The 31 m EPC weighs 188 metric tons including 173 metric tons of cryogenic propellant, which is used by the Vulcain 2 engine to provide 1390 kN of thrust (in vacuum) for as long as 540 seconds. The EAP stand 31,6 m tall, weigh 277 metric tons in total including 240 metric tons of solid propellant and provide thrust averaging at 5060 kN and up to 7080 kN. The ESC-A weighs 19 metric tons total including 14,6 metric tons of cryogenic propellant, which is used by the HM-7B engine to provide 67 kN of thrust for 945 seconds.

The flight VA235 brought two payloads, which were SKY Brasil-1 satellite positioned at the upper part inside the fairing and Telkom 3S satellite positioned at the lower part. The Telkom 3S satellite was enclosed inside an internal structure which served as the structure for the SKY Brasil-1 satellite to be attached to. This internal structure is called système de lancement double ariane (sylda). 

After liftoff, the EAP were the first to be jettisoned after the solid propellant was burned out. The fairing was next to be jettisoned after the Ariane 5 got out of the atmosphere. After that, the EPC separated from the ESC-A and fell down to earth. Next, the ESC-A ignited and continued pushing the payloads to their target orbit which was a geostationary transfer orbit. The first one which was separated is the SKY Brasil-1, then the Sylda was separated, and last the Telkom 3S was separated.

Below is the table of Ariane 5-ECA VA235 launch sequence:

Launch Sequence.

Orbit Insertion

After separation, Telkom 3S had an orbit with a perigee altitude of 250 km, an apogee altitude of 35736 km, and an inclination of 4 degrees. This orbit was a geostationary transfer orbit. Each time Telkom 3S reached apogee it did an engine burn to increase its speed in order to circularize its orbit and also lower the inclination of the orbit. This was done a few times until it reached a circular orbit with an altitude of 35736 km and an inclination of 0 degrees. The geostationary orbit is 35786 km in altitude, which is a little bit higher than the 35736 km-high circular orbit of Telkom 3S, so it did another engine burn to move into elliptical orbit with a perigee altitude of 35736 km and an apogee altitude of 35786 km, then another engine burn at the apogee to get into geostationary orbit. All of these processes took place in 10 days.

At first Telkom 3S was positioned at 135,5 degrees east for testing purposes and then it was moved to its final orbital position of 118 degrees east, so it needed to move west. This was done by doing two engine burns to move to a higher circular orbit. This orbit had a period slightly longer than a day so the satellite moved westward in longitude by 1 degree/day. After it reached the desired position, Telkom 3S was moved into geostationary orbit again.

Ariane 5 and Telkom-3S Trajectory.

Why Geostationary Orbit Has Slots?

The geostationary orbit has 1800 slots because of the distance between each slot is 0,5 degree of longitude. Why the geostationary orbit doesn't have more slots? This 0,5 degree of separation makes sure the distance between each satellite is around 1000 km, giving each satellite enough room to avoid a collision and interference.

This limited space makes the geostationary orbit slots very valuable and telecom companies are fighting over these slots. Each slot can have so many telecom companies waiting in line to put their satellites into orbit. This condition is worsened by satellite operators regularly file for more slots than they can physically use, claiming they are insuring against the risk of failure. This means many of the slots are empty and obstructing future companies or countries from entering the market.