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A satellite phone, popularly known as the sat phone, is a mobile phone which uses satellites, not landline or cellular broadcasting towers, to make or receive calls.
While making or receiving a call, the signal first travels to the orbiting satellite and then to an earth-bound gateway, before being routed to the receiver. The receiver's response will follow the same path in reverse, taking an equal amount of time to reach the caller.
The mobile equipment, which is also known as a terminal, varies in size. The instrument, which is fitted with retraceable antennae, is not as sleek as a mobile phone. A satellite phone resembles the models of mobile phones that were available in Indian markets ten years ago.
Sat phones are much more expensive than cellular phones. The oldest models cost approximately Rs 10,000 while the latest model, the iconic Iridium 9505A, costs a whopping Rs 49,975.
The cost of calls made and received on a sat phone depends on the network. The three main satellite networks are the Iridium, Globstar and Thuraya. Iridium uses low orbiting satellites that minimises conversational delays, but more importantly, it is the only satellite network that provides coverage across the world, including the oceans.
Globstar covers around 80 per cent of the earth's landmasses, excluding the northern and southern polar regions.
Thuraya covers parts of India, Asia, Africa, the entire Middle East and Europe. Sat phones are specifically manufactured for a particular network and do not work on other networks.
Some companies offer sat phones on rent, and the weekly rent is approximately $24 (Rs 1,200 approximately). Although the call charges on a hired phone remains the same, some service providers do not insist on roaming charges.
The cost of making calls from a satellite phone varies between Rs 7 and Rs 99 per minute. However, calling a sat phone from a land phone or a mobile phone is extremely expensive and charges range from Rs 149 to Rs 699 per minute.
A call from one sat phone to the other costs around Rs 749 a minute, but incoming calls are free. The sat phone also offers messaging service and the rates are approximately $0.59 (Rs 25) per message.
In spite of the high rates, sat phones were the preferred mode of communication of the 10 terrorists who attacked Mumbai. These terrorists used the sea route to launch their attack, and the only way to communicate with their associates was sat phones, as cellular networks would have failed on the ocean.
The sat phone requires a clear line of sight to the sky. The sat phone ensures connectivity from every nook and corner of the earth, be it on top of a mountain, in the middle of an ocean or in a remote desert.
The sat phone is often used in military operations and disaster and relief operations.
In the Mumbai terror attack, the sat phones were used only when the men were traveling out in the open sea. The terrorists switched to mobile phones the moment they entered the Taj, Oberoi and Nariman House. The sim cards for these mobile phones were purchased in West Bengal.
Sat phones have proved to be ineffective when used indoors. The caller needs to stand near a window for the call to go through, and there is a considerable delay in communication.