'No signal, no antennas': How did Indian astronaut communicate with Earth from space?
Unlike on Earth, space lacks air needed for sound waves to travel. This makes traditional voice communication impossible.
A Historic Moment for India in Space
Indian Air Force Group Captain Shubhanshu Shukla recently made history by reaching the International Space Station (ISS) as part of a Axiom-4 mission. From over 400 kilometres above Earth, he held a video call with Prime Minister Narendra Modi and has since interacted with students from various Indian schools. These conversations sparked a key question: how do astronauts communicate with Earth when space has no network or mobile towers?
The Soundless Void of Space
Unlike on Earth, space lacks air needed for sound waves to travel. This makes traditional voice communication impossible. Sound is a mechanical wave that requires a medium like air or water. Since space is a vacuum, astronauts must rely on an alternative radio waves, to communicate.
Radio Waves – The Backbone of Space Communication
Astronauts use radio waves, a type of electromagnetic radiation that does not need air to travel. Microphones and transmitters in their helmets convert speech into radio signals, which are then transmitted to Earth via satellite relays and antennas. These signals are later converted back into audio by ground stations.
NASA’s Global Communication Network
NASA’s communication system, known as Space Communications and Navigation (SCaN), supports all these connections. It includes massive 230-foot antennas positioned in remote locations around the globe, ensuring uninterrupted contact with fast-moving spacecraft. These antennas track and maintain links with astronauts at all times.
Relay Satellites and Ground Stations
Spacecraft like the ISS communicate with Earth through relay satellites, which hover in high Earth orbit. These satellites act as intermediaries, picking up signals from astronauts and passing them to ground stations. Whether it's a voice message, image, or video call, every communication follows the same path: transmitter → network → receiver.
High-Tech Systems on Board
Inside the ISS, astronauts have advanced communication systems with built-in microphones, headsets, and screens. These allow them not only to talk to mission control but also to email, browse the internet, and participate in live video conferences—like Captain Shukla’s with school students in Lucknow.
The Future: Laser-Based Space Communication
While radio remains the standard, NASA is developing laser-based communication systems. These use infrared beams to transmit data at much higher speeds, promising better clarity and faster connections in the future. Until then, radio waves and a network of antennas keep spacefarers connected to Earth.
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