Elon Musk’s SpaceX Starlink low earth orbit (LEO) satellite system has successfully transmitted text messages to and from unmodified smartphones on Earth. The news comes just six days after the launch of six Starlink LEO satellites designed to be orbiting cell towers. 

While details such as speeds and latency were not disclosed, the company reported that the launch and early tests were completed without any issues. The company also said that the initial messages were transmitted over a single “Direct to Cell” Starlink satellite, so it remains unclear whether the other five satellites also participated in relaying the messages.

“Connecting cell phones to satellites has several major challenges to overcome,” read a statement by the company. 

“For example, in terrestrial networks cell towers are stationary, but in a satellite network they move at tens of thousands of miles per hour relative to users on Earth. This requires seamless handoffs between satellites and accommodations for factors like Doppler shift and timing delays that challenge phone to space communications.”

The satellites are also capable of using 4G technology with an LTE modem onboard. However, the dynamic nature of orbiting satellites, moving at high speeds, presents a challenge in maintaining a consistent signal to ground-based users.

“To accomplish this, we architected the system, including satellite altitudes, beam size and placement, elevation angles, and number of satellites, such that we are just at the edge of physics where LTE is achievable and reliable,” said SpaceX.

At the moment, Starlink currently has about 5,311 LEO satellites in orbit, and has approval to add about 7,500 more by the end of 2027. In the UK, customers would pay £75 per month for the service, plus £449 for the home kit and £20 for shipping. 

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The service promises internet latency times of 25-50ms, downloads of 25-100Mbps and uploads of 5-10Mbps. Of the 2.3 million customers, only 42,000 are in the UK, mostly in rural areas. 

SpaceX says it aims to launch a constellation of satellites to enable basic text services in 2024, with support for voice, data, and IoT services due in 2025.