Mission scientists have detected the first signals from the Huygens Titan probe, relayed to Earth by its Cassini mothership.

Professor John Zarnecki, principle investigator on the UK science package, said: "Cassini has turned back to the earth and started to transmit data. It is fantastic. It means Cassini has flown its mission correctly. Now we have 40 mins of suspense, then we'll start seeing mission data."

The first data is not experimental data, but housekeeping information. Even so, it does tell us some things: the amount of current being drawn, for example, gives an indication of whether or not the experiments are running, Zarnecki explained. "It tells us things like is it on, is it working?" he said.

Earlier, he told a UK press conference by video link that the scientists at mission control had detected a frequency shift of around 20Hz in the signal Huygens has been sending to Cassini. This shift came after 147 minutes, about the expected descent time, so the scientists are tentatively saying this could be the landing.

"It is certainly grounds for hope," said Zarnecki. He cautioned that the real test of the mission was whether or not it managed to send back any data. Nevertheless, he added: "We are trying hard not to feel elated, but there are a few smiles at mission control."

Huygens has taken seven years to reach Titan, the second largest satellite in the solar system, and the only one with an atmosphere.

It made its journey on board NASA's Cassini mission, and separated from the mothership on Christmas day last year. Since then it has been coasting through space, dormant, until it was woken by onboard systems as it encountered Titan's atmosphere.

Researchers hope that its experimental data will solve some of the mysteries surrounding this enigmatic body. ®

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