Comet probe now stable as data analysis begins

Scientists have re-established communication with the Philae space probe, which has made history by landing on a comet.

The lander was described as “stable” despite concerns after a harpoon which was meant to tether it to the surface of the 2.5 mile-wide comet failed to deploy.

The Philae probe touched down on the 2.5 mile-wide comet yesterday afternoon after a 10-year, four billion-mile journey through space in an achievement hailed as one of the greatest in science.

Officials from the European Space Agency are expected to speak later about the data they have been able to analyse so far.

Those behind the achievement clapped, cheered and hugged each other after receiving confirmation that the probe had landed on comet 67P/Churyumov-Gerasimenko.

But celebrations were tempered by the later discovery that the probe’s two harpoons had not fired to fasten the craft down in the ultra-low gravity.

Scientists think the probe might have bounced after coming into contact with the surface.

Despite the mishap, the probe appears to be operating as intended and collecting data. However, there have been gaps in its radio link with the orbiting Rosetta mothership.

The lander is equipped with ice screws on the tips of its three legs which may help keep it grounded.

A radio signal confirming the landing was received by scientists at 4.03pm yesterday after taking almost 30 minutes to travel the 316 million miles to Earth.

The probe is equipped with cameras, a suite of 10 instruments and a drill that can bore out samples to a depth of 9in.

Scientists hope the mission will yield valuable information about the origin of the Solar System, the Earth, and possibly life.

As Philae begins to study the comet, Rosetta must manoeuvre from its post-separation path back into an orbit around the object.

Next year, as the comet grows more active, Rosetta will step further back and fly unbound “orbits”, making brief fly-bys to within five miles of the surface.

The comet will reach its closest point to the Sun on August 13 next year at a distance of about 115 million miles, roughly between the orbits of Earth and Mars.

Key numbers behind the comet probe:

• Rosetta mission cost: Close to €1.4bn, including Philae’s cost of €220m

• Philae distance from home: 316 million miles

• Mission length so far: 10 years

• Time taken for news to reach Earth: 28 minutes, 20 seconds

• Philae weight: 100 kilograms

• Comet 67P weight: 10 billion tonnes

• Number of names suggested for landing site: 8,000 (the name chosen was Agilkia)

• Length of lander’s stay on comet: No one knows yet

• Number of countries behind the comet landing: 14

• Announcement retweets: 28,000 in first hour