Philae (spacecraft) — Rosetta's comet lander

Design and instruments

Built as a compact, battery-powered lander spacecraft, Philae carried a suite of instruments for imaging, sampling, chemical analysis and physical measurements. Its equipment combined mechanisms for drilling and scooping with analytical laboratories and sensors to probe the comet's environment and internal structure.

• Imaging systems to document the landing site and context (e.g., panoramic and close-up cameras).
• Drilling and sampling tools designed to collect material from the surface and near-subsurface.
• Laboratory analyzers and spectrometers to identify organic and inorganic compounds.
• Thermal, magnetic and seismic sensors to measure physical properties of the nucleus.
• A radio experiment shared with the orbiter to probe the comet's interior.

Landing, operations and scientific return

Philae separated from Rosetta and descended to the comet, touching down on 12 November 2014. Anchoring systems intended to secure the lander did not function as planned, and Philae bounced from its initial touchdown point before settling in a more shadowed location. Because sunlight at the final site was limited, the lander's primary battery ran down after a short period, restricting continuous operations. Despite that, Philae completed a number of planned experiments, returned high-resolution images, acquired compositional data indicating the presence of organic molecules and volatile ices, and provided measurements of thermal and mechanical properties on the surface. After an extended period without contact, the lander briefly communicated with Earth again in mid-2015 before communications ceased.

Naming and cultural references

The name Philae was chosen through a public naming contest organized by ESA and was proposed by a teenager from Milan. It references the island of Philae in the Nile and its role, along with the Rosetta Stone, in understanding ancient Egyptian writing — a parallel to how the lander was intended to help complete Rosetta's study of cometary history. The connection to the decipherer Jean-François Champollion is often mentioned in descriptions of the mission because of the symbolic link between the two monuments and the twin spacecraft.

Legacy and notable facts

Philae is widely cited as the first spacecraft to make a controlled landing on a comet surface and remains notable for the quality of data it returned during a limited operational lifetime. Its unexpected landing circumstances and partial success have informed designs for subsequent small-body landers and highlighted engineering risks in low-gravity environments. Images and analysis from Rosetta later helped identify Philae's resting place on the nucleus and allowed teams to better interpret the data it gathered. The mission contributed to improved understanding of cometary composition and the early Solar System.

Further technical details and archival materials about the lander and the wider mission are available from mission pages and scientific publications that document Philae's instruments, operations and post-landing analyses. For general context on the Rosetta mission and its objectives see the mission pages and summaries maintained by the mission team and ESA.

ESA mission overview | Lander details | Rosetta probe | Comet 67P | Rosetta Stone | Champollion