Philae (spacecraft)
First spacecraft to soft-land on a comet nucleus.
Philae was a European Space Agency robotic lander that traveled with the Rosetta spacecraft for over a decade after leaving Earth, eventually separating to touch down on comet 67P/Churyumov–Gerasimenko. It landed on 12 November 2014, but bounced because its harpoons did not fire and a thruster meant to keep it on the surface failed to activate. After two bounces, Philae achieved the first soft landing on a comet nucleus, though its final uncontrolled touchdown left it in a poor location and orientation. The lander sent images and data to Earth for roughly 64 hours.
Despite the landing issues, Philae’s instruments captured the first images taken from a comet’s surface. Several of its tools performed the first in-situ analysis of a comet nucleus, providing data on surface composition and subsurface outgassing. In October 2020, the journal *Nature* published findings from Philae’s time on the comet.
On 15 November 2014, Philae entered safe mode and hibernated after its batteries drained, due to low sunlight and its awkward resting position. Controllers hoped more sunlight might recharge it. It sporadically communicated with Rosetta from 13 June to 9 July 2015, then contact was lost. Its location was known to within tens of meters but unseen until photographs from Rosetta on 2 September 2016 revealed it lying on its side in a deep crack, shadowed by a cliff. This helped interpret the images it had sent. Rosetta ended its mission by crashing into the comet’s Ma’at region on 30 September 2016.
The lander was named after the Philae obelisk, a bilingual inscription used with the Rosetta Stone to decode Egyptian hieroglyphs. Philae was monitored and operated from DLR’s Lander Control Center in Cologne, Germany, with support from CNES’s SONC in Toulouse, France.
Philae’s mission was to land on a comet, attach itself, and transmit data on its composition. Rosetta and Philae launched on an Ariane 5G+ rocket from French Guiana on 2 March 2004, traveling 3,907 days to the comet. Unlike the Deep Impact probe, which struck comet Tempel 1, Philae was not an impactor. Some instruments were first used autonomously during a Mars flyby on 25 February 2007; the CIVA camera returned images while Rosetta’s instruments were off, and ROMAP measured Mars’s magnetosphere. Most other instruments needed surface contact and stayed offline. An optimistic mission length after landing wa
- Mission type
- Comet lander
- Launch date
- 2 March 2004, 07:17 UTC
- Landing date
- 12 November 2014
- Operator
- European Space Agency (ESA), DLR, CNES
- Known for
- First soft landing on a comet nucleus; first in-situ analysis of a comet surface
Lore & Background
Philae was launched on an Ariane 5G+ rocket from French Guiana on 2 March 2004, 07:17 UTC, and traveled for 3,907 days (10.7 years) to comet 67P/Churyumov–Gerasimenko. The lander remained attached to the Rosetta spacecraft after rendezvousing with the comet on 6 August 2014. On 15 September 2014, ESA announced 'Site J' on the smaller lobe of the comet as the lander's destination, later renamed Agilkia. A series of four go/no-go checks were performed on 11–12 November 2014; one final test showed the lander's cold-gas thruster was not working correctly, but the 'go' was given anyway. Philae detached from Rosetta on 12 November 2014 at 08:35 UTC SCET.
Reader's Guide
Philae's significance lies in its achievement of the first-ever soft landing on a comet nucleus, despite the failure of its harpoons and thruster. The probe's instruments obtained the first images from a comet's surface and made the first in-situ analysis of a comet nucleus, sending back data regarding the composition of the surface and outgassing from the subsurface. Data from the SESAME instrument determined that the first touchdown site held a large amount of water ice under a layer of granular material, while the MUPUS instrument found the final landing site had the consistency of solid ice or pumice. The COSAC instrument detected molecules containing carbon and hydrogen in the comet's atmosphere. Philae's legacy includes the publication of its discoveries in the journal Nature in October 2020, and the eventual identification of its final resting place in photographs taken by Rosetta on 2 September 2016, lying on its side in a deep crack in the shadow of a cliff.
Did You Know?
- Philae is named after the Philae obelisk, which was used along with the Rosetta Stone to decipher Egyptian hieroglyphs.
- The lander bounced twice after its initial touchdown because its anchoring harpoons failed to deploy and a thruster did not fire.
- Philae transmitted data for about 64 hours before its batteries ran down due to reduced sunlight and an off-nominal orientation.
- Its final location was identified in photographs taken by Rosetta on 2 September 2016, lying on its side in a deep crack in the shadow of a cliff.
Frequently Asked Questions
What is Philae?
Philae is a robotic lander built by the European Space Agency that rode aboard the Rosetta spacecraft for more than ten years before separating to touch down on comet 67P/Churyumov–Gerasimenko in November 2014.
What went wrong during Philae's landing?
Its harpoons failed to fire and a small thruster meant to press it against the surface never activated, so the lander bounced twice before settling in an uncontrolled, awkward spot.
How long did Philae operate on the comet?
Despite ending up in a poorly oriented position, the lander still managed to beam images and scientific data back to Earth for roughly 64 hours before its batteries ran out.
Why is Philae considered a milestone in space exploration?
It was the first spacecraft ever to achieve a soft landing on a comet nucleus, and it carried out the first in-situ analysis of a comet's surface material.
What is Philae's current status?
The lander has been silent since its batteries were exhausted in late 2014 and now rests in a shadowed crevice on the comet's surface, effectively a derelict piece of hardware drifting through interstellar space aboard 67P.
More in Derelict landers 1-24
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