Philae Comet Lander Located — Just in Nick of Time

Philae Comet Lander Located — Just in Nick of Time

The European Space Agency (ESA) exuberantly announced today that imagery from a camera aboard its Rosetta spacecraft has finally located the Philae lander on the surface of Comet 67P.  After returning data for 57 hours in 2014, contact with Philae was lost.  It briefly resumed transmissions in 2015, but ceased again.  The imagery released today confirms that the problem is Philae’s position, which does not allow its solar panels to charge the battery.  The Rosetta mission will end on September 30, so the discovery came just in the nick of time.

The trials and tribulations of the tiny lander made headlines in November 2014 when it separated from Rosetta and headed down to the surface of the comet, the first time such a feat was attempted.  After initial contact, harpoons intended to secure Philae to the surface failed to fire, however, and it bounced twice more before landing elsewhere.  Philae communicates to Earth via Rosetta, which is in orbit around the comet, and communications were established even though ESA and the German space agency, DLR, which built Philae, did not know precisely where it was.

Philae had enough battery power for one round of experiments and it successfully completed 80 percent of them, but contact then was lost and mission managers assumed that the spacecraft landed in a position where sunlight could not reach its solar panels to charge a secondary battery that is aboard.  They hoped that as the comet neared the Sun, more sunlight would reach the panels.  Indeed, Philae “phoned home” briefly in June and July 2015, only to disappear again.

Rosetta has continued to orbit the comet, whose full designation is 67P/Churyumov-Gerasimenko after the two Ukrainian astronomers who discovered it, on its journey in toward the Sun and out again.  The comet-spacecraft duo came closest to the Sun (perihelion) in August 2015.  This is 67P’s first encounter with the Sun and thus it still contains the primordial material of which it was made 4.5 billion years ago making it of special interest to scientists.  

The comet and spacecraft are now on their way back to the outer edges of the solar system.  On October 1, they will move behind the Sun relative to Earth, preventing communications.  Coupled with other technical factors affecting the longevity of the spacecraft and its instruments, program managers decided to formally end the mission on September 30 when they will command it to make a controlled impact with the surface for one last set of observations. 

That final descent is still almost a month away, but the images showing Philae were taken by Rosetta’s narrow-angle camera, OSIRIS, when it was just 2.7 kilometers (1.7 miles) above the surface. Cecilia Tubiana of the OSIRIS team was the first to see the images and identify Philae.   ESA has been looking for Philae all this time and narrowed its location down to a few potential sites, but this is the first time its location could be confirmed.  Philae is “wedged into a dark crack,” ESA said, also proving that the problem is lack of sunlight to charge the secondary battery.

Image of Philae on the surface of Comet 67P from camera aboard ESA’s Rosetta orbiter, September 2, 2016.  Photo credit:  ESA

ESA also released a copy of the image with the spacecraft components labeled.

Image of Philae on the surface of Comet 67P with labels added by ESA to identify spacecraft components.  Photo credit: ESA

ESA Rosetta mission manager Patrick Martin said “[w]e were beginning to think that Philae would be lost forever. It is incredible we have captured this at the final hour.”   ESA Rosetta program scientist Matt Taylor added that now scientists have “ground truth” that will allow them to put Philae’s science data into the proper context.

ESA explains that Rosetta and Philae “aim to unlock the mysteries of
the oldest building blocks of our solar system — comets” and hence the
names are connected to the deciphering of hieroglyphics. 

  • Rosetta is named after the Rosetta Stone
    that allowed the deciphering of hieroglyphics and therefore an
    understanding of Egyptian civilization.
  • Philae is the name of an island in the Nile river where an obelisk was found with the final clues to enable the decryption.
  • Philae was flooded when the Aswan dams
    were built in the 20th century and a complex of Ancient Egyptian
    buildings, including the Temple of Isis, were moved to another island,
    Agilkia,   ESA held a contest to name Philae’s intended landing site on 67P and
    of 8,000 entries, more than 150 suggested Agilkia and that was the
    winner.  Although Philae briefly touched down there, its final landing site is named Abydos after one of the oldest cities in Egypt.

Rosetta and Philae were launched on March 2, 2004.  It took 10 years for them to reach their destination — the 4 kilometer (2.5 mile) diameter Comet 67P.  It was 540 million kilometers (335 million miles) from the Sun or 404 million kilometers (251 million miles) from the Earth at that time. As of today, they have traveled 7.9 billion kilometers (4.9 billion miles).  ESA has an interactive “Where is Rosetta” graphic that shows Rosetta’s location at every point along its route.

Rosetta is an ESA mission, but NASA provided three of its instruments and part of the electronics for a fourth.

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