The European Space Agency’s Rosetta mission has picked a location on Comet 67P/Churyumov–Gerasimenko where it aims to land the Rosetta’s lander, Philae.
Site J, the Rosetta probe’s landing site, is located on the head of Comet 67P/Churyumov-Gerasimenko; the inset shows a close-up of the site. Image credit: ESA / Rosetta / MPS for OSIRIS team MPS / UPD / LAM / IAA / SSO / INTA / UPM / DASP / IDA.
The 100 kg Philae will target Site J, an intriguing region on the ‘head’ of the comet that offers unique scientific potential, with hints of activity nearby. The backup, Site C, is located on the ‘body’ of the comet.
The probe is planned to reach the surface on 11 November, where it will perform in-depth measurements to characterize the nucleus in situ, in a totally unprecedented way.
Dr Jean-Pierre Bibring, a lead lander scientist at the IAS in Orsay, France, explained: “Site J in particular offers us the chance to analyze pristine material, characterize the properties of the nucleus, and study the processes that drive its activity.”
The race to find the landing site could only begin once Rosetta arrived at 67P/Churyumov–Gerasimenko on 6 August.
By 24 August, five candidate landing sites – named A, B, C, I and J – had been identified for further analysis.
A number of critical aspects had to be considered, not least that it had to be possible to identify a safe trajectory for deploying Philae to the surface and that the density of visible hazards in the landing zone should be minimal. Once on the surface, other factors come into play, including the balance of daylight and nighttime hours, and the frequency of communications passes with the orbiter.
According to Rosetta mission scientists, at Site J, the majority of slopes are less than 30 degrees relative to the local vertical, reducing the chances of Philae toppling over during touchdown.
The site also appears to have relatively few boulders, and receives sufficient daily illumination to recharge Philae and continue science operations on the surface beyond the initial battery-powered phase.
Provisional assessment of the trajectory to the site found that the descent time of Philae to the surface would be about 7 hours, a length that does not compromise the on-comet observations by using up too much of the battery during the descent.
Both Sites B and C were considered as the backup, but C was preferred because of a higher illumination profile and fewer boulders.
Sites A and I had seemed attractive during first rounds of discussion, but were dismissed at the second round because they did not satisfy a number of the key criteria.
A detailed operational timeline will now be prepared to determine the precise approach trajectory of Rosetta in order to deliver Philae to Site J.
