Philae first postcard after landing on Comet 67P!
SPOT FOR LANDING
Rosetta’s lander Philae will target Site J, an intriguing region on Comet 67P/Churyumov–Gerasimenko that offers unique scientific potential, with hints of activity nearby, and minimum risk to the lander compared to the other candidate sites.
Site J is on the ‘head’ of the comet, an irregular shaped world that is just over 4 km across at its widest point. The decision to select Site J as the primary site was unanimous. The backup, Site C, is located on the ‘body’ of the comet.
The 100 kg lander is planned to reach the surface on 11 November, where it will perform indepth measurements to characterise the nucleus in situ, in a totally unprecedented way.
But choosing a suitable landing site has not been an easy task.
“As we have seen from recent close-up images, the comet is a beautiful but dramatic world – it is scientifically exciting, but its shape makes it operationally challenging,” says Stephan Ulamec, Philae Lander Manager at the DLR German Aerospace Center.
“None of the candidate landing sites met all of the operational criteria at the 100% level, but Site J is clearly the best solution.”
“We will make the first ever in situ analysis of a comet at this site, giving us an unparalleled insight into the composition, structure and evolution of a comet,” says Jean-Pierre Bibring, a lead lander scientist and principal investigator of the CIVA instrument at the IAS in Orsay, France.
“Site J in particular offers us the chance to analyse pristine material, characterise 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 the comet on 6 August, when the comet was seen close-up for the first time. By 24 August, using data collected when Rosetta was still about 100 km from the comet five candidate regions had been identified for further analysis.
Since then, the spacecraft has moved to within 30 km of the comet, affording more detailed scientific measurements of the candidate sites. In parallel, the operations and flight dynamics teams have been exploring options for delivering the lander to all five candidate landing sites.
Over the weekend, the Landing Site Selection Group of engineers and scientists from Philae’s Science, Operations and Navigation Centre at France’s CNES space agency, the Lander Control Centre at DLR, scientists representing the Philae Lander instruments and ESA’s Rosetta team met at CNES, Toulouse, France, to consider the available data and to choose the primary and backup sites.
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.
The descent to the comet is passive and it is only possible to predict that the landing point will place within a ‘landing ellipse’ typically a few hundred metres in size.
A one square kilometre area was assessed for each candidate site. At Site J, the majority of slopes are less than 30º relative to the local vertical, reducing the chances of Philae toppling over during touchdown. Site J 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 Site J found that the descent time of Philae to the surface would be about seven 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. The landing must take place before mid-November, as the comet is predicted to grow more active as it moves closer to the Sun.
“There’s no time to lose, but now that we’re closer to the comet, continued science and mapping operations will help us improve the analysis of the primary and backup landing sites,” says ESA Rosetta flight director Andrea Accomazzo.
“Of course, we cannot predict the activity of the comet between now and landing, and on landing day itself. A sudden increase in activity could affect the position of Rosetta in its orbit at the moment of deployment and in turn the exact location where Philae will land, and that’s what makes this a risky operation.”
Once deployed from Rosetta, Philae’s descent will be autonomous, with commands having been prepared by the Lander Control Centre at DLR, and uploaded via Rosetta mission control before separation.
During the descent, images will be taken and other observations of the comet’s environment will be made.
Once the lander touches down, at the equivalent of walking pace, it will use harpoons and ice screws to fix it onto the surface. It will then make a 360° panoramic image of the landing site to help determine where and in what orientation it has landed.
The initial science phase will then begin, with other instruments analysing the plasma and magnetic environment, and the surface and subsurface temperature. The lander will also drill and collect samples from beneath the surface, delivering them to the onboard laboratory for analysis. The interior structure of the comet will also be explored by sending radio waves through the surface towards Rosetta.
“No one has ever attempted to land on a comet before, so it is a real challenge,” says Fred Jansen, ESA Rosetta mission manager. “The complicated ‘double’ structure of the comet has had a considerable impact on the overall risks related to landing, but they are risks worth taking to have the chance of making the first ever soft landing on a comet.”
The landing date should be confirmed on 26 September after further trajectory analysis and the final Go/No Go for a landing at the primary site will follow a comprehensive readiness review on 14 October.
Since ESA’s Rosetta spacecraft arrived at Comet 67P/Churyumov-Gerasimenko on 6 August, the race has been on to find a suitable location for the lander Philae. Five candidate locations were announced on 25 August for further investigation, in order to determine possible orbital and operational strategies for Rosetta to despatch the lander to each of them. By 14 September, the five candidate sites will have been assessed and ranked, leading to the selection of a primary landing site and a backup. The final two sites, along with their operational challenges and scientific expectations, will be presented during the briefing on 15 September.
Watch live as the target for Rosetta’s lander is announced at ESA Headquarters on 15 September, streaming starts at 0900 GMT / 1100 CEST.
Recorrendo à informação detalhada recolhida pela Rosetta , foi possível identificar cinco potenciais locais de aterragem para a Philae.
Embora não esteja relacionado com o projeto Rosetta, trata-se de um astronauta da ESA, Alexander Gerst, ao vivo hoje.
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“How many times have you wondered #RosettaAreWeThereYet? Rosetta has just arrived to comet 67P/C-G!”
After a decade-long journey chasing its target, ESA’s Rosetta has today become the first spacecraft to rendezvous with a comet, opening a new chapter in Solar System exploration.
Comet 67P/Churyumov–Gerasimenko and Rosetta now lie 405 million kilometres from Earth, about half way between the orbits of Jupiter and Mars, rushing towards the inner Solar System at nearly 55 000 kilometres per hour.
Depois de uma viagem de cerca de 10 anos, a sonda Rosetta tornou-se hoje no primeiro veículo espacial a “encontrar-se” com um cometa, inaugurando um novo capítulo na exploração do nosso sistema solar.
O cometa 67P / Churyumov–Gerasimenko e a Rosetta encontram-se agora a 405 milhões de km da Terra, aproximadamente a meio caminho entre as órbitras de Júpiter e de Marte, deslocando-se no interior do sistema solar a cerca de 55.000 km/h.
PHILAE’S PANORAMIC CAMERA
PHILAE TOUCH DOWN
A 23 de julho, o cometa 67P e a sonda Rosetta estavam a aproximadamente 403.500 mil km da Terra.
Para decorar as redes sociais
Fatos da Missão Rosetta
O custo total da missão é 1300 milhões de euros, incluindo o lançamento, a nave espacial, a carga útil científica (instrumentos e lander) e a missão e respetivas operações científicas.
A Rosetta foi lançada em 2 de Março de 2004 por um Ariane-5 a partir do Porto Espacial Europeu em Kourou, na Guiana Francesa.
A missão da Rosetta durará cerca de 12 anos – até dezembro de 2015.
A Rosetta assemelha-se a uma grande caixa preta.
Os instrumentos científicos estão montados na parte superior da caixa (o módulo de suporte de carga), enquanto que os subsistemas estão na “base” (módulo de suporte de “barramento”). De um dos lados da sonda encontra-se o prato parabólico de comunicações com 2,2 m de diâmetro, enquanto o módulo que aterrará no cometa está ligado à face oposta.
Em cada um dos lados da sonda estão dois painéis solares que podem rodar até 180 ° para captar a quantidade máxima de luz solar.
A massa total da Rosetta é de 3000 kg (totalmente abastecida), incluindo 1670 kg do propulsor e 165 kg de carga útil científica, enquanto o módulo de aterragem pesa cerca de 100 kg.
A principal nave espacial mede 2,8 x 2,1 x 2,0 m.
Os dois painéis solares têm 14 m de comprimento solares e uma área total de 64 m2 de fornecimento de energia elétrica.