OSIRIS imaged Philae in flight

On November 12, 2014, Rosetta’s lander Philae made its historical descent towards the surface of Comet 67P/Churyumov-Gerasimenko, where it bounced twice, and finally came to rest at a third touch-down in a yet unknown location. The OSIRIS camera imaged the bumpy ride.


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Mosaic of OSIRIS Narrow Angle Camera (NAC) images acquired from a distance of about 15.5 km from the surface. The resolution is 28 cm/pixel and the enlarged insets are 17 x 17 m. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA


The mosaic of OSIRIS images above covers 30 minutes of action, including the first touch-down. Images taken before and after first contact shows the marks made by the landing gear. All times are GMT. Philae comes flying in from the left at around 0.5 m/s, and bounces the first time at 15:43 GMT. It then takes off towards its second bounce, that took place at 17:25 GMT. It finally came to rest about seven minutes later. We’re all working hard to figure out where it is now!


The scientific imaging system OSIRIS was built by a consortium led by the Max Planck Institute for Solar System Research (Germany) in collaboration with CISAS, University of Padova (Italy), the Laboratoire d’Astrophysique de Marseille (France), the Instituto de Astrofísica de Andalucia, CSIC (Spain), the Scientific Support Office of the European Space Agency (The Netherlands), the Instituto Nacional de Técnica Aeroespacial (Spain), the Universidad Politéchnica de Madrid (Spain), the Department of Physics and Astronomy of Uppsala University (Sweden), and the Institute of Computer and Network Engineering of the TU Braunschweig (Germany). OSIRIS was financially supported by the national funding agencies of Germany (DLR), France (CNES), Italy (ASI), Spain (MEC), and Sweden (SNSB) and the ESA Technical Directorate.

Philae’s landing site selected

On September 10, the ESA spacecraft Rosetta finally entered a circular orbit around Comet 67P/Churyumov-Gerasimenko at a distance of 30 kilometers, after having traveled in a triangular pattern 50-100 kilometers from the nucleus since August 6.


 

A few days later, a decision was made regarding the primary landing site of Philae – area J was selected, placed on the top of the head of the comet nucleus, whose shape resembles that of a duck.


Site_J_Overview

The nucleus of Comet 67P/Churyumov-Gerasimenko resembles a rubber duck, with a “head” and a “body” connected by a thin “neck”. Philae’s primary landing site J is located on the top of the head, next to a circular flat-floored depression. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA


The region in question consists of irregular depressions and plateaus, covered by a fine powder. The surface here is relatively planar, contains few blocks, and is thus suitable for landing. However, it is still possible that unpleasant surprises awaits – on September 29 the distance from Rosetta to the comet is decreased to about 19 kilometers, and on October 10 to 10 kilometers, which means that the resolution of the camera OSIRIS will increase a factor three during the coming month. Therefore, we also monitor a secondary landing site – the reserve choice is area C.


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Close-up of landing site J. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA


Landing site C is located on the main body, roughly where the duck would have its tail. The area has many similarities with landing site J – it is covered by dust, has relatively few blocks, and consists of planar surfaces surrounded by circular flat-floored depressions. The final decision on landing site will be made on October 14.


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Close-up of landing site C. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA


The scientific imaging system OSIRIS was built by a consortium led by the Max Planck Institute for Solar System Research (Germany) in collaboration with CISAS, University of Padova (Italy), the Laboratoire d’Astrophysique de Marseille (France), the Instituto de Astrofísica de Andalucia, CSIC (Spain), the Scientific Support Office of the European Space Agency (The Netherlands), the Instituto Nacional de Técnica Aeroespacial (Spain), the Universidad Politéchnica de Madrid (Spain), the Department of Physics and Astronomy of Uppsala University (Sweden), and the Institute of Computer and Network Engineering of the TU Braunschweig (Germany). OSIRIS was financially supported by the national funding agencies of Germany (DLR), France (CNES), Italy (ASI), Spain (MEC), and Sweden (SNSB) and the ESA Technical Directorate.

Potential landing sites on the comet nucleus

The lander Philae, currently attached to the European Space Agency spacecraft Rosetta, will make its descent towards the surface of the nucleus of Comet 67P/Churyumov-Gerasimenko in early November. Five potential landing sites have now been selected, based on information collected during the first two weeks of observation from a distance of roughly 100 kilometers. This selection is based on flight dynamics constraints (both for orbiter and lander), communication opportunities (between Rosetta and Philae), illumination conditions (battery charging, overheating), surface characteristics (we do not want to land in pits, on boulders, on steep slopes or rough terrain), and last but not least – scientific relevance.


 

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Overview of the nucleus of Comet 67P/Churyumov-Gerasimenko and location of the five potential landing sites. The nucleus is about 4 kilometers across. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA


The potential landing sites have been labeled A, B, C, I, and J. Two of the sites, A and C, are located on the larger of the two lobes. The other three, B, I and J, are located on the smaller lobe. The labeling does not reflect any particular order of importance at this stage. The task now is to study the five sites in more detail, as Rosetta gradually approaches to within 30 kilometers of the nucleus. A decision on a primary landing site, as well as a backup, will be made on September 14. Whether to go for the primary or the secondary site will be determined whilst moving to within 20 kilometers of the nucleus, and a final decision will be made on October 14, roughly a month before the actual landing.


 

As a comet scientist, deeply involved in the Rosetta mission, this is a time of adventure, fascination, and the sense of discovery of something fundamentally important about our Solar System – but it also means long working hours, and not too much sleep. Which is why I have not been able to update this blog as often as I would like to – but with images like these, who can complain!


Rosetta_OSIRIS_NAC_comet_67P_20140816_SiteA

Site A is located on the larger lobe, with a good view of the smaller lobe. The terrain between the two lobes is likely the source of some outgassing. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA


Rosetta_OSIRIS_NAC_comet_67P_20140816_SiteB

Site B, within the crater-like structure on the smaller lobe, has a flat terrain and is thus considered relatively safe for landing. However, boulders and illumination conditions may pose a problem. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA


 

Rosetta_OSIRIS_NAC_comet_67P_20140816_SiteC

Site C is located on the larger lobe and is well illuminated but rich in surface features that potentially can make a landing risky. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA


Rosetta_OSIRIS_NAC_comet_67P_20140816_SiteI

Site I is a relatively flat area on the smaller lobe, but higher-resolution imaging is needed to assess the extent of the rough terrain. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA


 

Rosetta_OSIRIS_NAC_comet_67P_20140816_SiteJ

Site J is similar to site I, and also on the smaller lobe, offering interesting surface features and good illumination. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA


The scientific imaging system OSIRIS was built by a consortium led by the Max Planck Institute for Solar System Research (Germany) in collaboration with CISAS, University of Padova (Italy), the Laboratoire d’Astrophysique de Marseille (France), the Instituto de Astrofísica de Andalucia, CSIC (Spain), the Scientific Support Office of the European Space Agency (The Netherlands), the Instituto Nacional de Técnica Aeroespacial (Spain), the Universidad Politéchnica de Madrid (Spain), the Department of Physics and Astronomy of Uppsala University (Sweden), and the Institute of Computer and Network Engineering of the TU Braunschweig (Germany). OSIRIS was financially supported by the national funding agencies of Germany (DLR), France (CNES), Italy (ASI), Spain (MEC), and Sweden (SNSB) and the ESA Technical Directorate.

Rosetta’s comet in 3D!

The colorful image of Comet 67P/Churyumov-Gerasimenko is an anaglyph – by looking at it through glasses with a red and a green filter, a three-dimensional image is seen. This is a good way to get a feel for how irregular the terrain actually is.


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The two images used to create this anaglyph were taken by our camera OSIRIS on ESA’s spacecraft Rosetta on August 7, 2014. The images were taken 17 minutes apart to change the viewing geometry, through Rosetta’s motion and the nucleus rotation, which is necessary to create the 3D sensation. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA


For those who do not have such glasses – enjoy one of the original images below.


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An original image from OSIRIS used to create the anaglyph above. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA


The scientific imaging system OSIRIS was built by a consortium led by the Max Planck Institute for Solar System Research (Germany) in collaboration with CISAS, University of Padova (Italy), the Laboratoire d’Astrophysique de Marseille (France), the Instituto de Astrofísica de Andalucia, CSIC (Spain), the Scientific Support Office of the European Space Agency (The Netherlands), the Instituto Nacional de Técnica Aeroespacial (Spain), the Universidad Politéchnica de Madrid (Spain), the Department of Physics and Astronomy of Uppsala University (Sweden), and the Institute of Computer and Network Engineering of the TU Braunschweig (Germany). OSIRIS was financially supported by the national funding agencies of Germany (DLR), France (CNES), Italy (ASI), Spain (MEC), and Sweden (SNSB) and the ESA Technical Directorate.

 

Meet the heart of Comet 67P/Churyumov-Gerasimenko!

Our new images from the camera system OSIRIS on ESA’s spacecraft Rosetta shows that Comet 67P/Churyumov-Gerasimenko has a spectacularly shaped nucleus! The nucleus consists of two large pieces with different shape, connected at a small contact surface.


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A sequence of 36 processed images of Comet 67P/Churyumov-Gerasimenko taken 20 minutes apart on July 14, 2014, from a distance of about 12,000 kilometers. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA


 

One should not look too closely for details in a movie like this. The reasons is clear once we look at one of the original images below. The camera has a limited resolution and the original image consists of a number of squares, or “pixels”, that each have recorded a certain light intensity. We do not know how the nucleus looks like within each pixel – but we can guess!


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An original picture from OSIRIS before image processing. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA


 

During so-called image processing, mathematical algorithms are used in an attempt to re-create how an object really looks like, before it got smeared out by the pixels. Such algorithms are good at re-creating lost information, but they are not perfect. Real surface structures may have been lost completely, while false features that do not exist in reality may have been added.


Abbildung 1 b

A processed image from OSIRIS. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA


 

The only way to find out how the comet surface really looks like is to get closer – and in a short while Rosetta will be much closer to the comet!


The scientific imaging system OSIRIS was built by a consortium led by the Max Planck Institute for Solar System Research (Germany) in collaboration with CISAS, University of Padova (Italy), the Laboratoire d’Astrophysique de Marseille (France), the Instituto de Astrofísica de Andalucia, CSIC (Spain), the Scientific Support Office of the European Space Agency (The Netherlands), the Instituto Nacional de Técnica Aeroespacial (Spain), the Universidad Politéchnica de Madrid (Spain), the Department of Physics and Astronomy of Uppsala University (Sweden), and the Institute of Computer and Network Engineering of the TU Braunschweig (Germany). OSIRIS was financially supported by the national funding agencies of Germany (DLR), France (CNES), Italy (ASI), Spain (MEC), and Sweden (SNSB) and the ESA Technical Directorate.

OSIRIS: First glimpse of the comet nucleus!

Up to just a few days ago, the target of ESA’s Rosetta mission, Comet 67P/Churyumov-Gerasimenko, was just a dot in the sky, barely distinguishing itself from the stars by displaying a small temporary dust coma. But now Rosetta is getting so close to the comet, 40 000 kilometers – about a tenth of the distance between Earth and the Moon – that the OSIRIS camera starts to resolve the nucleus. The comet nucleus is still just a couple of camera pixels across, but as seen in the movie below, there is a hint of nucleus irregularity. The nucleus size and shape changes slightly, while it is rotating with its 12.4 hour period. From now on, the comet nucleus will just grow in size until it fills the entire field of view of the Narrow Angle Camera (NAC) in mid August. Stay tuned for more cool pictures from OSIRIS!


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First resolved images of comet 67P/Churyumov-Gerasimenko show the nucleus rotating with a rotation period of 12.4 hours. This set of 36 images was obtained by OSIRIS’ narrow angle camera (NAC) on June 27th and June 28th and covers one such period. © ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA


The scientific imaging system OSIRIS was built by a consortium led by the Max Planck Institute for Solar System Research (Germany) in collaboration with CISAS, University of Padova (Italy), the Laboratoire d’Astrophysique de Marseille (France), the Instituto de Astrofísica de Andalucia, CSIC (Spain), the Scientific Support Office of the European Space Agency (The Netherlands), the Instituto Nacional de Técnica Aeroespacial (Spain), the Universidad Politéchnica de Madrid (Spain), the Department of Physics and Astronomy of Uppsala University (Sweden), and the Institute of Computer and Network Engineering of the TU Braunschweig (Germany). OSIRIS was financially supported by the national funding agencies of Germany (DLR), France (CNES), Italy (ASI), Spain (MEC), and Sweden (SNSB) and the ESA Technical Directorate.

 

Comet 67P/Churyumov-Gerasimenko wakes up as ESA’s Rosetta spacecraft approaches!

I was at the OSIRIS Full Team meeting held at the Max Planck Institut für Sonnensystemforschung in Göttingen, Germany, last week. We had a great meeting, and the good news are piling up – the spacecraft Rosetta performs well, our imaging camera system OSIRIS is fully operational (as are all the other instruments), orbit manoeuvres are successfully executed to enable Rosetta to rendezvous with the comet in early August, and we have already started to do science.

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Between March 24th and May 4th, Rosetta approached comet 67P/Churyumov-Gerasimenko from a distance of around 5 million to 2 million kilometers. This sequence of images shows the comet’s movement against the background star field during this time. Rosetta (and the comet) are between 640 and 610 million km from the Sun. The comet is seen to develop a dust coma as the sequence progresses, with clear activity already visible in late-April. Exposure times are 720s for each image, taken with the OSIRIS/NAC through the Orange filter. credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

 

First of all, we have detected the nucleus of Comet 67P/Churyumov-Gerasimenko and are tracking its motion. Secondly, the lightcurve is being monitored regularly, which has allowed us to measure a 12.4 hour rotation period of the nucleus. The lightcurve is a periodic variation in the observed brightness of the nucleus. The variations arise since the nucleus is not spherical but irregular, so that the amount of solar light that is reflected by the nucleus towards the spacecraft is changing with time as the nucleus rotates. The third discovery is that the comet nucleus – which was dormant and quiet at our first observations in late March – now has become active.

Comet activity means that the ice in the nucleus surface layers has become heated sufficiently by sunlight to sublimate, i.e., turn directly to vapor without first becoming liquid. At these distances, at the time of writing 4.03 AU from the Sun, the temperature is too low to allow water ice to sublimate. Instead, more volatile substances like carbon monoxide and carbon dioxide are responsible for the activity. OSIRIS do not see these gases directly. However, the sublimation also liberates a large amount of micrometer-sized dust grains that are entrained in the gas as it rushed into space. OSIRIS detects the solar light that is reflected by this dusty coma, that currently measures about 2600 kilometers across.

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The OSIRIS Team. Yours truly is marked with the arrow. Credits: MPS