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Raumfahrt - ESA-Sonde Rosetta auf Kurs zu Komet 67P/Churyumov-Gerasimenko - Update

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7.02.2014

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Quelle: DLR

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Update: 24.02.2014

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ROSETTA’S SELF-PORTRAIT AT MARS

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Title Rosetta’s self-portrait at Mars
Released 24/02/2014 10:00 am
Copyright ESA/Rosetta/Philae/CIVA
Description
On 25 February 2007 at 02:15 GMT, Rosetta passed just 250 km from the surface of Mars. Rosetta’s Philae lander took this image 4 minutes before closest approach, at a distance of 1000 km. It captures one of Rosetta’s 14 m-long solar wings, set against the northern hemisphere of Mars, where details in the Mawrth Vallis region can be seen.
Mawrth Vallis is of particular interest to scientists because it contains minerals formed in the presence of water – a discovery made by ESA’s Mars Express.
This image was originally published in 2007 and was taken in black-and-white. Representative colour was added to the surface of Mars and, in this version, these colours have been slightly enhanced, along with some brightening of details in the solar wing.
On Sunday 2 March, Rosetta celebrates ten years since launch. The flyby at Mars was one of four planetary gravity assists (the other three were at Earth) needed to boost the spacecraft onto the correct trajectory to meet up with its target, comet 67P/Churyumov–Gerasimenko, in August 2014.
Rosetta will become the first space mission to rendezvous with a comet, the first to attempt a landing, and the first to follow a comet as it swings around the Sun.
 
 
 
Quelle: ESA

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Update: 10.03.2014

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Rosetta Ziel Komet 67P/Churyumov-Gerasimenko wieder zu sehen

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Komet 67P/Churyumov-Gerasimenko aufgenommen am 28. Februar 2014 mit Hilfe des Very Large Telescope. Links: Um den Kometen sichtbar zu machen, überlagerten die Wissenschaftler mehrere Aufnahmen. Die Bilder wurden zudem um die Bewegung des Kometen verschoben. Die Sterne im Hintergrund erscheinen dadurch als breit verschmierte Striche. Rechts: Durch Subtrahieren des Sternenhintergrundes wird der Komet sichtbar.
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Da ist er wieder: Nachdem Komet 67P/Churyumov-Gerasimenko im Oktober vergangenen Jahres von der Erde aus gesehen hinter der Sonne verschwand, ist der Zielkomet der ESA-Mission Rosetta nun wieder zu sehen. In der jüngsten Aufnahme, die Forschern des Max-Planck-Instituts für Sonnensystemforschung (MPS) und der Europäischen Südsternwarte (ESO) am 28. Februar 2014 mit Hilfe des Very Large Telescope gelang, zeigt sich der Komet heller als ein inaktiver Kern allein erwarten ließe. Das deutet daraufhin, dass bereits jetzt Eis vom Kometen verdampft und eine sehr dünne Atmosphäre um den Kern bildet. Im August dieses Jahres wird die Raumsonde Rosetta 67P/Churyumov-Gerasimenko erreichen und bis mindestens Ende 2015 auf seinem Weg um die Sonne begleiten. 
Um den Kometen aus einer Entfernung von 740 Millionen Kilometern sichtbar zu machen, überlagerten die Wissenschaftler mehrere Aufnahmen, die zu verschiedenen Zeiten am 28. Februar entstanden waren. Zuvor verschoben sie die Bilder leicht, um die Bewegung des Kometen auszugleichen. Die eigentlich fixen Sterne erscheinen dadurch als breit verschmierte Striche. Durch Herausrechnen des Sternenhintergrundes kommt der Komet selbst zum Vorschein: ein winziger Punkt im All.
Für die Forscher ist dieser winzige Punkt dennoch aussagekräftig. Denn schon jetzt ist 67P/Churyumov-Gerasimenko um 50 Prozent heller als auf dem letzten Bild vom Oktober 2013. Zwar hat sich der Komet in der Zwischenzeit der Erde um weitere 50 Millionen Kilometer genähert (und der Sonne um weitere 80 Millionen Kilometer), doch der Helligkeitsanstieg ist größer als erwartet. „Das neue Bild spricht dafür, dass der Komet bereits in einer relativ großen Entfernung von der Sonne beginnt, Gas und Staub zu spucken“, so Colin Snodgrass vom MPS. Dies bestätigt Auswertungen aus dem vergangenen Jahr, in denen Snodgrass und seine Kollegen Aufnahmen aus zurückliegenden Sonnenumläufen verglichen hatten. Auch diese Rechnungen legten nahe, dass die Aktivität des Kometen bereits ab März dieses Jahres von der Erde aus messbar sein müsste.
In enger Zusammenarbeit mit der ESA wollen die Forscher auch in den nächsten Monaten überwachen, wie sich die Helligkeit des Kometen entwickelt. Die Daten werden helfen einzuschätzen, was die Raumsonde Rosetta bei ihrer Ankunft am Kometen erwartet.
Quelle: ESA

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The science and mission operations teams looking after Rosetta have been hard at work in the six weeks since wake up on 20 January 2014. The post-wake-up period ending 2 March has been mainly dedicated to the preparation of the spacecraft for the up-coming payload commissioning phase.
The mission operations team at ESOC have had daily telecommanding communication slots with Rosetta, using ESA's 35m Estrack station at New Norcia, Australia, and also using the large dishes of NASA's Deep Space Network at Goldstone, Canberra and Madrid.
As for the health of the spacecraft, Rosetta is operating nominally in 'Normal Mode' and all platform systems have been fully re-activated. The Thermal, Power and Data Handling systems are all working. The reaction wheels – spinning wheels used to maintain Rosetta's orientation in space – are being exercised at very low speed to characterise their behaviour in this regime.
All instruments are off except for:
The Ultra Stable Oscillator for the Radio Science Investigation
Standard Radiation Monitor
Meanwhile, the science operations team at ESAC have been iterating commands with instrument teams and the mission operations team in preparation for commissioning and subsequent instrument operations up to and beyond comet rendezvous. All the commissioning and instrument operation activities have long lead times and so preparation starts months in advance. In fact, longer term planning, for science to be carried out beyond 2014, is already being prepared!
On the shorter term, however, Rosetta has to first arrive at the comet. Here is an overview of upcoming activities, with the ever-present proviso that dates, times and events may change due to operational requirements:
17 March – Switch on the OSIRIS imaging system; all other instruments will be switched on in the following approximately 6 weeks
24 March – Pending successful re-activation, OSIRIS will take a first look in the direction of the comet. The comet will be too far away (around 5 million kilometres) to resolve in these first images and its light will be seen in just a couple of pixels. These images will be acquired regularly for navigation purposes and to already start planning the trajectory corrections planned for  May.
In the meantime, Rosetta's NavCam has been briefly switched on for a check-out; NavCam imaging for operational purposes will start in May alongside OSIRIS.
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The image was acquired on 23 February 2014 and is pointed roughly in the direction of the constellation Aries (almost in the direction opposite to comet 67P). The bright star to the right of the centre is delta Arietis (δ Ari) the bright star at the top left is epsilon Arietis, ε Ari. The NavCam field of view is 5x5 degrees. Credit: ESA/Rosetta/NavCam
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May/June
May will see the start of a critical series of manoeuvres that will steadily bring Rosetta in line with the comet. Currently Rosetta is on a trajectory that would, if unchanged, take it past the comet at a distance of approximately 50 000 km and at a relative velocity of 800 m/s. The aim of the manoeuvres is to reduce Rosetta’s relative velocity to 1 m/s and bring it to within 100 km distance of the comet by 6 August.
The manoeuvres will be planned for every second Wednesday (fortnightly), starting with the following:
Around 7 May - First 'test' manoeuvre to decrease Rosetta’s relative velocity to the comet by 20 m/s
21 May – reduce relative velocity by 290 m/s
4 June - reduce relative velocity by 270 m/s
18 June - reduce relative velocity by 90 m/s
And finally, a nice historical note!
On 2 March 2014, Rosetta celebrated its 10th anniversary in flight!
Here is part of the text of the first Rosetta Mission Operations Report issued by the-then Flight Directors, Alan Smith and Manfred Warhaut (both now retired):
Ariane flight 158 lifted off right on-schedule at 07:17:51 UTC on March 2nd carrying with it the Rosetta spacecraft on the start of its 10-year journey to comet Churyumov-Gerasimenko. The solid boosters separated as expected at 07:20 UTC, followed 50 secs later by the fairing. The first stage burn continued until 07:27 UTC and injected the upper stage and Rosetta into a coast orbit. This was the first occasion that such an orbit phase has been flown by an Ariane 5 launch vehicle and the progress of the flight was monitored with mounting tension in the ESOC control centre. The ignition of the upper stage occurred 107 minutes later at 09:14 and was monitored from a ground station in Hawaii until the vehicle moved out of contact. Contact was made again from the Galliot station in Kourou and at 09:32:36, Arianespace announced the separation of Rosetta. There was great joy and excitement in the ESOC control centre when the ESA Kourou ground station acquired telemetry signals from Rosetta one minute later at 09:34. The spacecraft status was as expected and the automatic separation sequence was seen to be in progress. The initial rate reduction and Sun acquisition phase proceeded very smoothly, and this was followed by the deployment of the two solar array panels, which was completed at 10:11. The separation sequence was completed with the Sun reacquisition. The first telecommands were uplinked from the Kourou station at 10:34.
Quelle: ESA



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