De wetenschappers denken dat Philae nu ongveer 1,3 uur zonlicht per dag krijgt. Een dag op de komeet duurt 12.4 uur. Op dit moment hebben ze tot 20 maart om contact proberen te maken. Daarna zal er wederom gewacht moeten worden op de volgende kans.
http://blogs.esa.int/rosetta/2015/03/10/waiting-for-a-signal-from-philae/ | Gewijzigd: 14 maart 2015, 13:07 uur, door Joyce.s
Rosetta continues to recover well from the problems experienced during the close flyby over the weekend of 28 March that resulted in the spacecraft entering safe mode. Some of the science instruments are now switched back on again, and more will follow in the coming week.
As a result of the safe mode, Rosetta moved onto an ‘escape trajectory’ taking it approximately 400 km from Comet 67P/C-G. An orbital correction manoeuvre was executed on 1 April to start to bring the spacecraft back again, and with a second manoeuvre executed on 4 April, the target distance of 140 km was reached on 8 April.
But the previous difficulties in navigation mean that the operations team needs to be cautious while bringing the spacecraft even closer. In particular, they will need to assess the behaviour of the spacecraft’s star trackers in the environment of the increasingly active comet, since the previous navigation issues resulted from the star trackers becoming confused by comet particles.
“This has ultimately meant a complete replanning of the upcoming flyby trajectories,” says Rosetta spacecraft operations manager Sylvain Lodiot. “We’re first moving to a terminator orbit at a distance of 140 km and then we’re targeting 100 km. Then we will adopt a similar strategy to when we first approached the comet in August last year. That is, we will fly ‘pyramid’ trajectories, starting at about 100 km on 11 April, and we’ll monitor how the spacecraft reacts before moving closer.”
Three of these pyramid trajectories are currently planned up until the end of April. The team will assess the situation each week before deciding to move closer or, if necessary, to move further away again.
“We’re now assessing the impact of the new trajectory scheme on the planned science observations for the months ahead, including those which anticipated close flybys,” says Matt Taylor, Rosetta project scientist. “Our science operations team at ESAC is extremely busy working with the instrument teams to optimise science observations and associated spacecraft pointing for this new scheme. As we move forward, we will analyse what can be modified and improved in order to maximise science return within the capabilities of the spacecraft. We will be looking at examining all options to mitigate the issues we had and recover some of the science goals.”
We’ll provide details of future trajectory plans and the status of the science operations when this information is available.
ROSETTA’S LANDER PHILAE WAKES UP FROM HIBERNATIONRosetta's lander Philae is out of hibernation!
The signals were received at ESA's European Space Operations Centre in Darmstadt at 22:28 CEST on 13 June. More than 300 data packets have been analysed by the teams at the Lander Control Center at the German Aerospace Center (DLR).
"Philae is doing very well: It has an operating temperature of -35ºC and has 24 Watts available," explains DLR Philae Project Manager Dr. Stephan Ulamec. "The lander is ready for operations."
For 85 seconds Philae "spoke" with its team on ground, via Rosetta, in the first contact since going into hibernation in November.
When analysing the status data it became clear that Philae also must have been awake earlier: "We have also received historical data - so far, however, the lander had not been able to contact us earlier."
Now the scientists are waiting for the next contact. There are still more than 8000 data packets in Philae’s mass memory which will give the DLR team information on what happened to the lander in the past few days on Comet 67P/Churyumov-Gerasimenko.
Philae shut down on 15 November 2014 at 1:15 CET after being in operation on the comet for about 60 hours. Since 12 March 2015 the communication unit on orbiter Rosetta was turned on to listen out for the lander.
More information when we have it!
Rosetta is an ESA mission with contributions from its Member States and NASA. Rosetta's Philae lander is contributed by a consortium led by DLR, MPS, CNES and ASI.
Voor een uitgebreid artikel zie: http://www.bbc.com/news/science-environment-33126885
http://ichef.bbci.co.uk/news/624/media/images/83618000/jpg/_83618962_83618961.jpg | Gewijzigd: 15 juni 2015, 09:06 uur, door Joyce.s
13juni ontving de ESA weer berichten.
temperatuur daar is -35grC en 24watt power beschikbaar
Doordat vanaf nu de komeet weer verder van de zon komt kan de orbitor weer dichter bij het oppervlak komen om de komeet te vergelijken, voordat hij dicht bij de zon was en nu er na.
Het plan is dat ze op het einde van de missie, Rosetta op de komeet laten landen/neerstorten, in een maanden durende spiraal steeds dichterbij komend, en liefts op een glad oppervlak. Of er dan nog communicatie mogelijk is is onwaarschijnlijk. Het zal het einde betekenen van één van de meest succesvolle ruimte ontdekkingsreizen.
ESA - European Space Agency
http://blogs.esa.int/rosetta/2015/06/24/cometwatch-15-june/ | Gewijzigd: 24 juni 2015, 12:58 uur, door Justin
De data verbinding staat elke keer te kort open en de verbinding is niet stabiel.
Philae comet lander falls silent
The Philae comet lander has fallen silent, according to scientists working on the European Rosetta mission.
The fridge-sized spacecraft, which landed on Comet 67P in November, last made contact on 9 July.
But efforts to contact it again since then have failed, scientists have said.
The first craft to perform a soft landing on a comet, Philae initially bounced, landing in a position too dark for sunlight to reach its solar panels.
It woke up in June as the comet moved closer to the sun. But the latest data suggests something, perhaps gas emission from the comet's surface, may have moved it again.
"The profile of how strongly the sun is falling on which panels has changed from June to July, and this does not seem to be explained by the course of the seasons on the comet alone," said Stephan Ulamec, Philae project manager at the German Aerospace Center (DLR).
Philae's antenna may have been obstructed, and one of its transmitters appears to have stopped working, Rosetta team members said.
Bron:http://www.bbc.com/news/science-environment-33596274 | Gewijzigd: 31 januari, 16:08 uur, door Joyce.s
omdat de comeet steeds actiever geworden is dordat hij dichter bij de zon gekomen is is er meer emissie en is Rosetta's baan om de komeet ruimer nu zo rond de 180km, omdat dat veiliger is. Dat zorgt voor veel meer moeilijkheid om signalen op te vangen.
COMET SURFACE CHANGES BEFORE ROSETTA’S EYES
In the months leading to the perihelion of Comet 67P/Churyumov-Gerasimenko, Rosetta scientists have been witnessing dramatic and rapid surface changes on the Imhotep region, as reported in a paper to be published in Astronomy & Astrophysics
Since arriving at Comet 67P/C-G in August 2014, Rosetta has been witnessing an increase in the activity of the comet, warmed by the ever-closer Sun. A general increase in the outflow of gas and dust has been punctuated by the emergence of jets and dramatic rapid outbursts in the weeks around perihelion, the closest point to the Sun on the comet’s orbit, which occurred on 13 August 2015.
But in June 2015, just two months before perihelion, Rosetta scientists started noticing important changes on the surface of the nucleus itself. These very significant alterations have been seen in Imhotep, a region containing smooth terrains covered by fine-grained material as well as large boulders, located on 67P/C-G’s large lobe.
Sequence of ten images showing changes in the Imhotep region on Comet 67P/C-G. The images were taken with the OSIRIS narrow-angle camera on Rosetta between 24 May and 11 July 2015. The individual images are also available separately. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
We had been closely monitoring the Imhotep region since August 2014, and as late as May 2015, we had detected no changes down to scales of a tenth of a metre,” comments Olivier Groussin, an astronomer at the Laboratoire d'Astrophysique de Marseille, France, OSIRIS Co-Investigator and lead author of the study.
“Then one morning we noticed that something new had happened: the surface of Imhotep had started to change dramatically. The changes kept going on for quite a while.”
First evidence for a new, roughly round feature in Imhotep was seen in an image taken with Rosetta’s OSIRIS narrow-angle camera on 3 June. Subsequent images later in June showed this feature growing in size, and being joined by a second round feature. By 2 July, they had reached diameters of roughly 220 m and 140 m, respectively, and another new feature began to appear.
By the time of the last image used in this study, taken on 11 July, these three features had merged into one larger region and yet another two features had appeared.
Same sequence as above, with indication of dates and location of the morphological changes. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
“These spectacular changes are proceeding extremely rapidly, with the rims of the features expanding by a few tens of centimetres per hour. This highlights the complexity of the physical processes involved,” adds Olivier.
The sublimation of volatile species is clearly an important factor, as colour images of this region reveal the signature of exposed ice on some of the rims of the newly-formed surface features. The rapid ra
te of expansion is unexpected, however: models of sunlight-driven sublimation would predict erosion rates of just a few centimetres per hour, and thus the scientists believe that additional mechanisms are required to explain the observations.
A simple possibility is that the surface material is very weak, allowing for more rapid erosion, but it is also possible that the crystallisation of amorphous ice or the destabilisation of so-called ‘clathrates’ (a lattice of one kind of molecule containing other molecules) could liberate energy and thus drive the expansion of the features at faster speeds.
Colour images of the Imhotep region on Comet 67P/C-G, taken with the OSIRIS narrow-angle camera on Rosetta on 18 June (upper row), 2 July (middle row) and 11 July 2015 (lower row). The first column shows images taken in the orange filter (649 nanometres); the second column shows the ratio between images taken with the blue filter (481 nanometres) and the orange filter for the 18 June and 2 July images, and the ratio between images taken with the blue and the red (701 nanometres) filters for the 11 July image; the third column shows a composite obtained by combining the images in the previous two columns. The yellow arrows indicate some of the new features that were detected on Imhotep. These colour images show that some patches on the surface of the comet reflect orange/red light less effectively and blue light more effectively than their surroundings. They appear as white in the central column, where the colour ratio is shown. This indicates the presence of frozen water ice at or just below the surface of these patches. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
The erosion could be accompanied by increased rates of gas outflow, including H2O, CO2, or CO. The scientists also searched in OSIRIS images for evidence of increased dust rising from Imhotep as the surface morphology evolved, but did not find any.
While it is unlikely that many small (micron-sized) dust particles were released as the features formed and expanded, it is possible that the same amount of mass was released in a smaller number of larger (millimetre-sized) particles, which would produce less reflected light and thus be harder to detect with OSIRIS.
In addition, a significant fraction of the dust released may have immediately fallen back to the surface, accumulating at the base of the expanding rims.
Activity seen above the Imhotep region with the OSIRIS narrow-angle camera on Rosetta on 23 May 2015 (left), before significant morphological changes were seen in this region, and on 23 June 2015 (right), after the changes had begun to appear. (Times are in UT.) The positions of the first two new features that were seen in Imhotep are marked with A and B. The white arrows indicate the direction along which an increase of activity would have been seen in the case of jets lifting from the newly arisen features. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
Although the scientists were initially surprised to see such significant changes taking place on smooth terrains such as those seen in Imhotep, the location of this region close to the comet’s equator guarantees that it receives large amounts of sunlight.
“We are looking forward to combining our OSIRIS observations with data from other instruments on Rosetta, to piece together the origin of these curious features,” concludes Olivier.
Ruimtesonde Rosetta ontdekt zuurstofmoleculen op komeet
De ruimtesonde Rosetta heeft zuurstofmoleculen ontdekt op de komeet 67P/Churyumov-Gerasimenko.De gaswolk die uit de komeet komt, bevat gemiddeld 4 zuurstofmoleculen op elke 100 watermoleculen.
Waarschijnlijk is de zuurstof al miljarden jaren geleden, tijdens de vorming van de komeet, opgenomen uit de gaswolk waaruit ons zonnestelsel is ontstaan.
Dat meldt een team met onder meer onderzoekers van de Universiteit Leiden in het wetenschappelijk tijdschrift Nature .
De onderzoekers analyseerden meer dan drieduizend opnames van de komeet 67P/Churyumov-Gerasimenko, die tussen september 2014 en maart 2015 zijn gemaakt door Rosetta.
Aan de hand van metingen met een spectrometer aan boord van de ruimtesonde hebben de wetenschappers in kaart gebracht welke stoffen zich in de gaswolk rond de komeet bevinden.
Rosetta vond eerder al waterdamp, koolmonoxide, kooldioxide en diverse stikstof-, zwavel- en koolstofverbindingen op 67P/Churyumov-Gerasimenko. Zuurstof was nog niet ontdekt.
De vondst van de zuurstofmoleculen komt zeer onverwachts. "Voor mij is dit het meest verrassende chemische resultaat van de Rosetta-missie tot nu toe", verklaart de Leidse onderzoeker Ewine van Dishoeck nieuwssite Astronomie.nl .
"Decennialang hebben we gezocht naar interstellaire zuurstof zonder veel succes en nu vinden we haar zomaar in grote hoeveelheden in een komeet."
Door: NU.nl/Dennis Rijnvis
| Gewijzigd: 31 januari, 16:08 uur, door Joyce.s
Project komeetlander Philae stopt na opraken energie ruimtesonde Rosetta
Het project met de komeetlander Philae stopt woensdag defintief nu de energie van de ruimtesonde Rosetta op is. Philae stuurde zijn informatie door via de sonde naar de aarde.Dat kondigde de Duitse ruimtevaartorganisatie DLR dinsdag aan.
Door een gebrek aan energie zullen de systemen in de Rosetta worden uitgeschakeld. Als de Philae onverwacht nog berichten stuurt, komen die dus niet meer aan op aarde. Begin dit jaar besloot de vluchtleiding al om geen opdrachten meer te sturen.
De Philae landde op 12 november 2014 op de komeet. Dat was een unieke prestatie, maar de landing ging niet helemaal goed. De Philae kwam op een andere plek terecht dan de bedoeling was: in de schaduw. Daardoor haperde de verbinding en na ruim twee dagen viel het contact weg. Sindsdien is er maar eventjes weer contact geweest.
De Rosetta blijft nog een paar maanden rond de komeet draaien. Op 30 september slaat zij in op de komeet.Door: ANP
Bron:http://www.nu.nl/wetenschap/4298660/project-komeetlander-philae-stopt-opraken-energie-ruimtesonde-rosetta.html?redirect=1 | Gewijzigd: 31 januari, 16:08 uur, door Joyce.s
Ruimtesonde vindt robot Philae terug
De ruimtesonde Rosetta heeft zijn verdwenen landingsrobot Philae gelokaliseerd. De lander bleek 'verborgen' in een spelonk op de komeet 67P, waar hij in november 2014 na een reis van tien jaar was aangekomen.De Europese ruimtevaartorganisatie ESA deelde maandag in Parijs mee dat de ontdekking van Philae op het nippertje heeft plaatsgevonden, aangezien Rosetta over een maand buiten dienst wordt gesteld.
De camera van de sonde traceerde de lander vanaf een hoogte van 2,7 kilometer. Hij bleek nog maar twee van zijn drie poten te hebben.
Philae voerde als eerste in de geschiedenis een gecontroleerde landing op een komeet uit. De lander weegt ongeveer honderd kilo, heeft een diameter van een meter en is slechts tachtig centimeter hoog. De instrumenten aan boord bevatten onder meer een boor die monsters van de bodem moest nemen. Al snel na de landing bleek de batterij uitgeput. Die kon zich later door zonne-energie opladen. Desondanks kon de ESA de lander niet traceren.
De komeet 67P werd in 1969 ontdekt en heeft een diameter van 4 kilometer. In 2014 bevond de komeet zich op 264 miljoen kilometer van de aarde.Door: ANP
http://www.esa.int/var/esa/storage/images/esa_multimedia/images/2016/09/philae_close-up_labelled/16114912-1-eng-GB/Philae_close- up_labelled_medium.jpg | Gewijzigd: 31 januari, 16:09 uur, door Joyce.s
Op 30 september zal Rosetta - opzettelijk - crashen op komeet 67P/Churyumov–GerasimenkoOn Sept. 30th, Europe's Rosetta spacecraft will deliberately crash land on Comet 67P/Churyumov–Gerasimenko, ending the probe's two year mission in orbit around the comet's nucleus. With cameras and other instruments taking data until the last moment, Rosetta will descend into a mysterious region known as Ma'at home to several "active pits," which are spewing jets of gas and dust into space. Rosetta's death plunge could be exciting, indeed. Monitor ESA's Rosetta blog for updates.
ESA HANGOUT: PREPARING FOR ROSETTA’S GRAND FINALE
ESA’s Rosetta spacecraft is set to complete its incredible mission in a controlled descent to the surface of Comet 67P/C-G on 30 September. Join mission experts on 19 September, 1200 GMT / 1400 CEST to discuss Rosetta’s final days and hours of operation, including expectations for the images and other scientific data that will be collected as the spacecraft gets closer and closer to the surface. We’ll also discuss the exciting discovery of Philae that was made earlier this month.
Watch it live here: https://www.youtube.com/watch?v=x9lIPUjFe40
Andrea Accomazzo, Flight operations director
Sylvain Lodiot, Rosetta spacecraft operations manager
Claire Vallat or Richard Moissl (TBC), Rosetta science ground segment liaison scientist
Laurence O’Rourke, Rosetta downlink science operations manager (lander search coordinator)
Moderated by Emily Baldwin, Space Science Editor
De grote finale van Rosetta nadert
Rosetta is set to complete its historic mission in a controlled descent to the surface of its comet on 30 September, with the end of mission confirmation predicted to be within 20 minutes of 11:20 GMT (13:20 CEST).
28 September 2016
Details of how, when and where to follow the key moments online, starting with a review of the mission’s impressive haul of science highlights on 29 September, can be found below:
29 September 12:30–15:30 GMT / 14:30–17:30 CEST, science highlights
Tune in to the livestream viewer at rosetta.esa.int or via https://livestream.com/ESA/rosettagrandfinale or ESA's Facebook page on 29 September for dedicated talks celebrating the scientific highlights of the mission.
Matt Taylor (ESA’s Rosetta Project Scientist): Introduction
Mohamed El-Maarry (OSIRIS team, University of Bern): Landscapes of Chury
Valerie Ciarletti (CONSERT team, Universités Paris-Saclay): Getting the ground truth about the nucleus
Thurid Mannel (MIDAS team, University of Graz): Dust under the microscope
Jean-Baptiste Vincent (OSIRIS team, Max-Planck Institute for Solar Physics, Göttingen): Cometary activity and fireworks
Andre Bieler (ROSINA team, University of Bern/University of Michigan): Comet activity variation and evolution
Charlotte Goetz (RPC team, Institute for Extra-terrestrial Physics, TU Braunschweig): The singing comet
Cecila Tubiana (OSIRIS team, Max-Planck Institute for Solar Physics, Göttingen): Rosetta’s link to Earth
Kathrin Altwegg (ROSINA team, University of Bern): The cometary zoo
Björn Davidsson (Asteroids, Comets and Satellites Group, JPL): Formation of our Solar System
Matt Taylor: Final comments and close
29 September 20:50 GMT / 22:50 CEST, final manoeuvreRosetta is expected to execute its ‘collision manoeuvre’ at 20:50 GMT / 22:50 CEST, at an altitude of about 19 km, which will set it on course to collide with the comet within 20 minutes of 10:40 GMT / 12:40 CEST at the comet on 30 September. An update to confirm the manoeuvre will be provided via the Rosetta blog and via Twitter through the spacecraft’s account @ESA_Rosettaand via @esaoperations shortly after the manoeuvre is completed.
Images from the descent are expected to be shared from the early morning of 30 September onwards, via ESA’s Space in Images and Rosetta social media channels (in the first instance on Twitter via @ESA_Rosetta).
30 September 07:55–08:05 GMT / 09:55–10:05 CEST, last commands and confirmation of landing time
At 08:00 GMT / 10:00 CEST the last commands will be uploaded to the spacecraft to fine-tune the spacecraft’s pointing, based on the Navigation Camera images taken shortly after the collision manoeuvre. It is at this stage that a refined time for Rosetta’s impact will be known: it is currently predicted at 10:40 GMT / 12:40 CEST (±20 minutes) at the comet but it is expected to be narrowed down to within ±2 minutes.
There will be a short transmission streamed viarosetta.esa.int,https://livestream.com/ESA/rosettagrandfinale and ESA's Facebook page confirming this information, and once known, we will update the time indicated at the top of this page and via our blog and social media channels.
Note that due to the signal travel time, the end of mission will be confirmed 40 minutes after the impact has actually occurred, within 20 minutes of 11:20 GMT / 13:20 CEST.
30 September 10:30–11:40 GMT / 12:30–13:40 CEST, end of mission coverageLive streaming will begin at 10:30 GMT / 12:30 CEST via rosetta.esa.int,https://livestream.com/ESA/rosettagrandfinale and ESA's Facebook page featuring status updates from mission controllers live from ESA’s European Space Operations Centre in Darmstadt, Germany. Note that the start time may be subject to ±20 minute change depending on the final confirmed impact time.
All times are subject to change due to circumstances beyond our control – check this page for the latest update.
| Gewijzigd: 31 januari, 16:09 uur, door Joyce.s
Crashlanding Rosetta deel 1
Over 45 minuten begint de live uitzending van de crashlanding
Link live stream: http://rosetta.esa.int/
Voor de geïnteresseerden (die geen tijd hebben om het nu te volgen): ik ga het geheeld bijhouden en hier posten
COLLISION MANOEUVRE COMPLETE
Rosetta has completed its final manoeuvre and is now on a collision course with Comet 67P/C-G.
A small thruster burn starting 20:48:11 UTC and lasting 208 seconds has set the craft on course towards its final destination.
The spacecraft's navigation cameras will soon take a set of five images to confirm that the spacecraft is on target, and to refine the predicted impact time.
These are expected to be downlinked by 0300 UT / 0500 CEST and we therefore expect that the next report, with the updated time and at least one of those NAVCAM images, will be around 0400 UT / 0600 CEST.
DESCENT IMAGES BEGIN!We've started to get images from Rosetta's descent. This one was taken by the OSIRIS narrow-angle camera at 01:20 UT, from a distance of around 16 km.
The image scale is about 30 cm/pixel and the image measures about 614 m across.
IMPACT TIME UPDATE: 10:38 UTBased on the Navigation Camera images taken shortly after last night's collision manoeuvre, flight dynamics analysis has refined the predicted time of Rosetta's impact into the Ma'at region on the small lobe of Comet 67P/C-G to 10:38:32 UT+/- 2 minutes at the comet.
Because of the 40 minute signal travel time between Rosetta and the Earth today, confirmation of the mission's end will arrive at ESA's mission control at 11:18 UT/ 13:18 CEST +/- 2 minutes.
Follow rosetta.esa.int for live coverage later today.
ROSETTA’S LAST NAVCAM IMAGE
Rosetta's Navigation Camera captured five images shortly after the collision manoeuvre last night, which are being analysed by flight dynamics to confirm the spacecraft is on track to impact its target in the Ma'at region of Comet 67P/C-G later today.
The last image returned from the spacecraft was taken at 00:59 UT onboard the spacecraft, and downlinked to Earth a couple of hours later. It was taken at a distance of 17.4 km from the centre of the comet. The image scale is 1.5m/pixel and the image measures about 1.5 km across.
Lightly enhanced NAVCAM image taken on 30 September 2016 at 00:59UT. ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
The five images were used by the flight team to update the estimate of the landing time and final pointing of the spacecraft. The revised impact time is now predicted as 10:38:32 UT+/- 2 minutes at the comet.Because of the 40 minute signal travel time between Rosetta and the Earth today, confirmation of the mission's end will arrive at ESA's mission control at 11:18 UT/ 13:18 CEST +/- 2 minutes.
The full set of five images will be published later this morning.
Follow rosetta.esa.int for live coverage.
The original unprocessed image is provided below:
IMPACT SITE IS COMING IN TO VIEW!
We just received this image from the OSIRIS wide-angle camera, taken at 02:17 UT at the comet. It shows the target impact region just coming in to view in the lower left –look for the distinctive shape of the Ma'at pits.
It was taken from a distance of about 15.5 km; the image scale is about 1.56 m/pixel and the image measures 3.2 km across.
COMETWATCH FINALE: ROSETTA’S LAST NAVCAM IMAGESosetta's Navigation Camera captured five images shortly after the collision manoeuvre last night, which were used by flight dynamics teams to confirm the spacecraft is on track to impact its target in the Ma'at region of Comet 67P/C-G.
The NAVCAM images were acquired at 22:53, 23:25, and 23:56 UT on 29 September and 0027 and 0059 UT on 30 September (on board spacecraft time) when the spacecraft was between about 20 and 17 km from the comet centre.
The first two images show the scan of the spacecraft over the large comet lobe, featuring the Seth, Hapi and Ash regions, before the Hatmehit and Ma'at regions on the small lobe came into view.
The full set of lightly enhanced images are presented below. Click for distance and scale info.
22:53UT 29 September 2016
ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
23:25 UT 29 September 2016. ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
23:56 UT 29 September ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
00:27 UT 30 September 2016 ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
Lightly enhanced NAVCAM image taken on 30 September 2016 at 00:59UT. ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
@ESA_Rosetta control team now seeing the final commands (sent earlier) being processed on board #CometLanding:
Nog 10 minuten voordat de livestream begint | Gewijzigd: 30 september 2016, 17:28 uur, door Joyce.s
Crashlanding Rosetta deel 2
Live uitzending is begonnen. Touchdown staat gepland om 12:20 uur.
Nog een keer link: http://rosetta.esa.int/ Over 3 uur en 40 minuten gaat het daadwerkelijke spektakel plaatsvinden.
Gedurende die tijd zal de stream live blijven, zodat je naar de activiteiten in de controlekamer kunt kijken. Tot dusverre verloopt alles volgens plan.
Inmiddels is Rosetta alweer iets dichterbij de komeetoppervlakte gekomen.
COMET LANDING DESCENT IMAGE – 11.7 KM
Comet 67P/C-G viewed with Rosetta's OSIRIS NAC on 30 September 2016, 8.9 km from the surface. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
As Rosetta gets closer and closer to Comet 67P/Churyumov-Gerasimenko, the OSIRIS narrow-angle camera captured this beautifully detailed image of the comet surface at 06:53 GMT from an altitude of about 8.9 km.
COMET LANDING DESCENT IMAGE – 8.9 KM
Nog een link die bekeken kan worden: http://livestream.com/ESA/rosettagrandfinale
Aangezien het nog "even" wachten is tot moment supreme, hierbij een kort filmpje wat Rosetta allemaal heeft gedaan:
ESA Operations @esaoperations 9 min.9 minuten geledenSylvain Lodiot @ESA_Rosetta Operations Manager: "Passivisation commands confirmed executed". SW patch is live. No turning back #CometLanding
Vragen en antwoorden over Rosetta:Why is the mission ending?
The decision to end the mission on 30 September ultimately comes as a result of the spacecraft’s ever-increasing distance from the Sun. Comet 67P/C-G, and therefore Rosetta, is currently heading out towards the orbit of Jupiter, resulting in significantly reduced solar power with which to operate the craft and its instruments. In addition, by early October, the teams would be faced with a month-long solar conjunction – when the Sun lies between the Earth and Rosetta and the comet. This would result in significantly reduced communication capabilities (including downlinking science data) for around a month. Combined with an ageing spacecraft and payload that have endured the harsh environment of space for over 12 years – not least two years close to a dusty comet – this means that Rosetta is reaching the end of its natural life and so 30 September was considered the optimum date to conclude the mission.
How is the mission ending?
Rosetta will descend to the surface of Comet 67P/C-G in a controlled impact. During this descent, unique scientific observations will be possible, including very high-resolution images and sensitive measurements of gas and dust, at distances closer than Rosetta has ever been before.
Why aren’t you putting the spacecraft in hibernation again?
Unlike in June 2011, when Rosetta was put into a 31-month hibernation for the most distant part of its journey, this time it is riding alongside the comet. Comet 67P/Churyumov-Gerasimenko’s maximum distance from the Sun (over 850 million km) is more than Rosetta has ever journeyed before. The result is that there is not enough power at its most distant point to guarantee that Rosetta’s heaters would be able to keep it warm enough to survive. Instead of risking a much longer hibernation that is unlikely to be survivable, and after consultation with Rosetta’s science team in 2014, it was decided that Rosetta would follow its lander Philae down onto the comet.
Where will the spacecraft land on the comet and why?
Rosetta will end its mission with a controlled impact in the Ma’at region, on the small lobe of Comet 67P/Churyumov-Gerasimenko. The region was chosen because it is scientifically very exciting: it is home to a number of active pits, measuring over 100 m across and 50 m deep, to which a number of dust jets emerging from the comet have been traced back. The pit walls also exhibit lumpy structures called ‘goosebumps’, with sizes of a few metres, which could be the signatures of early cometesimals that merged together to create the comet in the early phases of Solar System formation. Therefore, scientists will obtain close-up images, along with information on the dust, gas, and plasma environment very close to such pits, which will help them understand their connection to the comet’s observed activity, and as well to learn more about how they relate to the formation and evolution of the comet. Thus a trajectory has been planned for Rosetta that will see it fly over a region of pits, with a touchdown point a smooth area between two of them.
How precisely can you target the touchdown point?
There are a number of uncertainties associated with Rosetta’s descent, including the precise timing and duration of the final manoeuvre burns, the distance from the comet at that time, the non-uniform gravity of the comet, and the effects on the spacecraft of outflowing material from the comet. A large set of trajectories has been calculated taking into account plausible variations in each of these parameters, each resulting in a different touchdown point. Present best estimates predict that Rosetta will impact somewhere within a 700 x 500 metre ellipse centred on the nominal target point.
Why aren’t you planning to descend directly into a pit?
In order for Rosetta to take the best possible images during the descent, the spacecraft and targeted touchdown point need to be in sunlight, in order to generate power and be illuminated, respectively. The interiors of the pits on Comet 67P/C-G are dark when not directly in sunlight. Plus, in order to ensure that the final data are sent back to scientists, the spacecraft needs to be in line-of-sight visibility until touchdown. So, while the pits will be targeted for imaging during the descent, the actual touchdown is planned to take place adjacent to one of them. However, given the uncertainty in the precise touchdown point described above, there is at least the possibility of ending up in a pit.
Is the target site close to Philae, and will Rosetta be able to see Philae during its descent?
Rosetta’s planned touchdown site is on the small comet lobe, but on the opposite side from where Philae has been located at Abydos. Due to a combination of orbital dynamics and illumination reasons, the current trajectory plan does not see Rosetta pass over Philae during the descent.
What are the key operations and timings during the last days of the mission?
On 24 September, Rosetta will leave its current close, flyover orbits and transfer into the start of a 16 x 23 km orbit that will be used to prepare and line up for the final descent. In the evening of 29 September (20:50 UTC) a manoeuvre will place Rosetta on a collision course with Comet 67P/C-G, initiating the descent from an altitude of 19 km above the surface. The spacecraft will fall freely towards the comet, without further manoeuvres, collecting scientific data during the descent. (See a simple overview graphic of this timeline here).
Impact is expected to occur on 30 September at 10:40 UTC at the comet, with an estimated error of ± 20 minutes. As the signal travel time between Comet 67P/C-G and Earth on that day will be 40 minutes, confirmation of impact is expected at our mission control, ESOC, at 11:20 UTC / 13:20 CEST, again with an estimated error of ± 20 minutes. It is anticipated that this uncertainty will be reduced as the end of the mission approaches. All times are presently nominal and subject to final definition of the descent trajectory, as well as possible circumstances beyond our control.
Which scientific instruments will be on during the descent?
The planning for the scientific investigations to be made during the descent are still on-going, and involve a complex trade-off between the amount of power available from Rosetta’s solar panels, the amount required to run each instrument, and the downlink data rate possible on the day. At present, it is expected that the final sequence of observations will include images and measurements of the gas, dust, and plasma properties. Update 26 Sept: All instruments except COSIMA, MIDAS and VIRTIS will be on. More details here.
Which data will be available on the day of the final descent?
For obvious reasons, all scientific data collected during the descent must be relayed back to Earth in quasi real-time, and will not accumulate in the on-board mass memory storage for subsequent downlink as is usually the case. Data transmission will end as soon as the spacecraft impacts the comet. It is expected that some of these data, most notably some of the images, will be made available to the public as soon as possible on the day, allowing for some nominal processing time.
Update 28 Sept: For more details see the blog post "Science 'til the very end" (and see here for the latest livestream schedule, although it is expected that images will also be released via ESA Space in Images and @ESA_Rosetta in the first instance, outside of this schedule.)
Once the spacecraft is on the surface of the comet, will there be any chance to communicate with it?
As soon as Rosetta hits the surface, its main systems will be turned off, including the attitude and control systems, as well as the main transmitter, the latter in order to meet regulations aimed at avoiding interference on deep space network communications channels. The software that will enable this ‘passivation’ will be uploaded to the spacecraft a week prior to the planned end of mission, and it will be activated around the time of the collision course manoeuvre, approximately ten hours prior to impact. No automated re-activation will be possible after the systems have shutdown on impact. In any case, as soon as Rosetta hits the surface, its high-gain antenna will very likely no longer be pointing towards Earth, making any potential communications impossible.
How will we know that Rosetta reached the surface?
When Rosetta woke up from hibernation on 20 January 2014, its renewed contact with Earth was signalled by the appearance of a spike in a spectrum analyser display at ESOC at the expected frequency. Conversely, when Rosetta reaches the surface of the comet on 30 September and the main transmitter is turned off, this spike should disappear from a similar display, confirming to mission controllers and the world that impact has occurred.
How fast will Rosetta impact the surface?
One of the key features of the trajectory design is to minimise the spacecraft's relative velocity at impact. The current scenario predicts that the impact velocity will be around 90 cm/s, around walking pace. It is worth keeping in mind that Rosetta was not designed as a lander, and some of its appendages including the 32m-wide solar panels will be damaged by the impact. This energy dissipation will very likely ensure that the escape velocity will not be exceeded during any bounce, thus preventing Rosetta from returning to orbit after impact with Comet 67P/C-G.
If Rosetta does bounce back into space, would we know?
No, because Rosetta’s main systems, including the main transmitter, will be turned off at the moment of impact.
Is it possible that the spacecraft might crash sooner than 30 September?
Yes. At present, the spacecraft is in a close flyover phase, approaching to within roughly two kilometres of the comet surface at closest approach. This makes for a complex interaction between the spacecraft, the non-uniform gravity of the comet, and the outgassing of materials from the surface. In flight dynamics terms, operating in this phase is much more challenging than during the Philae landing. To make this final phase possible, certain flight rules have had to be suspended, including one that forbids manoeuvres that might bring the spacecraft onto a collision course with the comet if the manoeuvre was interrupted during its execution. Also, operating very close to the comet means that there is always the chance of an outburst adversely affecting the spacecraft. Thus there is definitely a possibility of losing the spacecraft before 30 September.
Are there other risks you’ll be paying particular attention to?
Yes, the extreme circumstances of the final flyover phase are placing high demands on Rosetta. For example, the spacecraft reaction wheels will be operating at much higher speeds than normal because the spacecraft slew rates will be higher during this phase. Higher torques on the wheels increase the chance of a malfunction.
What happens if the spacecraft goes into safe mode before 30 September?
As with any other safe mode, the operations team will aim to recover the spacecraft and evaluate the impact on the trajectory and short-term operational timeline. But at some stage, as we get closer to 30 September, there will be a point of no return. For example, there may not be enough time to recover the spacecraft such that the science instruments can be pointed towards the comet before the final impact. Furthermore, if there is a safe mode after the passivation patch has been activated (approximately ten hours before impact), then the spacecraft will automatically switch off before impact and will not be recoverable. As the one-way signal travel time on 30 September will be 40 minutes, there is no chance of real-time communication and rapid emergency reaction to such issues.
http://www.esa.int/Our_Activities/Space_Science/Rosetta/Rosetta_s_grand_finale_frequently_asked_questions | Gewijzigd: 30 september 2016, 17:29 uur, door Joyce.s