Rosetta Blog

Rosetta's OSIRIS team responds to blog comment

amehta — Fri, 20 Nov 2009 12:59:15 +0100

Stubbe Hviid, OSIRIS Operations Manager, has sent us a response to a comment made on this post:

"In the last pic, I'm wondering what the tiny dots are (multiple white and one black) : due to Osiris?, to data processing?, to objects above clouds? (X,Y) for the black at (760pxl/2048, 456pxl/1083) and for one white at (753/2048, 172/1083). At least the block dot is also present on the first pic."

Stubbe says that the white dots are caused by cosmic ray events. When the images were taken, the spacecraft was in open space (of course). This means that the spacecraft experiences the full effect of the solar wind and high energy particles. These high energy particles are detected by the CCD as light flashes. On the surface of the Earth, we normally do not see these cosmic ray events because the atmosphere shields us.

The white dots due to the cosmic ray events are completely normal. For example, the coronagraph of ESA's SOHO satellite regularly experiences a bakeout. With respect to SOHO bakeout, Stubbe added:

It is the same effect but a different kind of detector. OSIRIS also has the capability to 'bake out' the CCD (also called annealing). As a rather extreme example of this, here's an image we took of Comet Machholz back in 2005, during which Rosetta was caught in a Coronal Mass Ejection solar flare with a radiation level about 100 000 times higher than normal.

Views of Rosetta from Earth: Quick thanks

danielscuka — Tue, 17 Nov 2009 11:52:34 +0100

Note a comment left by J.M. Mondelo, who observed Rosetta on 12 November 2009 (thanks for the link and great pictures!). -- Daniel

Rosetta receding

amehta — Tue, 17 Nov 2009 11:46:50 +0100

Kristin wrote to us early on Saturday morning, 14 November.

During the night of 13/14 November, the team at ESA's Optical Ground Station, Tenerife, imaged Rosetta receding from Earth. The spacecraft's brightness was very low as they were looking at the non-illuminated side of the solar arrays; in contrast, during approach, sunlight was reflected from the solar arrays toward us (this explains the long exposure time and bad image quality compared with the approach observations done on 11/12 and 12/13 November).

This movie was recorded between 04:51 and 05:20 UTC on 14 Nov. It consists of 10 images with an exposure time of 2 min and a separation of 3 min. The field is located in Leo and has a size of 5 x 5 arcmin; North is up and East is left. The telescope was tracking the stars so that Rosetta appears as a stripe while the stars appear as dots. Rosetta moves roughly from East to West. The bright star at the bottom of the image has magnitude 12.5, and the bright star at the top has magnitude 13.4.

This image was taken at 05:39 UTC on 14 Nov with an exposure time of 5 min. The field is located in Leo and has a size of 5 x 5 arcmin, North is up and East is left. The telescope was tracking the stars so that Rosetta appears as a stripe a little above centre-right of the image. The spacecraft moves less than 1 arcmin during the 5 min exposure, roughly from East to West. The brightest star at the bottom of the image has magnitude 12.6. Note that the vertical bright line that crosses Rosetta is a camera artefact. Kristin Wirth wrote:

"I will leave the Teide Observatory and Tenerife now, and head for the airport. I really enjoyed my time at the Optical Ground Station, together with a great team and at a special location - opposite the Teide mountain, with the clouds below us. I would like to thank everybody for their support, in particular Lilian Dominguez Palmero who operated the telescope for me." -- Kristin

And we're going to take this opportunity to thank Kristin for all her great help and input for the Rosetta Blog over the past week!

Finally, a 'farewell' (for now) from us both and a sincere 'thank you' to every one who visited the Rosetta Blog - it has been a lot of fun and we have especially enjoyed seeing the many comments left by visitors.

We plan to be back again in 2010 as Rosetta continues on her fascinating journey to the outer Solar System - including preparations for deep-space hibernation and the encounter with asteroid Lutetia on 10 July 2010 (from a distance of just 3000 km!). --Amruta & Daniel

Swirling clouds over the South Pacific

amehta — Mon, 16 Nov 2009 14:00:13 +0100

New images from the OSIRIS team received over the weekend!

Click to download the hi-res version

False-colour composite of cloud structures in an anticyclone over the South Pacific. It depicts a portion of the scene below with five times the resolution. The image was taken with the narrow-angle camera on 13 November at 06:48 CET, using orange, green and blue optical filters

Click to download the hi-res version

Taken three minutes before the image above with the wide-angle camera, this image is shown in a logarithmic scale to bring out details in the varying light intensity. As a result the scene looks roughly the same as it would appear to the human eye.

Click to download the hi-res version

The same area in the South Pacific imaged with the orange filter of the narrow-angle camera in a logarithmic intensity scale.

--Amruta

New animation shows Earth approaching

danielscuka — Sat, 14 Nov 2009 09:45:06 +0100

As a reader commented, the images clearly show Earth smiling back at Rosetta!

The OSIRIS team has composed this animation from a sequence of images taken once every 24 hours, beginning when Rosetta was at a distance of 50 000 km at 22:28 UTC last night. The resolution is 6.5 km/pixel. Access the animation in the main ESA web site. -- Amruta

Getting some help from Orville on the blog...

danielscuka — Fri, 13 Nov 2009 18:04:58 +0100

It's been a long day here on the Rosetta Blog - and we're finally getting some much-needed help from the Rosetta Flight Control Team's mascot, Orville - who, apparently, speaks French! :-) We'll log off for the the day now - thank you for visiting the Rosetta Blog -- Daniel

Earth seen by Rosetta's Navigation Camera

amehta — Fri, 13 Nov 2009 17:35:47 +0100

Rosetta's operations team just handed us a couple of breath-taking images taken by the spacecraft's navigation camera (navcam). The camera is actually designed for navigation purposes, so they aren't to be compared with the full-colour scientific capabilities of OSIRIS - but they are amazing views!

This image was captured at 14:23 UTC (15:23 CET), when Rosetta was at a distance of approximately 236 000 km from Earth's centre. It shows a cloud-covered North America in some detail. (Click on 'Full story' for a second cool pic!) -- Daniel

This image shows a cloud-covered North America, and was captured at 14:03 UTC (15:03 CET), when Rosetta was at a distance of approximately 224 000 km from Earth's centre. It is not quite as nice as the first, and shows a few smears from the CCD camera output.

The navcam is used for precise determination of the orbit and optical visualisation. The output of the camera tells you where the centre of the object that is in the centre of the field of view is - it also gives physical parameters of the object.

The photos were taken to test the camera's operation with a large physical object. Previously, Steins was also imaged, but it is rather small (about 5 km across). Next year, the camera will be used to view Lutetia, which is much larger (about 95 km across). In the camera field of view, Lutetia shoudl appear about as large as the Earth looks in these images.

Some cool tech stuff... RPC-LAP & SREM

danielscuka — Fri, 13 Nov 2009 16:52:07 +0100

We're received a couple of emails from several colleagues around ESA and at the science teams working on Rosetta from other institutes. They've kindly sent in some of the data they've seen during the swingby campaign, and herewith we'd like to publish a couple of cool 'techie' updates.

The first came in from Anders Eriksson, the PI (principle investigator) for Rosetta's RPC-LAP at the Swedish Institute of Space Physics, Uppsala, and the second from ESA's Petteri Nieminen, working on Rosetta's SREM instrument at ESA/ESTEC, the Netherlands. Click on 'Full story' for details. -- Daniel

This received from Anders (click image for high-res):

Nice blogging on the Rosetta ESB3! Perhaps you are interested in the attached plot (above): I confess it isn't as sexy as the Osiris images, but it is fun in that it shows the thruster firings on November 10 (night). When the thrusters are fired (for reaction wheel offloading, in this case), a portion of the gas released gets ionized by the solar UV radiation, creating a plasma cloud easily detected by the Langmuir probes of the RPC (Rosetta Plasma Consortium), turned on since Monday night. We knew the time slot for the wheel offloading, but not the exact timing: however, from the data we can say that they did three thruster firings within a few minutes, and we can quite accurately time them.

At each firing, we see a sudden jump in the probe potential, decaying at a slower rate as the cloud disperses. The scale at the left is really in volts, showing the potential of one of our probes with respect to the spacecraft. The three peaks reach different height, probably just because of a sampling effect (we only take one sample per second for the moment).

This came in from Petteri (click image for high-res version):

These diagrams show the SREM radiation measurements as Rosetta passed through the Earth's radiation belts during the fly-by.

The top two panels: The distance of Rosetta from the Earth is shown in Earth radii, together with count rates for three of the SREM channels. The TC3 channel is sensitive to electrons (>500 keV) and protons (>10 MeV), TC1 for electrons (>2 MeV) and protons (>27 MeV), and S34 for protons only (>11 MeV).

The bottom two panels show the Earth's magnetic field strength, and the derived electron fluxes in different energy ranges as a function of geomagnetic coordinates.

Credits: ESA/ Paul Buehler / PSI

Thanks guys!!

Swing-by accuracy

danielscuka — Fri, 13 Nov 2009 16:24:49 +0100

Just heard from the Flight Dynamics folks here at ESOC, and SOM Andrea Accomazzo dropped by with early news: It appears that Rosetta was just slightly more than 1.1 km from the planned swing-by target! This performance, if confirmed, means that her trajectory was more accurate than predicted. The perigee passage time (= time of closest approach) was less than 0.01 seconds different from the last prediction made before the swing-by. -- Daniel

Rosetta sees a living planet - latest OSIRIS images

danielscuka — Fri, 13 Nov 2009 15:16:49 +0100

Click on images to access full-size version. For detailed captions and information, access the ESA web portal.