Rosetta Blog

Rosetta Blog http://webservices.esa.int/blog/blog/5 Coverage of the Rosetta mission as she makes a series of complex gravity assist manoeuvres around Earth (Mar 2005, Nov 2007, Nov 2009) and Mars (Feb 2007), plus the exciting encounters with Asteroids Steins (Sep 2008) and Lutetia (Jul 2010). News and updates from the Rosetta Dedicated Control Room at ESOC, ESA's European Space Operations Centre, Darmstadt, Germany. administrator 2013-05-19T00:55:47Z Rosetta image of asteroid 21 Lutetia 9 July - 2 mn km from target http://webservices.esa.int/blog/post/5/1231   <div style="text-align: center"> <img src="http://webservices.esa.int/blog/gallery/5/NAC_2010-07-09T03.01.52.383Z_ID10_1251276002_F22.jpg" /> </div>   CREDIT: (C) ESA 2010 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA The OSIRIS imaging team have just sent in an image! Modest, yes, but the target's in sight! :-) It shows asteroid 21 Lutetia from a distance of 2 million km, rapidly decreasing, and was acquired by the Narrow Angle Camera of the OSIRIS imaging system on board ESA's Rosetta spacecraft on 9 July 2010 at around 03:00 CEST. Rosetta is due to make closest approach at 18:10 CEST 10 July. This image was acquired as part of the optical navigation campaign, in which images acquired by the OSIRIS scientific imager and by Rosetta's on-board navigation cameras are being used to refine estimates of Lutetia's orbital trajectory.       General Optical Navigation 2010-07-09T19:01:45Z danielscuka Optical navigation campaign complete http://webservices.esa.int/blog/post/5/1229 The last optical navigation slot (Slot 19) was just completed a few minutes ago. With this data, ESA Flight Dynamics are now going to compute the final orbit for the flyby, and make a final decision on whether mission controllers should use the last Trajectory Correction Manouevre (TCM) slot, at 12hrs before closest approach on 10 July. -- Daniel Optical Navigation Operations Flight Dynamics 2010-07-09T10:58:35Z danielscuka 5.8 million kms and getting closer... http://webservices.esa.int/blog/post/5/1221 This was sent in by the Flight Dynamics team at ESA/ESOC a couple hours ago - it is an image acquired by Rosetta's Navigation Camera A (NAVCAM A) on 6 July at 05:45:02 CEST as part of the continuing navigation campaign. The picture shows Lutetia as a bright point of light in the middle of the image. The distance to Lutetia from Rosetta was roughly 5.8 million km. Thanks, Sabine! (Click image for larger size) <a id="res_18734" href="http://webservices.esa.int/blog/gallery/5/20100706T034502.jpg"> <div style="text-align: center"> <img src="http://webservices.esa.int/blog/gallery/5/previews-med/20100706T034502.gif" border="0" alt="Image taken by NAVCAM A on 2010/07/06 03:45:02 UTC. Lutetia is the bright object in the middle of the 5x5 deg FOV. At that time, the distance was roughly 5.8 million km." /> </div> </a>           General Optical Navigation Operations Flight Dynamics 2010-07-07T14:39:46Z danielscuka Rosetta thruster burn to align probe with asteroid target http://webservices.esa.int/blog/post/5/1192 <a id="res_427" href="http://webservices.esa.int/blog/gallery/5/29_exploded_L.jpg"><img src="http://webservices.esa.int/blog/gallery/5/previews-med/29_exploded_L.jpg" border="0" alt="The Rosetta orbiter - spacecraft design Rosetta resembles a large aluminium box whose dimensions are 2.8 x 2.1 x 2.0 metres. The scientific instruments are mounted on the 'top' of the box – the Payload Support Module – while the subsystems are on the 'base' or Bus Support Module. Credits: ESA/AOES Medialab" align="left" /></a>The Rosetta team here at ESOC are preparing for a thruster burn tomorrow, 18 June, designed to manoeuvre the deep-space probe onto an altered trajectory that will take it to the desired fly-by point on 10 July (burn starts 08:24 CEST). Now here's an interesting bit of space science: based on data gathered during this month's complex optical navigation campaign, the spacecraft is currently predicted to make closest approach at just 2639 km from Lutetia - quite a bit closer to the asteroid then the hoped-for 3160 km. Closer would be better, don't you think? So why are the Rosetta team burning fuel to take the point of closest approach 526 km further away from the target? It turns out that 2639 km would be too close - more details under 'Full story' -- Daniel  Exploded view of Rosetta showing internal and external components. There are 24 10N thrusters mounted externally.   <hr width="100%" size="2" /> Yesterday, the flight dynamics team working on Rosetta issued their most recent optical navigation campaign report, which gave a prediction of the fly-by distance based on 38 NavCam and 15 OSIRIS images acquired in the past several weeks. If no thruster burns are conducted, Rosetta is currently predicted to make closest approach at 2639 km from Lutetia at 15:45:00.03 UTC (17:45:00.03 CEST), with an uncertainty of 7.47 seconds. But, as ESA's Andrea Accomazzo, Rosetta Spacecraft Operations Manager, explained in an email, this distance is too close: <blockquote> If we fly closer than 3160 km, then the asteroid image will 'fill up' the cameras' field of view at closest approach. And then not only will we not see the full asteroid but, since the camera image guides the spacecraft attitude, we also would not know at what spot on the asteroid surface we are pointing. Moreover, the science teams have prepared commands for the spacecraft's instruments assuming a certain pre-set distance range from the asteroid. If we do not pass by within this planned range, we might hamper their observations. It is true that we will use fuel for this correction, but it is very little compared to entire mission and it is far below the amount allocated for this flyby. To be precise, we will only use something in the order of 300 g of fuel. </blockquote> Andrea said the trajectory correction manoeuvre will start at 06:24 UTC (08:24 CEST), with the thrusters switching 'ON' 8 seconds later. The burn will run for 188 seconds, and will be commanded automatically since Rosetta will not be in ground station contact at the time. Full results will be downloaded during the next ground contact a few hours later via DSA-1, ESA's 35m deep-space station at New Norcia, Australia. The Rosetta Flight Dynamics head, Trevor Morley, added that: <blockquote> Although the main reason for tweaking the Rosetta trajectory is to increase the fly-by distance, a secondary reason is to ensure that the solar phase angle passes through zero so that at about 18 minutes before closest approach (at a separation distance of 16 400 km) the asteroid, as viewed from the spacececraft, will be seen fully illuminated [and better for observations]. </blockquote> The results of the thruster burn will be analysed to generate new fly-by predictions, but by tomorrow at lunchtime the spacecraft should be lined up to pass by Lutetia at 3160 km at 15:44:55.57 UTC (17:44:55.57) - all figures subject to final confirmation. This story illustrates well the deep cooperation required to make space science a success. Extensive planning for Lutetia flyby started months ago at ESA and within the various science teams working on her instruments. Based on this preparation - and like Goldilocks' porridge - the flyby must be conducted within a certain range of distances - not too far, not too close - just right.   General Optical Navigation Operations 2010-06-17T18:07:51Z danielscuka Tracking a pinpoint of light: Rosetta's first glimpse of asteroid Lutetia http://webservices.esa.int/blog/post/5/1191 <a id="res_17990" href="http://webservices.esa.int/blog/gallery/5/lutetia_31052010_rosetta_esa.png"> <div style="text-align: center"> <img src="http://webservices.esa.int/blog/gallery/5/previews-med/lutetia_31052010_rosetta_esa.gif" border="0" alt="This image was acquired 31 May at 03:45 UTC (05:45 CEST) by NavCam A and shows Lutetia as a point of reflected sunlight - it's the small dot at the approximate centre of the image." /> </div> </a> A lovely little photo kicks off our Lutetia fly-by coverage! This first image of asteroid Lutetia was captured on 31 May 2010 by Rosetta's Navigation Camera A (there are two, 'NavCam A' and 'NavCam B') and was processed by the Flight Dynamics team here at ESOC, ESA's European Space Operations Centre, in Darmstadt, Germany. (Click on 'Full story' for more details) -- Daniel <hr width="100%" size="2" /> Admittedly, the image appears to show little more than a pinpoint of light against a random background of stars. But it's a crucial first glimpse of Rosetta's next target and is one of several dozen images that are being used by the Flight Dynamics experts to adjust Rosetta's trajectory up to closest approach to the asteroid on 10 July. Since the end of May, the images have been acquired every few days by the two NavCams and by OSIRIS Narrow Angle Camera (NAC), part of Rosetta's high-resolution scientific imaging system. The pictures are crucial inputs to the ongoing navigation campaign, in which the spacecraft's own images are being used to precisely calculate the location of Lutetia and Rosetta and their relative separation. Results of the image analysis are fed back into flight planning algorithms to generate highly accurate trajectory correction manoeuvres (thruster burns) designed to bring Rosetta to an optimised fly-by point in space, approximately 3160km from Lutetia, on 10 July. The same optical navigation technique was used in 2008, when Rosetta flew past asteroid 2867 Steins. Prior to Rosetta's flybys, the Sun-centric orbits of both Steins and Lutetia - thought to be ancient remnants of our Solar System's birth - were relatively unknown to scientists (at least, not well enough known for fly-by targetting). The imaging is necessary to refine their orbital models and Rosetta's thruster burns. This work is performed by ESA's flight dynamics experts, a team comprising some of Europe's savviest mathematicians, physicists, engineers and computer scientists, who work closely with Rosetta's Flight Operations Team and the mission scientists. The image was acquired 31 May at 03:45 UTC (05:45 CEST) by NavCam A and shows Lutetia as a point of reflected sunlight - it's the small dot at the approximate centre of the image. The brightest star that can be seen in the camera's field of view (FOV) is beta Virginis, lying 35.6 light-years from earth in the constellation Virgo. It shares its name with ESA's Hipparcos mission, launched in 1989, which generated the Hipparcos Catalogue, a high-precision catalogue of more than 100,000 stars. General Optical Navigation 2010-06-17T10:06:47Z danielscuka Cool animation: (2867) Steins getting closer http://webservices.esa.int/blog/post/5/409 <a id="res_487" href="http://webservices.esa.int/blog/gallery/5/20080825-0903_c_mf.gif"><img src="http://webservices.esa.int/blog/gallery/5/previews-med/20080825-0903_c_mf.gif" border="0" align="left" /></a> Sabine Kielbassa, Rosetta Flight Dynamics specialist sent this in earlier. She and her colleague, Michael Flegel, put together this animation for us last night (click on image at left for full animated GIF). The animation is composed of images taken once a day by NAVcam A between 25 August and 3 September. These images were used for the optical navigation campaign, as Rosetta followed Steins, refining its trajectory to close in on the asteroid. The images have been adjusted so that the stars are of roughly the same brightness from day to day, although the exposure times decrease, and Steins becomes brighter as Rosetta appoaches. --Amruta  General Optical Navigation Multimedia 2008-09-05T16:09:57Z
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