Editor's note: A very quick update before we head off to Toulouse to cover ATV docking - all's well that end's well with Rosetta's longer-than-expected manouevre campaign. SOM Andrea Accomazzo confirmed this morning that the final manourvre was indeed completed on 17 February
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I met on 10 February with Rosetta Spacecraft Operations Manager Andrea Accomazzo here at ESOC to catch up on all that's happened with Rosetta since our last update on 18 January.
Click to listen (or download) a full, 8:00-min recording of his explanation below, but to summarize, here is what has been happening:
Rosetta experienced a safe mode - an automatic reset of the spacecraft - that happened during the thruster burn late in the evening of 18 January
The safe mode stopped the thruster burn and placed the spacecraft into a basic, safe, Earth-pointing mode, waiting commands
The teams here at ESOC spent the next few days determining the cause - which seemed to relate to how the thrusters function when in continuous operation
In part by using a number of advanced tools and techniques developed here by the Advanced Mission Concepts and Technologies Office, the Rosetta team were able to isolate the problem
The flight control team worked with flight dynamics experts to devise a new mode of operation for the thrusters - basically commanding them to switch rapidly on and off instead of running continuously as before
The new thruster mode was extensively tested and simulated using software and the Rosetta engineering model, which is kept here at ESOC for just such purposes.
A new set of manoeuvres were planned and uploaded, and during the last week of January, the spacecraft successfully re-started the manoeuvre campaign
It has now completed almost 98% of the required change in velocity and is more or less lined up to meet Comet 67P/Churyumov-Gerasimenko in 2014
The final manoeuvre of this new campaign will be conducted today, starting at 19:38 CET and running for about 43 minutes
Andrea and the rest of the team here at ESOC are just delighted! An initial problem that caused real concern and could have become critical has been investigated, analysed and a fix found - which enables the spacecraft to perform even better than before.
We'll update you again when we have news on the start of Rosetta's long hibernation, scheduled now for the June 2011 timeframe. -- Daniel
Please accept our sincere apologies for being so long in updating the blog!
A number of events conspired to enforce a lag in reporting the results of the manoeuvre activities in January. First, an unexpected 'safe mode' occurred - in which the spacecraft experienced a problem and basically reset itself, waiting for fresh commands - on 18 January during one of the planned long-duration burns.
Next, the flight control team were very involved in resetting Rosetta, figuring out what caused the safe mode and implementing a fix - which they did. :-)
This took time, during which we didn't post while we waited for news on the success of the fix. Further, in the middle of January, your hard-working Rosetta blog editorial team got a bit occupied with ESA's new ATV Johannes Kepler blog.
To make up for all the delay, we're planning a very nice update next week and will speak with Spacecraft Operations Manager Andrea Accomazzo at ESOC to get the full details on the past fortnight of activities. -- Daniel
Rosetta's next orbital correction manoeuvre (OCM) is taking place tonight. The thruster burn began at 17:59 CET (spacecraft time) and will run until shortly after midnight (371 mins total). The planned change in speed is 274 m/s with respect to the Sun. Like last night, the Rosetta teams at ESOC will be on shift until late!
Some bits of info collected from around ESOC earlier today on the Rosetta burn last night:
First - An update from the Rosetta flight control team: yesterday's burn went according to plan! The team noted a very slight over performance - meaning that the thrusters provided more of a boost than planned but still well within the expected range (more on that below). For the flight control & flight dynamics teams, the last shift ended at 04:30 CET this morning (just after the burn ended).
Next - the detailed burn schedule is posted below (click on the 'Full story' link), sent in by Roberto Porta, one of the Rosetta Spacecraft Operations Engineers at ESOC. Note that we'll wait to do any further blog updates until we get the final results after the last slot, now booked for 23 January.
Finally - we received a note from Trevor Morley, the team lead for flight dynamics support for Rosetta. Trevor wrote:
Preliminary assessment of last night's manoeuvre based on Doppler data indicates that the velocity change was about 1 m/s more than the planned 300 m/s. Such an error is well within the expected performance accuracy and the accumulation of such errors over the first four legs of the manoeuvre will be compensated for by an eventual re-optimisation of the 5th and final leg (an 'orbit trim'). This re-optimisation will be based upon an accurate reconstruction of the orbit for which purpose both ESA and NASA delta-DOR measurements will be made in addition to routine Doppler and range measurements.
'Delta-DOR' refers to the ultra-accurate position determination technique used by both ESA and NASA. Delta-DOR uses two widely separated antennas to simultaneously track a transmitting probe in order to measure the time difference ('delay time') between signals arriving at the two stations. The technique of measuring this delay is named Differential One-way Range (DOR). More details via the ESTRACK pages in the ESA web site. -- Daniel
Some nice photos just sent in from ESA/ESOC where the flight dynamics team and the flight control team are watching closely this evening as Rosetta conducts an important thruster burn to help line up the spacecraft for her rendezvous with a comet in 2014. Scroll down for details!
Rosetta Spacecraft Operations Engineer Roberto Porta
on console in the Rosetta dedicated control room
Members of the flight dynamics team on shift to monitor tonight's manouevres
And here's what Rosetta Spacecraft Operations Manager Andrea Accomazzo is seeing on his screen: a display based on telemetry received from Rosetta showing the jump in thruster temperature as the burn got underway about an hour ago at 20:03 CET.
A quick update from ESA/ESOC: one of the most important trajectory correction manoeuvres (TCM) as Rosetta line-ups for her encounter with Comet 67P/Churyumov-Gerasimenko in 2014 is now taking place.
Tonight's burn, which began at 19:03 UTC (20:03 CET) spacecraft event time (meaning the time at Rosetta, which is now over 629 mn km from earth), is expected to produce a 'delta-v' - or change in velocity with respect to the Sun - of 300 m/second. The burn is part of a series in the coming days that should produce an overall change of 778 m/second - one of the longest-running burns conducted to date by any of the Agency's deep-space missions.
This series of burns are crucial in that they are necessary to help Rosetta line up for her final approach to 67P/Churyumov-Gerasimenko.
ESA's first deep-space ground station at New Norcia (Western Australia) - now communicating with Rosetta.
Rosetta Spacecraft Operations Manager Andrea Accomazzo and members of the flight control team are watching progress closely from the Rosetta Dedicated Control Room at ESOC; he sent in a mail a few minutes ago to report that they are monitoring evolution of propellant pressure and making sure that everything is working as expected on board the spacecraft.
Signals from Rosetta are being received on Earth via ESA's giant 35m deep-space tracking station at New Norcia, Australia.
We'll check with the team tomorrow and provide more details here in the blog. -- Daniel
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
Rosetta Spacecraft Operations Manager Andrea Accomazzo has just sent a note to update us on the latest orbit determination done by ESA's Flight Dynamics specialists supporting the flyby. He writes:
With the latest orbit determination and following the flight rules, there will be no manoeuvre [needed] at the TCM [trajectory correction manouevre] slot 40 hours before the flyby. Also, it is considered that there will be no need to use the manoeuvre slot at 12 hours before the flyby, unless a anything changes.
Basically, this news means that Rosetta is lined up on the correct trajectory to bring her to the desired fly-by point on 10 July. :-)
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)
This just in:: The Flight Dynamics team here at ESOC have confirmed that Rosetta is dead on track to rendezvous with asteroid Lutetia on 10 Jul at the planned time and, as a result, the manoeuvre slot that was available on Sunday, 4 July (~1 week prior to closest approach), will not be used. The current estimate for closest approach is now fixed as: 15:44:55.97 UTC (spacecraft event time).
There are additional manoeuvre slots available 3 days, 40 hours and 12 hours prior to closest approach; the team will assess whether these will be needed next week. -- Daniel
Today, ESA's flight dynamics team compiled a fresh forecast on Rosetta's fly-by time and distance, based on analysis of last week's thruster burn and additional ground station data received from NASA's DSN network. The results? The closest approach is forecast to occur at a distance of 3169 km from Lutetia at a predicted time of 15:44:55.51 UTC (with a 3-sigma uncertainty of 7.43 seconds). -- Daniel
On 10 July 2010, Rosetta will pass by asteroid (21) Lutetia, with closest approach predicted to take place at 15:44 UTC (17:44 CEST).
This will be the spacecraft's second asteroid encounter with an asteroid of the main asteroid belt between Mars and Jupiter.
Rosetta is expected to pass the asteroid with a relative velocity of 15 km/s at a minimum distance of 3160 km (all figures subject to change). The selected flyby strategy allows continuous observation of the asteroid before, during and after closest approach. Most of the scientific instruments on Rosetta will be switched on for investigations. Imaging and spectral observations will be obtained covering ultraviolet to sub-millimetre wavelengths. A number of in situ measurements will be made of the asteroid as well as of its direct environment.
The target, (21) Lutetia, is a large asteroid with an estimated diameter of about 95 km. It has been classified as either C-type or M-type, meaning that remote sensing observations have shown features that hint at characteristics of carbonaceous chondrite (a type of meteorite that contains organic chemicals and water), but also to a metallic surface composition. This contradiction makes (21) Lutetia an extraordinarily interesting object for close inspection from space.
More info to follow in the coming days here in the Rosetta Blog!
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
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
Mission controllers have just confirmed that ESA’s comet chaser
Rosetta has swung by Earth at 8:45 CET as planned, skimming past our
planet to pick up a gravitational boost for an epic journey to
rendezvous with comet 67P/Churyumov-Gerasimenko in 2014.
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