Kristin - who has been very helpful with our blog - spoke to us an hour or so ago from Tenerife. She comments on the activities at ESA's Optical Ground Station, the observations last night and tonight and - of course - the weather (clear for tonight!) -- Daniel
Tonight and tomorrow night, through the inky blackness of the night sky over Tenerife, Spain, a green laser is beaming into space to see if Rosetta's instruments can pick up the pin-point of light.
Kristin was hard at work all night with the team at Tenerife, and she sent us this image of the laser in operation.
Image credit: ESA/K. Wirth
Kristin told us that they aimed the laser at Rosetta twice while the OSIRIS Imaging System's Narrow Angle Camera was taking images with Tenerife in the field of view, using a band pass filter suitable for seeing the green laser; the aim is to help calibrate the NAC. The experiment will be continued tonight as well (another image of the team at work after the jump).
When Europe's comet chaser Rosetta swings by Earth tomorrow for a critical gravity assist, tracking data will be collected to precisely measure the satellite's change in orbital energy. The results could help unravel a cosmic mystery that has stumped scientists for two decades.
Since 1990, scientists and mission controllers at ESA and NASA have noticed that their spacecraft sometimes experience a strange variation in the amount of orbital energy they exchange with Earth during planetary swingbys. The unexplained variation is noticed as a tiny difference in speed gained or lost during the swingby when comparing that predicted by fundamental physics and that actually measured after the event.
This excellent animation was created by stitching together a series of images captured last night from ESA's OGS in Tenerife, and was sent to us by email at around 03:00 CET this morning by Kristin Wirth, working at the station.
The animation covers about 30 minutes and consists of images taken every 3 minutes, with an exposure time of 2 minutes. Rosetta moves roughly from East to West (North is up). The background stars are tracked, therefore Rosetta is seen as a short 'streak' line. Credits: Jyri Kuusela, Lilian Dominguez Palmero - Ataman Science S.L.
She's on her way! :-)
Kristin says the team will also observe tonight (Thursday) and we hope they have equally good luck! Thanks Kristin and all the folks at the OGS.
Just got a note from ESA's Kristin Wirth; she's just arrived at the Optical Ground Station (OGS) at the La Teide Observatory, Tenerife. Observations are planned for tonight and we hope she and the colleagues there have success - weather permitting! More details on Thursday AM. -- Daniel
On 8 November, Rosetta's OSIRIS instrument imaged the Moon from 4.3 million km as the satellite sped towards Earth for her final gravity-assist swingby, scheduled for 13 November 2009.
The OSIRIS team at the Max Planck Institute for Solar System Research, Lindau, Germany, has just sent us this image of the Moon, acquired on Sunday, 8 November at 4:10 CET.
Rosetta was at a distance of 4.3 million kilometres when the image was taken, flying in towards Earth from the night side. Sure, this is a rather small glimpse - but it's the first visual proof that she's on her way home!
The image shows the Moon as seen through the OSIRIS NAC (high-resolution narrow-angle camera) using the orange filter from a distance of 4.3 million kilometres at 8/11 03:10 UTC. Rosetta is flying towards the Earth coming in from the night side which is the reason for the very narrow illuminated crescent.
On its ten-year journey to rendezvous with a comet, ESAs Rosetta probe is visiting home for the third and last time on 13 November. It will be the last of its four planetary gravity assists - in 2007 Rosetta also had a swingby at Mars - each time picking up energy to reach its final target in 2014. Although a delicate moment for spacecraft controllers, the Earth swingby will be used to test all the science instruments and to make an innovative contribution to the search for water on the Moon.
This A & B-Roll from ESA TV was released last week and describes the Earth swingby, the science observations and the next key moment of the mission including interviews with Rosettas ESA Project Scientist, its principal investigators and the spacecraft controllers (note: this is a low-res preview).
Though time will be short, several science observations are planned
around the swingby to exploit Rosetta's unique perspective and powerful
The planned observations include imaging with the scientific
camera system OSIRIS, an attempt to look for water on the Moon with
MIRO, study of the magnetosphere with the suite of Rosetta plasma
instruments, and observations of Earth's atmosphere and a search for
The instruments will be turned on one-by one starting today and will stay on through the swingby.
The goal of the swingby is to assist Rosetta to ultimately reach
Comet 67P/Churyumov-Gerasimenko for its prime mission. This means that spacecraft operations will have priority over science activities on 13
An artist's impression of the OSIRIS imaging system. (ESA/AOES Medialab)
During the two nights before closest approach (13 November) and
one night afterwards, members of the Rosetta team will conduct
observations from ESA's Optical Ground Station in Tenerife, Spain. They
will also carry out an experiment to investigate whether a laser beam
can be detected by OSIRIS.
After a request posted in our blog from Detlef Koschny, an ESA colleague and a keen amateur star watcher, Kristin Wirth from the Rosetta science team has just sent us three finder charts, corresponding to inbound approach, point of closest approach and outbound recession. ((Thank you, Kristin!!)) These will help you know where to look for Rosetta in the sky.
Please note, however, that - even with these finder charts - actually spotting Rosetta will still be a challenge and is probably something that a more experienced amateur may wish to attempt. Note that our finder charts are relatively large scale and may be too crude to give exact help. Also, our finder charts are based on an observer's location on Tenerife; those elsewhere in Europe will find them less helpful.
In earlier blog postings (here and here) we already explained that Rosetta will be difficult to observe because of the weak brightness and low position on the sky. These finder charts are meant to give an overview - the two charts for approach and recession illustrate the path of Rosetta against the sky background (the magnification is so low that the observer's position is irrelevant). The chart for the night 12/13 Nov might be sufficient to find Rosetta because of its movement relative to the stars. It tells any keen astronomer where to look for it - of course, it you have an image where Rosetta still is a dot (and not a line) and you want to identify it among the stars, charts with a higher magnification and for your precise location will be needed.
Those with a bit more experience can generate custom Rosetta ephemerides (position) information on 13 November via NASA's Horizons website:
I got a note this morning from Rosetta Spacecraft Operations Engineer Sylvain Lodiot, who in turn received an email from a teenage friend of his from France, Baptiste. Sylvain wrote:
I received an email from a friend of mine (he is teenage and really keen on all ESA stuff). He says that he followed the blog live for the trajectory correction manoeuvre held on 22 October from school! Baptiste wishes us all the best for the manoeuvre today (which has been cancelled) - and the instrument switch ON starting on 6 November.
Thanks, Baptiste, for following Rosetta's progress - and please standby tomorrow for a more detailed listing of which instruments will be switched on and their planned targets (Merci, Baptiste, pour suivre les progrès de Rosetta - et s'il vous plaît attendre jusqu'à demain pour une liste plus détaillée des instruments qui seront allumés et leurs objectifs prévus). -- Daniel
After the 86-second thruster burn on 22 October, Rosetta has lined up on a near-perfect Earth approach trajectory. Flight dynamics and mission control experts at ESOC, ESA's European Space Operations Centre, have determined that today's manoeuvre slot will not be used (click on 'Full story' for details). -- Daniel
We just confirmed this morning that ESA's European Space Operations Centre will host a press briefing on the morning of the swingby for interested media. This will be the third Earth swingby, the last of Rosetta’s four planetary gravity assists. Closest approach to Earth is expected at 08:45 CET (07:45 UT).
The spacecraft is operated from ESOC, located in Darmstadt, Germany (right where we are!). Click on 'full story' for contact details.
To continue where we left off on Friday, for stargazers who'd like to glimpse Rosetta from ground as she closes in...
No. 1 factor? Visibility conditions, obviously, which will depend on the location of the observer. During approach Rosetta will be in the sky's Southern hemisphere. If we consider observers in Europe, it helps to be in the South (which is why Kristin gets to go to Tenerife!).
For observers on the Canary Islands:
18:30 UTC: Rosetta rises, range is 460 000 km.
23:30 UTC: Max. elevation of 42º reached, range is 280 000 km.
04:20 UTC: Rosetta sets, range is 120 000 km.
For observers in Berlin:
17:40 UTC = 18:40 CET: Rosetta rises.
21:30 UTC = 22:30 CET: Maximum elevation of 18º reached.
01:30 UTC = 02:30 CET: Rosetta sets.
Berlin is considerably worse than Tenerife, especially the low elevation. For an observer in Central Europe, Rosetta will be visible in the first part of the night, low in the South.
Rosetta’s movement on the sky will be slow before 13 November 05:00 UTC, so the visibility times and elevations are similar for the night before. But for the night of 11/12 November, the range is roughly 1 million km, i.e. considerably larger than during the following night.
The weak magnitude (17 - 12 mag expected) and low elevation imply that at least a medium size telescope is needed (sorry guys!). Kristin suggests an 80 mm aperture, but 300 mm or more would be preferable.
We asked Kristin Wirth, Rosetta Science Operations Manager, based at ESAC - ESA’s European Space Astronomy Centre, Spain, to give some tips to amateur astronomers interested in tracking Rosetta from the ground. Kristin is leading an observation campaign from ESA’s Optical Ground Station on Tenerife, Spain, and she readily provided a tonne of information.
Kristin told us that for an observer on Earth the movement of Rosetta relative to the stars is slow, except for a few hours around perigee passage - Earth closest approach (CA) on 13 November (7:45 UTC/ 8:45 CET). Rosetta will be approaching from the southern part of constellation Cetus and receding from Leo.
The path of Rosetta through the constellations around CA is as follows (times are in UTC, 13 November):
7:20 Piscis Austrinus
8:00 Serpens Caput
8:30 Coma Berenices
At closest approach the distance of Rosetta from the surface of the Earth is about 2500 km. Rosetta is flying fast: at 00:00 UTC on 13 November, the distance to Rosetta will be 260 000 km.
During approach, the Sun-Earth-Rosetta angle will be roughly 140º, so that observers on the ground will be looking at the illuminated solar arrays. We can expect a magnitude of 17 - 12 mag. This is about the same brightness of Pluto (which is about 1,150 times fainter than naked-eye visibility, according to Wikipedia).
But during recession, the Sun-Earth-Rosetta angle will be about 70º so that we will be looking at the dark side of the solar arrays and the magnitude will be much weaker.
Kristin’s observations at the ESA OGS on Tenerife will finish before Rosetta sets over Tenerife, at 04:20 UTC on 13 Nov.
This means that even before closest approach, Rosetta will only be a weak source of light and a ‘serious’ telescope will be necessary – but still within amateur range. Kristin recommends a 300 mm aperture.
She has also provided tips for observing from Central Europe and the Canary Islands (she will be at Teide Observatory, much to the ire of some of her colleagues :) ). Her tips will follow in a separate post.