How does Lutetia compare to the other asteroids and comets visited by spacecraft?
The Planetary Society's Emily Lakdawalla has posted an excellent, updated "Comets and Asteroids" poster showing, to scale, all such bodies visited by spacecraft so far.
The latest addition is, of course, 21 Lutetia!
She's done an excellent job of correlating images sizes and scales. Access her full post and the full-size image here. -- Daniel
First pre-flyby images now available!
First pre-flyby images now available! Largest view of Lutetia shows asteroid at a distance of 80,000 km. Better yet to come!!
All images: CREDIT: (C) ESA 2010 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA
Less than 330,000 km!
Richard Moissl on the OSIRIS team just wrote: "We are closing in at a steady pace (less than 330,000km distance to the asteroid now) and the narrow angle camera is starting to resolve surface structures." -- Daniel
OSIRIS imaging team hard at work
This just in from Richard Moissl, working on the OSIRIS team at the Max Planck Institute for Solar System Research here in Germany. Richard writes: "Since 6:18 UTC (08:18 CEST), Osiris has been imaging the approach with both cameras, the narrow angle camera (NAC) and the wide angle camera (WAC), collecting images with 10-minute intervals."
The OSIRIS team will keep us updated (and we'll pass along info right here in the blog) - and we are looking forward to seeing the results of their work later today! A quick reminder: one of the unavoidable limitations to publishing images will be download slots. -- Daniel
Rosetta’s blind date with asteroid Lutetia
Like many first dates, Rosetta will meet Lutetia on a Saturday night, flying to within 3200 km of the space rock. Rosetta started taking navigational sightings of Lutetia at the end of May so that ground controllers can determine any course corrections required to achieve their intended flyby distance.
The close pass will allow around 2 hours of good imaging. The spacecraft will instantly begin beaming the data back to Earth and the first pictures will be released later that evening.
Full article in ESA web portal here.
General , Optical observation
17 November, 2009 11:46
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
Rosetta darts across the sky: images taken last nght
We received several images and animations from Kristin this morning, of observations that she's been carrying out from ESA's Optical
Ground Station in Tenerife, Spain as the satellite approached Earth. The animation
above comprises images recorded 13 November, 03:05 to 03:25. It
comprises 18 images with an exposure time of 15 s and a separation of
69 s. The field is located in the constellation of Cetus and has a size
of 10 x 10 arcmin. The telescope was tracking Rosetta so that the
spacecraft appears as a dot in the centre of the image while the stars
appear as stripes.
This image was captured at 03:59 CET, 13 November, with an exposure
time of 2 minutes. The field is located in the constellation Cetus and
spans 10 x 10 arcmin. The telescope was tracking the stars so that
Rosetta appears as a stripe in the centre of the image while the stars
appear as dots. Rosetta moves 3 arcminutes during the 2-minute
exposure. Compare the movement with the image above, taken at 22:58
CET. The brightest star in the top left corner of the image has a
magnitude of 12. This is the last image taken before Rosetta's closest approach to
Earth, immediately afterwards its elevation fell below 18 deg which is
the limit of the telescope.
This still image was taken at 22:58 CET on 12 November. The total
exposure time was 2 minutes. The field is located in the constellation
of Cetus and has a size of 10 x 10 arcmin. Rosetta appears as a dot in
the centre of the image while the stars appear as stripes. The stars
move for almost 1 arcminute during the exposure. The brightest star in
the bottom left corner of the images has a magnitude of 15.
Kristin's still there tonight as well, to see if Rosetta can be detected as it recedes. But the spacecraft will be much
weaker in the sky than during the approach because an observer on
ground will be looking at the unilluminated side of the solar arrays.
Rosetta will have risen high enough for the telescope to point toward
it at 04:30 CET. Its elevation will then increase; dawn starts shortly
after 07:00 CET.
General , Optical observation
12 November, 2009 16:15
ESA to Rosetta: Green laser into the sky
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).
Full story »
General , Optical observation
12 November, 2009 07:22
Rosetta seen from ESA Optical Ground Station, Tenerife, Spain
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.
(Click title of this post to leave comments)
General , Optical observation
11 November, 2009 20:48
Tonight's optical observations
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
General , Optical observation
06 November, 2009 09:50
Tips for sky junkies III: finder charts
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:
Click on 'Full story' to access hi-res versions of the charts. -- Amruta
Full story »
Tips for sky junkies II
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.
You can obtain coordinates for your own location via the Horizons website.
Tips for sky junkies I: Keeping an eye on Rosetta from ground
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.
Click here for a full-size version of this graphic
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.
The lowdown from an expert
Michael Khan is a Mission Analyst here at ESA's ESOC Establishment in Germany. He maintains a blog that we read from time to time to find out rather cool things about ESA and other missions.
He's just posted a detailed description on Rosetta's swingby geometry on his blog, 'Go for launch', so we thought we'd share the knowledge. His post is also available in German.
Up next: Kristin Wirth, Rosetta Science Operations Manager's tips for skygazers who want to catch Rosetta closing in.
--Amruta & Daniel