Cassini observations of satellite mutual events

[chris]

Cassini has captured a total solar eclipse by Enceladus on Mimas. Here is one image of the event:

http://saturn.jpl.nasa.gov/photos/raw/r ... eID=191654
Edit: Corrected above link

For a similar view in Celestia, see the CICLOPS Looking Ahead page for Rev. 110:

http://ciclops.org/view/5620/Rev110?js=1

The orientations of the images are slightly different, but important features match up in the Cassini image and Celestia view. Note the fraction of Mimas illuminated by Saturnshine and the shape of the shadow cast by Enceladus.

Thanks to Jason Perry (aka volcanopele) for mentioning these events over on unmannedspaceflight.com.

--Chris

[volcanopele]

I think this is the image link you were looking for:

http://saturn.jpl.nasa.gov/photos/raw/r ... eID=191654

I'm sorry I didn't orient the Celestia view in the Looking Ahead article correctly, I should have been able to get that if I paid more attention to Cassini orientation at the time. The correlation between the Celestia view in the article and the actual image linked in this post isn't a coincidence, I used the central times for each exposure to find the best "total" eclipse image.

[t00fri]

Cassini has captured a total solar eclipse by Enceladus on Mimas. Here is one image of the event:

http://ciclops.org/view/5620/Rev110?js=1

For a similar view in Celestia, see the CICLOPS Looking Ahead page for Rev. 110:

http://ciclops.org/view/5620/Rev110?js=1

The orientations of the images are slightly different, but important features match up in the Cassini image and Celestia view. Note the fraction of Mimas illuminated by Saturnshine and the shape of the shadow cast by Enceladus.

Thanks to Jason Perry (aka volcanopele) for mentioning these events over on unmannedspaceflight.com.

--Chris

Interesting...Yet I would have been grateful, if Jason had quoted the precise event time.
His displayed Celestia image@Ciclops is so bad quality that I can hardly see anything. I had to lit it up first with GIMP.

Fridger

[volcanopele]

Unfortunately, we've been asked to remove the image times from all the Celestia graphics in the Looking Ahead articles.

The Mimas image actually is brightened from the original, I'm sorry it looks dark on your screen.

[t00fri]

Unfortunately, we've been asked to remove the image times from all the Celestia graphics in the Looking Ahead articles.

The Mimas image actually is brightened from the original, I'm sorry it looks dark on your screen.

That's even more interesting that the event time had to be hidden? Can I understand the reasoning for this ? . Isn't it listed in the standard resource about mutual events?

Fridger

[volcanopele]

The times on all the Celestia screenshots are removed from the Looking Ahead articles. This is done to keep the images uncluttered.

The time by the way for that image is May 13 @ 12:28:50 UTC

[t00fri]

The times on all the Celestia screenshots are removed from the Looking Ahead articles. This is done to keep the images uncluttered.

The time by the way for that image is May 13 @ 12:28:50 UTC

Thanks,

here is the event time from the standard resource (in TT, however!):

ftp://cdsarc.u-strasbg.fr/pub/cats/J/A+ ... tab4-7.dat
ftp://cdsarc.u-strasbg.fr/pub/cats/J/A+A/485/293/ReadMe
+++++++++++++++++++++++++++++++
2009/05/13 2E1 P 13:41:58 13:42:19 13:43:28 13:44:32 13:44:37
13:44:59 .815 .815 1.830 1.760 181 183 3.0 .014 .015
+++++++++++++++++++++++++++++++

As I discussed in another neat mutual event between Mimas and Enceladus
here:
viewtopic.php?f=2&t=13650

2009/04/07 1E2 A 6: 8:43 6: 9: 2 6: 9:47 6: 9:58 6:10:32 6:10:51 .465 .465 .679 .632 128 129 2.9 .014 .017

that Celestia matches perfectly, one has to switch on my LT = light travel delay feature and select Earth. Moreover UTC has to be converted to TT (terestial time) (by adding 66") to be compared with the catalog entry above.

Fridger

[t00fri]

Here is what I find imagewise,

http://saturn.jpl.nasa.gov/photos/raw/r ... eID=191654

N00136239.jpg Cassini photo, looking on Mimas from Cassini at about 1,270,385 kilometers away.




Celestia: also looking at Mimas from Cassini, the shadow of Enceladus being nicely visible in the lower right. The orientations are about matching, unlike the Looking Ahead article on the Ciclops site.


Looking pretty similar and the predicted event times from Celestia (13:43:53 UTC @Earth) match very well the above standard reference prediction:

In the image, the UTC in the Saturnian system is displayed as UTC on Earth by adding 1h 14' 38.1 " of light travel delay with the LT feature. If one adds moreover 66" due to the UTC -> terrestial time conversion as of 2009, then the eclipse matches VERY closely the predicted TT event time from the catalog!

Fridger

[t00fri]

To provide a more "dynamic" feel about Enceladus' shadow moving across Mimas, I made a little video (640x480, MPEG4, Xvid) that plays well here under Windows and Linux:

http://www.celestiaproject.net/~t00fri/images/ ... 3may09.avi
(you may have to download it first, if your line is slow...)

I think it's quite instructive...

Enjoy,
Fridger

[danielj]

I go to Mimas,put in the right time,but instead of seeing the Enceladus shadow,I saw Mimas all black.What I did wrong?

[t00fri]

I go to Mimas,put in the right time,but instead of seeing the Enceladus shadow,I saw Mimas all black.What I did wrong?

Daniel,

you surely put in the WRONG time. Time is a delicate quantity, since it differs depending in which frame you define it.

For you the easiest is to keep the LT (light travel delay) switched off.
Do these steps:

1) goto cassini (type cassini, hit G key)
2) set time to : May 13, 2009, UTC: 12:28:00 (note UTC not local time!!!!)
3) goto Mimas (type Mimas, hit G key)
4) hit Y key (to have Mimas stay put!)
5) start running time SLOWLY now (hit L once or twice) and watch the Enceladus shadow come across Mimas around 12:29 UTC
6) If you saw the shadow, hit J and you can follow the process backwards
7) hit again J and you go forward again...

8 ) if you get bored...do something else


NOTE: Don't do any shortcuts or a different sequence of actions!


Good luck,
Fridger