IPB

Welcome Guest ( Log In | Register )

2 Pages V  < 1 2  
Reply to this topicStart new topic
Pioneer 11's 'near miss' at Saturn
Ian R
post Jun 1 2007, 11:17 PM
Post #16


Lord Of The Uranian Rings
***

Group: Members
Posts: 798
Joined: 18-July 05
From: Plymouth, UK
Member No.: 437



According to the American Geophysical Union's publication entitled Pioneer Saturn, here are the details regarding the object(s) discovered orbiting Saturn by Pioneer 11:

1979 S1 - imaged by the photopolarimeter.
1979 S2 - discovered by the charged-particle experiment.
These were later determined to be the same object, also later observed from Earth and called 1980 S3. This was later named Epimetheus.
________________

1979 S4 - This is a different object, co-orbital to S1/S2, also later seen from Earth and called 1980 S1. This went on to be offically labelled Janus.
________________

Some of the information on the page that Phil linked to seems to contradict what I've stated above. However, since the paper in the Pioneer Saturn journal was written by Brian Marsden, I'm pretty confident of its accuracy.

Ian.


--------------------
Go to the top of the page
 
+Quote Post
scalbers
post Jun 2 2007, 04:26 PM
Post #17


Senior Member
****

Group: Members
Posts: 1621
Joined: 5-March 05
From: Boulder, CO
Member No.: 184



The details might be elsewhere in this forum & the internet, but I believe that Janus was also photographed from Earth in 1966 during an edgewise ring presentation. Did it simply take until 1980 to confirm its orbit? I recall the name Janus being used from the 1966 timeframe.


--------------------
Steve [ my home page and planetary maps page ]
Go to the top of the page
 
+Quote Post
nprev
post Jun 2 2007, 05:00 PM
Post #18


Merciless Robot
****

Group: Admin
Posts: 8783
Joined: 8-December 05
From: Los Angeles
Member No.: 602



QUOTE (scalbers @ Jun 2 2007, 09:26 AM) *
I recall the name Janus being used from the 1966 timeframe.


True. The famous French astronomer Audouin Dollfus observed a moon during 1966 when the rings were edge-on which he named Janus. It's thought that this was in fact the Janus (he might have also seen Epimetheus), but confirmation had to wait until Voyager 1.


--------------------
A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
Go to the top of the page
 
+Quote Post
Ian R
post Jun 2 2007, 06:48 PM
Post #19


Lord Of The Uranian Rings
***

Group: Members
Posts: 798
Joined: 18-July 05
From: Plymouth, UK
Member No.: 437



Yes, this is the discovery image from 1966:

Attached Image


http://66.249.91.104/translate_c?hl=en&...an/decjanus.htm


--------------------
Go to the top of the page
 
+Quote Post
Phil Stooke
post Jun 2 2007, 07:44 PM
Post #20


Solar System Cartographer
****

Group: Members
Posts: 10127
Joined: 5-April 05
From: Canada
Member No.: 227



The problem with 'Janus' as seen in 1966 was that the various observations of this tiny object at the edge of the rings could not be fitted to a good orbit. Now we know that this was caused by having observations of two objects in essentially the same orbit, but that unexpected and unprecedented situation was not considered. As a reliable orbit could not be defined the situation remained unclear until the spacecraft data began to come in. The near-ring area could not be seen after ring-plane crossing because of glare, so there were no observations between 1966 and 1979. In retrospect, Dollfus observed both Janus and Epimetheus.

Phil


--------------------
... because the Solar System ain't gonna map itself.

Also to be found posting similar content on https://mastodon.social/@PhilStooke
NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain)
Go to the top of the page
 
+Quote Post
Ian R
post Nov 5 2020, 06:51 AM
Post #21


Lord Of The Uranian Rings
***

Group: Members
Posts: 798
Joined: 18-July 05
From: Plymouth, UK
Member No.: 437



Using Mark Showalter's superlative Saturn Viewer, we can now see that Dollfus did indeed discover Janus with the image I posted earlier:

Attached Image


--------------------
Go to the top of the page
 
+Quote Post
Ian R
post Nov 5 2020, 07:26 AM
Post #22


Lord Of The Uranian Rings
***

Group: Members
Posts: 798
Joined: 18-July 05
From: Plymouth, UK
Member No.: 437



We can also confirm that Pioneer 11 was the first spaceprobe to image Epimetheus, with photo F-12E taken 00:29 hrs, 1979-SEP-01. The F-ring and Tethys are also visible:

Attached Image


The Saturn Viewer produces a plot of the same situation albeit as seen from Earth; here, the view is from beneath the ring plane (Pioneer was above it). Adding to the confusion is Dione, which is somewhat in the foreground and out of Pioneer's field-of-view in the image above. But the issue is seemingly settled: 1979 S1 was indeed Epimetheus:

Attached Image




--------------------
Go to the top of the page
 
+Quote Post

2 Pages V  < 1 2
Reply to this topicStart new topic

 



RSS Lo-Fi Version Time is now: 28th March 2024 - 08:30 PM
RULES AND GUIDELINES
Please read the Forum Rules and Guidelines before posting.

IMAGE COPYRIGHT
Images posted on UnmannedSpaceflight.com may be copyrighted. Do not reproduce without permission. Read here for further information on space images and copyright.

OPINIONS AND MODERATION
Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators.
SUPPORT THE FORUM
Unmannedspaceflight.com is funded by the Planetary Society. Please consider supporting our work and many other projects by donating to the Society or becoming a member.