Where rest of inner solar system in Cassini picture from Saturn?


by jackmell
Tags: cassini, picture, rest, saturn, solar
jackmell
jackmell is offline
#1
Jul23-13, 08:39 AM
P: 1,666
Here's the Cassini image from Saturn. Suppose I map an x-y coordinate system on that picture with the earth (that pale blue dot down there) at the origin. Without looking at anything else, can you place points at the perimeter of the square picture, giving the angle pointing to where the sun and the remaining inner planets are located? Where exactly is Cassini located relative to Saturn? Where is the plane of the ecliptic for that matter? Is it viewable in the picture? If so, would be nice to upload the picture and draw a yellow arc showing it. Just thought it would be interesting to other astronomy people in here that's all.

http://www.cbsnews.com/8301-34763_16...res-of-saturn/
Phys.Org News Partner Astronomy news on Phys.org
Quest for extraterrestrial life not over, experts say
Continents may be a key feature of Super-Earths
Astronomers discover first self-lensing binary star system
davenn
davenn is offline
#2
Jul23-13, 06:37 PM
Sci Advisor
PF Gold
davenn's Avatar
P: 2,243
you would have to know the date and time of the image so that the locations of the other planets
could be calculated. Without that info you would have no place to start
and they may not even be within the viewing angle of that image at the time


Dave
collinsmark
collinsmark is offline
#3
Jul23-13, 07:15 PM
HW Helper
PF Gold
collinsmark's Avatar
P: 1,842
Quote Quote by davenn View Post
you would have to know the date and time of the image so that the locations of the other planets
could be calculated. Without that info you would have no place to start
and they may not even be within the viewing angle of that image at the time
The image was taken just a few days ago.

19 July 2013, over the course of 15 minutes, 21:27 to 21:42 UTC. (Many images were taken, then stitched together mosaic-like.)

According to NASA JPL's simulator, Venus was to the left of the sun (which would put it on the opposite side of Saturn, if not obscured by Saturn). Mercury is on the right side (same side as the Earth in the photo), but closer to the sun (angular distance as seen from Saturn). I'm guessing that both Venus and Mercury were hidden by Saturn ('just a guess though).

Here's the simulator link:
http://space.jpl.nasa.gov/

Saturn is eclipsing the sun, so the sun is somewhere behind Saturn.
Use these parameters:
Show me The Sun as seen from Saturn [Edit: Or better yet, choose Cassini!]
On Jul 19 in the year 2013 at 21:30 UTC
Field of View (choose one)
  • I want a field of view of 20 degree(s) <== Check this one.
  • I want the body to take up percent of the image width

collinsmark
collinsmark is offline
#4
Jul23-13, 07:26 PM
HW Helper
PF Gold
collinsmark's Avatar
P: 1,842

Where rest of inner solar system in Cassini picture from Saturn?


Oh, and just to clarify: Obviously Venus is not in this particular image:


[The dot on the bottom right is Earth.]

Venus would be on the other side (to the top-left side of Saturn), if it's even visible at all. It's probably obscured by Saturn, but I'm not completely sure. But that's my guess.

But that's not the final "big" image. There's more stitching that needs to be done (with many more smaller images), and the "big" image result won't be released for another six weeks or so.
jackmell
jackmell is offline
#5
Jul23-13, 07:53 PM
P: 1,666
Quote Quote by collinsmark View Post
The image was taken just a few days ago.

19 July 2013, over the course of 15 minutes, 21:27 to 21:42 UTC. (Many images were taken, then stitched together mosaic-like.)

According to NASA JPL's simulator, Venus was to the left of the sun (which would put it on the opposite side of Saturn, if not obscured by Saturn). Mercury is on the right side (same side as the Earth in the photo), but closer to the sun (angular distance as seen from Saturn). I'm guessing that both Venus and Mercury were hidden by Saturn ('just a guess though).

Here's the simulator link:
http://space.jpl.nasa.gov/

Saturn is eclipsing the sun, so the sun is somewhere behind Saturn.
Use these parameters:
Show me The Sun as seen from Saturn
On Jul 19 in the year 2013 at 21:30 UTC
Field of View (choose one)
  • I want a field of view of 20 degree(s) <== Check this one.
  • I want the body to take up percent of the image width
That is so cool! Here's the image I got:

I did not realize the sun was in front of Saturn. Doesn't look like that at all in the picture. I assume they did that to cut out the glare correct?

From the NASA picture, there is a possibility that Mercury could still be in the picture but not easy to see. I wonder if that's possible or may show up with other images?
Attached Thumbnails
view of sun from saturn.jpg  
collinsmark
collinsmark is offline
#6
Jul23-13, 08:09 PM
HW Helper
PF Gold
collinsmark's Avatar
P: 1,842
Quote Quote by jackmell View Post
I did not realize the sun was in front of Saturn. Doesn't look like that at all in the picture. I assume they did that to cut out the glare correct?
Essentially, yes. (That and the fact that the glare risks damaging the camera, if the camera took an image pointed toward the sun.)

For that reason, there's only been a few images ever taken of the Earth from very far away (as in outside the inner solar system), ever. (Well, images that we know of anyway.)
  • There's this one that we're talking about in this thread, taken a few days ago from Cassini, 898 million miles (1.44 billion kilometers) away.
  • Another was Cassini's image in 2006 from 926 million miles (1.49 billion kilometers).
  • One taken 23 years ago by NASA's Voyager 1 spacecraft from 4 billion miles (6 billion kilometers away).

And that's pretty much it.
Janus
Janus is offline
#7
Jul23-13, 09:00 PM
Emeritus
Sci Advisor
PF Gold
Janus's Avatar
P: 2,352
I used Celestia to do this. Mercury looks like it would be obscured by the rings. Venus and Mars would be hidden By Saturn.
Attached Thumbnails
saturn.jpg  
SteamKing
SteamKing is offline
#8
Jul24-13, 11:41 AM
HW Helper
Thanks
P: 5,553
If Saturn is in shadow, the Sun must be on the other side.
collinsmark
collinsmark is offline
#9
Jul25-13, 12:47 PM
HW Helper
PF Gold
collinsmark's Avatar
P: 1,842
I need to correct an oversight I made.

Quote Quote by collinsmark View Post
The image was taken just a few days ago.

19 July 2013, over the course of 15 minutes, 21:27 to 21:42 UTC. (Many images were taken, then stitched together mosaic-like.)
The "time" I specified in my previous post is the time at which Earth would be in the picture, according to clocks on Earth. In other words, if you wanted to be in the image, you needed to be outside and in view of Saturn at that time on Earth. (There's 10 to 20% chance I was in the picture! But I may have been obscured by cloud cover that day. )

But what I neglected is that time takes into account the time it takes light to travel to the Cassini probe near Saturn. Cassini didn't actually start "snapping" images until about an hour and 20 minutes after the time I previously posted! (It takes light about an hour and twenty minutes to go from Earth to Saturn.) The difference is negligible when it comes to positions of the planets, but it is significant regarding Cassini's position relative to Saturn.

Doh!

So, using that information in the simulator link:
http://space.jpl.nasa.gov/

I now use these these parameters:
Show me Earth as seen from Cassini
On Jul 19 in the year 2013 at 22:50 UTC
Field of View (choose one)
  • I want a field of view of 30 degree(s) <== Check this one.
  • I want the body to take up percent of the image width
And ended up with something roughly like this:



Sorry for the confusion.

[Edit: from the simulator's FAQ page:
The simulator renders images as if you were only at the center of the viewing body. Also, light time is not included yet in the body positions, and this can have potentially noticeable effects for multibody or distant occultations.
So I'm thinking the new parameters, advancing by around an hour and 20 minutes, is a better model.]


Register to reply

Related Discussions
Saturn hurricane spotted by Cassini General Astronomy 2
Jupiter and Saturn - Back and Forth in the Early Solar System? General Astronomy 3
Cassini Mission to Saturn Celebrates 10 Yrs Since Launch General Discussion 0
Trying to Debunk Object Near Saturn in new Cassini Photos General Discussion 22
Cassini flyby of Saturn's moon Phoebe General Astronomy 0