IPB

Welcome Guest ( Log In | Register )

29 Pages V  « < 27 28 29  
Reply to this topicStart new topic
KBO encounters
JRehling
post Jul 28 2017, 09:08 PM
Post #421


Senior Member
****

Group: Members
Posts: 1987
Joined: 20-April 05
Member No.: 321



Tom, the occultation / photometry paradigm permits almost unlimited resolution, in principle. This is how Kepler could determine the radii of planets over 5,000 light years away, Pluto and Charon were mapped during a series of mutual transits, and many asteroids have had their size and shape measured from Earth. The opportunities are, unfortunately, very limited and not readily of our choosing. It's a lucky coincidence that NH is barreling towards the Milky Way, which enormously increases the probability of occultations. If we'd sent a flyby past Pluto a few decades earlier/later, this would not have been the case.

Just last night, I completed a pair of images of Iapetus showing the steep difference in its brightness now versus 40 days ago. It'd be a tall order for an earthbound telescope to resolve Iapetus' surface features, but noting the difference in brightness was performed by Giovanni Cassini in 1705!

Absolutely no earthbound telescope built (or even conceived) could resolve a KBO at kilometer scale, but this occultation method would work even if the target were a thousand AU away.
Go to the top of the page
 
+Quote Post
hendric
post Jul 28 2017, 09:21 PM
Post #422


Director of Galilean Photography
***

Group: Members
Posts: 834
Joined: 15-July 04
From: Austin, TX
Member No.: 93



If I did my maths right, to get 1km resolution at 30 AU requires a 716km aperture at 500nm wavelength. At 20cm (radio waves), it would take ~286,000km, so hypothetically possible if done with synthetic aperture using a lunar radio telescope. smile.gif

It would be amazing if we got a Dactyl like moon, or a contact binary. My money though is on a fairly smooth surface made up of 2-3m sized objects stuck together, similar to what we saw on 67P. Of course, those won't be resolved by NH.


--------------------
Space Enthusiast Richard Hendricks
--
"The engineers, as usual, made a tremendous fuss. Again as usual, they did the job in half the time they had dismissed as being absolutely impossible." --Rescue Party, Arthur C Clarke
Mother Nature is the final inspector of all quality.
Go to the top of the page
 
+Quote Post
Holder of the Tw...
post Jul 28 2017, 10:10 PM
Post #423


Member
***

Group: Members
Posts: 453
Joined: 17-November 05
From: Oklahoma
Member No.: 557



QUOTE (hendric @ Jul 28 2017, 03:21 PM) *
If I did my maths right, to get 1km resolution at 30 AU requires a 716km aperture at 500nm wavelength


Not quite so large as that. The 2.4 meter Hubble can already resolve Pluto, seeing features around 1000km big on that body. To resolve to 1 km you need a mirror about 1000 times bigger. So two to three kilometers.

Which is bigger than anything I've got.
Go to the top of the page
 
+Quote Post
JRehling
post Jul 29 2017, 01:22 AM
Post #424


Senior Member
****

Group: Members
Posts: 1987
Joined: 20-April 05
Member No.: 321



Note that HST's highest resolution photos of Pluto were taken in ultraviolet light – not a coincidence! Shorter wavelengths have smaller diffraction patterns and allow higher resolution, all other things being equal. In visible light, resolution would be about 25% worse.

I believe the construction of HST's Pluto albedo maps involved combining multiple images with a very well known shape model – Pluto had to be a sphere – which is a luxury one wouldn't have in trying to resolve the shape of a tiny body. So those maps had a better resolution than any one image of an unknown object could ever be.
Go to the top of the page
 
+Quote Post
hendric
post Jul 29 2017, 01:31 PM
Post #425


Director of Galilean Photography
***

Group: Members
Posts: 834
Joined: 15-July 04
From: Austin, TX
Member No.: 93



Hubble's albedo maps used the mutual eclipses between Pluto and Charon to determine how much the system brightness dropped as each body was covered up by the other. With advanced geometry and lots of computer time, scientists were able to make a best-guess as to the actual surface. Pretty good job, IMO!


--------------------
Space Enthusiast Richard Hendricks
--
"The engineers, as usual, made a tremendous fuss. Again as usual, they did the job in half the time they had dismissed as being absolutely impossible." --Rescue Party, Arthur C Clarke
Mother Nature is the final inspector of all quality.
Go to the top of the page
 
+Quote Post
stevesliva
post Aug 3 2017, 09:11 PM
Post #426


Senior Member
****

Group: Members
Posts: 1328
Joined: 14-October 05
From: Vermont
Member No.: 530



The target is binary, or oblong:
http://pluto.jhuapl.edu/News-Center/News-A...p?page=20170803
Go to the top of the page
 
+Quote Post
Explorer1
post Aug 4 2017, 01:38 AM
Post #427


Senior Member
****

Group: Members
Posts: 1439
Joined: 13-February 10
From: Ontario
Member No.: 5221



Gosh! I briefly thought this might be the case with the initial negative occultation result (i.e. the slimmer axis caused it to miss the star). Looks like we're getting two for the price of one!
Talk about good luck! (unless binaries are super common....)
Go to the top of the page
 
+Quote Post
climber
post Aug 4 2017, 04:36 PM
Post #428


Senior Member
****

Group: Members
Posts: 2784
Joined: 14-February 06
From: Very close to the Pyrénées Mountains (France)
Member No.: 682



Naming contest's gona be more challenging rolleyes.gif


--------------------
Go to the top of the page
 
+Quote Post
alan
post Aug 9 2017, 04:56 PM
Post #429


Senior Member
****

Group: Members
Posts: 1833
Joined: 20-November 04
From: Iowa
Member No.: 110



QUOTE
Alex Parker‏ @Alex_Parker

To those curious as to what the 2014 MU69 occultation data looked like, see @AlanStern's new PI's Perspective post:
http://pluto.jhuapl.edu/News-Center/PI-Per...tive_08_08_2017


https://twitter.com/Alex_Parker/status/895033405263446016

Go to the top of the page
 
+Quote Post

29 Pages V  « < 27 28 29
Reply to this topicStart new topic

 



RSS Lo-Fi Version Time is now: 25th September 2017 - 01:30 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 a project of the Planetary Society and is funded by donations from visitors and members. Help keep this forum up and running by contributing here.