Dawn Survey Orbit Phase, First orbital phase |
Dawn Survey Orbit Phase, First orbital phase |
Jul 20 2011, 10:56 PM
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#61
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Senior Member Group: Admin Posts: 4763 Joined: 15-March 05 From: Glendale, AZ Member No.: 197 |
-------------------- If Occam had heard my theory, things would be very different now.
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Jul 21 2011, 12:04 AM
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#62
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Member Group: Members Posts: 796 Joined: 27-February 08 From: Heart of Europe Member No.: 4057 |
Thank you all!
I prepared one more cross-eye/anaglyph stereo image, using second published hi-res image. -------------------- |
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Jul 21 2011, 09:07 AM
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#63
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Member Group: Members Posts: 568 Joined: 20-April 05 From: Silesia Member No.: 299 |
Today is Thursday, maybe we'll see images acquired on July 18 ?
http://dawn.jpl.nasa.gov/mission/status.asp Dawn team usually publishes something on Thursday. -------------------- Free software for planetary science (including Cassini Image Viewer).
http://members.tripod.com/petermasek/marinerall.html |
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Jul 21 2011, 11:17 AM
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#64
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Member Group: Members Posts: 813 Joined: 29-December 05 From: NE Oh, USA Member No.: 627 |
Awesome!
Thanks machi |
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Jul 21 2011, 02:17 PM
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#65
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Solar System Cartographer Group: Members Posts: 10162 Joined: 5-April 05 From: Canada Member No.: 227 |
Recent images would be of a narrow crescent, but in a few days we will be seeing the northern hemisphere... brand new territory again, and from closer range.
Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PD: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Jul 21 2011, 02:25 PM
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#66
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Senior Member Group: Moderator Posts: 2785 Joined: 10-November 06 From: Pasadena, CA Member No.: 1345 |
With such a lumpy surface, the high-phase images should be pretty dramatic.
-------------------- Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
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Jul 21 2011, 04:05 PM
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#67
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Member Group: Members Posts: 204 Joined: 29-June 05 Member No.: 421 |
The distance for that image was (or should have been) 15222 km (center of Vesta). You already know the angular extent of one pixel. You tell me where you are wrong... I'm curious about the answer as well. I get a diameter of 615km trying to replicate the calculation, and I don't see anything wrong with how Emily is doing it. But that is well outside the biggest dimension of the oblate spheroid model. Is it just that the oblate spheroid is that lousy of a fit for vesta's true shape? |
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Jul 21 2011, 04:46 PM
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#68
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Solar System Cartographer Group: Members Posts: 10162 Joined: 5-April 05 From: Canada Member No.: 227 |
Hopefully this will be out of date very soon, but here's a composite view of all the closer images we have seen so far. Please let me know if I am missing any.
Phil (EGD points out - I should have scaled the first to match the long axis dimension, not the polar axis!) -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PD: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Jul 21 2011, 05:35 PM
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#69
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Junior Member Group: Members Posts: 35 Joined: 10-July 11 Member No.: 6055 |
Recent images would be of a narrow crescent, but in a few days we will be seeing the northern hemisphere... brand new territory again, and from closer range. Phil It was my understanding that a good portion of the northern hemisphere will be in darkness (winter) for the first months of the mission, am I mistaken in believing that? -kap |
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Jul 21 2011, 05:44 PM
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#70
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Solar System Cartographer Group: Members Posts: 10162 Joined: 5-April 05 From: Canada Member No.: 227 |
Only the north polar area itself will be hidden - most of the northern hemisphere will be visible now.
Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PD: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Jul 21 2011, 05:56 PM
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#71
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
I'm curious about the answer as well. I get a diameter of 615km trying to replicate the calculation, and I don't see anything wrong with how Emily is doing it. But that is well outside the biggest dimension of the oblate spheroid model. Is it just that the oblate spheroid is that lousy of a fit for vesta's true shape? Thanks for checking my math, and now I feel a little more confident in questioning the factor-of-2 enlargement. Here's the DPS abstract on Vesta's dimensions from Hubble data (289, 280, 229 km semi-major axes, or 578, 560, 468 for diameter), which refers to a previous conference abstract with a diameter based on an occultation (561 +/- 3 km). In no way are any of these consistent with any principal axis diameter above 600 kilometers. So either the enlargement factor or the range to the target has not been reported correctly. I know I'm beating a dead horse here and I think the Dawn team now regards me as kind of a pest and really I am very excited about seeing a new world. But it's hard to do outreach when I know that some of the information that I'm getting must be wrong. -------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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Jul 21 2011, 06:04 PM
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#72
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
Regarding the enlargement, I like neither the blurriness nor the jaggedness of the limb. Both, I think, do a disservice to the FC which I think is supposed to be a very fine instrument. Now that details can be resolved, it's much better just to post images that are not enlarged. Consider the most recently released image of Vesta. Now consider a Cassini image of Phoebe with the same number of pixels. The Cassini image looks so much crisper, and a comparison between the blurry-looking FC image and really any other deep-space camera image makes FC look like a crappy instrument, when we know it's not. it's not a fair comparison, because the Cassini image started out with 800 pixels, while the Dawn one started out with only 400. But most people don't know that; they just see a blurry, pixelated image.
-------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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Jul 21 2011, 07:54 PM
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#73
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Junior Member Group: Members Posts: 52 Joined: 16-November 06 Member No.: 1364 |
I know I'm beating a dead horse here and I think the Dawn team now regards me as kind of a pest and really I am very excited about seeing a new world. But it's hard to do outreach when I know that some of the information that I'm getting must be wrong. Please realise that at this stage, we face similar uncertainties. There is one thing about which I am 100% sure: the enlargement factor is 2. But then, there are so many possibilities: 1. I calculated the distance wrong, and my colleague made the same mistake 2. The SPICE kernel we used is wrong 3. We used the wrong SPICE kernel 4. The camera FOV has shrunk 5. Your measurement is correct ... We are using trajectory *predictions*! Would it make a difference if I say that we (the FC team) are going through an extremely busy period, in which our main priority is to ensure the FC is in good health and taking images as planned? |
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Jul 21 2011, 09:00 PM
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#74
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The Poet Dude Group: Moderator Posts: 5551 Joined: 15-March 04 From: Kendal, Cumbria, UK Member No.: 60 |
... I think the Dawn team now regards me as kind of a pest ... I'm sure that's not the case. ...but if any of them do think like that, then I really think they should be grateful that a respected and accomplished science journalist like yourself is so excited by, and passionate about, the mission, wants to ensure its success by writing about it for a public audience, and is trying hard to get the facts straight in order to write accurate reports. -------------------- |
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Jul 21 2011, 09:06 PM
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#75
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
I apologize for being such a pest. I think I don't properly appreciate or understand the differences in navigational certainty between an ion-powered mission -- and one that's approaching a small body with relatively poorly constrained mass -- and the kind of orbital or flyby missions I'm accustomed to writing about. I'm glad to have a definitive answer about the enlargement factor, and now at least I think I understand which bits of information are the sources of the uncertainty. I had assumed wrongly that the range to the target was one of the more precisely known bits of information. So, sorry! I hope you'll take my pestiferousness as a sign of my real interest in and excitement about the mission!
-------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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