CE-2 flyby of Toutatis |
CE-2 flyby of Toutatis |
Dec 17 2012, 08:06 PM
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#106
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Junior Member Group: Members Posts: 43 Joined: 11-March 10 From: Houston, Texas, USA Member No.: 5259 |
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Dec 17 2012, 08:41 PM
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#107
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Member Group: Members Posts: 796 Joined: 27-February 08 From: Heart of Europe Member No.: 4057 |
This one, I suppose.
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Dec 17 2012, 10:05 PM
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#108
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Junior Member Group: Members Posts: 43 Joined: 11-March 10 From: Houston, Texas, USA Member No.: 5259 |
This one, I suppose. You've picked a language I can't handle, please translate the relevant portion. Hsieh hsieh ni. |
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Dec 17 2012, 10:28 PM
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#109
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Interplanetary Dumpster Diver Group: Admin Posts: 4404 Joined: 17-February 04 From: Powell, TN Member No.: 33 |
Here is what most of us are using. I know the Google translation is rough, but it is what most of us non-Chinese speakers are using. Not clear as to why you couldn't do this.
QUOTE Two stars collided probability of less than one ten-millionth Intersection speed of nearly 11 kilometers per second, Chang E II will Tutadisi [Toutatis] asteroid collision? Wu Weiren smiled and said: "If you hit, it created a miracle in order to avoid causing trouble Chang E II track detuning by some, and let them pass." Zhou Jianliang said: "through the precise measurement and control, we can control the distance between the Chang-e II and Tutadisi asteroid if they collided, the impact of the asteroid is small but we should not have caused it any impact. "he said, need to take pictures on the Tutadisi" Chang E on the 2nd design orbit is to make them as close as possible without collision. Our current monitoring and control capability, the minimum distance if they rendezvous designed for 15 km, the collision probability is less than one ten-millionth. According to reports, Chang E II with Tutadisi asteroid rendezvous when the distance is only 3.2 km. -------------------- |
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Dec 18 2012, 04:00 PM
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#110
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Junior Member Group: Members Posts: 43 Joined: 11-March 10 From: Houston, Texas, USA Member No.: 5259 |
Here is what most of us are using. I know the Google translation is rough, but it is what most of us non-Chinese speakers are using. Not clear as to why you couldn't do this. Thanks! Since the article mentions the actual 3.2 km fly-by, does this mean it was published AFTER the actual fly-by -- or is it dated before the encounter? ADMIN - Jim, UMSF is a place for discussion and collaboration. It's not a short order grill where you can show up at the counter and make demands. That is exactly how your previous three posts have come across. You have the same resources available to you through the Internet that the rest of us have. Investigate it yourself and let us all know. |
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Dec 18 2012, 05:06 PM
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#111
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Junior Member Group: Members Posts: 43 Joined: 11-March 10 From: Houston, Texas, USA Member No.: 5259 |
Unnecessary quoting removed
Acknowledged and agreed! |
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Dec 18 2012, 05:40 PM
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#112
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Junior Member Group: Members Posts: 95 Joined: 5-September 07 Member No.: 3662 |
The success of this flyby makes one wish for a few spacecraft stationed at one of the Earth-Moon Lagrange points that we could dispatch, with sufficient notice, for flyby inspections of other closely approaching NEOs. A visual camera and perhaps a near-IR imager with well-chosen filters or an imaging near-IR spectrometer, maybe even a magnetometer, would make for a nice payload. I suspect that in some cases, navigation strategies might exist that could eventually return the spacecraft back to the Lagrange point for additional encounter opportunities.
Jeff |
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Dec 18 2012, 07:01 PM
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#113
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Senior Member Group: Members Posts: 3419 Joined: 9-February 04 From: Minneapolis, MN, USA Member No.: 15 |
The success of this flyby makes one wish for a few spacecraft stationed at one of the Earth-Moon Lagrange points that we could dispatch, with sufficient notice, for flyby inspections of other closely approaching NEOs... Good concept. However, since you'd have a wide variety of approach trajectories for these various NEOs, any such on-demand intercept spacecraft would likely need to start out its mission with an awful lot of delta-V available in its fuel reserves. With enough energy packed into the fuel tanks, and with possibly a small fleet of such interceptors, you could use some to perform high-delta-V intercepts once or twice in their lifetimes, and others to perform low-delta-V intercepts many times. Not only would this be a good way to collect data on the various NEOs that pass through the neighborhood, it would be really good operational experience for deploying a small fleet of interceptors whose purpose is last-minute trajectory deflection on objects that are spotted late and could impact Earth. We obviously don't have good or proven strategies for last-minute deflection technology at the present time, of course... but by the time we decide what measures would be effective, we would have a lot of good operational experience at deploying on-demand spacecraft to intercept approaching objects. -the other Doug -------------------- “The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” -Mark Twain
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Dec 18 2012, 07:20 PM
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#114
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
Michael Khan from ESA has done a little trigonometry using the distance information on that graphic and came up with the head-scratching result that, assuming the distance and time information on the graphic is correct, Chang'E 2 passed the asteroid at 59 kilometers:
The other thing that has me a little puzzled is that the images on the multi-view montage must not all be shown at their original pixel scale; the range to the target decreases by only a little more than half, yet the apparent size enlarges by more than a factor of 10. Examining them closely, the smallest image looks fairly clean, while the largest one has artifacts that suggest it's been enlarged. -------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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Dec 18 2012, 09:08 PM
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#115
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Member Group: Members Posts: 796 Joined: 27-February 08 From: Heart of Europe Member No.: 4057 |
I did some calculations based on two highest resolution images (47 km/16:30:05, 93 km/16:30:09) and resulting distance is anywhere between 0 - 33 km. Time for closest approach is 16:30:00-01. Errors are caused by inaccuracies in time information.
It looks that some informations are definitely incorrect. Because we have evidently images with 5 and 10 meters resolution, I think that 240 km and 16:30:24 are wrong informations. Another possibility is that flyby distance wasn't 3.2 km, but 32 km. 32 km can be result in all calculations (based on informations 47 km/16:30:05, 93 km/16:30:09, 240 km/16:30:24). -------------------- |
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Dec 18 2012, 09:21 PM
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#116
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Senior Member Group: Members Posts: 2516 Joined: 13-September 05 Member No.: 497 |
Examining them closely, the smallest image looks fairly clean, while the largest one has artifacts that suggest it's been enlarged. Isn't this just the same image replicated at different sizes, as was pointed out earlier? If it was a full sequence, one would expect to see a big change in phase angle from inbound to outbound since the geometry changes rapidly around C/A. [Unless the whole image sequence was taken a fair time out from C/A, which doesn't make a lot of sense. Still don't know what the camera FOV or IFOV was or how the spacecraft was pointed during the fyby. Was it just inertially fixed?] -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Dec 18 2012, 09:51 PM
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#117
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Solar System Cartographer Group: Members Posts: 10162 Joined: 5-April 05 From: Canada Member No.: 227 |
The illustration might just be an 'artist's impression' of the approach, not the actual image sequence. We don't really know what audience it was intended for. It might not support too much analysis.
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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Dec 18 2012, 10:21 PM
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#118
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Member Group: Members Posts: 796 Joined: 27-February 08 From: Heart of Europe Member No.: 4057 |
If it was a full sequence, one would expect to see a big change in phase angle from inbound to outbound since the geometry changes rapidly around C/A. If flyby distance was really 3.2 km, then changes in phase angle were minimal even few seconds after flyby . I did simple graphic with two images, for which we know (?) distance. For comparison I've added 240 km distance. Still don't know what the camera FOV or IFOV was or how the spacecraft was pointed during the fyby. Was it just inertially fixed? If Paolo is right, then FOV is 7.2° and camera has 1024×1024 CMOS detector (or maybe 1280×1024). This roughly corresponds to published resolution 10m/93 km, 5m/47 km. -------------------- |
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Dec 18 2012, 10:47 PM
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#119
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
This page linked to earlier discusses the camera's resolution as follows (in Google translation, but it seems a pretty straightforward discussion of the relationship between range and resolution):
QUOTE Zhou Jianliang said pixels of the camera is not high. Shooting in the distance of 500 kilometers, the picture is only 33 × 33 pixels, 300 kilometers picture about 55 × 55 pixels. That fits with the smallest image in the multi-image view, which is about 60 pixels long at a reported range of 240 km. Mike, I agree I don't see any rotation from one image to the next, but I do see more detail in the largest image than could possibly have arisen from enlargement of the smallest one. I think there's at least two images here but I don't know how many more than that. In the discussion leading up to the flyby I'd heard that the plan was to take only two images! -------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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Dec 19 2012, 01:23 AM
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#120
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Senior Member Group: Members Posts: 2516 Joined: 13-September 05 Member No.: 497 |
Mike, I agree I don't see any rotation from one image to the next, but I do see more detail in the largest image than could possibly have arisen from enlargement of the smallest one. True, but the small one could be a shrink of the large one. Seems like there are two images in machi's last post, but I'm not sure where they came from -- video grabs? Still -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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