KBO encounters Options

[xtruel]

Hi,

I’m regular follower of NH and I’m also interested in the 2nd leg of the mission, i.e the 2016+ KBOs encounters. Does anyone know when operations about this leg (starting with searching objects of interest with HST or some other earth-based means, I suppose) are expected to begin ?

[nprev]

Hiya, X. If I remember correctly, the KBO search isn't really going to kick into gear until 2010 because Pluto (and the cone of possible follow-on destinations) is in Sagittarius from our viewpoint right now, which is the galactic core region...too much background optical 'noise' from all those stars to distinguish targets. Once it moves clear, the hunt will begin. Don't think that HST will participate (might be wrong), but several large ground-based observatories will certainly be involved.

[Alan Stern]

Hiya, X. If I remember correctly, the KBO search isn't really going to kick into gear until 2010 because Pluto (and the cone of possible follow-on destinations) is in Sagittarius from our viewpoint right now, which is the galactic core region...too much background optical 'noise' from all those stars to distinguish targets. Once it moves clear, the hunt will begin. Don't think that HST will participate (might be wrong), but several large ground-based observatories will certainly be involved.

KBO searches will be conducted in 2011-2012, when the relevant KB fields are out of Sag as Nprev described. Target characterization and prioritization will occur in 2013-2014. Target selection will be in 2015.

HST's FOVs are too small to use profitably for searches. We will use wide field imagers on groundbased, big guns like Keck, Subaru, etc.

-Alan

[Paolo]

Pluto (and the cone of possible follow-on destinations) is in Sagittarius from our viewpoint right now, which is the galactic core region...too much background optical 'noise' from all those stars to distinguish targets.

Remember when they called asteroids "the vermin of the sky"?

[nprev]

...our definition of celestial vermin seems to be shifting, doesn't it? Bloody core stars...

[xtruel]

Thanks for these quick replies

Given the tiny angular size of expected objects, It seems likely that science data about them to be collected by earth-based means, in order to perform target characterization & selection, will be limited, and may be already known in its headlines. Orbit characterization, absolute magnitude, color may be among these. Are there others ? In particular, will it be possible by earth-based means (or HST) to detect & characterize a binary object and is there a reasonable probability to find one ?


I also wonder if there is some hope that NH after its KBO mission may be aimed at an « inner Oort-Cloud object » (Sedna-like) as these objects raise currently deepest mysteries about how they formed, how they have been put in there, etc... . This would need some fuel left, and also long term NH survey and survival. Clearly this is not currently planned, but this may be the first realistic opportunity to have a close look at Oort cloud...

[Greg Hullender]

Trouble is, it'll take NH almost 10 years to go 40 AU, and the inner edge of the Oort Cloud is estimated to be about 2000 AU out. A 500-year extended mission is probably asking for too much. :-)

http://en.wikipedia.org/wiki/Oort_cloud

Since Sedna's the only thing like Sedna, I think it'll be hard to guess that we'll find another before 2015 AND that it'll be reachable by NH.

That does raise an interesting question, though. From the NH mission page: http://pluto.jhuapl.edu/mission/mission_timeline.php it's not clear how much time NH could have to reach a KBO. A ten-year extended mission could roughly reach the perihelion distance of Sedna from the Sun, but is anyone contemplating an XM that long? How long can we reasonably expect NH to work?

--Greg

[Alan Stern]

Trouble is, it'll take NH almost 10 years to go 40 AU, and the inner edge of the Oort Cloud is estimated to be about 2000 AU out. A 500-year extended mission is probably asking for too much. :-)

http://en.wikipedia.org/wiki/Oort_cloud

Since Sedna's the only thing like Sedna, I think it'll be hard to guess that we'll find another before 2015 AND that it'll be reachable by NH.

That does raise an interesting question, though. From the NH mission page: http://pluto.jhuapl.edu/mission/mission_timeline.php it's not clear how much time NH could have to reach a KBO. A ten-year extended mission could roughly reach the perihelion distance of Sedna from the Sun, but is anyone contemplating an XM that long? How long can we reasonably expect NH to work?

--Greg

We're hoping for a 4-6 year extended mission (XM), taking us to perhaps 50 AU. The heart of the KBO population is at 42-43 AU, and after that it thins out. By 55 AU we're out of the Classical Belt and into the much more dilute Scattered Belt.

We expect to fly by 1 or perhaps 2 KBOs each ~40 km in diameter in the XM. Larger ones are too few and far between to reach with our fuel supply unless we are very lucky, but the statistics are against us.

My job as PI is not to fly as far as we can but to maximize the value of the KB exploration we can achieve. This translates to accomplishing one post-Pluto KBO flyby within 2 or 3 years if we possibly can (to ensure against later failures) and to pick up a second KBO for comparative purposes if possible thereafter.

-Alan

[surreyguy]

Is larger necessarily better? Planets (in the hydrostatic sense) are always interesting, of course, but geology has a way of erasing information. A 40km KB equivalent of a chondritic meteorite would be fascinating, if frustrating given only a few hours of remote sensing are possible.

I love the audacity of it, though, to go off to study something without having discovered it yet.

[Alan Stern]

Is larger necessarily better? Planets (in the hydrostatic sense) are always interesting, of course, but geology has a way of erasing information. A 40km KB equivalent of a chondritic meteorite would be fascinating, if frustrating given only a few hours of remote sensing are possible.

I love the audacity of it, though, to go off to study something without having discovered it yet.

We'll see it for days on the way in, possibly longer. And FYI, 40 km is Eros size.

Alan

[nprev]

Just out of curiosity, Alan, is encounter relative velocity for KBOs basically a constant? These things have very small heliocentric relative speeds if they are not in highly elliptical orbits, so NH's outbound velocity is presumably a criterion for deciding whether or not to select an object based on encounter timing & size (i.e., you'll get a lot more hang-time for a 500km diameter KBO then a 40km).

[Alan Stern]

Just out of curiosity, Alan, is encounter relative velocity for KBOs basically a constant? These things have very small heliocentric relative speeds if they are not in highly elliptical orbits, so NH's outbound velocity is presumably a criterion for deciding whether or not to select an object based on encounter timing & size (i.e., you'll get a lot more hang-time for a 500km diameter KBO then a 40km).

Nprev-- All KBO encounters are at approx the same relative speed, ~12-15 km/sec, independent of KBO size. Don't know whatyou mean about hang time...

Alan

[nprev]

Oh, sorry. What I meant is that presumably more data (esp. imagery) could be acquired when encountering a larger object then a smaller one; for example, a larger one would have resolvable features further out & also post fly-by.

[Alan Stern]

Oh, sorry. What I meant is that presumably more data (esp. imagery) could be acquired when encountering a larger object then a smaller one; for example, a larger one would have resolvable features further out & also post fly-by.

True, but the stats just make it unlikely--too few and far between. Best we can realistically hope for is 70 km diameter if I choose to go to just one instead of 2 KBOs. That's what the Monte Carlo models for detection statistics within our accessible region after Pluto tell us. Nontheless, the KBOs we will get will be 10^5 times the masses of km-scale comets and will teach us an enormous amount about KBO evolution, chemistry, geology, etc.

-Alan

[surreyguy]

Thanks for the correction, Alan. And yes, I should have said 'parent body of' somewhere in there.

Here's hoping that you get enough options to do some trading (red? grey? hot? cold? scattered?).

[tasp]

Not sure I am thinking this through correctly, but if the number of smaller objects increases fast enough, do we get to the statistical likelihood of a useful non targeted encounter (light curve, size determination, confirm no satellite/binariness) of any objects in the 5 km size?

Maybe a better question is, are there enough 5 km 'rocks' that the possibility of useful science (with no additional fuel used) in a 6 year XM exists ?

Seems like the NH spacecraft 'useful encounter sphere' is rather large, and as it traverses the belt would it intersect anything tiny but interesting?

[Alan Stern]

Not sure I am thinking this through correctly, but if the number of smaller objects increases fast enough, do we get to the statistical likelihood of a useful non targeted encounter (light curve, size determination, confirm no satellite/binariness) of any objects in the 5 km size?

Maybe a better question is, are there enough 5 km 'rocks' that the possibility of useful science (with no additional fuel used) in a 6 year XM exists ?

Seems like the NH spacecraft 'useful encounter sphere' is rather large, and as it traverses the belt would it intersect anything tiny but interesting?

Could be, but no one knows (i) how many objects there are that small-- or how to see them from Earth, so it's impossible to estimate well and even harder to find one and aim for it. NH can't do the job-- the imaging FOVs are too small and the bit rates too low. Believe me, we've thought of all this years ago.

Alan

[tasp]

Thanx.

I guess we get to work out the statistics for the smaller bodies the old fashioned way.

Counting craters on the bigger ones we can see.

[nprev]

Alan, what is the search magnitude limit for the hunt? If you're talking 70km objects or smaller at that distance, I'm gonna guess mag 24 or lower...amazing!!!

[Alan Stern]

Alan, what is the search magnitude limit for the hunt? If you're talking 70km objects or smaller at that distance, I'm gonna guess mag 24 or lower...amazing!!!

28th magnitude.

[nprev]

THAT is a definite "wow!!!!" Absolutely amazing; didn't know that modern CCDs would go that low, even with such enormous light buckets!

Man...I can really understand the need for the field to be clear of Sag now much better. I thought that maybe you guys could still do something now, but it'd have to be a major object to stand out from that mess.

[xtruel]

Trouble is, it'll take NH almost 10 years to go 40 AU, and the inner edge of the Oort Cloud is estimated to be about 2000 AU out. A 500-year extended mission is probably asking for too much. :-)

http://en.wikipedia.org/wiki/Oort_cloud

Since Sedna's the only thing like Sedna, I think it'll be hard to guess that we'll find another before 2015 AND that it'll be reachable by NH.

That does raise an interesting question, though. From the NH mission page: http://pluto.jhuapl.edu/mission/mission_timeline.php it's not clear how much time NH could have to reach a KBO. A ten-year extended mission could roughly reach the perihelion distance of Sedna from the Sun, but is anyone contemplating an XM that long? How long can we reasonably expect NH to work?

--Greg

My former question may be reformulated as follows : After completion of extended mission at KB, NH’s mission officially ends. Spacecraft will be at something like 50 AU. Maybe some fuel will still be left. From this point, will be something else worth trying ? Previous outbound spacecraft (Pioneers, Voyagers) have all been maintained until they really die, we may expect the same for NH. I had in mind a possibility of targeting some object at scattered belt (however small it might be) which may be a SDO or an object currently cruising near perihelion whose orbit type is similar to Sedna (70-1000 AU or the like), thus qualifying as “inner Oort cloud object” as I’ve read somewhere. But according to Alan’s info I now believe this as unrealistic as SDOs are simply too far apart. So next possible milestone would be escape from heliosphere ?

This is very long term thinking, I agree…

[vjkane]

So next possible milestone would be escape from heliosphere ?

This is very long term thinking, I agree…

The Voyagers and Pioneers had capable particles and fields instruments. Anyone know if NH's SWAP and PEPSSI instruments would be good for exploration of the heliopause? Also, NH left Earth with a smaller than expected payload of plutonium. How far could it go and still (1) operate the instruments and (2) call home?

[Alan Stern]

The Voyagers and Pioneers had capable particles and fields instruments. Anyone know if NH's SWAP and PEPSSI instruments would be good for exploration of the heliopause? Also, NH left Earth with a smaller than expected payload of plutonium. How far could it go and still (1) operate the instruments and (2) call home?

We could probably run the s/c and 1 instrument to the mid-2020s to explore the heliosphere 50-70 AU, but that's not the mission-- the mission is to maximize the KB science, and that means spending all the fuel to do that.

Alan

[IM4]

We have no candidates for close KBO enccounters, but what about distant ones? My program predicts that en route to Pluto and beyond NH will pass by several Centaurs within 1-3 AU :

CODE

_____Object_________ Distance(AU)____Date_____
83982  Crantor         2.76325     2010-Mar-08
15810  1994 JR1        0.50739     2016-Jun-03
       1996 KV1        2.61944     2017-Nov-23

That's too far for detailed imaging but I believe useful photometric science (phase curve or something) can be obtained with LORRI or other instruments. Of course that make sense only if LORRI is sensitive enough, since apparent magnitude of these objects will be ~ 16-17m.
Are there any plans for such kind of science?

[Alan Stern]

We have no candidates for close KBO enccounters, but what about distant ones? My program predicts that en route to Pluto and beyond NH will pass by several Centaurs within 1-3 AU :

CODE

_____Object_________ Distance(AU)____Date_____
83982  Crantor         2.76325     2010-Mar-08
15810  1994 JR1        0.50739     2016-Jun-03
       1996 KV1        2.61944     2017-Nov-23

That's too far for detailed imaging but I believe useful photometric science (phase curve or something) can be obtained with LORRI or other instruments. Of course that make sense only if LORRI is sensitive enough, since apparent magnitude of these objects will be ~ 16-17m.
Are there any plans for such kind of science?

Yes.

[IM4]

Yes.

Interesting.
Any details?

[Explorer1]

Looks like the 'flyby' of Crantor came and went. Did anything significant happened?
Probably not, since no mention on the NH twitter feed, I checked.

[Hungry4info]

Couldn't blame them if they didn't do anything. Not a whole lot you could do at 2.76 AU.

[Vultur]

The first post in this thread says the search would start in 2010 - has it started yet, or will it be later this year?

[nprev]

Actually, Alan said in this post that the search won't start till next year.

[Alan Stern]

The first post in this thread says the search would start in 2010 - has it started yet, or will it be later this year?

Our best imager, LORRI, can resolve the size of an object from roughly 10^5 object diameters away. So for a 100 km object, for example, we have to be w/i 10^7 km just to resolved it; if you want crude shape information, cut that to 10^6 diameters, and if you want "geology," well, better come to approx 30,000 diameters or better. The point here is Crantor and other distant flybys don't yield much of use, so we have not expended effort on them.

As to our KBO search, John Spencer is leading the organizational effort to recruit search teams; Andrew Steffl is helping John. Our plan is to conduct the search in 2011 and 2012, though Scott Shepard at least has already begun.

-Alan

[Greg Hullender]

Yeah, I think the last few times we've asked this question (maybe we need an FAQ section for each long-term mission) the answer was "not until we're past the orbit of Uranus."

--Greg

[illexsquid]

Our best imager, LORRI, can resolve the size of an object from roughly 10^5 object diameters away. So for a 100 km object, for example, we have to be w/i 10^7 km just to resolved it; if you want crude shape information, cut that to 10^6 diameters, and if you want "geology," well, better come to approx 30,000 diameters or better.

Alan, thanks for the info, but I'm a little confused... I assume that for crude shape information, you mean cut the maximum distance to 10⁶ kilometers, since 10⁶ diameters would be 10⁸ kilometers. But which do you mean for the "geology" figure? 30,000 diameters would be 3 million kilometers for our theoretical 100 km object, which is tough enough, but 30,000 kilometers is more or less a bullseye: better targeting than even Apophis will manage . It seems to me you could get at least some worthwhile surface-feature resolution at a greater distance than that. The famous LORRI images of Tvashtar's plume resolved fine details at 2.5 million km. On the other hand, I know that spacecraft (and ground) resources are limited, and you have to be sure you're getting enough meaningful data for any expenditure. Could you give any hints as to when you think it might be worthwhile to observe during one of these flybys?

[Gsnorgathon]

The Tvashtar plume images were taken a lot closer to the sun than any KBO images will be. I imagine blurring due to longer exposure times would reduce resolution at comparable distances.

[john_s]

I'll chip in here. Alan was talking about science at Centaurs that we might fly past on our way to Pluto- none of those will get close enough to be resolved. For the KBO target(s) beyond Pluto, we will deliberately target to get within a few tens of thousands of kilometers or closer- from 20,000 km, for instance, we would get 500 pixels across a 50 km KBO- sufficient to do some serious geology. LORRI can get well-exposed, unsmeared, images at Pluto's distance from the sun (it was designed to do that, of course), and while illumination conditions will be more challenging further out in the Kuiper Belt, there's enough performance margin that we expect to be able to do the same there.

At Crantor's distance, a LORRI pixel is 2000 km across, much bigger than Crantor itself. So there's no hope of getting any shape information.

And to make sure no-one is still confused on this point, we will not be searching for KBOs with NH itself- huge ground-based telescopes with wide-field imagers can do that much better, even though they're stuck at 1 AU.

John

[john_s]

Talking of KBOs, here's a heads-up that YOU can probably help us to find Kuiper Belt objects for New Horizons to fly by after Pluto, starting in a month or two. We're working with the Zooniverse folks to set up a "KBO Zoo" where you will be able to help us identify moving objects (i.e. potential KBOs) in the Milky Way star fields that we'll be imaging with the Subaru, Magellan, and Canada-France-Hawaii telescopes this summer. Details once the site is up and running.

John

[Astro0]

If we find it, can we name it?! I always thought that "Astro0's Orb" had a nice ring to it!

[stevesliva]

We're working with the Zooniverse folks to set up a "KBO Zoo" where you will be able to help us identify moving objects (i.e. potential KBOs) in the Milky Way star fields that we'll be imaging

Sweet!

[nprev]

THAT is a rockin' piece of citizen science outreach, John! Very much looking forward to it!

[hendric]

John,
That's great news, can't wait to participate in the search for targets!

[MahFL]

The Search for KBO's to begin.

[john_s]

Look for another release in a few weeks, describing how you can help us sift through all those images.

John

[dilo]

Look for another release in a few weeks, describing how you can help us sift through all those images.

Great, I cannot wait!!!

[tfisher]

Talking of KBOs, here's a heads-up that YOU can probably help us to find Kuiper Belt objects for New Horizons to fly by after Pluto, starting in a month or two.

Any update on this?

[elakdawalla]

It's in beta, still several weeks from launch.

[NGC3314]

What John said - just found out that some of the people behind Galaxy Zoo have teamed with the NH folks to not only look for potential target KBOs (TNOs, whatever name won't get me in trouble), but enlist citizen scientists in the search And if UMSF isn't full of them, I don't know what is . (OK, Galaxy Zoo itself, but that's a different audience...)

At least one additional Zoo of great interest in UMSF is also in the works.

[hendric]

Just got this in the Zooniverse newsletter. I think it should be safe to post here!

New Beta Test for IceHunters

Last week we tested a new Zooniverse project "Ice Hunters" with
Galaxy Zoo: Supernovae and Galaxy Zoo users. Thanks to the help of
more than 3700 of you, we are now ready to expand our beta test to the
full Zooniverse.

To try out the site as a beta tester, go to:
http://demo.icehunters.org
The tutorial is here:
http://demo.icehunters.org/tutorial

The site will launch to the public in late May or early June, so
please keep this address to yourself for now. IceHunters uses data
around the world to look for Kuiper Belt Objects (KBOs), Variable
Stars, and Asteroids. The ultimate goal is to find the Kuiper Belt
Object (or Objects) that the New Horizons spacecraft will be
redirected to after in flies past Pluto in 2015. The data to find that
object is being taken right now. While we wait for it, we have loaded
in testing data from 2004 and 2005; images filed with unknown KBOs,
variable stars, and asteroids that appear as blobs and streaks in the
residuals of the subtracted images. Your name will be associated with
your every discovery, and catalogues will be published next winter.
Help us find new icy bodies today: http://demo.icehunters.org

[john_s]

Here's an update on how the KBO search is going so far.

This year, after several preliminary searches, we are finally kicking off the full-up search campaign. Our searches are possible only near new moon, and so we have obtained a bunch of telescope time once a month, starting with the late April new moon, and continuing in late May (when, by the luck of the draw of the telescope time allocation committees, we have the most time), late June, and late July. Time is divided between the Magellan telescopes in Chile, the Subaru telescope on Mauna Kea, Hawaii, and the Canada-France-Hawaii telescope also on Mauna Kea.

The first run, in late April and early May, on Magellan, went spectacularly well. We had superb weather and seeing (one night's report described "seeing deteriorating to 0.6 arcsec"- if you're an observer you'll know that's an unusual statement), and the data quality looks excellent. We're now in the process of reducing the data- the key step will be the matching and subtraction of pairs of observations taken hours or days apart, so we can remove the gazillion background Milky Way stars and leave behind the moving objects, which will include our potential KBO targets.

In a few weeks we'll be posting subtracted images on a site being developed by our partners at the Galaxy Zoo, where you'll be able help us to search for the moving objects. The late-May data may be the first posted- the late-April run is lower priority because the KBOs are harder to distinguish from asteroids by their motion in April. In the meantime, there's a beta version of the site already available, using data from an earlier (2004) search- I'll post more on that later today, when the site has had a couple more improvements.

John

[dilo]

Finally we can help you, I am so excited!
Just found a dozen objects in first 5 demo images; software is quite simple/straightforward, perhaps image quality section can be improved with more specific comments.
Thanks for this great opportunity!

[john_s]

As hendric and others have noted, the beta version of our KBO search site, Ice Hunters, is now online at demo.icehunters.org. We're not making a big public announcement till we launch the site with the 2011 data in a month or so, but in the meantime we'd love to have people sign up and start looking for objects the 2004 data currrently posted. This beta version will help us get the bugs out of the pipeline so everything is ready for the new data, but the 2004 data in the beta version are intrinsically scientifically useful too. Those data also covered the New Horizons search area, and may well include KBOs that New Horizons can access. Ideally, we'll find KBOs in our 2011 campaign that we can then trace back to detections in these 2004 data- in that case we'll be able to determine accurate orbits for those objects much more quickly, to see whether the spacecraft can reach them.

Thanks in advance for your help!
John

[stevesliva]

Just found a dozen objects in first 5 demo images; software is quite simple/straightforward, perhaps image quality section can be improved with more specific comments.

They are inserting fake ones to test you. Want to be rated well? Find the ones near the edges.

I'm not sure the fake ones are paired with a black blob... I get excited when I see those... more likely to be real.

I've also been wondering what binary and ternary KBOs would look like... same frame? Seems like that occurs a fair amount.

[john_s]

Actually there are no fake objects in the 2004 data on the beta site, so positive/negative pairs are likely to be a real slow-moving objects. However we probably will add artificial objects (with realistic motions, so they can also produce positive/negative pairs) in the 2011 images when they are posted- it's important to add artificial objects to the data to test what fraction of objects of a given brightness we can actually find.

Single objects, without a negative partner, may be moving objects in which the subtracted frame is taken a long time after the original frame, or they may be variable stars which have changed brightness between the times of the two images.

Oh, and most binary KBOs are very close to each other in the sky- often you need Hubble to separate them- so might or might not be resolved in our images.

John

[stevesliva]

Thanks john... I saw an old powerpoint of yours which mooted the fake KBOs, and was finding so many white blobs I figured you must be doing it already!

Also interesting regarding binaries. Makes me wonder whether the multiple "KBO" frames are just ones where the algorithm turned certain stars into white fuzzy blobs.

[hendric]

John,
Thanks for the update! I was curious, are you using a 16 or 32 bit FITS workflow? It seems like some of the images are suffering from a weird clipping like the subtraction was done on signed data but the conversion to an image format was done on unsigned data. Maybe you could provide a couple of sample images and we could hold a contest for the best subtraction algorithm.


You said binary KBOs are likely to still be point sources on these images, what about binary asteroids/centaurs?

Also, is there a fixed image scale for these pictures, or do they vary?

[MahFL]

Oh dear I can't use IE7, which is on my work PC, bummer.

[john_s]

John,
Thanks for the update! I was curious, are you using a 16 or 32 bit FITS workflow? It seems like some of the images are suffering from a weird clipping like the subtraction was done on signed data but the conversion to an image format was done on unsigned data. Maybe you could provide a couple of sample images and we could hold a contest for the best subtraction algorithm.

I can pass on this question to Marc Buie, who is doing the subtraction algorithms, but I'd be very surprised if there were artifacts related to bit clipping. The subtraction of different point-spread functions, even after convolution to try to match them, can produce some pretty strange artifacts though. Maybe you could PM an example to me...

As to subtraction algorithms, part of the trick is to have something that works automatically on hundreds of different image pairs- we don't have the resources to manually fine-tune every example. However some preliminary tests on our 2011 data suggest that we'll be able to do better subtractions than we've achieved on the 2004 data- we'll see when we turn the crank on the full data set.

You said binary KBOs are likely to still be point sources on these images, what about binary asteroids/centaurs?

Probably the same- again most binary asteroids have been discovered using adaptive optics or Hubble.

Also, is there a fixed image scale for these pictures, or do they vary?

All are the same scale, 0.2"/pixel in the case of SuprimeCam on Subaru, which produced all the beta images.

John

[hendric]

Thanks for the reply John. I figured after I sent my message that there must be a limitation on the amount of CPU processing you want to do with each image, so that you can complete the whole queue in a reasonable amount of time. I'll try to PM you some examples.

[tfisher]

I can discern 8 parallel, nearly horizontal, rows of artifacts per image tile. Once you start looking for it you can see this on every image. Any idea what causes that? Maybe some side effect from the subtraction algorithm?

[Edit:] Well, I had about 30 images in a row with those parallel rows of artifacts; now I'm not seeing them any more.

[nprev]

John, though this is not a technical commentary, have to say that the user interface is quite effective, and even a rank amateur like me picked up on the methodology rather quickly. Suggestion: Might not be a bad idea to explain in the tutorials why stars are black in the middle (because they are very distant point-sources of light & therefore wash out the exposure in a smaller area than would be expected for a KBO because the latter are much closer; helps people understand why blobs=good.)

Okay, back to searching for one of the next targets!

[john_s]

I can discern 8 parallel, nearly horizontal, rows of artifacts per image tile. Once you start looking for it you can see this on every image. Any idea what causes that? Maybe some side effect from the subtraction algorithm?

[Edit:] Well, I had about 30 images in a row with those parallel rows of artifacts; now I'm not seeing them any more.

If you see them again, maybe make a screen grab and send me a copy by PM...

Thanks,
John

[john_s]

Suggestion: Might not be a bad idea to explain in the tutorials why stars are black in the middle (because they are very distant point-sources of light & therefore wash out the exposure in a smaller area than would be expected for a KBO because the latter are much closer; helps people understand why blobs=good.)

Thanks for the suggestion- it would be nice to have a bit more technical explanation for those who are interested. However the presence of black blobs isn't due to stars being further away or being "smaller" sources (the KBOs themselves are point sources for all practical purposes, and are as small as the star images). Rather, it's because stars don't move, so each positive image of a star is combined with a negative image of the same star when the subtraction is done- imperfections in the subtraction leave some negative (black) pixels as a result. The KBOs have moved on by the time the negative image is taken, so there's no superimposed negative image- all you get is the unadulterated positive image. Hope that makes sense...

John

[nprev]

Swing and a miss...but knew there had to be a reason for the pronounced dichotomy! Thanks, John. At the very least, a 'why not' rationale for the most easily misidentified objects should improve your SNR a bit.

[hendric]

I figured the black star centers was because of a "perfect" subtraction, ie 255-255=0, and the outside stays white because the gaussian applied to the PSF isn't exact.

tfisher,
I also saw those same parallel lines. I think it's caused by a bad CCD in the array. It doesn't quite seem perfectly horizontal though, it seems like it slants down one direction.

I have seen some giant hot pixels, hence my previous "binary" questions. I was pretty excited about seeing two move in the same direction until I saw the same two objects in a couple of images. Is it sad that I can now recognize parts of the CCD based on the hot pixels? I'm not sure if I should mark the hot pixels as blobs, since they meet the criteria, but I think I can notice them now since the KBOs seem fuzzy-edged but the hot pixels are hard-edged.

Sample of the hot pixel images. (animated gif)


Also, seen something a few times that is either a rapidly changing dust/gas cloud, or shmutz on the CCD. Seen something similar in the same spot a few times, but only got one screen cap of it, so my money is schmutz.


Here's my best example of what looks like ringing.


And my favorite bunch of blobs so far.

[john_s]

I figured the black star centers was because of a "perfect" subtraction, ie 255-255=0, and the outside stays white because the gaussian applied to the PSF isn't exact.

Nope, because zero is actually gray- we stretch the differenced images to show both positive and negative residuals, and so we can properly see the noise in the sky (which is scattered around zero, for a good sky subtraction). We certainly don't do byte arithmetic.

I have seen some giant hot pixels, hence my previous "binary" questions. I was pretty excited about seeing two move in the same direction until I saw the same two objects in a couple of images. Is it sad that I can now recognize parts of the CCD based on the hot pixels? I'm not sure if I should mark the hot pixels as blobs, since they meet the criteria, but I think I can notice them now since the KBOs seem fuzzy-edged but the hot pixels are hard-edged.

Well spotted- yes, those are CCD defects, and the hard edges are diagnostic (sometimes the edges also show "ringing" due to the convolution). If you are sure you're seeing a hard-edged defect, don't mark it, but if in doubt, certainly err on the side over-clicking rather than under-clicking.

John

[hendric]

John,
Good to know, I wasn't implying you're doing byte math, just trying to give a simple example. I understand now about using -/+ math and stretching it to make gray the middle.

I think this is an example of the horizontal banding tfisher referred to. It's not perfectly horizontal, but displaces downwards a few pixels across the whole image.


Here's something interesting. Assuming these two asteroids are at the same distance (I'm using 2.5 AU, center of the belt ), they're only ~ 20,000 km apart.

[tfisher]

I think this is an example of the horizontal banding tfisher referred to. It's not perfectly horizontal, but displaces downwards a few pixels across the whole image.

Yes, that matches what I have been seeing.

Thinking a bit more, I bet it starts out completely horizontal as the image comes from the ccd. But to subtract two images, they first have to be reprojected to a common frame of reference, so it isn't quite horizontal anymore.

[tfisher]

Poking around more at the horizontal artifacts... They occur even in the images on the tutorial page. Here's a quick experiment. I took the "Image 1: Original from 2004-Jun-09 at 11:40 UT" and subtracted this image from itself translated vertically by one pixel. Then I remapped colors so nearly equal values are white and all others are black. The result is attached, showing approximately horizontal lines where there are equal pixel values just above one another.

Interestingly, the "Image 2" has almost to-the-pixel identical lines. If this was coming from a ccd readout problem I would have guessed they wouldn't match up so well. So maybe it is a bug from the image reprojection step?

Attached thumbnail(s)

 

[john_s]

Thanks for these examples, Richard and all!

Here's something interesting. Assuming these two asteroids are at the same distance (I'm using 2.5 AU, center of the belt ), they're only ~ 20,000 km apart.

Though of course if one's at 2.50 AU and the other's at 2.51 AU, they are 1,500,000 km apart... And they might be variable stars too- we're still getting a feel for all the stuff that's buried in these data.


John

[hendric]

Oh sure, if they're not the same distance. I figure the odds are better that two streaks in the same direction with very similar lengths are co-orbital vs happenstance alignment.

[stevesliva]

I thought this was a thing of beauty, as far as finding transients in dense starfields go.

[nprev]

Okay, I'll play: I see two, possibly binary.

This particular processing method seems to make them stand out, if I was correct.

[tfisher]

Are Kuiper belt objects distributed like a belt, or more like a shell?

When I find close asteroids (the ones with three closely spaced bright marks), they always seem to move approximately horizontally across the image. But when I find distant bright blobs with a corresponding dark blob, they seem just as likely to be separated in any direction.

Or is it just that there are so many other sources of variable brightness besides KBO's, that most of the time when there are a bright blob seeming paired with a dark one it is just a chance occurrence. Like two out-of-sync variable stars near each other from our viewpoint?

[john_s]

Most KBOs are in a flat disk, like the asteroids (though there are dramatic exceptions), and here we're looking in the plane of the disk so most KBOs we find will be trundling along in the same direction at similar rates. That's good, because it means most are heading in the general direction of the New Horizons trajectory (though we expect only a few percent of the KBOs we find to be accessible to the spacecraft).

And yes, most point-like variable or moving objects in the frames are probably *not* KBOs - they're variable stars or sometimes even artifacts such as CCD defects, as discussed previously. That's why we need all this help in cataloging everything, so we can sort out the few objects that really are of interest to us. So thanks again!

John

[nprev]

John, interim progress report. 238 objects identified in 801 images, which means I see a candidate on the average in 29% of the images...call it one of every three. How does this compare with the expected results? Might have been skewed in the first few dozen or so, but I think I got it down now.

Also, is anyone gonna follow up on asteroid finds? I assume so, since they're scored as well.

Want to say again how much I enjoy the user interface; it's well thought-out, VERY easy once you get used to the detection methodology, and downright addictive!

EDIT: Forgot to add a suggestion: a "back" button! A couple of times I spotted a candidate just after I clicked "done"; couldn't fix it!

[nprev]

Possible bug report: I'm on the road now & just tried doing a few images from the hotel. Did about 10, and the stat counter is frozen at 1900 objects discovered (wrong), 814 images viewed (never changed.)

[Tman]

Hi, that happens because of the last update on Sunday. You may have to go via a log-out and in, then it should run again.

[nprev]

Sure enough; thanks, T! (Der...there's was even a warning about this had I scrolled down the screen a bit...)

[john_s]

The Ice Hunters project is now out of beta and is officially open for business!
Thanks to everyone who worked on the beta version- the feedback from that work has helped improve the site, and the work was directly useful too- the team is now sifting through all the objects identified by the beta testers.

The official site will continue the work rather than repeating what's already been done- we'll complete analysis of the data from the preliminary 2004 and 2005 searches, and then move on to the data from the 2011 search program currently under way.

Here is the official release, and thanks to Emily for a great writeup on her blog today.

Here's an update on the 2011 telescopic campaign. Following a spectacular run on the Magellan telescope in Chile in late April and early May, we had poorer luck with the weather during the late May/early June dark time, but still got useful data at both Magellan and at the Subaru telescope on Mauna Kea in Hawaii. We're now preparing for the late June/early July run, which will again use both Magellan and Subaru, plus the Canada/France/Hawaii telescope also on Mauna Kea. This time I'm looking forward to going to the telescope myself- I'll be at Subaru on the nights of July 1st and 2nd.

John

[Alan Stern]

The Ice Hunters project is now out of beta and is officially open for business!
Thanks to everyone who worked on the beta version- the feedback from that work has helped improve the site, and the work was directly useful too- the team is now sifting through all the objects identified by the beta testers.

The official site will continue the work rather than repeating what's already been done- we'll complete analysis of the data from the preliminary 2004 and 2005 searches, and then move on to the data from the 2011 search program currently under way.

Here is the official release, and thanks to Emily for a great writeup on her blog today.

Here's an update on the 2011 telescopic campaign. Following a spectacular run on the Magellan telescope in Chile in late April and early May, we had poorer luck with the weather during the late May/early June dark time, but still got useful data at both Magellan and at the Subaru telescope on Mauna Kea in Hawaii. We're now preparing for the late June/early July run, which will again use both Magellan and Subaru, plus the Canada/France/Hawaii telescope also on Mauna Kea. This time I'm looking forward to going to the telescope myself- I'll be at Subaru on the nights of July 1st and 2nd.

John

And thanks to John Spencer for expertly spearheading this key corner of the NH project--observations, data pipelines, IceHunters, all of it! Now all you UMSFers: Go get in the game-- we need KBO targets-- an I'd say few are better suited to make the discoveries than the UMSF gurus!

[nprev]

Great Godfrey!!! A PI has called for aid!!!

<Superman voice> THIS looks like a job...for UMSF!!! Go forth & find a target for New Horizons, friends!!! </Super! >

[NickF]

EDIT: Forgot to add a suggestion: a "back" button! A couple of times I spotted a candidate just after I clicked "done"; couldn't fix it!

I find it helps to move the mouse pointer away from the 'Done Marking' button after I click it. Too easy to click through otherwise!

[Guest_Sunspot_*]

It's very addictive

[nprev]

Yeah, ain't it? I'm over something like 2100 images now.

[nprev]

Okay, now @ 2257 images with a detection rate of 18% (incl. asteroids). How does this compare with everyone else's stats so far?

[Stu]

18%? And you haven't shown us a *single* image yet. That's disgraceful! Don't you know how important sharing pictures is?

[nprev]

<abashed look> I didn't think anyone was gonna want to see images of circled little blobs...I stand corrected! Okay, will post anything I see that seems cool from now on.

One thing I've noticed is that there do seem to be multiple objects sometimes. Probably this is a misperception on my part due to the processing technique combined with the 286 processor in my head, but I have to wonder if sometimes we're seeing not exactly binary but somehow loosely associated KBOs. Of course, given the distances involved, true binaries wouldn't be distinguishable in these images & any two given objects are likely millions of km apart.

EDIT: Okay, Stu, just did another small batch, and these are esp. for you!

First, a small asteroid (not marked, upper right), and a little possible KBO (marked.)

Attached thumbnail(s)

 

[stevesliva]

My finding rate is much higher, but the number of images I've seen is much lower... wouldn't be surprised if folks like nprev are prioritizing images for others to see.

Finding some interesting yin-yang perhaps slowly moving objects in some of the newer images:

[elakdawalla]

Ha! I just independently saw that exact same one and called it the exact same thing in a comment at icehunters.org a few minutes ago! And also noticed your username among the other people who'd notated that one! Clearly great (UMSF) minds think alike

[nprev]

Now HERE'S a beauty: one asteroid plus one possible KBO:

Attached thumbnail(s)

 

[centsworth_II]

Now HERE'S a beauty...

Really! I have to admit being a little confused by the messier images but that one is "textbook". Nice outreach to those of us too busy or lazy to investigate the search site ourselves. I'm sure it will spur some more interest and participation.

[NickF]

If we're comparing rates, I've highlighted 201 potentially interesting objects in 891 images (22.6%, username 'nef').

Here's one of my favourites so far

[nprev]

Eek! We're heading into an asteroid field (upper left)!!!

Attached thumbnail(s)

 

[nprev]

...and dig THIS behemoth. Perhaps a TNO rather than a KBO? Dunno.

Attached thumbnail(s)

 

[nprev]

Last one of the day: A two-fer?

EDIT: Please disregard the third circle around nothing; just a stray click, fixed it before submitting the image to Icehunters.
EDIT2: Damn it, looks like I might've missed a small asteroid just below the rightmost KBO candidate!

Attached thumbnail(s)

 

[nprev]

Sorry, but I HAD to post this. Satellite trail? NEO?

Attached thumbnail(s)

 

[Marz]

Great stuff!!! I've gone through 114 images with 96 objects. Perhaps I'm being too overzealous with some of the blobs I've marked, since the margins seem like they were edited during the subtraction process. However, their center is white, so I figure it's better to flag it as something to investigate.

I hope we hit the jackpot! Seems like a great way to filter data for a sky survey -- farm it out to the eager masses!

[nprev]

Thanks for that comment, Marz. Been wondering if I've been too conservative, actually, but my viewpoint has been that I want to get stuff that's pretty much unmistakable...no idea whether that's the "right" approach, of course. I think that statistically this should balance out well; obviously, one of the key discriminators must be whether multiple observers tag the same pics & objects, and that seems like the best possible filter for the inherent subjectivity of these observations.

Gotta say, though, that this has been FUN!!! If anyone's been on the fence about jumping in, let me tell you there's no reason at all to hesitate; beats the hell out of surfing tired news or whatever when you're on the Web & not doing anything in particular...

[NickF]

Gotta say, though, that this has been FUN!!! If anyone's been on the fence about jumping in, let me tell you there's no reason at all to hesitate; beats the hell out of surfing tired news or whatever when you're on the Web & not doing anything in particular...

Indeed. How often in your life are you given the opportunity to spot something floating in the Kuiper Belt?

[nprev]

I'm thinkin' maybe just this one time, Nick, 'cause I ain't gonna live forever...let's take full advantage of it!!!