Exposing PseudoAstronomy

July 26, 2015

#NewHorizons #PlutoFlyby – The Pseudoscience Flows #8: Where Are the High-Res Pictures?


This will be another short post, but it’ll hopefully tide you over while I’m home for 3.5 days before headed back to Maryland for a New Horizons Science Team Meeting. First off, you should read my Part 6 post about how the data are being downloaded from the New Horizons probe to Earth.

With that said, Richard Hoagland has moved up in the world and has his own radio program on Art Bell’s network. Richard gets 10 hours per week (2 hrs per week night). I finally figured out my recording software and so was listening today to his Friday night / Saturday morning broadcast where he had on his significant other (Robin Falkov) and amateur image processor and image anomaly = intelligent artifact finder Keith Laney. But that’s somewhat beside the point, for this is the pseudoscience for this post:

  1. Richard Hoagland thinks that if he were managing the mission and the the probe might die tomorrow, he would send back the best pixel scale images first.
  2. Therefore, we must have done that.
  3. But, they are not being released.
  4. Therefore, “NASA” is hiding these 70-80 meter per pixel images because “NASA” is trying to figure out what all the buildings mean.

Spot anything wrong with that line of reasoning? How about steps 1 and 2, the basic premise.

Richard Hoagland is wrong.

From a fundamental standpoint, besides everything I wrote in that part 6 blog post. If you’re in charge of the mission, and you fear there is a small possibility that your probe might die, you would want to bring down the most representative data, and the data that will tell you the most about different things across the body rather than a tiny less-than-one-percent-of-the-surface-area image that would itself take many hours to downlink without lossy compression.

And – ¡gasp! – that’s what we did! We brought down images that give us the broadest possible view, and we brought down data from the other instruments that do the same. Remember: New Horizons doesn’t just have a black-and-white camera. It has seven other science instruments!

Besides that, more organizationally and methodically, there are literally hundreds of individual science questions/goals that we had for New Horizons’ data to answer. Every single observation made was linked to one or more of those goals. And, those goals were prioritized not only into four main tiers*, but within each tier they were prioritized, as well. Each was audited multiple times by many different mission scientists and very carefully worded and planned. And — guess what! — 70-80 m/px images of a tiny area of Pluto are not in the Tier 1 goals. So, when you want to prioritize your data downlink during that crucial few-days period after the closest approach, you’re going to bring down the data to answer the most Tier 1 goals/questions.

So … yeah. Richard is wrong in his conspiracy because his assumptions are wrong which he assumes are correct. Put another way: Richard thinks something, which (to him) makes it fact, and then he makes conclusions of conspiracy based on that “fact.” But his basic thinks is wrong, therefore everything else that came after that thinks is wrong.

*This is why after the “anomaly” during the July 4 weekend, the announcement was made that “No Tier 1 goals will be affected.” That’s because the data that would have been taken during those few days were not crucial to any of those goals/questions. One observation, for example, was a “family portrait” that would be the last time New Horizons could fit the entire system in a LORRI field of view. That was more for public outreach, so it was a 3.9.x goal, but it also would have helped determine orbits of outer satellites which means it doubled as a tier 2 goal.

July 21, 2015

#NewHorizons #PlutoFlyby – The Pseudoscience Flows #5 — My Own Error


I’m going to shift a bit here, though the next two posts on this topic are already planned (though Sharon over at Doubtful News just pre-empted me tonight on the Crrow777 stuff that’s hit Newsweek). Instead of discussing pseudoscience that I’ve seen elsewhere, I’m going to discuss my own. Not pseudoscience, per se, but where science can go wrong when you have little sleep and are under extreme pressure to do things quickly.

But before I get specifically to this, I want to emphasize: News reports that there are “no craters on Pluto” are wrong. There are clearly impact craters. It’s that there are no unambiguously yet observed impact craters on Sputnik Planum. That out of the way:

I made a boo-boo. But, science is ultimately self-correcting because if it’s wrong, then when people try to duplicate it, they will get different results …

I generally study impact craters (among other things). One of my primary science areas of research for the Pluto-Charon system is to understand their crater populations to tease out what the impacts are like out there 40AU from home and what the geologic history of the bodies are. To do that, you have to map craters. I’m going to be focusing on that in the coming months (and currently) and I’m also going to be focusing on how our mapping changes as we start to get lossless data and higher pixel-scale data (not higher “resolution,” for “resolution” means number of pixels, while “pixel scale” refers to the length per pixel). This latter focus has been something I’ve been publishing on in the last year.

As I’ve mentioned before on this blog, images right now are being sent down lossy compressed. Meaning they are full of JPEG artifacts that wash out a lot of small features … like impact craters. So when mapping, I’m assigning a subjective confidence level that indicates how certain I am that a feature is a crater or not. Since we have repeat imagery, already, I’m going over each area multiple times, blindly, with the different images.

One area that’s hit the news is Sputnik Planum, on the “left” side of the bright albedo feature Tombaugh Regio. It’s bright, and it’s young, and we know it’s relatively young because it has no unambiguous impact craters in the images that we have so far. I’m very careful with that phrasing: unambiguous impact craters in the images that we have so far.

Except, I thought I found one. A rather large one. But I didn’t.

When I initially mapped it in the image that came down a week ago (the full-frame image that was unveiled the morning of the encounter), I gave it a confidence level of 4 out of 5. We had the lossy-compressed JPEG version of the image, and after we had attempted to remove some of the JPEG artifacts through Fourier Transform truncation and then deconvolved it with the point-spread function of the camera (the camera inherently blurs things a teeny bit), it looked like a crater, and I was pretty certain it was a crater. Since it was many pixels wide and the image had a pixel scale of 3.8 km/px, that is a significantly sized crater, at least 30 km in diameter.

Except, it wasn’t. We have since gotten a mosaic at 2.2 km/px of the planet, and we have gotten higher pixel scale images at 400 m/px that have not yet been released. In none of these is that very large, very obvious crater present.

What happened?

We made a tiny artifact bigger by image processing. It was a simple cosmic ray hit.

Here’s what happened:

  1. Cosmic ray hit the detector, meaning there was a very bright pixel with a lot of electrons in it.
  2. This detector has the annoying property that if you have a bright spot, a dark streak forms behind it. You can see this in all of the over-exposed hazards search images. So the bright pixel now had a dark streak behind it.
  3. This was lossy JPG compressed on the spacecraft by a severe amount. Heavy JPG compression can make things “ring” because it represents the data as a series of cosine waves.
  4. One of our basic image processors took that image and first deconvolved it, sharpening the ringing JPEG noise.
  5. He then looked at the image in frequency space and made a series of clips that when brought back into spatial space (what we’re used to) will dampen a lot of the obvious JPG blockiness and make for an image that is more aesthetic and helps to make out a lot more features because you don’t have the 8×8 grid of JPG blocks dominating.

This is perfectly reasonable to do, and so long as you understand the kinds of artifacts that it can introduce and don’t over-interpret it, you’re fine.

Unfortunately, it makes this particular kind of cosmic ray hit on this particular detector look like a very clear, very obvious impact crater. Despite my best efforts at not over-interpreting early images that clearly showed artifacts from the image processing, I over-interpreted this feature.

Fortunately, it never made it into a press release or a paper (though I will be talking about it in a paper I’ll be writing as a cautionary tale), but when doing stuff like this, I’m always reminded of how (and this is going to sound arrogant) I’m different from a pseudoscientist, and how working on skepticism for the past (nearly) decade has helped me to become a better scientist. Someone like Richard Hoagland, Mike Bara, Keith Laney, or the guy I talked about in the last blog post probably would not hesitate to make a big deal out of these kinds of features.

To be blunt, I’m a crater expert. I am considered to be an expert in mapping impact craters due to my experience at mapping over 1 million impact craters across 7 solar system bodies (so far). Yet, I made this significant mistake. What separates me from the pseudoscientist, though, is that when I was presenting this to people, I said that this looks very much like a certain crater, but we need to wait to see the uncompressed version of the image, and we need to wait for the higher-resolution maps before saying it’s certain. And if it isn’t, “it will be very interesting to figure out why it isn’t a crater.” I specifically said that in a team meeting on Sunday.

Many things right now are provisional simply because of the very lossy image compression. Features like craters are particularly difficult to tease out, unless they are very large and very obvious (as are many). Contrast that with the people trumpeting “geometric structures” on Pluto and Charon in these images. Of course there are “geometric structures” that were “artificially created” … all in the lossy JPG compression algorithm! I keep thinking I’m repeating myself with this — and I am — but people still keep making this claim.

But, I’m perfectly willing to be corrected. In fact, I have now written 1000 words about how and why I was wrong, and the exact reasons and process that led me to that erroneous conclusion: Based on better data, I can re-examine things and see what went on and if it’s real. Contrast that with what I listened to earlier today which was a discussion between Richard Hoagland, Keith Laney, and the host of Skywatchers Radio. This quote involves all three men, talking about the Norgay Montes image released last week, and where one stops and the other starts doesn’t really matter, for all three were complicit in this train of thought:

“Look around in that image. You will be amazed. The more you look, the more you’ll see. It’s pretty incredible. Blow the image up as much as possible and look at every little part of that image. There’s so much artificial stuff in there! Again, as denoted by the geometry.”

QED

July 20, 2015

#NewHorizons #PlutoFlyby — The Pseudoscience Flows, Part 4


An eagle-eyed Facebooker on the Facebook page for my podcast (thanks Warwick!) pointed this ‘un out to me on the Before It’s News website. Something like the equivalent of the Daily Mail but with more of a UFO bent.

Apparently there are huge cities on Pluto.

This was one of the pseudosciences that I knew going in was going to be prevalent, though I expected it to be more explicit first from Richard Hoagland and Mike Bara who are more vocal about their pareidolia and reading into image artifacts.

The entire crux of this guy’s arguments is that he sees a blockiness in the released images. He claims that he knows and can prove they are not JPEG artifacts for two reasons:

(1) He’s using a TIFF image and not JPEG, and
(2) the blockiness runs at a diagonal and not parallel to the image edges.

For the second reason, I have two words and two punctuation symbols for you: “Rotate & crop.” To add a a few more words: Most released full-disk images have been rotated such that the north pole is “up” in the image. The spacecraft didn’t take them that way. We rotated them to be consistent. Therefore, the original blocky compression artifacts run parallel to the image edges, but now they run diagonal because it’s been rotated! Pretty simple. Yet it has eluded this conspiracist.

Similar elusion is of a simple fact that all because your current file format is one type, that does not mean the original file format was that type. To be more explicit, all because the NASA press release you got this image from happens to be a TIFF on the NASA website, that does not mean that the original image downlinked from the spacecraft was not lossy-compressed JPEG. Which it was. No image downlinked from the craft since July 12 has been lossless, they have all been lossy. Via a 10:1 ratio, meaning they are very lossy. All because I can take a JPEG and use any image software to re-save it as a TIFF does not mean that TIFF will not contain those original JPEG artifacts.

The JPEG blocks are 8 pixels on a side, and many of the released images have been up-sized (I don’t know why, I argued against that, but I have no influence over NASA’s nor APL’s graphics people).

He also assigns the wrong image credit, as “NASA/JPL-Caltech/MSSS.” It’s “NASA/APL/SwRI.” That’s not hard to get right. It’s called reading the caption for the image that you take from NASA.

I’d say that this is one of the sillier conspiracies I’ve heard so far, but it’s really hard to choose. Especially with what’ll be parts 5 and 6.

Perhaps the best line from the video: “No one’s actually accused me of, uh, pixelation, yet, but I’m sure someone will. Uh, some— some spook, probably, some guy from MI6 will come on here … heh! Who knows? Or someone from NASA will try and debunk it. But we’ll see! We’ll see what they have to say.”

Ah…. if only I worked for NASA, or MI6. Maybe I’d drive a nicer car. But it doesn’t take someone from British Intelligence to tell the guy that IT’S JUST BEEN ROTATED!!!

P.S.: Also within the video are other various claims. Like a large hexagonal crater (no, that’s his mind trying to break a circle into line segments), and that NASA purposely brightened the image so that it washes out detail near the pole. No, that’s called the sub-solar point, which is where the sun is directly shining, so you can’t see any topography, only brightness differences of the actual material on the surface. It washes everything out.

July 14, 2015

#NewHorizons – The Pseudoscience Flows, Part 2


“Of course, I have no proof of this …”

Thus just said Keith Laney on Richard C. Hoagland’s internet radio program on Art Bell’s Dark Matter radio network. He was shocked an hour ago at the incredible details being revealed in the publicly released images this morning. Then, about 10 minutes ago, we had a NASA guy come into our geology room and tell us that we were so popular that we crashed NASA’s website. I knew that it was a matter of moments before the conspiracy folks would spin something.

And so, they did: NASA was releasing such good stuff and such “revealing” images of Pluto (despite them being lossy JPGs of lossy JPGs — the lossless version of this image will be downloaded probably the first week of August), that their website was shut down by Those In Control.

Sigh.

Also, two misconceptions: Richard spent quite a bit of time complaining and being mystified that there was no live radio signal from the craft. New Horizons has one moving part, the door to the Alice instrument. That’s it. Other craft usually have a science platform that can be rotated. New Horizons doesn’t. So we can either take data of Pluto and its system, or talk to Earth. Guess which we’re going to do when we’re closest?

It was another moment of arrogance, actually, on Richard’s part. He was astounded that no news media were asking this question during the NASA press conference. He remarked that the reason that HE thought of the question as opposed to the news media was that he has a lot more experience in this sort of thing. No … it’s because they know how to read Wikipedia.

The other misconception is not just Richard’s but is being played across many different media: The signal tonight is a “phone home” of the spacecraft health. Data won’t be until many, many hours later.

July 13, 2015

#NewHorizons – The Pseudoscience Flows


Introduction

Sigh. We knew this would happen. But I’m always intrigued as to what form it will really take. I’ve been monitoring some sites, some people, and here’s some that I’ve found so far. Two mainly.

Pluto was ejected from Earth during the Great Flood

Ol’ Terry Hurlbut, one of the premier editors/contributors to Conservapedia, is a young-Earth creationist. He has an Examiner.com site and his own ConservativeNewsAndViews.com site which duplicates said Examiner content and has contributions from other, like-minded über-right-wingers and young-Earth creationists. His contribution is fairly straight-forward: Pluto formed recently – but not as recently as Earth – during Noah’s Flood. Why?

Well: Pluto is red. Rusty red. Therefore it has rust. Therefore it must have iron that was in an oxygen-rich environment. Therefore it came from Earth. QED

Richard Hoagland

Richard is a moving target these days. There’s a lot of drama – the basics of which have to do with the feud between Art Bell and the program he founded but its current incarnation, Coast to Coast AM. Steve Warner, host of the “Dark City” internet radio program (also on Art Bell’s network), got a two-hour interview with Richard late last week and it went up just two days ago.

Richard himself will have (or depending on when you read this, has had) a 6 5 hour special from 3-9 2-7AM PDT on Tuesday morning, July 14, the morning of the flyby. He offered a preview on the “Dark City” interview, and I jotted down a few notes:

1. The Pluto system is young or artificial: Because no rings or tiny moons have yet been found, as was predicted (and therefore “MUST” be found IF the system is natural), then the bodies are either made of material that does not produce rings or tiny moons (ergo artificial) OR it’s incredibly young (ergo artificial).

2. Richard thinks it was created by a Type II civilization (can harness the energy of a solar system) that died 65 million years ago and so isn’t enough time to accumulate rings / tiny moons. It has archives/libraries where our “true” history is stored, and it didn’t suffer from the exploding planet that created the asteroid belt at that time which is also why neither Pluto nor Charon should have many craters.

3. He expects the “regular, geometric patterns” that are evidence of this civilization to be prominent. He also thinks the cantaloupe terrain on Triton is buildings buried by methane ice that NASA released but just never mentioned, and he expects to see more of it on Pluto.

4. “We’ve already found some staggering, repeating, right-angle geometry that has no business being there, and yet no one has commented about it because they don’t know what to say!”

5. The “weird computer outage” was a warning to NASA to not show what’s really there … from “somebody.” Either Alan Stern (the mission PI) will go along with it, or he’ll show what’s really there. Because of the IAU controversy, Richard is betting on Alan’s integrity to show “us” what’s really there. (Note: Richard says this about every PI or non-US country for every space mission. If Richard can pull the noise out of the images the way he wants to find “regular geometry,” Alan has integrity and Richard wins. If Richard can’t pull it out, Alan was threatened and Richard wins.)

6. The IAU vote was done to increase public engagement (through controversy / soap opera) of Pluto so that Alan can do the big reveal that it has alien archives on it in a few days.

To Be Continued?

I’m incredibly busy these days, so I’m not sure if I’ll have time to post more of these. But, I wanted to let you know what I’ve found so far that’s the most “coherent.”

July 1, 2015

Podcast Episode 135: How New Horizons Takes Photographs, Interview with Dr. John Spencer #NewHorizons


How New Horizons’
Imaging team works with the
Spacecraft photographs.

You asked for it, you got it: A podcast episode about the New Horizons spacecraft mission to Pluto. If I was going to do an episode, I wanted it to be something that you’re not going to get from NASA, not going to get from a random website about the mission or the cameras … something different and unique.

I think we did that with this episode, which is an interview with Dr. John Spencer who has been one of the primary mission planners, is co-deputy of the geology science team, and leads the search for hazards. We recorded this on June 01, but none of it is out of date other than speculation about new moons or rings – or any hazards – found. As you know from press releases, none have been found as this goes to press, though as this goes out, John Spencer and his team are actively working on the latest batch of data to be downlinked from the craft to search for more.

Anyway, the episode focuses on image processing – real image processing – and how we work with spacecraft data, and we touch a little bit on image-based conspiracies and how we’re at least going to try to not give conspiracy theorists their standard, easy ammunition (like painting over image anomalies to give a pure black area so they can claim “NASA is blacking out part of their images!!!”).

I’m hoping to bring you at least another one or two episodes about New Horizons, but we’ll see. There should be at least one more episode to come out in July despite me being home only 8 days of the month.

Disclaimer: While I am involved in the New Horizons mission, my podcast work (and anything branded under “Exposing PseudoAstronomy”) is completely separate from my work efforts. The views and opinions expressed on this episode are completely my own and don’t reflect NASA, other mission personnel, nor Southwest Research Institute.

April 4, 2015

March 14, 2015

Podcast Episode 128: The Saga of Comet Hale-Bopp and its Fugacious Companion, Part 2


Great Comet Hale-Bopp,
Part 2: On remote viewing
The comet’s partner.

Second in the three-part series: The saga of the great and powerful Comet Hale-Bopp and the conspiracy, mystery, intrigue, lies, schemes, hoaxes, and suicides that accompanied it. The idea came when I started listening to a new Art Bell set of interviews that I had obtained, and I realized early in the episode (November 14, 1996) that I was listening to THE interview that started the whole thing. I found another dozen or so interviews and decided to make an episode out of it that has blossomed into three episodes.

The three episodes are meant to be stand-alone in that they don’t need the others to be understandable. But, put them together and they tell the story in a lot more depth. This second part is about one of the primary drivers behind the Hale-Bopp companion, Courtney Brown, and his remote viewing claims. While he provided the hoaxed photographs to Art Bell and Whitley Strieber (per Part 1), he claimed that all of his evidence for the companion was “good data” and based on remote viewing.

Part 3 will be on the Heaven’s Gate cult and aftermath and continued conspiracy, including a brief entry by Richard Hoagland.

I have decided that, while I may do my interview with Dave Draper on potentially pseudoscientific conference abstracts before Parts 2 or 3 are finished, I will wait to put it out, such that Parts 1-3 will be back-to-back-to-back.

While there was one logical fallacy in the episode (argument from authority), I instead used the segment to discuss part of the skeptical toolkit: The BS Meter. And, what should trigger it and what you should do about it. The bottom-line is that you should question any claim that sets off your BS meter, and even when something seems innocuous and small and not even part of what could have led to the anomalous result, you should still check it.

And, finally, I plan to do a small tribute to Leonard Nimoy, no earlier than April 1. The tribute will be from you: If he or any of his characters affected you (especially as perhaps related to an interest in science or astronomy or critical thinking), please send in a few sentences. Or, record no more than 30—60 seconds and send the file to me. I will read/play them either on episode 130 or 131.

Finally, this episode is coming out a bit early because I’m leaving for a week for a planetary science conference and won’t be able to do much of anything else while I’m there.

March 2, 2015

Podcast Episode 127: The Saga of Comet Hale-Bopp and its Fugacious Companion, Part 1


Great Comet Hale-Bopp,
Part 1: On the claimed photos
Of your companion.

I’ve been working on this episode for awhile: The saga of the great and powerful Comet Hale-Bopp and the conspiracy, mystery, intrigue, lies, schemes, hoaxes, and suicides that accompanied it. The idea came when I started listening to a new Art Bell set of interviews that I had obtained, and I realized early in the episode (November 14, 1996) that I was listening to THE interview that started the whole thing. I found another dozen or so interviews and decided to make an episode out of it. About three months and over 10,000 words of notes and transcripts later, this is the release of Part 1 of what will be a three-part series on Hale-Bopp.

The three episodes are meant to be stand-alone in that they don’t need the others to be understandable. But, put them together and they tell the story in a lot more depth. This first part is about the image – the “hard science” – claims about the companion. Next one will be on the remote viewing claims and aftermath, and the third will be on the Heaven’s Gate cult and aftermath and continued conspiracy, including a brief entry by Richard Hoagland.

I have decided that, while I may do my interview with Dave Draper on potentially pseudoscientific conference abstracts before Parts 2 or 3 are finished, I will wait to put it out, such that Parts 1-3 will be back-to-back-to-back.

There were two logical fallacies pointed out in this episode: Argument against authority, and correlation ≠ causation (cum hoc ergo propter hoc).

And, finally, I plan to do a small tribute to Leonard Nimoy, no earlier than April 1. The tribute will be from you: If he or any of his characters affected you (especially as perhaps related to an interest in science or astronomy or critical thinking), please send in a few sentences. Or, record no more than 30—60 seconds and send the file to me. I will read/play them either on episode 129, 130, or 131.

February 4, 2015

New Horizon’s First Images of Pluto from Its Approach Phase – What’s Going On?


Introduction

New Horizons is a spacecraft headed to Pluto. It launched nearly a decade ago, but it will arrive in July of this year and do a fly through the system. Doing lots of amazing science.

One of the instruments is LORRI, a long-focal-length camera that will be the prime imager for much of the mission because it will be able to take the highest spatial resolution images. It will also be used (was being used and is being used, too) for optical navigation — make sure we’re headed in the right direction.

Just a few minutes ago, on the anniversary of Clyde Tombaugh’s birth (the guy who discovered Pluto), NASA released the first image from LORRI of Pluto and its main satellite, Charon, taken during the Approach Phase. There’s a lot going on here – one point in particular that I just know is prone to misunderstanding later on – so I want to talk a bit about this image.

Disclaimer

I am involved with the New Horizons mission. I am not a NASA employee. This is my personal blog and everything on it is my opinion, are my words, and is done completely independently (time-wise, resource-wise, person-wise) from my work on New Horizons. In fact, it is on record that this blog is legally distinct from my professional work. Nothing I say here should be taken as an official statement by NASA or the New Horizons team.

Resolution / Pixel Scale

That out of the way, let’s get to the meat of this post. Also, I’m going to use “resolution” and “pixel scale” a bit loosely here, so pedants need to forgive me right away.

LORRI is an amazing camera. It is a 1024×1024 pixel detector, and each pixel has an effective angular size of 4.95 µrad (micro radians, or about 1.02 arcsec). 1 arcsec is about the width of a human hair from 10 meters (33ft) away. (source)

At the moment, New Horizons is around 200,000,000 km away from Pluto. That’s okay, it still has 5.5 months to get there. Pluto is approximately 1180 km in radius. That means, from some simple trigonometry (remember SOHCAHTOA?), Pluto is about 1.2 arcsec in radius, or 2.4 arcsec in diameter. Charon is very roughly half Pluto’s diameter, so it’s around 1.2 arcsec in diameter. Charon and Pluto orbit on opposite sides of their center of mass, which means they are around 8.6 Plutos away from each other, or around 9.1 arcsec separated.

Okay, lots of numbers there. Basically, that means that right now, if we had perfect optics, Pluto is about 2 pixels across, Charon 1, and they’d be around 8 pixels away from each other, max (since their orientation on the plane of the sky is not perpendicular to the spacecraft right now).

(No) Perfect Optics

No such thing exists. Given the best, most perfect optics ever, you can never get infinitely fine details. This is because light will behave as a wave, and give rise to Airy disks and patterns meaning that the light will spread out as it travels through the optics. Unless you had an infinitely wide optical system.

When you factor everything together about the optics and system and detector and other things, from a point source of light, you get a point-spread function (PSF). This is the practical, measured spreading out of the light. In astronomy, we often measure the PSF based on fitting a Gaussian distribution to a star, since a star should be a point source and just cover one, single pixel.

With a telescope aperture of 208mm for LORRI, and a passband of light centered around 0.6 µm (red light), the Airy disk should be around 1.22*0.0006/208 = 6.8 µrad. That’s around 1.4 LORRI pixels. Amazing coincidence!

Actually, not. When designing an instrument, you typically want to just about over-sample the Airy disk. You don’t want to under-sample because then you’re losing valuable resolution and information. You don’t want to over-sample because then you’re just wasting money on a detector that is too “good” for your optics, and other issues that come about when you have small pixels. So, designing a system that’s around 1-3 pixels per Airy disk is good.

When you go to a practical PSF, it’s going to be a bit bigger just because no system is perfect.

What’s the Point?

Oh yeah, back to Pluto.

First New Horizons Image of Pluto and Charon from Approach Phase

First New Horizons Image of Pluto and Charon from Approach Phase (©NASA/APL/SwRI)

Let’s put these parts together: Right now, Pluto should be around 2 pixels across, Charon 1, and a separation of around 7-8 pixels. But, add in the PSFs due to the laws of optics. That means that the light should now be spread out a bit more.

And that is why this image looks like it does. It’s also been enlarged by 4x, such that each original LORRI pixel has now been resampled. So, if you look at the image NASA released, and you blow it up a lot, Pluto looks like it’s around ten pixels across, and Charon around five.

To repeat: The released image shows Pluto to be around 10 pixels wide, and Charon around 5. Despite the theoretical values now (2 pixels and 1 pixel, respectively). That’s because (1) the PSF spreads the light out because we live in a world with real and not ideal optics, and (2) the released image was enlarged by a factor of 4.

Moving Forward

New Horizons is zipping quickly along. In May, it will surpass all previous images taken and we will truly be in new territory and a new era of discovery (so far as imaging the Pluto system — note that the other instruments have already taken a lot of data and are learning new things). That best image that exists so far of Pluto shows Pluto to be approximately 8 pixels across.

And that’s why I started this post out by stating, “one point in particular that I just know is prone to misunderstanding later on.” So, today, NASA released an image that shows Pluto with as many pixels across as what it will take in late May, when it will have that number of pixels across.

See why I wanted to bring this up now? I can just hear the pseudoscientists claiming that NASA is lying about the power of the New Horizons telescopes, they’re deliberately down-sizing images (later, based on images released now), and various other things. While they’ll still almost certainly say that, at least you know now why that’s not the case, and what’s really going on now versus then.

There are only 2 (well, about 4, since it’s 2×2) “real” pixels in the Pluto disk right now, the others are interpolated based on expanding the size to make the image look nice for this release, celebrating the image and Clyde Tombaugh’s birthday. In four months, we’ll have all these pixels, but they won’t be based on a computer algorithm, they’ll be “real” pixels across Pluto taken by LORRI. Convolved (“smeared”) with a PSF that’s about 1.5-2 pixels.

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