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Displays of space junk

I am curious to know the Lie Factor for the drawings on pages 48-49 in Envisioning Information ie some of the space junk is about 50 times as big as the smallest islands in the West Indies! And I know there is a disclaimer about the scale of the drawings at the bottom right of page 49.

My question is whether in this instance it was a good idea to include these drawings to support what I consider are obviously strong personal views - the accompanying text contains many emotive words eg "the trashing of space", "phenomenal", "disheartening...images" - when the factual text description of how much space junk there is actually speaks for itself. Because if I can see the Lie Factor is huge then a proponent of future testing of space weapons, or someone who wants to put more junk up into space, surely will and then they could use it to discredit opposing arguments. (BTW I wholeheartedly believe that we should pick up all our trash when we leave a place.)

Have you underestimated the intelligence of the readers? Or was it considered worth doing so in order to get this issue in front of as many (educated and perhaps influential) people as possible?

Yours sincerely,

Jim Moore

PS I love these books!

-- Jim Moore (email)

Graphics Showing Space Junk

Nick Johnson, who worked at a military contractor in tracking possible ICBMs and distinguishing a missile attacks from space junk, prepared the 2 drawings used in my Envisioning Information. He told me in 1988 that he decided to make the space-junk object symbol just a little bit bigger than a random speck that might show up in making xerox copies!

You can think of each symbol as simply a locator and not a scaled object; an icon for a piece of space junk. We do this all the time with symbols (the transmitter-tower icon on maps for pilots is wildly out of scale, every road on nearly every map is 100s of feet wide if it were in scale, the little square marking the location of a house on a large-scale map has the world filled with 5000 square foot houses). In this case, it is also a very good idea to inform viewers that it is a symbol not a scaled object; that was done in the original and in my book.Of course a big hint is that the little marks are not scaled is that they are all the same size.

You have to make some kind of locator mark. How else could one locate space junk?

Well, another way is to show orbits (the circling track of each object), with a resulting great web-mesh around the earth. Would someonce claim the fine line showing the orbit was way too wide, out of Earth scale?

And for any kind of serious analysis, there will be all kinds of quantitative measures of space junk (particularly estimates of risk to satellites and astronauts). We need not worry a all about losing the argument because the space-junk icons are too big.

The graphic, as printed in Envisioning Information, does not stand alone; there are lots of other descriptions and measures of space junk in the text. I included this example in my book because it illustrated micro/macro designs as applied to an interesting topic of interest the world over.

Of course I used value-laden words in writing about space junk! Although the orbiting frozen bags of sewage, a really nice camera (a Blad as I recall), and the 34 Soviet unshielded nuclear reactors do speak for themselves.

The topic remains relevant; development of Star Wars anti-satellite and anti-missile systems will add lots of debris. Maybe if there is enough space junk up there, then ICBMs will be useless!

Here is a current, non-visual summary of space junk as reported by there are 4,000,000 pounds now in orbit, and the estimated probability of a penetration of the Space Station in a 10-year period is .45.

-- Edward Tufte

Response to Space debris drawings and the Lie Factor

The reason spacejunk is contentious is because of the danger to new launches and existing satellites from its kinetic energy. Kinetic energy should therefore be taken into account in the representation of its size. A West Indian island bumping into the ISS at one kph would do less damage than a shard of metal hitting it at 25,000. I know that this has not been done exactly or to scale, but what the graphics show is that there is a lot of risky stuff whizzing about up there and just how densely it is concentrated. I don't think there's a lie factor, more a "best attempt" at representing something that cannot be exactly replicated as a static drawing in two dimensions.

-- Martin Ternouth (email)

Response to Space debris drawings and the Lie Factor

A little animation of orbital debris at the end of 1997 is at

It would be nice to see an update. And to compare 1997 and 2002.

[link updated January 2005]

-- Edward Tufte

Space Junk Update

The latest news on space junk: Andrew C. Revin, "Wanted: Traffic Cops for Space," New York Times, February 18, 2003:

This report from the Times has some good diagrams, especially a simple chart of the actual sizes of small objects in relation to their kinetic energy (expressed more as metaphors than quantities). Some scaling problems occur in the illustrations showing the earth.

Also there is a excellent photograph from NASA showing a crater from a paint chip striking a window in the shuttle--except there is no scale on the image nor an object of known size in the common visual field! The image is probably a few inches wide although it looks like a galaxy. The lack of scale here is a reminder of the lack of scale, despite a 22.5-fold vertical exaggeration, on the Venus fly-by movie-images constructed the Jet Propulsion Laboratory and NASA; see my book Visual Explanations, p. 23-24.

Such dequantification also shows up in the amazing images from the Hubble Space Telescope; what is the size, the distance away, and the location in the sky of the objects shown in the Hubble photographs? Scientific images are scientific because they have scales of measurement; the dequantification of images takes astronomy down the road toward astrology. It is especially important to provide scaling in images for public consumption, since the public might not have the contextual feel for scale that the experts do. And without scales, the NASA images start to look like Hollywood sets rather than scientific evidence.

-- Edward Tufte

Response to Space debris drawings and the Lie Factor

China's successful test of an antisatellite missile on January 11 increased space debris by 1% overnight. See the online story here. This site has some high-resolution graphics of the debris field.

-- Prem Thomas (email)

William J. Broad, "Orbiting Junk, Once a Nuisance, Is Now a Threat," The New York Times, February 6, 2006 here

This article is accompanied by a superb set of news graphics (be sure to go through the entire portfolio of graphics, as indicated by the tabs near top). Especially good is the sequence showing the dispersion of the debris from the recent Chinese destruction of a weather satellite.

The solar panels on the Hubble space telescope were, from 1993 to 2002, were hit by space junk 725,000 times, with about 5,000 impacts on the panels large enough to be seen by the unassisted eye.

The Times provided no credit line for the graphic artists who did this fine work. Furthermore, no source for the informaiton is provided (presumably it is from a group at NASA).

-- Edward Tufte

In the paper newspaper, the sources and designer are credited (NYTimes, February 6, 20076, page F1):

"Source: STK software graphics courtesy of Center for Space Standards and Innovation (; NASA (photos); Size of objects greatly magnified for visibility. David Constantine/The New York Times"

Maybe I missed these credits on the website version. Can a Kindly Contributor do a thorough search?

-- Edward Tufte

Thanks. I produced all these graphics. The source and credit lines appear in the top right corner of the online version.


-- David Constantine (email)

The source and credit lines differ from the print edition to the internet edition, presumably for good reason. On the internet edition, "sources and credits" are on a drop-down which requires clicking. In regular news stories on the internet, the reporters' names (and their sources) are right there with the story, not stashed away of a drop-down requiring a click. Graphic reporters and their sources should receive credit identical to word news reporting. Why the reluctance of the Times to give reportorial credit to graphics news reporting?

More importantly, the space-junk graphic news reporting is fine work by David Constantine and Monica Evanchik.

-- Edward Tufte

I am part of a team that works on these debris images. The images you refer to are from our software STK ( used to create analytical graphics for land, sea, air and space. It is particularly well suited for space, its pedigree in understanding complex attitudes and sensor to earth modeling.

The Chinese ASAT is the largest debris event recorded (~1037). CSSI is a part of AGI. Dr TS Kelso runs CELESTAK the public source of the track data (TLE -Two Line Element) used in the images. Track data is a function of resources, technology and size/reflectivity of the pieces. Prevailing thoughts are that these data represent a portion of the perhaps 35k actual pieces. Currently I have been taking the track data and performing analysis to determine the statistical make-up of the other ~34k pieces then generating them in images showing actual tracks posed next to the generated data - estimating the full size of the field. I generate these by applying a deltaV and propagating in our full force model (atmos drag, solar pres..)

The full debris field images are even more haunting. We are trying to develop new ways to understand the threat posed by such fields through visualization and other formal close approach analysis.

-- Tim Carrico (email)

Here's a composite based on screenshots from David Constantine's Littered Skies, featured on the front of the New York Times Science section on 6 February 2007. The accompanying article is Orbiting Junk, Once a Nuisance, Is Now a Threat, by William J. Broad.
The final four images depict the debris of the Chinese satellite destroyed on 11 January 2007 at 5 minutes, 1 hour, 1 day, and forward in time to 1 month after impact.

-- Edward Tufte

At the very end of "Teaser Trailer #2" for the upcoming Pixar film WALL*E, there is a humorous exaggeration (presumably!) of space junk, which is so thick that a rocket must knock a number of satellites from orbit before escaping earth's gravity. You can see the whole trailer at

-- Nathan Vander Wilt (email)

SciAm article with a colour-coded graphic and a time-series chart of space junk from 1950 to 2200.

-- Jim Moore (email)

New Australian research centre to remove space junk, save satellites and spacecraft

-- Jim Moore (email)

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