05 November 2014

Mooning Saturn: The Maps are Out!

It may well be the longest and most complex project I've ever embarked on but the results are emphatically worth it.  Although I am primarily tasked to investigate the geologic history and evolution of icy bodies across the Middle Solar System (considering the distant Kuiper Belt of small icy objects, the giant planets are more correctly in the middle zone), that work has some extra benefits.  The mapping of topography and shapes of features requires precise knowledge of their locations on the surfaces of the icy moons.  As I like to do things like this to completion (call it ADD or OCD if you like), the result is a complete set of updated camera vectors for all relevant Voyager, Galileo, and Cassini images of icy satellites.  More on camera vectors in moment but the benefit of this is that all these images can then be accurately reprojected to any map format and combined to make a true global map of each body.  Using color images as well and you can make a color map!  

The first bonus of all this work (and I do mean months of hard labor over a keyboard) was the Atlas of the Galilean Satellites (P. Schenk, Cambridge Univ. Press, 2010) showing global and high-resolution maps of each of the 4 large moons of Jupiter known since Galileo first discovered them in 1610.  This volume includes the first and only fully registered and accurate positioning of all the Galileo images of these moons, and each mosaic is faithfully reproduced therein.  It is recommended to anyone interested in these bodies, in planetary imaging, and in the naked beauty of the Universe.

I also recently released the updated color map of Triton (see my previous 2 posts), and now the same has been done for the 6 largest midsize icy moons of Saturn [Mimas, Enceladus, Tethys, Dione, Rhea, and Iapetus] known before the Space Age began in 1957.  (I would like to do Hyperion and Titan in this way but am doubtful I will be able to get to it before upcoming events overwhelm.)  These are the maps that, after 18 months of work were released yesterday on NASA Photojournal and described in detail in an article in the latest Planetary Report.  These new maps are the most accurate in terms of location, the highest resolution, and the first to show both albedo/brightness variations realistically and the first to be in full color.  Not only that, they reveal these worlds to have a beauty all there own (as described in the Planetary Report article).
Cover of the Fall 2014 issue of Planetary Report, showing part of Enceladus.  I should open an art gallery . . . 
Getting feature locations in planetary images is a complex business.  So before getting into the maps I will attempt to explain.  The images come down from space with information about the exposure, including the time and position of the camera (i.e., the camera vector), as well as spacecraft location and other things.  This information is the instructions given to the camera, but the spacecraft always has a teeny bit of wobble and the information is always slightly inaccurate as a result.   Once sufficient number of images have been built up to cover most of the surface, someone (such as myself) can then go in and select a bunch of match-points that identify features in multiple images.  Each points should all have the same location in each image but do not due to the wobble.  Once cataloged, the pointing vectors are adjusted (a 'bundle-block adjustment') in a least-squares program until the differences in the match-point locations are minimized.  Ideally these difference should be zero but seldom are.  Anyway, this new information is then passed back to the images and we can then know precisely where features are.

Why is this important?  Obviously we want accurate maps of planets so we can send landers to the right place, and make future observations of changes or unusual features, but we also want to make accurate topographic maps from stereo images and such and that requires accuracy.  Scientific work on geologic processes also requires accuracy in position or we get the wrong answer and waste time and money.  And if we have inaccurate pointing information our maps are misaligned and we can't make the kind of mapping product like those released yesterday.
An example of a misaligned map (left) and an accurately aligned map (right).  Courtesy USGS.
So, this brings us to the new maps.  As noted above, these are the best maps produced to date of these objects.  They will be updated periodically as our understanding of their rotation state improves and as the last sets of images come through in 2015, but positionally they will not change much more if at all.  Several close encounters of Tethys, Enceladus, Dione and even a few more shots of Mimas are on tap for next year.  The maps are at different resolutions because the bulk of images for each satellite were obtained at different resolutions because of the Cassini tour geometry and speeds and the size of the objects.  The goal was to make maps at the highest resolution possible with as uniform a resolution as possible.  I (slightly) favored resolution in each case, and the result was 250 meters for Tethys and Dione, 400 meters for Rhea and Iapetus, 200 meters for Mimas, and 100 meters for Enceladus, which has been the focus of numerous Cassini encounters and is the best mapped icy body in the Solar System.

These are the first global maps to realistically show brightness variations across the surface.  Hence you can see the really dark trailing hemispheres of Tethys, Dione and Rhea very well.  Bright lineations on Dione and Rhea also stand out as do various bright and dark features such as rayed craters.  Like all maps, compromises were required to get a uniform map product, as each image was acquired under its own uniquely different lighting and viewing conditions.  When a choice was required I usually chose feature definition (from shading) over brightness variation, for example.

Tale of Two Hemispheres.  These global projections show how different Saturn's icy moons can look, depending on the view.  The top is the leading hemisphere, covered in smooth deposits and sinuous rilles.  Note the young bright ray crater Creusa near top.  The bottom view is of the darker heavily cratered trailing hemisphere, which is scarred by arcuate young fracture networks.
The other new feature of these maps is that they are the first accurate maps in color (I think somebody may have done preliminary color maps elsewhere but they are not as complete or accurate as these positionally or in color registration).  These new maps are in 'Superman' colors, just beyond the range of normal human color vision.  The color choice was not made to annoy anybody.  Cassini did obtain some images in the R-G-B range of the spectrum close to human vision but these are insufficient images to construct global maps at high resolution.  The natural visual colors of these bodies do reveal information but they tend to be rather bland.  Cassini did obtain routine higher resolution coverage of these moons in the near-IR and the UV wavelengths and these are used to make the global maps.  "Dialing up' the colors to include these spectral ranges also brings out color contrasts between geologic features much better than the olde R-G-B range.

In addition to the global maps, Cassini obtained a number of higher resolution mosaics, many of them in color.  Some of these are shown in the Planetary Report article.  This will be the topic of a future blog.

It is all well and good to use maps like these for scientific investigations.  That is why we go there, to learn about how the Solar System works.  But sometimes it is worth stepping back for a few moments and marveling at the amazing Universe we are part of.  Each world out there is unique and holds numerous discoveries and surprises (check out the Planetary Report issue for some of those, but if you search earlier blogs here, and also our 2011 Icarus article where I describe them as well.)  These worlds are also little jewels in a vast empty Cosmos, fascinating and wonderful to behold.  I hope to have more on these maps soon, but for now enough blubbering!  The maps are released to the public to enjoy for free.   After all, this is YOUR space program!  

To view and download the maps, go to the LPI or JPL websites (The JPL releases will have been dated 2014-11-04 they have scrolled of their page).  The maps are released in global and hemispheric views, and with and without annotation, suitable for wall poster printing!  The global map can be dropped into GoogleEarth or similar global rendering software.  We have released on the LPI website moves showing these moons in rotation and flyby.  We are working on how to make them downloadable.  In the meantime, they are also on the LPI YouTube channel for quick viewing (other related high-res videos can be found on my galsat400 YouTube channel).

If you plan to use them in publications, productions, or presentations, the proper credits are:  
Global map(s) of Saturnian moon(s) [name of moon(s)] were produced by Dr. Paul Schenk (Lunar and Planetary Institute, Houston TX. Image data are from the Imaging Science Subsystem (ISS) camera on the Cassini orbiter (NASA, JPL).

23 August 2014

Triton: Addenda and Errata

Today’s blog features a correction and some additional details on the new Triton map and movie  blog posted a few days ago  >  stereomoons.blogspot.com/2014/08/triton-at-25.html.  <

First, a correction.  The surface compositions of Triton and Pluto are indeed similar but not quite identical.  Triton has nitrogen, methane, carbon dioxide and carbon monoxide on its surface, and probably some water ice, but of those ices Pluto does not have carbon dioxide or water ice that we can measure from Earth.  What those differences may mean for geologic and atmospheric history no one can say as yet with confidence, but all the more reason for going to Pluto and someday back to Triton.

As a matter of personal opinion, I am sometimes asked which planets I’d like to see explored next.  Europa is first on the list, but after that we have the ice giant planets Uranus and Neptune and their strange families of icy moons (including Miranda, Ariel, and Triton to name a few).  These large bodies are distinct and different from the gas giants Jupiter and Saturn but have been visited only once, by Voyager 2 with instruments designed in the 1970s.  What we could learn by going back has been amply demonstrated by the innumerable discoveries of Cassini at Saturn.  

Triton, whose surface may be younger than a few million years and may be geologically active today, is one of the most fascinating bodies on the Solar System.  Its maximum surface temperature is only 35 degrees above absolute zero, and yet volcanoes and geysers have remade its surface, possibly within the lifetime of the human species.  Even the Voyager scientists, who had become accustomed to surprises after the discoveries on Io, Ganymede, Titan, Miranda and the rest, were left almost speechless as Voyager made its final planetary visit.  As Larry Soderblom exclaimed at the press briefing when he showed the first Triton images, “What a way to leave the Solar System!”

T-shirt printed up to during the Neptune encounter 1989.  The t-shirt and owner are now 25 years older.
Neptune was fabulous too with its strange and dynamic cloud patterns and its odd, incomplete ring system.  One of my first efforts in serious image processing was to reconstruct the Neptune ring high-phase-angle observations.  These were the best images of the rings we got, but the long exposures saturated Neptune itself and created bright haloes that were difficult to suppress.   Normally exposed Neptune crescent images were substituted but the heavy filtering required for the bright haloes also enhanced noise in the images.   The end result was a montage showing a crescent Neptune and the entire ring system.   This was done back in 1992 or 93, so I’m sure I or someone else could do a better job now.  It is a composite of 5 (or 6?) different exposures taken at different times and distances from Neptune, but all the data are real.  
Crescent mosaic of Neptune from Voyager 2 on departure, August, 1989.
Triton Map: Enhancement and 'Color'. The enhancement applied to the Triton map in the August 21 post was a modest contrast-stretch only; no differential color enhancement was applied.   Surface brightness contrasts on Triton exist but are not as strong as on Pluto.  The color does have a greenish cast in equatorial areas.  This seems to be real, but there are ‘concerns’ with Triton’s color.  First, the color images were sometimes smeared or noisy, due to long exposures under very low solar lighting intensity for which the cameras were not designed.  This explains some of the splotchy color mottling that is apparent in a few areas.  Secondly, there are some uncertainties in the photometric properties of Triton.  Earth-based spectra of Triton obtained in the 1970’s and 80’s differ in the inferred visual color of Triton and it was not possible to get an exact color ‘calibration’ on Triton.  We did our best, but the colors may not be only approximate, given the slightly different color sensitivity of the Voyager 2 camera.    

The Triton map is suitable to drop into Google Earth or similar programs!  You can now zoom and spin on Triton in any way you like.    

Neptune in the Movie.  Several have asked why Neptune doesn’t appear in our movie.  Several reasons, the most important of which is that we ran out of time for the August 25 anniversary.  The second is that we compress almost 10 days of the encounter into 1 minute.  Neptune would probably appear in 2, maybe 3 of those frames.  We are looking into it.  We know that Neptune and Triton do appear together in the sky about a day out from Triton, and again 6 days later, but do not appear in proximity to each other on the way in, apparently.  We may attempt to add Neptune back in for a final version later this year.

21 August 2014

Triton at 25

Triton at +25, Pluto at -1: Twin Planets Separated by Gravity

[An addenda and errata for this post has been uploaded on Aug 23. Click here to go to it and read more.]

It has been quite a long time since my most recent post but it doesn't mean I haven't been busy!  I have been working long hours preparing a new set of global maps of icy moons, the first of which is being released today.  This is the new high-resolution color map of Neptune's large and crazy moon Triton (The next set will be released within a month, and the Galilean Satellite global maps were released in the Atlas of the Galilean Satellites in 2010.)  

August 25, 2014 is an interesting date in Solar System exploration.  It is foremost the 25th anniversary of the Voyager 2 encounter with Neptune and Triton.  This was the grand finale of that landmark mission, which over the span of 10 years completed the first exploration of the giant Outer Planets.  It is thus a good day to release the new Triton map. 

I was a freshly minted post-doc at JPL in 1989, having arrived the year before.  Having been a summer intern for Voyager Science Support under Dr. Ellis Miner 10 years before during the Voyager 2 Jupiter encounter, and then 2 years later for Saturn, I felt a bond with the mission and its support teams.  Many of these people I know today!  But in 1989 I had no connection with the Project.  Fortunately I knew Bill McKinnon, my thesis advisor, and he knew folks on the Imaging Team.  In the spirit of celebration surrounding the Neptune encounter, the two of us were snuck into the Inner Sanctum in Building 264, third floor, where I had been an intern 10 years before.  (True, 'someone' objected to us being there but we were snuck back in anyway and no one else complained.  It was a grand and special event and [almost] everyone was happy to be part of it and share it with a few colleagues.)

One of the few shots of myself (back left) during my Voyager internship during the Jupiter Summer of 1979.  Project Scientist Dr. Ed Stone is in front of me at the head of the conference table.
Here are some of the photos (on film!) I took during the Neptune encounter 10 years later . . .
Bill McKinnon, and some of the TV crews assembled to report the Neptune encounter, 1989.
A JPL billboard showing Voyager's progress.
Jay Inge making an airbrush map of Triton, the last body mapped in this way.
Linda Spilker (nee Horn) gleefully monitoring IRIS data from Neptune on the printer.
Linda and Kelly Beatty (Sky & Telescope) looking over data printouts.
Linda Spilker looking over IRIS results the old fashioned way!
Watching the monitors during Encounter.  Jonathan Eberhart (Science News) is in the foreground. 
Larry Soderblom, chief of the satellites group, discussing the mission with the press.
A monitor shows the current image of Triton.
Dave Grinspoon, Caitlin Griffith, Bob Strom, Bill Boynton, Eugene Shoemaker, Joe Veverka.
Dave Grinspoon, Buck Janes, Carl Sagan, and Torrence Johnson
Lastly, that's me in front, with Jeff Moore right behind.  What a grand time!
Thanks to the Voyager Project for letting some of us in to share it.
I along with everyone else at JPL in those days was treated to the Voyager Neptune encounter live every day on our closed-circuit TV monitors (this was just a few years before the WWW, cell phones, etc.).  Each day Neptune and Triton got a little bit bigger and more detailed as new images were flashed to the monitors.  The fantastic cloud patterns of deep blue Neptune were fun, but for Triton, we didn't even know how large it was, so everything was new.  It wasn't until a week before encounter that we learned the radius of Triton for the first time.  The surface itself finally became clear only on August 24, the day before closest approach, when Triton's strange features became distinct.   The new map being presented today is the product of those images.

The Voyager Project also published a Travel Guide (before pdf's!) describing the Neptune encounter.  It contains many gems of wisdom and fun facts.  Included are the following quotes from a section in which Voyager 2 leaves a hypothetical diary during its trip out of the Solar System.

Note the little 'flip-movie' of the encounter at bottom left.
"Star Date -1.259 (1990)  Today I am filled with an intense sorrow.  The encounter with Neptune has ended.  It is a but a tiny star in the background.  Part of my sorrow is from not being able to visit Pluto before my departure, for it is a very mysterious body.  . . .  I wish that I, or my sister spacecraft, had been the one to unveil some of the mysteries of Pluto.  The Project never seriously considered a visit to Pluto because it would have meant foregoing Voyager 1's encounter with Saturn's moon Titan. . . . However, it will be many decades before man will send another spacecraft out to that part of the solar system."  (!)

Like Voyager 'said,' one of the things left undone was the exploration of the trans-Neptunian realm.  Voyager 1 was going too far north, and Voyager 2 too far south.  Other than Pluto itself we had no knowledge of the "Kuiper-Edgeworth Belt" or just Kuiper Belt, until 1992, when the first non-Pluto object was discovered in that zone. Since then hundreds more icy objects have been found.  These objects are smaller than Earth, have icy surface compositions, and extend well beyond Neptune.  New Horizons is the first dedicated exploration of that zone.  It crosses the orbit of Neptune on August 25, 2014, on the same day as the 25th anniversary of Voyager passing Neptune.  It is also now a mere 11 months from Pluto, its main target, which it will reach in mid-July 2015.

In a double sense this is fitting, as Triton is a near twin of Pluto.  Triton and Pluto are both slightly smaller than Earth's Moon, have very thin nitrogen atmospheres, frozen ices on the surface (carbon monoxide, carbon dioxide, methane and nitrogen), and similar bulk composition (a mixture of ices, including water ice, and rock.  Triton however was captured by Neptune long time ago and has been wracked by intense heating ever since.  This has remade its surface into a tortured landscape of overturned layers, volcanism, and erupting geysers.

What will we see at Pluto?  Guesses have ranged from active geology to cold and cratered, so we are in for a suspenseful Summer next year!  Triton is of importance as it offers clues to what geologic features might look like on Pluto, given that the icy crusts of both bodies are probably rather similar and would presumably react in similar ways under internal stress and heat.   So if there were or are volcanoes on Pluto they could look similar to those we see on Triton.

So what does the Triton map show and how was it constructed?  The Triton map was constructed from images acquired in the clear, orange, green and blue filters (ultraviolet filter images were also used and this map will be posted at a later date).  The images were co-registered in an updated control network, which determines where the camera was pointing in each frame with precision so that feature geography is well known.  Photometric adjustment of each image was also done so that shading due to the curvature of the surface can be corrected.  The map also includes the departing crescent imagery, which is apparent in the left hand part of the map.  I hope to post the actual mosaic components in a future post.

Go Here to Find Full Resolution Triton Map and a Movie Recreating 1989 Voyager Flyby (the video is large and may take a few minutes to download):


Triton global map (scaled-down by a factor of 16!).  Dark areas were in shadow or not observed.

[A Note on the Use of the Triton Map and Video:  All the Triton maps and videos are in the public domain and may be used freely.  Credit should be notes as:  Triton map produced by Dr. P Schenk, Lunar and Planetary Institute, Houston.  Triton video produced by Dr. P. Schenk and J. Blackwell, Lunar and Planetary Institute, Houston  (or LPI may be used if short form desired).   Use of map and video does not constitute an endorsement of any other product.]

The result is a smooth map showing uniform shading and reasonably accurate brightness and color representation.  Note that the orange filter used by Voyager is not quite the same as our human optical red sensors but is close enough.  Although the map approximates natural colors, there are some uncertainties in the color calibration and  the "true colors" of Triton in 1989 may be slightly different.

In the intervening quarter century and its many discoveries, I think we have tended to forget how strange and exotic Triton really is!  Its effective surface age may be a little as 10 million years, clearly implying that active geology is going on today.  The cantaloupe terrain, which I interpreted back in 1993 as due to crustal overturn (diapirism), hasn't been seen anywhere else.  The volcanic region with its smooth plains and volcanic pits large and small, is  the size of Texas.  And the southern terrains still defy interpretation.

The Triton map also gives a sense of the quality of the Pluto map we hope to get.  The Triton encounter was rather similar to our upcoming Pluto encounter in that New Hoizons will zip through the Pluto system at a high speed, a leisurely 11 kilometers per second compared to 25 km/s for Voyager at Triton, and both bodies rotate rather slowly, ~ 6 days.  This means that for both bodies we will have seen one side well at high resolution and the other side at much lower resolution, roughly 25-to-40 kilometers.  The northern polar regions of Pluto and Charon will also be in darkness as seen by New Horizons, as they were for Triton.

One important difference is that New Horizons carries more powerful remote sensing instruments and will obtain infrared spectroscopy that Voyager, built in the early 1970's, could not.  We should be able to map the distribution of ices across the surface.  We will also resolve features several hundred meters across large areas and as small as ~90 meters in smaller regions of Pluto.  Voyager's best resolution on Triton was ~300 meters in a limited area.  This should be more than enough to map crater distributions, volcanoes, faults, and erosional processes. It will also be sharp enough to see if Pluto has any atmospheric plumes (or geysers) like Voyager saw at Triton.  These can be seen as thin dark and bright streaks on the Triton map.

Producing global maps of Pluto and Charon will take some time as the playback of data from that great distance will be rather slow.  It will take most of next autumn to return all the images and data from Pluto so we will have to be patient.  The end result should be maps of the surfaces of Pluto and Charon even better than we have for Triton.  It will be most interesting to compare Pluto with what we saw at Triton to see if there are any similar features, and to see whether or not Pluto has ever been geologically active.  

Next month:  Moons of Saturn, in color.

17 October 2012

The End of an Era - A Personal Look Back at the Shuttle


Shuttle Endeavour leaves Houston on its final transcontinental flight, September, 2012

The transfer of shuttle Endeavour to California this past month, including several flyovers in Houston I  witnessed and videoed, signals the last "flight" of the Space Shuttle era.  For us late Baby Boomers and beyond, the Shuttle was a continuous element of our adult lives from its inception.  It has also been linked indirected with my own career more than once.  The flyovers and public viewing in Houston last month were perhaps not so surprisingly emotive personally, given the link professionally and the link through time.  What follows is a personal retrospective on Shuttle history, a reflection on the journey we all, as individuals and as a nation, have taken with the Shuttle for the past 4 decades.


Endeavour flies past the Mercury-Redstone at JSC on its last trip - September 2012

Much of Shuttle history derives directly from its origins.  The shuttle program was founded in 1972 as the space agency fought for some sort follow-up to Apollo, lest exploration of space die on the Moon.  The high adventure of the Apollo moon landings gave flight to some fanciful and wild dreams for the future of manned space exploration, including orbiting stations, shuttles to orbit, deep space probes to the planets . . .   Articles in 1969 frequently featured subterranean Moon-bases and orbital infrastructure not far removed from what we saw on the big screen the year before in 2001: A Space Odyssey. Many of these visions had their roots in much earlier dreams, especially those from the 1950's following the War and capture of the german rocket scientists, the chief of those being Werner von Braun.  Dreams of space conquest were famously captured in the paints of Chesley Bonestal, and others and in articles in Collier's.  The shuttle was hoped to be the beginning of this next era, but the future in space did not quite follow this path.  Neither Congress nor Nixon were in a spending mood in space.  The result was a vehicle built from compromise, perpetually struggling to justify it existence from the day of its inception.

optimistic tho faded clip from a Buffalo newspaper July 12, 1969 . . . 

Despite its triumphant and anguished history, Americans are justifiably proud of their men and women on the Space Shuttle, and we tend to invest a lot of national pride in them, even when flights seemed to be routine, reduced to the mundane of lofting cargo to the Space Station.  We often tend to neglect that pride.  The Shuttle program took us on a powerful ride to places we didn't anticipate, from exhilaration to despair.  It is fitting to pause to reflect on some of those moments.

September 17, 1976
Enterprise Rollout
Four years after funding start, the first test Shuttle, Enterprise, rolls out of the assembly building, joined by the cast of Star Trek.  Destined for flight and landing tests, it would represent the fleet at the Air and Space Museum until Shuttle retirement 35 years later.  It's only trips to the launch pad were integration and structural tests at KSC and the later abandoned Vandenberg Shuttle launch facility in California.

August 12, 1977 
Approach and Landing Tests (Enterprise)
Enterprise was taken airborne by its 747 carrier and cut loose for several free-flight and landing tests in southern California.  Now largely forgotten, the first of these 5 flights was telecast live on several networks (in the days before Cable, the Internet, cell phones, etc.).  The landing tests went very well and there was genuine enthusiasm but development problems continue, especially concerning loose heat shield tiles on the underbelly and with the main engines.  The first launch was initially scheduled for 1979.  Skylab's orbit decayed, and the Shuttle was not ready to save the laboratory before it entered the atmosphere and crashed into the Australian desert in 1979.  Meanwhile the first launch of Columbia slipped, and slipped . . .

April 12, 1981
First Shuttle launch 
STS-1 (Columbia)  
The launch had been scheduled for April 10 but halted at T-9 minutes when the on-board computers failed to chat properly.  Disappointed, we all geared up again for the 7 am (EDT) liftoff two days later, now coinciding with the 20th anniversary of the first manned orbital flight by the Soviet Union's Yuri Gagarin.  We watched with curiosity and amazement.  This was something new, though far riskier than we knew at the time.  We were just coming out of the unsettling 1970's, the oil crises, gas lines, Iranian hostages, Soviet Afganistan invasion, job losses in steel and other key industries . . .  The Reagan administration was only a few months old, but the hostages had been released, he had just survived an assassination attempt 2 weeks before (the low point of his popularity swing in 1982 was yet to come), Disco was finally dead, and the 6 year hiatus in manned spaceflight highlighted by continual reports of shuttle construction difficulties was finally almost over.  As a happy accident of timing, the shuttle launch became part of a national reawakening out of the angst of the prior decade (the crushing debt load incurred as part of that rebirth would have to be dealt with later).
I was in first year at graduate school in Illinois and listened on the radio during the 7 am launch, disappointed that I couldn't find a TV at that hour.  The strapped together tanks and rockets gave Columbia a very different look to the Saturn V, described by some as a "space-age Taj Mahal," it's external tank painted white in those days.  The Shuttle also had a more muscular feel to it in contrast to the slower moving Saturn and "leapt off the pad."  Astronauts John Young and Bob Crippen became national heroes for a while.  A wide frontier of unknown possibilities seem to open before us.  The flight captivated us.  Here was something new, an engineering marvel, and it all went off perfectly (almost) on the very first flight.  Wow.

June 18, 1983
STS-7 (Challenger)
With the shuttle emerging from its test flights into "operational" status, things seem to settle into a routine of sorts, and this opened the doors to some long neglected opportunities.  The first major Shuttle highlight and media show after STS-1 was the flight of the first american female astronaut, the late Sally Ride.

August 30, 1983
STS-8 (Challenger)
First African-american astronaut, Guion Bluford, was in fact the first "minority" astronaut of any kind.  It was also the first Shuttle night launch and night landing, always a spectacle.  The flight also featured the first close call of the program, and a warning sign, as one of the booster nozzles very nearly burned through during launch.  This could have caused the entire ascending vehicle to tumble out of control.

February 3, 1984
STS-41-B (Challenger)
This mission produced one of the most famous and iconic images from the Shuttle era, that of Bruce McCandless floating free in space, the first untethered space walk in history.  It also marked the clumsy change in flight designation numerology, and the first landing at Kennedy Space Center, Florida, marking the first return to launch site and closing one of the last remaining links to the Shuttle's promised reusability.

April 6, 1984
The Solar Max Repair mission was the first to capture and repair a satellite in orbit, fulfilling another of the promised objectives of the program.  It did not go smoothly at first, as the attempt to capture the satellite by astronaut Nelson failed and the satellite began to tumble.

June 26, 1984
STS-41-D (Discovery)
First launch abort after engine ignition of the Shuttle (and first such since Gemini 6 in 1965).  There was also a brief hydrogen fire on the pad shortly afterwards, but it was contained before any damage could occur.

January 24, 1986
STS-51-C (Discovery)
First classified DoD shuttle mission.  'nuf said.  The military was still building the Vandenberg shuttle launch complex in California at this time.

January 28, 1986
STS-51-L (STS-25, Challenger)  
Five years into flight, we had come to think of shuttle launches as somewhat routine, and watched with scorn, frustration, and open mockery as NASA struggled in seemingly futile attempts to launch the thing on schedule.  Something wasn't working right but we mostly assumed it would work itself out eventually.  One thing was clear, the shuttle wasn't exactly living up to its touted capability of 100 routine launches a year.  The machine was already proving much more complex and costly than had been (irrationally) projected.  

Still, this seeming irregularity was taking on many of the familiar hallmarks of air travel, with its weather and other delays.  This time there was "citizen" astronaut on board, school teacher Christa McAuliffe.  After numerous delays, and a hard freeze the night before, launch proceeded over strenuous engineering objections.  School children across the country were watching live on CNN.  Despite this novelty, many only saw the launch when their programming was interrupted by the news bulletin.   

High in the sky for all to see, the familiar rocket plume abruptly blossomed into a large orange cloud as the two solid rockets shot out free and began wandering the sky.  The image of the giant "Y" or perhaps a "Why?" in the sky over Florida, formed by the two solid rocket booster exhaust plumes trailing forward, became seared into the memory of anyone old enough to understand its meaning.  Those familiar with shuttle launches knew it was wrong but some wondered.  The fact that it occurred 1 day after the anniversary of the Apollo-1 fire in 1967 was jarring.

I myself woke late (I was in graduate school studying planetary science at Washington University in Saint Louis) to try and catch any new images from the Voyager 2 Uranus encounter 4 days earlier.  Instead I was caught up in the coverage 15 minutes after the explosion.  The rest of the day was spent in a mental and emotional haze.  Working effectively just wasn't going to happen.  The TV coverage (there was no internet) continued throughout most of the day, followed by Reagan's memorable address to the nation that afternoon.

The national shock was enormous, the "JFK" moment of our generation.  The New York Times noted the importance of the event with its headline "The Shuttle Explodes," not "a" but "The" shuttle.  Quoting Don Davis, "The Challenger Disaster was a mortal blow to the optimistic dreams of widespread access to space such as we still had then."  Many felt the shuttle program had only just begun to fulfill its potential and the march into space had been cruelly interrupted.  A great determination to pick ourselves up off the ground, dust ourselves off, and get back on our winged horse and resume the great adventure took hold.

Each step in the redesign and testing of the systems components was reported in detail over the next 2 years, as were the finding of crew remains and the hearings that exposed the management weaknesses of NASA and its improper handling of the shuttle system outside its design limits and this launch in particular.  It was also by now clear that the Shuttle was much more complex and tempermental than hoped for.  Also, the decision to use one vehicle for all our launch services and especially using humans to launch telecom satellites was now obviously seriously flawed and the Shuttle manifest was quietly reshuffled.  NASA scrambled to readjust launch manifests but some vehicles could not be moved and exploration vehicles like Galileo, Ulysses, HST and Magellan remained tethered to the shuttle launch system, delayed by years as a result.  The effects on Galileo included a 6-year delay and a serious antenna failure, both of which would impact on my own work on the Jovian satellites.  Yet it is the kick in the gut that day that lingers.

April 15, 1986
Titan 34D rocket explodes 8.5 seconds into flight
May 3, 1986
Delta rocket explodes 90 seconds into flight
Coming within months of the Challenger accident, these two successive launch failures came as a new shock as our space program seemed to falter.  Both vehicles would be launching again within a year but the US seemed suddenly impotent in space, with little if any reliable access to orbit.

September 28, 1988
Return to Flight
STS-26 (Discovery)
The tension and anticipation across the nation and at the JPL auditorium where I watched the countdown was palpable.  If the nation could have stood on the pad and pushed the thing skyward I think they might have.  At the time, the Reagan era was grinding to its drawn-out conclusion but distractions were few and the entire nation focused on the launch.  The drama of launch was hightened further by a false alarm threatening to hold the count at T-0:31.  Even the voice of NASA, Jack King, was having a little trouble maintaining coherency, but watching the launch replays (you can see them on YouTube) and hearing that whooping cheer at liftoff can still give one a sense of the relief and exhilaration felt as "american's return to space," in Jack's words, as the long 2 and half year grounding came to an end.  Reactions differed but few watching remained emotionally indifferent.  I still choke up a little every time I watch the replay.

STS-26 "Return to Flight" CNN coverage

November 15, 1988
STS-27 (Atlantis)
This classified DoD mission remains shrouded in mystery but the second post-Challenger flight is also highlighted by unusually severe thermal tile damage, foreshadowing the destruction of Columbia 14 years later.

November 15, 1988
NASA was still wounded by Challenger when the Soviet Union launched their version of the Shuttle, Buran.  Many questioned our national choices in space, pointing to the apparent soviet successes on space station Mir, their new launch vehicle Energia and now this new Space shuttle, seemingly a better version of our own.  Although motivated by fears of a military gap, their shuttle suffered from similar doubts about purpose and value. Within 3 years the nation that brought forth Buran would itself break apart, and the historic space agency it founded would be brought to the brink of collapse.  The Mir space station would later suffer a series of near catastrophic accidents and breakdowns.  This would be the soviet shuttle's only flight.  Buran itself was destroyed when its hanger collapsed in 2002.

April 24, 1990
Hubble Space Telescope deployment
STS-31 (Discovery)
The HST was to be a great leap forward in astronomy, lifting our sights above the turbulent atmosphere that protects us to see deeper and more clearly than possible from the ground.  Great discoveries were expected and the flight was well covered.  Designed to be serviced by astronauts, the HST also seemed to embody the stalled hopes of the Shuttle system in which astronauts, in a real-life version of the McCall painting on the walls of the Air and Space Museum, would wander the skies like auto mechanics, servicing a vast space infrastructure.  Challenger killed that dream, but part of it lived on in the telescope, and fortunately so when it soon became apparent that the mirror had been ground improperly.  NASA and its telescope instantly became cannon fodder to late-night comedians and critics alike.  

December 2, 1993
Hubble Servicing Mission
STS-61 (Endeavour)
The first scheduled servicing flight to HST became much more than that when it also became a mission to fix the optics and salvage NASA's reputation.  The early 1990's were a difficult time as a number of old decisions were coming back to haunt the agency and it's capability to perform was seriously in doubt.  The most embarrassing of these was the condition of its flagship space telescope.  The telescope was well over budget and beset with technical problems, most of which were not completely solved by launch time.  In the 3 years since launch so many of the machines systems had either broken or proven flawed that 5 full days of spacewalks had to be scheduled to repair them all.  Gyros, solar panels, magnetometers, etc., all had to be replaced or repaired, the most pressing of these being the perfectly flawed primary optical mirror.  The Hubble was in danger of becoming an albatross.  NASA's very future was riding on the success of this mission, or so it seemed to many.

The key element in the repair effort was the exceptionally clever set of small precision lenses to be placed in the light path to adjust for the distorted main mirror.  The night launch added to what was already for NASA one its most dramatic launches since Apollo.  The spacewalks went off with few hitches and NASA's detailed preparations payed off handsomely when the first sharp clear images were released later that month.  Their efforts helped make Story Musgrave and his companion spacewalkers folk heroes for a while, the first of their kind since Sally Ride and the crew of STS-1.  That week may well have been the high-water mark of the Shuttle program.  The fact that the fix came just in time for Hubble to return spectacular images of a comet striking Jupiter in 1994 was a wonderful coincidence and seemed a very good omen indeed.  All seemed right with NASA again.

Shuttle Endeavour approaching HST,  
the distorted solar panels plainly visible to the crew

June 27, 1995
Shuttle-Mir docking
STS-71 (Atlantis)
The sight of the soviet space station from the shuttle was fascinating from the gee-whiz POV and a foretaste of the International Space Station that replaced it. The 7 flights to Mir marked the beginning of the first true sustained international collaboration in manned space.

October 29, 1998
John Glenn returns to space
STS-95 (Discovery)
Although widely panned as a publicity stunt, the return to space of the first american to orbit the Earth (the first human was Yuri Gagarin, a Soviet citizen), was widely watched.  Those old enough to remember his original flight in 1962 were either happy to see him return or oddly disinterested.

December 4, 1998
First ISS Assembly Launch
STS-88 (Endeavor)
At this time, the shuttle began to concentrate almost all of its efforts in support of the Int'l Space Station, beginning with the launch of the Unity component to mate with the previously launched Zarya russian component.  The concept of using manned vehicles and their inherent complexity, cost and risk to lift hardware had long been discarded but the Shuttle no longer had (or was given) any other role to play.  It was available, and all the hardware had been designed to fit in the shuttle anyway, and it kept the nation "in space".  Oddly, the shuttle's next loss would not involve the ISS at all but occur on its last dedicated science mission.

February 1, 2003
STS-103 (Columbia reentry)
When the Columbia broke apart in the skies over north Texas, less than a week after the annual Challenger anniversary, the nation wept again.  The TV kept replaying the amateur video of the splitting contrails streaking across the skies of north Texas, as the Shuttle broke apart at 200,000 feet and debris rained down.  They were 15 minutes from landing and only a few minutes from the end of atmospheric reentry.  This time it was different.  With Challenger, we had only begun this new phase of man's journey into space.  Loss of Challenger left us with a resolve get back into space but this time the feeling was more of resignation and defeat, like having the wind knocked out of you.  We all seemed to say to ourselves "oh no, not again."  I was at a retreat in rural central Texas and woke to what sounded like a clap of distant thunder in a clear sky, learning only an hour later that it was the sonic boom of the shuttle 200 miles to the north over Dallas as it began to break apart.

This was also only 18 months after September 11, and in the middle of the run-up to the Iraq war.  Israel's first astronaut was also aboard, and they too mourned.  We resolved to restore the Shuttle fleet to operations but the shuttle's fragile nature could no longer be ignored (a piece of foam had knocked a hole in the wing, leading to a burn-through on reentry), nor could the return of complacency and the sometimes casual insistence that the shuttle could operate like a city bus.  In essence, the rather routine damage that had been occurring at launch due to shedding foam was becoming ingrained as acceptable, leading to the false conclusion that the orbiter could not be seriously damaged.  Regardless, the compromises that went into the original shuttle design were now being openly discussed and NASA and the nation finally began to openly debate how to replace the aging fleet, leading directly to the 2004 Bush decision that the shuttle be retired and replaced.  That first fact is now upon us.  The future course is before us . . .

memorial tributes, February 3, JSC entrance  . . .

July 26, 2005
STS-114 (Discovery)
Return to Flight
Different than 1988, this mission signaled the beginning of the end-phase of Shuttle history and we all knew it.  There was relief to be flying again but the sense of future was lacking.  The irreversible decision to retire the fleet by 2010 had already been taken by Mr. Bush.  Each subsequent mission was operated with great labor and care so as to minimize risk, but the remaining focus was almost solely on completion of the Space Station. The fact that foam damage occurred again during launch led to a year-long interruption as the problem was reexamined yet again and largely if not finally solved.

August 8, 2007
STS-118 (Endeavor)
The mission featured the flight of teacher Barbara Morgan, after a 21 year battle to get her mission as the back-up for Christa McAuliffe.  Although NASA refused to call her a Teacher in Space, not wishing to stir memories of Challenger or disturb Christa's long sleep, it was still nice to see this dream come true.

October 23, 2007
STS-120 (Atlantis)
Much of the Shuttle and Space station work went unheralded and unnoticed, even when testing human skill and ingenuity, as they often did.  Case in point: the space walk by Parazynski to repair tears in a ISS solar panel at the utmost reach of robotic and human arms. 

May 11, 2009
STS-125 (Atlantis)
Final Hubble Space Telescope servicing mission.   The joint Shuttle-HST story may be one of the most enduring of the shuttle era.

April 22, 2010
Boeing X-37 Spaceplane
This highly classified mission, a sort-of miniature Space Shuttle, heralds one possible future for space.  The need to separate the crew and cargo capabilities of the Shuttle was clear but could the X-37 fill the first of those goals?  The air force is mum.

May 14, 2010
STS-132 (Atlantis)

February 24, 2011
STS-133 (Discovery)

May 16, 2011
STS-134 (Endeavour)
Beginning with the retirement flight of Atlantis, the nation starts a year-long celebration, commemoration, goodbye for its' Shuttle.  Each in turn, the 3 remaining spacecraft are taken on their final flights, completing the job of Space Station construction to which they had been assigned for most of the past decade.  STS-134 (Endeavour) mission commander Mark Kelly, husband to Congresswoman Giffords,  was to be the final Shuttle commander until Atlantis was rescheduled for an additional, final, flight (STS-135).

July 8, 2011
STS-135 (Atlantis)
Final Flight
Joy, pride, melancholy, and a few tears, the final flight of Atlantis and of the Shuttle fleet is watched nationwide.   Those of us who were old enough to remember the first Shuttle flight 30 years ago that spring (and indeed the difficult 'birthing' process of the development years), could not help but recall with similar emotions those times and the vivid memories of the Shuttle's triumphs and defeats.
So much had changed across our planet and society in the 30 years since 1981, technologically, socially, politically . . . it would take days to review them all.  The Shuttle itself also matured technically, with glass cockpits and other improvements, but it remained the same basic space truck, a line of continuity through a quarter of a century of history.


Although dictated by the remorseless logic of aerodynamics and weight restrictions, the Space Shuttle possessed a certain beauty.  From the triple stack of the tank and two external boosters, down to the black on white lines along the edge and wing, the Shuttle's design lines gave it an architectural monumentalism, especially when it was painted all white during its first launches, and seen in some of the images posted above.  The orbiter itself is a work of engineering art.  The sight of the elegant winged vehicle drifting gracefully across the black void, Earth in the background, is one of those scenes that is on my list of must do's but never could and now never will see.  The images of the Shuttle in space are some of the prettiest of the space age.

Much has changed since the first launch in 1981. Over the next three decades we witnessed the Internet, DVD, the cell phone explosion, music CDs followed by MP3 players, iPods and iPhones, two Gulf Wars, September 11, and all that followed.  Part of our present difficulty stems from the virtual national bankruptcy inflicted on us as a result of the gross mismanagement of the second of those wars.  It is important to remember here also that the decision to retire the Shuttle is entirely a G.W. Bush legacy.  The decision for retirement was a direct result of the loss of Columbia over the skies of Texas, and the final realization of the Shuttle's inherent limitations in safety and capability, with a shift of funding and resources toward the building of a new and more versatile space vehicle.  Whether that will now happen depends ongoing debates.  Oddly enough, the Shuttle program began with a 6 year hiatus in manned flight, and we look to repeat that again.