Recently we’ve been talking about long-distance repair, and how any probe launched beyond the Solar System is going to have to fix its own problems rather than relying solely on transmissions from Earth. New Horizons, halfway to Pluto/Charon in terms of distance, isn’t yet in that category. It’s going to eventually make its way into the Kuiper Belt, but for now, it’s close enough for controllers to wake it up periodically for checks. In fact, the next wakeup call, which comes tomorrow, begins a nine-week period of rigorous tests.
Long-term missions like New Horizon demand annual checkouts, and this one (as opposed to last year’s) is to be comprehensive, ranging from conducting heliospheric cruise science to uploading a series of code enhancements and bug fixes to the spacecraft’s fault protection software. The spacecraft’s backup systems will be checked and its seven scientific instruments re-calibrated. Principal investigator Alan Stern describes the process in his latest report.
I wanted to work New Horizons in this morning anyway because of Ron Miller’s image in that report of what we might find when the spacecraft reaches its destination. After the surprises we’ve had every step of the way in exploring the Solar System, it wouldn’t be at all out of line to find geysers like these on Pluto — think of the ‘ice volcanoes’ of Triton, or the geysers of Enceladus. Here the artist is imagining liquid nitrogen or methane as the source, creating a weird and evocative landscape that we’ll glimpse only too briefly come the 2015 flyby.
Not all fixes to a spacecraft involve repairing malfunctioning systems. In the case of New Horizons, it’s also necessary to keep a close eye on the course. With the vehicle well into the outer Solar System, it’s interesting to speculate about what forces could be causing the need for a course correction. No, it’s not the so-called ‘Pioneer Anomaly,’ but the reflection of thermal photons from New Horizons’ radioisotope thermoelectric generator (RTG) striking the back of its high-gain antenna. A tiny effect multiplied over four years has consequences.
The fix is to be a June 30 course correction involving a change in speed of about 1.5 kilometers per hour. The 30-second thruster burn will make New Horizon’s first course change since late 2007. Also coming up this summer are cruise observations of Jupiter, Uranus, Neptune and Pluto itself, along with four weeks of observations of the space plasma environment near the orbit of Uranus.
Stern’s report mentions a workshop at the Space Telescope Science Institute in Baltimore devoted to Pluto’s recently discovered moons Nix and Hydra. One of the goals here is to get a precise fix on the orbits, sizes and masses for the two moons, useful information in planning for the 2015 flyby. Says Stern:
Studying Nix and Hydra from here on Earth (or even in Earth orbit) is hard, owing to their great distance, small size and extreme faintness. But over the past five years we’ve accurately mapped out their orbits, determined their colors, and constrained their diameters to be between about 40 and 145 kilometers (about 25 and 90 miles). It has also become clear that Nix and Hydra are somehow intimately related to Charon, as evidenced by their similarly circular and near-zero inclination orbits, and their orbital periods, which are extremely close to being exact multiples of Charon’s.
Eventually we’ll be sending missions to destinations much further than Pluto/Charon. As of this writing, New Horizons is 2,506,760,000 kilometers from the Sun, making for a light-delay time of 2 hours, 12 minutes. Getting around light delays of months or even years will involve the kind of AI systems we’ve talked about in recent posts. The Project Daedalus starship study envisioned robotic ‘wardens’ that could handle needed repairs, but these days we can talk about ‘evolvable’ hardware and ‘genetic algorithms’ as we look toward systems that can heal in-flight maladies and create the necessary tools to keep a space probe whole.
Congratulations to JAXA, the Japan Aerospace Exploration Agency, for the successful launch of the IKAROS space sail, launched from the Tanegashima Space Center along with the Venus Climate Orbiter yesterday evening US time. The launch was a beautiful sight via JAXA’s Internet feed and we now have the opportunity to shake down solar sail technologies in space, from deployment to navigation and maneuvering. The mission sequence ahead is shown in the diagram below, but as we wait for further news, a special nod of appreciation for IKAROS project leader Osamu Mori and the fine team that has made this solar sail a reality.
Image: After separation from H-IIA, IKAROS will spin at up to 20 rpm, deploying the sail membrane and generating solar power by means of thin film solar cells (minimum success level) within several weeks. Acceleration and navigation using the solar sail will then be demonstrated (full success level) within half a year. Credit: JAXA.
The AKATSUKI climate orbiter is a fascinating mission in its own right, but we focus on IKAROS because our brief in these pages is the technologies that may one day be adapted for deep space, and solar sails have a bright future in helping us travel without carrying propellant. Future sails will experiment with microwave and laser beaming as we learn how sails can operate far from the momentum-inducing photons of the Sun. Also fascinating in terms of IKAROS is JAXA’s hybrid design, which will generate solar power aboard the craft and, in coming iterations, test the capabilities of an integrated ion engine. Japan’s ultimate sail target is Jupiter.
The video below shows how IKAROS will deploy its sail, a maneuver that is the most crucial of the mission. Meanwhile, Louis Friedman reported to Planetary Society members yesterday that the LightSail program is on track for the launch of LightSail-1, the first in a series of three sail attempts that will dovetail nicely with IKAROS’ investigations of solar sail capabilities. LightSail-1 is to be ready for launch by the end of this year, with the actual launch date dependent upon the choice of launch vehicle. Like IKAROS, LightSail-1 will piggyback aboard another mission.
Local space news is complemented by news from the heliopause as we learn that the recent problems of Voyager 2 were caused by ‘one flip of a bit in the memory of an onboard computer,’ according to NASA. Scientists at the Jet Propulsion Laboratory were able to recreate the effect on a computer at their site and, on May 19, were able to reset the computer bit, with engineering data confirming success on Thursday. If all continues to go well, the receipt of science data will resume on May 23. Thus would end the furthest repair operation yet attempted, but only a precursor to what will be needed as we push into the Kuiper Belt and destinations beyond.
I once had an uncle who, in his eccentric way, taught me the glories of reading widely and across many disciplines. Every year he would visit us from Florida and each time he came, he was off on another tangent, usually a scientific pursuit of some kind, and now and then a venture into linguistics. One of his more memorable visits found him arriving with a set of slides he had made from books on Egyptian hieroglyphics, and we went through them one at a time as he explained what he had learned about Egyptian culture by mastering these symbols.
Hieroglyphics Meet the Machine
I think about that every time I ponder the fate of digital data, and this Reuters story, which mentions hieroglyphics, triggered the memory. For as Andreas Rauber (University of Technology of Vienna) points out, hieroglyphics — or, for that matter, stone inscriptions or medieval manuscripts — have a shelf life of millennia, and have proven it. In my own wandering way, I was for a time focused on medieval manuscripts and recall wonderful moments at the British Museum and the Háskóli Íslands (Reykjavík) studying documents that recorded the stories, as well as the daily business and musings, of societies a thousand years old.
There’s a fascination in working out the conventions of a medieval scribe, but in the modern world, we have an equally thorny task in sorting out digital formatting. We live by data in our time. 100 gigabytes of data (the article points out this is equivalent to about 23 tons of books) have been created for every individual on the planet, and Adam Farquhar (British Library) notes that this amounts to about a trillion CDs worth of data spread across the globe. Farquhar and Rauber are worried about our continuing access to these data. Says Farquhar:
“Einstein’s notebooks you can take down off the shelf and read them today. Roll forward 50 years and most of Stephen Hawking’s notes will likely only be stored digitally and we might not be able to access them all.”
International Data Corporation says the size of the digital universe will expand by ten-fold, from 161 billion gigabytes (exabytes) in 2007 to 1800 exabytes in 2011. The figure is predicted to double every eighteen months. Yet amidst the data avalanche, we live in a world where CDs and DVDs have an exceedingly short life expectancy and many data backups may simply fail when the time comes to access them. We’re learning how to spread the backup into the ‘cloud’ of networked computers, but haven’t solved the many security issues that involves.
Preserving Changing Formats
Even more telling is the fact that we continue to change data formats seemingly at whim. Change that improves things is always welcome, but our digital rush to the future often seems to move to its own whimsical music. Trying to upgrade the software I use for Centauri Dreams, I find that the new version’s coders have re-written key aspects of the programming environment, so that all the formatting I put into the header design would simply fail if I made the ‘upgrade’ without digging into the code myself and making a set of manual fixes.
Well, I’ll do all this because new features are available (and be aware of this in the next week or so if the site suddenly starts acting strangely), but there is such a thing as backwards compatibility. And this is the tiniest of problems compared to what decades, not to mention centuries, of ongoing change could do to data stored cavalierly because access is assumed.
What Rauber and Farquhar intend to do about all this is to preserve a ‘digital genome’ deep in the Swiss Alps in a secret bunker, where the needed information to read all our formatting is made available to future generations. The sealed box is buried somewhere near the town of Gstaad, in a data facility known as the Swiss Fort Knox in the Bernese Oberland, an installation that consists of two underground data centers that are 10 kilometers apart but connected by high-speed networking. The facility is in a former military nuclear bunker designed to offer physical protection against all manner of environmental disasters.
Going Deep in Switzerland
Behind the burying of this ‘digital genome’ is the Planets project, which links European libraries, archives and research institutions in an attempt to preserve both software and hardware assets as older versions of each are superseded. Inside the box are at risk digital formats, from JPEG photographs to messages in Java, films in .MOV format and documents in PDF. Here’s how the project describes the contents of the Planets TimeCapsule:
Each object is stored in its original format and a new format more suitable for long-term preservation such as PDF/A, TIFF, JPEG2000 and MPEG4. The objects are stored on media that range from paper, microfilm and floppy discs to CDs, DVDs and flash-drives and HDDs.
Inside the box are the original and new objects, storage media, and some reading devices. It also includes conversion tools that were used to migrate the objects as well as software to open and view/use these objects and supporting software all the way down to an operating system; descriptions of the file formats, of the file systems and encodings used on the storage media; and description of all these objects and their relationship to supporting technology and recognised standards.
And yes, an online version is to be provided, while replicas will be available to libraries, archives, science museums and other interested parties. The need will surely grow for it to be augmented on a regular basis as our formats continue to sprout changes and extensions. Anyone who has been using computers for a sufficient time will be aware of how acute this issue can be. I think of the hundreds of articles, reviews and columns I wrote in the 1980s using the now defunct XyWrite program, which began with straight ASCII data formats but gradually changed so that its files were unreadable without the program. I would have to locate some very old software if I had a need to get into the digital versions of all this work today.
For more about the Planets project, you can download a brochure here. I notice that it’s in the baleful PDF format, all but universal for the dissemination of scientific papers, yet balky and bloated and forever at the mercy of Adobe. Every digital ‘upgrade’ has its advantages, or at least most of them do, and getting the most out of our data is in the hands of good coders, but as our bits and bytes head inexorably into the future, we’d better hope that data preservation eventually becomes built into every operating system we run on our machines, and that the future web of interconnections keeps the knowledge of past formats always at hand.
Raw images from Cassini’s Enceladus encounter yesterday are becoming available, the most fascinating of which show the view of the plumes as the spacecraft approached the moon from the night side. And check the image below, which is an extraordinary combination of Cassini targets the like of which I never thought I would see. At the bottom of the image, darkened almost to invisibility, is Enceladus’ south pole as the spacecraft speeds over its surface (click on the image to enlarge). Swinging into view beyond it are Saturn’s rings and Titan, its atmosphere clearly visible. Cassini will make a Titan flyby late this evening, in the early hours of May 20 UTC, this time passing to within 1400 kilometers of the surface in a study that will fill out Titan’s thermal map.
Enceladus and Titan are so aligned that Cassini will be able to make this second flyby with no additional maneuvering required. By studying the gravitational pull on the spacecraft, researchers hope to learn more about Titan’s internal structure, including whether a liquid ocean is found under the surface. At Enceladus, the goal is to analyze data from the ultraviolet imaging spectrograph to look for molecular hydrogen in the plumes, a reading that will offer clues about the moon’s interior. The following image is also a stunner, clearly showing the backlit plumes that give Enceladus such high astrobiological interest.
Meanwhile, Steinn Sigurðsson (Penn State) notes that the large number of spacecraft now operational in the Solar System, many powered down for cruise, provide interesting possibilities for deep space studies. Indeed, the Keck Institute for Space Studies is sponsoring a two-day mini-workshop at the Kavli Institute for Theoretical Physics on potential exoplanet observations. A case in point is the work performed by EPOCh (Extrasolar Planet Observations and Characterization), part of the EPOXI extended mission of the Deep Impact spacecraft, which examined the Earth/Moon system to learn how future planet hunter spacecraft would evaluate their findings.
Of course, doubling or tripling up on ongoing science is not always easy, as Sigurðsson notes:
…scheduling is completely subservient to prime mission requirements, including delays and rescheduling; and, particularly during the pre-prime mission cruise phase, the secondary science must not jeopardize the mission, instruments or spacecraft.
So, there is a trade-off there between wanting to exercise the instruments and get calibrations etc, vs risking damage, for example to moving parts (reaction wheels, gyros etc), power systems (degradation, thermal cycling etc), and optics and electronics due to exposure or thermal cycling.
The best course for using existing spacecraft, then, may be to wait until their primary missions are over. Even then, the choices are not easy:
…ongoing observations have a cost: communications, spacecraft operations and data analysis cost real money, and have a significant manpower demand, which adds up, so it is not obvious that it is cost-effective or worthwhile to run the secondary science, for the community overall – as opposed to the particular group wanting to use the particular capability.
Such factors mean there will be much to discuss at the workshop. You’ll recall from our previous coverage of EPOCh that the spacecraft, now enroute to comet Hartley 2, has targeted several known transiting exoplanets in a search for undiscovered worlds in those systems. Results of the analysis are now becoming available and demonstrate how missions can be extended in useful ways for the benefit of the exoplanet community. One wonders whether Cassini has possibilities in this direction after its extended mission is complete.
For one look at EPOCh results, see Ballard et al., “A Search for Additional Planets in the NASA EPOXI Observations of the Exoplanet System GJ 436,” submitted to the Astrophysical Journal (preprint).
Two versions of Icarus are on my mind today. Well, actually three. The first is the Japanese solar sail/solar cell hybrid called IKAROS, scheduled for launch today but scrubbed because of the weather at Tanegashima. The new launch date is Thursday May 20 at 2158 UTC (1758 EDT). IKAROS will piggyback aboard the JAXA H-2A booster with the Venus Climate Orbiter (AKATSUKI), and will be a ground-breaking shakedown of solar sail technologies in interplanetary space. Needless to say, we’ll follow this one with interest as solar sails move to the next level of testing.
Meanwhile, Kelvin Long reports that Project Icarus, the joint-undertaking between the British Interplanetary Society and the Tau Zero Foundation, made the pages of the London Metro newspaper recently. Be sure to click ‘This Week’s Graphic’ at the bottom of the article to view the whole story. Icarus, often discussed in these pages, is the successor to the BIS Project Daedalus starship study, and seeks to examine fusion propulsion and other technologies in light of the advances we’ve made in the last thirty years. The Metro has a bit of fun with the project but also makes a few errors, including discussing Ad Astra’s VASIMR design as an example of fusion propulsion.
The article also cites Epsilon Eridani as Icarus’ destination, although that’s very much up in the air as the team continues to evaluate the matter, knowing how important the ongoing studies of Alpha Centauri are, and the possibility that WISE may turn up a brown dwarf closer than Alpha Cen. And while it’s useful to get antimatter described in so public a venue, the Icarus team is not looking at antimatter as anything more than a possible fusion catalyst, which reduces the amount needed to far more manageable proportions and builds on work begun at Pennsylvania State University through projects like AIMStar, which was a conceptual design for a mission to 10,000 AU using antimatter in a fusion engine that would reach the Oort Cloud.
All the jokey bits aside, the Metro story does one thing I’ve rarely seen accomplished in the media when it comes to interstellar ideas — it looks at using the Sun’s gravitational focus to enhance communications. Thus this:
[Einstein’s] theory of relativity predicted a phenomenon known as gravitational lensing. Massive objects — like stars and galaxies — have enough gravitational influence that light (or radio waves) that pass that object become bent in toward it. This means that when they have passed the object, they have been bent in towards each other (just as light passing through a lens has). All the observer has to do is find the point where they come together (the focal point) and he will observe a greatly amplified signal — effectively shortening the communication distance between Icarus and Earth.
We’d better untangle this, too. The communication distance between Icarus and the Earth isn’t ‘shortened’ by gravitational lensing, but the amount of power needed to get a usable signal back to Earth from Icarus is hugely reduced, which means a reduction in the Icarus payload, and that’s a very good thing. With gravitational lensing, too, while there is a focal point, the gravity-focused signal continues along the focal axis for distances beyond the 550 AU lensing distance from the Sun, so there is no need to stop a lensing spacecraft at 550 AU for station-keeping. To my knowledge, Icarus is the first mission concept other than the FOCAL design being developed by Claudio Maccone to explore the possibilities of the gravitational lens.
Image: Landscape with the Fall of Icarus was once thought to be the work of Pieter Bruegel, though the attribution is dubious. You can see the fallen Icarus in the water near the ship, even as the shepherd at the center of the painting looks skyward, as if pondering Icarus’ journey, and perhaps seeing the still airborne Daedalus circling the scene. Credit: Wikimedia Commons.
Thinking about Icarus and the public brings me to the third ‘Icarus’ I’ve thought about today, the classical figure himself. Icarus was, of course, the son of Daedalus, the man who created wings and flew into the heavens. I’ve had a few emails asking whether a starship named Icarus wasn’t asking for trouble. After all, the original Icarus flew too close to the Sun and fell to his death. But an internal document circulating among the Icarus team helps to explain the matter. It cites a quote from Arthur Eddington’s Stars and Atoms (Oxford University Press, 1927):
In ancient days two aviators procured to themselves wings. Daedalus flew safely through the middle air and was duly honoured on his landing. Icarus soared upwards to the sun till the wax melted which bound his wings and his flight ended in fiasco. The classical authorities tell us, of course, that he was only “doing a stunt”; but I prefer to think of him as the man who brought to light a serious constructional defect in the flying-machines of his day. So, too, in science. Cautious Daedalus will apply his theories where he feels confident they will safely go; but by his excess of caution their hidden weaknesses remain undiscovered. Icarus will strain his theories to the breaking-point till the weak joints gape. For the mere adventure? Perhaps partly, this is human nature. But if he is destined not yet to reach the sun and solve finally the riddle of its construction, we may at least hope to learn from his journey some hints to build a better machine.
Thus the purpose of Project Icarus, to strain theory to the breaking-point to find the weak joints. As an engineering study, Icarus isn’t about building a starship soon, but rather about making an assessment of where our technology is today and where we stand in terms of our understanding of interstellar flight. Over 10,000 hours of research time went into the original Daedalus study, some of it in the whimsical setting of London’s Mason’s Arms pub, which tells me the Daedalus team was possessed not only of a burning desire to study interstellar flight, but also of a sense of humor. The current team shows many of the same traits, reminding us that designing a probe that can go into deep space is a marvelous help for keeping things in perspective.
In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For many years this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image courtesy of Marco Lorenzi).
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