Ariane 5 coloca em órbita dois satélites europeus de telecomunicações 11.03.2006 - 23h43 AFP
O foguetão Ariane 5 colocou hoje em órbita dois satélites europeus de telecomunicações, informou a Arianespace, a partir do centro espacial europeu na Guiana Francesa.
O Ariane 5 descolou às 22h33 naquele que foi o seu primeiro voo do ano. Devido a falhas técnicas, o voo já foi adiado três vezes desde o fim de Fevereiro.
A bordo do Ariane 5 seguiram o satélite de telecomunicações militares Spainsat, para o operador espanhol Hisdesat, e o satélite de difusão de rádio e televisão Hot Bird 7A, para o operador europeu Eutelsat.
A Arianespace prevê cinco a seis lançamentos ainda este ano, a partir do centro espacial de Kourou, para colocar em órbita uma dezena de satélites. No ano passado, o operador de transporte espacial europeu realizou cinco voos do Ariane 5 e três de Soiuz, para onze satélites.
Há vinte anos, na noite de 13 para 14 de Março de 1986, a sonda Giotto da ESA encontrou-se com o Cometa Halley. Foi a primeira missão da ESA no espaço profundo e fez parte de um esforço internacional ambicioso no sentido de desvendar os enigmas que rodeiam este objecto misterioso.
On February 15th NASA Administrator Michael Griffin testified before the House Science Committee about the newly submitted NASA budget for fiscal year 2007. The hearing was polite and nonconfrontational, and based upon the tone it was clear that Griffin still enjoys a tremendous amount of bipartisan support in Congress. Nevertheless, Griffin was in an awkward situation, forced to explain why NASAs budget featured substantial increases in funding for the agencys human spaceflight programs, and virtually no growthin fact, an actual cut once inflation is factored infor the agencys science programs. Less than a year earlier Griffin had announced that he would not take any money from the agencys science budget to pay for problems with its human spaceflight projects. With the refreshing frankness and honesty that is a true rarity in Washington, Griffin openly admitted that he had broken that promise. Since the introduction of the Vision for Space Exploration in 2004, it has been viewed with skepticism and considerable concern in the scientific community, including in those disciplines, such as astronomy, that are major NASA stakeholders. In the case of the Hubble Space Telescope, this concern was escalated into open conflict, with potentially damaging consequences. Similar conflict now looms with the release of the FY2007 budget request and the cuts to the science program that it proposes. The concern and conflict have been caused in part by a cultural clash between the scientific community and the agency. Both parties need to work together to find a middle ground that will enable the agency to pursue its new mandate while continuing to implement its successful and popular science program. From mission to science agency and back At the end of the George H. W. Bush administration, NASA was a rudderless agency. The administrations Space Exploration Initiative had fallen flat, and its central programthe Freedom space stationwas increasingly targeted by budget cutters looking to increase the peace dividend at the end of the Cold War. In June 1993, an amendment to eliminate the space station program was defeated by one vote on the floor of the House. While the addition of the Russians to the rechristened International Space Station program relieved some of the pressure and gave NASA a prominent international role in forging ties with Americas former adversary, the agency was still casting about for a role for the program that wouldin partvalidate the cost of the station. Forbidden by the Clinton Administration to talk about further goals such as a return to the Moon or a Mars mission, the agency turned to a scientific rationale. The space station began to be billed as a world-class laboratory in space. As the space station program limped along through the 1990s, robotic space science missions began to generate positive publicity for the agency. The Hubble observations of Comet Shoemaker-Levy 9 hitting Jupiter in 1994 and its spectacular images of distant galaxies and colorful nebulae, the successful arrival of the Galileo mission at Jupiter in 1995, and the successful landing of the Mars Pathfinder spacecraft on July 4, 1997, provided a string of major successes for the agency. These missions, coupled with the announcement by NASA researchers of potential Martian fossils in a meteorite in 1996, gained positive publicity for the agency at a time when the human spaceflight program was generating little excitement among the public. NASA leaders, realizing the value of these investigations, responded by increasing the budget for science. At the end of the first Bush Administration, science in the agency was struggling to maintain its hold on one fifth of the NASA budget; by the end of the Clinton Administration, science missions had grown to account for one third of the agencys spending. More importantly, the public identified NASA as a science agency: even the space shuttle program was selling itself on the strength of its scientific and educational accomplishments. During this period, NASA began to evolve from a mission agency to a science agency, a transformation that had a dramatic effect on the way NASA operated. Both science and mission agencies can support scientific research, but the way in which they do so is different. Mission agencies, such as the Office of Naval Research or the National Cancer Institute, support basic research that can be tied to the goal of that agencya better sonar system or a new cancer drug, for instance. The National Science Foundation, on the other hand, supports science for its own sake. It is designed to be reactive to new discoveries or new avenues of research. In short, it is the scientific community that advises science agencies about the areas in which they should invest. As science climbed in importance at NASA, the agency leadership increasingly turned to the scientists for new projects to pursue. In the wake of the Columbia accident, it was clear that NASAs human space flight activities were in need of a new rationale. Critics charged, among other things, that robots could do better science with both fewer dollars and a negligible risk to human life. In response to the accident and the need for a reinvigorated mission, the Bush administration released its Vision for Space Exploration in January 2004. The first major presidential direction that had been given to the agency since the failure of the Space Exploration Initiative, the Vision and its sweeping set of goals became the focus of the agency. Accomplishing them would require NASA to change its culture and return to its mission-oriented roots. Setting science priorities This change from science priorities to mission priorities is profound because of the way that the scientific community sets priorities. The best example of this is astronomy. Because astronomers are largely dependent on government support for new observatoriesa situation forced upon them primarily because of the high cost of many of their instrumentsthey have developed a sophisticated priority-setting system based on the scientific peer review process and the creativity of members of the community. The culmination of this process over the past forty years has been a series of survey reports on astronomy and astrophysics conducted by the National Academies. Conducted roughly every ten years, these decadal surveys summarize the current state of knowledge in the field and then look ahead and identify the most important scientific questions to be addressed and the tools needed to address them. From a policy perspective, the key feature of these reports is a prioritized list of ground- and space-based observatories requiring federal investment. The process by which the survey is conducted is designed to sift and funnel the various proposals for new observatories into a single prioritized list for the government to implement. The decadal survey process is of considerable value to both the astronomy community and to the science agencies, in part because the survey process directly engages the community. For example, the decadal survey committee and panels that conducted the survey in 19992000 were comprised of 125 astronomers from around the nation, and dozens more participated through various information gathering sessions. By engaging such a large fraction of the nations astronomers, the survey process is able to credibly represent the consensus of the community as a whole. Debates between members of the community are held inside the survey process, and the members of the community choose the winners and losers. When agencies such as NASA and the National Science Foundation fund the missions included on the decadal survey priority list, they are confident that the taxpayers dollars are supporting the most valuable projects. Furthermore, the consensus nature of the reports can be used as a shield against lobbying on behalf of individual projects, saving agency officials and congressional staff from having to be the arbiters of scientific disputesroles they may not be qualified to play. Historically, the large majority of projects recommended in the decadal surveys have been completed, without messy public debates such as those which accompanied the Superconducting Supercollider. The result is a win-win situation for the astronomers and the government: the government is confident that it is investing in the most valuable observatories, and the astronomers are confident that their desires are being heard and acted upon by the government. Perhaps the biggest testament to the value of the astronomy and astrophysics decadal surveys is that in the late 1990s, NASA requested that the National Academies conduct decadal surveys for the other scientific areas in NASAs portfolio such as planetary exploration, solar and space physics, and earth sciences. Priorities in conflict NASAs request for additional decadal surveys shows how far the agency had swung towards the science agency culture. By requesting the surveys, NASA was asking the scientific communities to set the agencys science priorities for the coming decade. When the Vision for Space Exploration was released with its own set of priorities for the agency, the competing priorities were set on a collision course. The former set of priorities was filtered from the bottom up, while the latter directed from the top down. The agency needs to find a way to reconcile the two sets of priorities in a decision-making process that keeps the best science while preparing it to complete its mission. Unfortunately, the first steps in defining a new relationship between the science priorities of the stakeholders and the needs of NASA as a reinvigorated mission agency have not gone smoothly. In an attempt to reassert the mission agency culture, NASAs FY2005 budget request, released in February 2004, divided the agencys science portfolio into exploration science and other science categories. The agency proposed that funding for science in the other category would remain essentially flat until 2020, while exploration would roughly double in size over the same period. In astronomy, the tilt was incredibly pronounced. NASA proposed in mid-2004 to accelerate the third-ranked space observatory in the decadal survey, the Terrestrial Planet Finder, and to double its proposed scope. To fund this acceleration and expansion, the second-ranked priority and a suite of other missions the agency had been planning were postponed indefinitely. This decision was based on NASAs interpretation of the Vision for Space Exploration and its determination that the Terrestrial Planet Finder mission was exploration-oriented and the other missions were not. In short, NASA was asserting its mission priorities over the astronomers science priorities. Had this change proven to be the sole reorientation involved in implementing the Vision, the astronomy community might have been persuaded to accept the new ground rules and work with the agency. Unfortunately, the budget decisions were announced in the wake of then-Administrator Sean OKeefes decision to cancel Hubble Servicing Mission SM-4. The administrator made the decision without notifying or discussing it with the NASA Advisory Council and its scientific subcommitteesa marked change from past agency practice. The Hubble decision, combined with the reorientation of the program away from the communitys priorities, portrayed an agency that was no longer willing to work with the astronomy community. The astronomers began to search for other avenues to make their voices heard. In short order they found that Maryland Senator Barbara Mikulski was eager to help. The Space Telescope Science Institute and NASA Goddard Space Flight Center, the key institutions supporting Hubble, are both in Maryland. Furthermore, Senator Mikulski was the ranking member of the Senate subcommittee that controlled NASAs appropriations, putting her in a powerful position to change Hubbles fate. After months of wrangling it became clear that the senator was not going to allow NASA to eliminate the Hubble mission. By the next spring OKeefe had resigned, and his successor, Michael Griffin, had publicly committed to saving Hubble if the space shuttles return to flight was successful. By working through the political process, the astronomers had won a pyrrhic victory. NASA was committed to conducting SM-4 once the space shuttle had returned safely to flight, but more than a year later the shuttle is still grounded. The astronomy program is spending roughly $200 million per year on Hubble, a large fraction of which is spent merely keeping the agency ready to fly SM-4. That money might well be wasted if the agency is unable to fly before Hubbles batteries failassuming the shuttle indeed returns safely to flight. Meanwhile, in this time of lean federal budgets, other NASA astronomy missions are being delayed or canceled. A conversation between NASA and the astronomy community about whether SM-4 is the best mission in which to invest could be beneficial to all involved, but because the astronomers sought a political solution such a conversation is very unlikely. Even if such a conversation were possible, it is unclear how such a conversation might take place. Administrator Griffin chose to disband NASAs advisory committees until he could rework how they functioned. Historically, the advisory committees have been the venue in which the agencys top-down priorities and the communitys bottom-up priorities have been brought together. NASA has reestablished the NASA Advisory Council, but without its previous scientific subcommittees are in place. Without these committees, it is unclear how or whether the scientific community is able to have input into NASAs decision-making process when decisions need to be made on a short timescale. Moving forward, NASAs Science Mission Directorate needs to develop a mechanism to integrate the agencys mission priorities with the communitys science priorities. NASA and the science community have come to depend on one another. The agency cannot return to an Apollo-like posture where the science priorities are driven almost entirely by the needs of the space flight program. On the other hand, the scientific community must realize that a healthy, vibrant exploration program is incomplete without a viable human spaceflight capability. By working together, NASA and the community should be able to maintain the remarkable success of the past decade while successfully implementing a new program of exploration. ________________________________________ Brian D. Dewhurst is a Senior Program Associate for the National Academies Board on Physics and Astronomy. A version of this article originally was published in the January/February 2006 issue of Space Times: The Magazine of the American Astronautical Society.
Building the International Space Station (ISS) has been a painful political and technological struggle from the beginning. When Ronald Reagan agreed to allow NASA to go ahead with its space station dream in 1984, it was to be a symbol of American technological prowess, made possible and perhaps easy by regular flights of the space shuttle. Tragically, it didnt turn out that way. The Shuttles flaws prevented it from becoming the low cost and reliable DC-3 of space that so many people in and out of NASA had hoped it would be. After the 2003 Columbia disaster, the shuttles return to flight (RTF) process has been long and, for NASA, pretty embarrassing. The successes of first RTF mission last summer were overshadowed by the pieces of foam from the external tank falling off and creating a real hazard. Providing all goes well with a series of wind tunnel tests and if the ongoing internal debate among the space operations engineers goes well, the next and final RTF mission, STS-121, will launch in Mayor perhaps July. After Discovery lands the agency hopes to resume ISS assembly flights as soon as September with STS-115. It will take at least seven shuttle missions to complete the truss, solar array, and heat radiator assembly. This mean that the heads of agency decision to launch ESAs Columbus and Japans Kibo modules before the main power and temperature control system is fully installed was not made on the basis of logic. Instead, it looks as if two factors are involved: first, the Europeans and Japanese are afraid that unless they get their station elements up there as fast as possible they will never arrive. Second, once their modules are attached they automatically receive certain privileges, including a bigger say in ISS operations. Mike Griffin seems to have decided to humor them. Satisfactorily finishing the ISS was one of the original primary goals of the Vision for Space Exploration. There are several reasons for this, but they have never been properly articulated by the administration or NASA. The first and most obvious reason to complete the station is that America should finish what it starts, while a related reason is that if at all possible its a good idea for a nation to keep its international commitments. Building the ISS with the Russians may not have kept many of their scientists and engineers from working on Irans missile and nuclear programs, but is has created a set of human relations that are valuable for their own sakes. Orbiting below the Earths radiation belts, the ISS is an imperfect place to study the effects of long-duration spaceflight on the human body. Nevertheless, it is the only place NASA now has where such studies can be done. Without the accumulated experience gathered on the ISS, long-term trips to the Moon and eventually Mars will inevitably be more difficult and dangerous. The ISS is also the place where NASA and its partners are testing new ideas for pressure suits, life support systems, and tools. Knowing how large numbers of smaller items and systems work and interface in space cannot be simulated on Earth. For the next fifteen years or so the ISS will be the only permanent human presence off Earth. The idea that after 2015 the US will wholly abandon it is just not in the cards. What is far more likely is that the US will scale back its role on the station and allow the Russians and the others to assume an ever greater, controlling role. The Europeans and Japanese will then be able to perform all the scientific research they had hoped to do at an earlier stage of the program. The US may decide that it wants to use the ISS for similar research, but that is not a decision it has to make any time soon. One of the so far unspoken roles of the ISS is that it, along with the shuttle, serve as anti-models for US future plans. Instead of relying on foreign partners, NASA is choosing to build the main elements of its future space exploration systemsthe Crew Exploration Vehicle, Crew Launch Vehicle, and Heavy-Lift Launch Vehicleitself. As a backup, NASA is going to support the private sector via the Commercial Orbital Transportation System (COTS). The plans includes the possibility that someday American astronauts will fly to the ISS, or even to the Moon, as passengers on a commercial spacecraft. This is no longer as absurd as it once sounded. After all, American military personnel can deploy overseas either on Air Force planes or regular passenger aircraft: it depends on the mission. The COTS program has at least the promise of providing alternative manned space access somewhat along the lines of the EELV program, which was designed to ensure that if one rocket fails, the US military will still have a way to get its payloads into orbit. Once the US has begun to build an outpost on the Moon, maybe around 2025, it is only prudent to have at least two ways of transporting people there and back. While the CEV and a lunar lander will be the main vehicles, having a proven commercial service available will not only provide a greater level of safety, but it will allow of the early creation of private sector lunar operations. Unlike the ISS, which is a fine example of intergovernmental relations, COTS is leading towards manned space operations with room for both governments and capitalists. NASA has had a hard time finding ways to effectively integrate non-governmental actors into its operations. If it can stick to its current concept and if the American entrepreneurial community responds, then just maybe the US will no longer have to take a back seat to Russia when it comes to the commercial exploitation of human spaceflight operations. ________________________________________ Taylor Dinerman is an author and journalist based in New York City.
Last Tuesday night a Proton M rocket lifted off from the Baikonur Cosmodrome in Kazakhstan, carrying the Arabsat 4A commercial communications satellite. The launch initially seemed to proceed normally, but several hours after liftoff International Launch Services (ILS) declared a launch anomaly: for reasons yet to be determined, the Protons Breeze M upper stage shut down prematurely and released the Arabsat satellite while still in a low transfer orbit. Without the upper stage, the satellite lacks the ability to reach its final geostationary orbit (GEO), and its operators will likely declare it a total loss, if they have not done so already.
Last weeks failure was eerily similar to one in December 1997 when another Proton suffered a launch failure and stranded its payload, AsiaSat 3, in an elliptical transfer orbit. (That failure involved a different upper stage, the Block DM.) While AsiaSat declared the satellite a total loss, the spacecrafts consortium of insurers, along with manufacturer Hughes Space and Communications (now part of Boeing), were able to salvage the spacecraft. Although the spacecraft lacked the propellant needed to reach GEO, controllers were able to perform an innovative series of maneuvers that sent the spacecraft around the Moon twice, allowing it to reach GEO. The satellite, renamed HGS-1 and later PAS-22 after being acquired by PanAmSat, was able to operate in a limited capacity for several years. According to at least one report, there is a discussion underway now to see if there is a way to use a similar technique to salvage Arabsat 4A.
The successful salvage of AsiaSat 3 raised awareness of the use of unconventional trajectories in spaceflight, not just for rescuing stranded communications satellites but also for a whole host of other applications. Some experts foresee using trajectories far more complex than the one used for AsiaSat 3, taking advantage of the chaotic physics of multibody dynamics to send spacecraft to the Moon and beyond more efficiently than conventional trajectories. Such trajectories could also explain natural phenomena like the formation of the Moon and even, perhaps, why there is life on Earth.
Vespa versus Ferrari Chaotic dynamics has its roots in one of the most famous conundrums of classical physics: the three-body problem. In the late 19th century the French mathematician Henri Poincar, trying to prove that the solar system is stable, found instead that the three-body problem could not be solved analytically. A slight change in initial conditions can result in a dramatically different outcome, making the system look unpredictable if that initial change is too small to be measured.
The classic Hohmann transfer and capture maneuver is a fuel hog, says Belbruno. Theres got to be a better way to do it. This sensitivity to initial conditions may be a challenge to theoreticians, but it provides an opportunity for those who want to leverage it in spaceflight applications. One of the first to explore the potential of chaotic dynamics in spaceflight is Ed Belbruno, a visiting researcher at Princeton University. Working as an orbit analyst at JPL twenty years agonew to the field of astrodynamics but with a doctorate in mathematicshe looked to alternatives to the traditional method to sending spacecraft to the Moon and planets. That approach, a Hohmann transfer orbit from the Earth and a capture maneuver at the destination, works well, but requires a high change in velocity, or delta-v, to perform the capture maneuver. Barring the availability of alternative deceleration techniques, like aerobreaking, this delta-v requirement translates into substantial propellant, and thus a heavier spacecraft.
I view this, along with some of my colleagues, as a fuel hog, said Belbruno during a session on chaos and astrodynamics at the American Association for the Advancement of Science (AAAS) annual meeting in St. Louis last month. Theres got to be a better way to do it.
Belbruno asked if there was a way for a spacecraft to perform a ballistic capture maneuver: to arrive at the Moon, for example, on a specific trajectory that would allow it to enter orbit without any delta-v at all. While his JPL colleagues at the time were convinced that it wasnt possible, Belbruno studied the problem and found there was a way, as he put it, to slowly creep up on the Moon, arriving such that all the forces were balanced, allowing the spacecraft to go into orbit rather than escaping from or crashing into the Moon.
Belbruno first proposed taking advantage of weak stability boundary theory in 1986 for a proposed small lunar orbiter that could be launched from a Get Away Special canister in the shuttles cargo bay. The spacecrafts thrusters were too weak to perform a conventional capture maneuver, so Belbruno proposed an alternative trajectory, using the spacecrafts thrusters to slowly spiral out from Earth and coast to the weak stability boundary, where the spacecraft would be captured into the Moons orbit, then use the thrusters to spiral down to the final orbit. The drawback was that it took the spacecraft two years to reach the Moon. The reaction the concept got within JPL, Belbruno recounted, was along the lines of very interesting, but who cares? It takes three days to get to the Moonweve been there alreadywhy take two years?
That comment encapsulates the tradeoffs involved with the application of chaotic dynamics to spacecraft trajectories: while techniques like weak stability boundary transfer are far more fuel-efficient than traditional approaches, they take far longer to execute. Its akin to the difference between a Vespa scooter and a Ferrari sports car: the Vespa gets far better gas mileage, but the Ferrari will get you to your destination much faster.
Belbruno did get a chance to put this concept into action in 1990 when the Japanese were trying to salvage its first lunar mission. Hiten was in a highly elliptical Earth orbit; a companion spacecraft, Hagoromo, was deployed from Hiten to go into lunar orbit, but suffered a communications failure. Belbruno developed a series of maneuvers that, over the course of three months, put the spacecraft temporarily into lunar orbit in October 1991. Later, ESA used a version of Belbrunos lunar Get Away Special trajectory for its SMART-1 lunar orbiter mission.
Future applications The success of Hiten and SMART-1 shows that chaotic dynamics does offer a viable alternative to traditional trajectories. The challenge in using these techniques lies not in the theory, which is based on work over a century old, but in the details implementing them in practice. This is nothing new in terms of anyone thinking of it, but it is new in terms of operationally implementing it, said David Folta of the Flight Dynamics Analysis Branch of NASAs Goddard Space Flight Center, speaking in the same AAAS conference session as Belbruno.
Traditional versus chaotic dynamics is akin to the difference between a Vespa scooter and a Ferrari sports car: the Vespa gets far better gas mileage, but the Ferrari will get you to your destination much faster. Chaotic dynamics sensitivity to initial conditions poses a problem for those who try to take advantage of it. Minor effects that are often ignored in conventional trajectory design, such as solar wind and atmospheric models, must be taken into account when using chaotic dynamics or else the trajectory can quickly diverge. This stuff getsgee, annoying isnt the word, Folta said, but after running many, many simulations, trying to come up with the right trajectory, it does become annoying.
To grapple with all those effects, Folta and his Goddard colleagues have developed models that take all those possible perturbations into account in trajectory analysis. Our models are the best we can possibly get to at this point, he said. Those models include high-precision gravitational models for the Earth and Moon, solar radiation pressure, and the solar wind. Its even to the point where the software includes relativistic effects.
Folta is looking at ways that chaotic dynamics can be used to support NASAs Vision for Space Exploration by developing trajectories for lunar spacecraft. One example he presented compared the differences between a conventional, or direct transfer trajectory, versus a weak stability transfer approach for putting a spacecraft into a 100-kilometer circular lunar orbit. The weak stability transfer approach requires nearly 20 percent less delta-v than the direct approach, which in turn can result in mass savings for the spacecraft. The tradeoff, again, is time: the direct approach gets the spacecraft to the Moon in four days, while the weak stability transfer trajectory, which sends the spacecraft out to a distance of 1.5 million kilometers from the Earth, takes 98 days to reach lunar orbit.
Such approaches can be used for a wide range of lunar missions, including polar and elliptical orbits to provide constant communications coverage over the lunar poles. The most fascinating, though, is a way thattheoreticallycould allow future servicing of the James Webb Space Telescope (JWST). Unlike Hubble, which is in low Earth orbit, JWST will be located at the Earth-Sun L2 Lagrange point, about 1.5 million kilometers from the Earth. Whereas Hubble was designed to be regularly repaired and upgraded by shuttle missions, there are no plans to make JWST servicable because of its location. However, Folta said there is a way around this by taking advantage of the intersections between Sun-Earth and Earth-Moon dynamics that would allow JWST to maneuver back closer to the Earth. Because of this intersection we could actually bring the JWST back into the Earth-Moon system. Someone could go out into the Earth-Moon system in three or four days and repair what they needed do, and then we could send JWST back out. The cost of doing that, in terms of propellant for JWST? Two kilograms, according to Folta.
The Big Splat explained The applications of chaotic dynamics go far beyond spacecraft trajectories, however. Belbruno belies that it can provide further evidence for the formation of the Moon itself. The current leading model for the formation of the Earth-Moon system is the collision of a Mars-sized body with the proto-Earth, the so-called Big Splat hypothesis. The model does a good job of explaining many of the attributes of the Earth-Moon system, including the differences in composition of the two worlds, but one major outstanding question is where the impactor came from: was this a chance encounter or an inevitable outcome of the dynamics of solar system formation?
Chaotic dynamics requires taking into account many factors that would otherwise be ignored. This stuff getsgee, annoying isnt the word, Folta said, but after running many, many simulations, trying to come up with the right trajectory, it does become annoying. Belbruno examined a hypothesis by Richard Gott, a Princeton astrophysicist, that protoplanetary material accumulated at one of the two stable Earth-Sun Lagrange points, L4 and L5. As the debris accumulated, it would start to oscillate around the Lagrange point more and more, to the point where it would eventually collide with the Earth. The problem, Belbruno said, was that classical dynamics methods suggested that such a collision would be highly improbable.
Belbruno instead looked at the problem using chaotic dynamics. He found that when the oscillation reaches a certain point the object breaks out of the Lagrange point into solar orbit, making repeated close approaches to the Earth. When the object spins around, the chance of a collision is very high, he said: about 75 percent, according to a paper he published in the Astronomical Journal in 2005. In addition, the velocity of such an impact, according to this approach, is close to what is predicted by the Big Splat model.
Chaotic dynamics might also explain the propagation of life from solar system to solar system through a process called lithopanspermia, where rock fragments bearing primitive life are blown off the surface of one world, such as in an asteroid impact, and transported to another. Classical dynamics suggests that the odds of a rock making it from one solar system to another are very low, given the distances and volumes of space involved. However, Belbruno argues that weak stability boundary transfer makes this more likely this can work, at least in fairly dense star clusters. This shows that, maybe, life did not evolve independently on different solar systems, but propagated from one to another, he said.
Lithopanspermia might seem outlandish, but chaotic dynamics seems less so now than when Belbruno was alone in advocating it at JPL two decades ago. Besides designing the trajectory used by Hiten to reach the Moon and laying the groundwork for the SMART-1 trajectory, another of his accomplishments was proposing the rescue of AsiaSat 3. He and Rex Ridenoure first suggested to Hughes in January 1998 that the spacecraft could be sent around the Moon and brought back to GEO using only the propellant onboard the spacecraft. However, while they proposed a weak stability boundary transfer approach, Hughes elected to go with a more conventional free return trajectory around the Moon; the free return approach cost more propellant but allowed controllers to keep the spacecraft in tracking range. However, given the advances chaotic dynamics has demonstrated, one wonders if the owners of Arabsat 4A will be as conservative today when contemplating the options for their stranded satellite.
Jeff Foust (firstname.lastname@example.org) is the editor and publisher of The Space Review. He also operates the Spacetoday.net web site and the Space Politics weblog. Views and opinions expressed in this article are those of the author alone, and do not represent the official positions of any organization or company, including the Futron Corporation, the authors employer.
By Guy Gugliotta Washington Post Staff Writer Monday, March 6, 2006; A07
Since 1960, humans have tried 35 times to send missions to Mars. Depending on how you count, as many as 21 have failed. Spacecraft blew up on launch, never left Earth's orbit, crashed into the Martian surface, missed going into orbit and zoomed off into space, inexplicably shut down or simply disappeared.
"Mars is hard, and Mars is unpredictable," said Jim Graf of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Mars doesn't treat you very well."
Despite this record, Mars today has three satellites orbiting overhead, two rovers crawling around its surface -- and it appears destined to have an operating, robotic "human presence" in the neighborhood indefinitely.
The plan is to solve the mystery of how a world apparently once wet and warm turned into the chill, windblown wilderness that is Mars today. "We want to know whether it was habitable, whether life got started and, if it did, how it evolved," said geologist Raymond E. Arvidson of Washington University in St. Louis, who reviews the Mars program for NASA.
This Friday afternoon, barring a catastrophe like those that have doomed four missions in the past eight years, NASA's Mars Reconnaissance Orbiter will begin the rocket burn that will put it in orbit as the planet's fourth working satellite.
This is not a slam dunk. For a nail-biting half-hour during and after this process, the spacecraft will be out of contact behind Mars, while project manager Graf and the rest of the mission team wait to find out whether the planet has captured the new satellite or shot it back into space, never to return.
"We're on the money right now," Graf said at a recent news conference as the orbiter began its final approach. "But we are getting into the dangerous portion of the mission. A lot can go wrong, and if we don't succeed, we will fly right by the planet."
But win or lose, the human presence will endure. Functioning spacecraft have been on station at Mars since 1997, with new missions planned for launch in 2007, 2009 and beyond. And if humans ever actually land there to fulfill President Bush's "Vision for Space Exploration," they will have benefited from decades of research detailing such aspects as radiation hazards and the likeliest places to mine water ice.
"The missions we're doing for the next 10 years are pathfinders," said Arvidson, who chairs NASA's Mars Exploration Program Analysis Group. "We're doing the robotic precursor work -- picking out the best sites where humans on the surface can do the detailed studies."
At the dawn of the space age 50 years ago, many people still had the idea that Mars might be a habitable planet, not as threatening as the Mars of H.G. Wells's "The War of the Worlds" but a place that might harbor advanced life forms. "We were still making maps with canals on them," Arvidson recalled.
That archetype was dashed in 1965 when the flyby of the Mariner 4 spacecraft showed a barren, crater-pocked surface like Earth's moon. But over time, patient exploration revealed a much more complex landscape -- one perhaps sculpted in the past by flowing water.
Mars's three currently operating satellites -- NASA's Mars Global Surveyor, which arrived in 1997, NASA's Mars Odyssey and the European Space Agency's Mars Express -- developed this theory, and in 2004 the Mars rover Opportunity confirmed it by identifying sedimentary rock laid down in what had been a set of ancient lake beds.
"We have used the 'follow the water' strategy," said the Jet Propulsion Lab's Fuk K. Li, who oversees NASA's Mars exploration program. "In trying to understand whether life ever arose on Mars, water is key."
The Reconnaissance Orbiter will continue the theme. The spacecraft has a telescopic camera sensitive enough to spot boulders in ancient flood channels, a spectrometer to identify minerals formed by water processes, a "climate sounder" to measure atmospheric water vapor, and a radar capable of probing beneath Mars's surface in search of ice, or, possibly, liquid water.
"This is going to be a real intellectual leap forward," said Michael Meyer, NASA's lead scientist for the Mars program. "You can start looking at [geological] processes -- hot springs, gullies, volcanoes -- and we can spot many more minerals."
But first, the spacecraft has to get there safely. Launched from Cape Canaveral Air Force Station on Aug. 12, 2005, the $720 million Reconnaissance Orbiter has had up to now a flawless trip, needing only two course corrections to get into position for orbit insertion near Mars's south pole.
About 4:25 p.m. Eastern time Friday, the spacecraft's main thrusters will begin a pre-programmed 27-minute burn to reduce its speed by 2,200 mph, allowing Mars to capture it into orbit.
About 20 minutes later, the spacecraft will disappear behind Mars for a half-hour. During that time the burn will end, but engineers will not know the fate of the mission until they regain radio contact.
At that point, if all goes well, the Reconnaissance Orbiter will be in a highly elliptical, near-polar orbit, with its closest approach 249 miles above the south pole, and its farthest point at 27,340 miles from the north pole.
After systems and instrument checkouts, engineers will begin "aerobraking" by the end of March, dipping the spacecraft into the Martian atmosphere on every pass to slow it down and bring it into a much tighter ellipse.
This will take about six months and "must be done in a controlled fashion," Graf said, because upward "spikes" in the Martian atmosphere could increase friction on the satellite, causing it to overheat. Mistaking English measurements for metric measurements during aerobraking caused NASA's Mars Climate Orbiter to break up in the Martian atmosphere in 1999.
Current plans call for the Reconnaissance Orbiter to settle into a working "science orbit" between 199 and 158 miles above the Martian surface and spend two years surveying, mapping, hunting for water and investigating landing sites for future Mars missions.
At the end of that time, engineers will shift the spacecraft into a higher orbit from 217 to 255 miles above the surface, where it will serve primarily as a communications relay. The orbiter has more data capacity than the rest of the Mars satellite fleet combined, Meyer said, holding "about as much information as there is in a video store."
The heads of space agencies from Canada, Europe, Japan, Russia and the United States met at the Kennedy Space Center on March 2 to review International Space Station cooperation and endorse a revision to the station configuration and assembly sequence. At today's meeting, the Heads of Agency were also briefed on the status of ongoing International Space Station operations and flight hardware development activities across the partnership. The partners reaffirmed their agencies' commitment to meet their mutual obligations, to implement six person crew operations in 2009 and an adequate number of shuttle flights to complete the assembly of the space station by the end of the decade.
The partners also affirmed their plans to use a combination of transportation systems provided by Europe, Japan, Russia, and the United States to complete space station assembly in a timeframe that meets the needs of the partners and to ensure full use of the unique capabilities of the space station throughout its lifetime.
The International Space Station Heads of Agency expressed their appreciation for the outstanding work being conducted by the space station on-orbit crews and ground support personnel. They commended them for their creativity in making full use of available resources to operate the space station, prepare for assembly missions and carrying out scientific research aboard the station.
The uninterrupted flow of Russian vehicles, the outstanding performance of Canadarm2, the successful shuttle logistics flight, and the resourcefulness of all of the partners' ground-based engineers, researchers and operations personnel have served to highlight the strength of the International Space Station partnership and the importance of international cooperation in space operations.
The partners look forward to the upcoming space shuttle flight of the STS-121 mission, a return to International Space Station assembly activity and a permanent crew of three.
They also noted the upcoming launch of key space station elements such as: three additional power trusses to support overall International Space Station needs and the needs of the partners; the European Space Agency Automated Transfer Vehicle; the U.S. Node 2; the European Space Agency Columbus Module; the Canadian two-armed Special Purpose Dexterous Manipulator Dextre; the Japanese Experiment Module Kibo; the Russian Multipurpose Laboratory Module and the Japanese H-2 Transfer Vehicle.
These elements of the space station program will bring to fruition the partnership's goal of operation and use of a permanently inhabited civil International Space Station.