Posted on 02/26/2002 6:45:06 AM PST by blam
Tuesday, 26 February, 2002, 15:05 GMT
Scientists plan Pluto flyby
Golden opportunity to study Pluto
By Dr David Whitehouse
BBC News Online science editor
Many scientists are keen to plan for a Pluto encounter as the planet and its large moon, Charon, represent one of the true frontiers in the solar system that no spacecraft has ever visited.
This is despite the fact that the money for a mission to Pluto is in jeopardy as Nasa contemplates its future spending plans.
If scientists do not make plans now and be ready to act swiftly if the money becomes available, they may miss a golden opportunity to study the planet at the end of the Solar System.
They say if they do not get there soon, they may miss amazing sights that will not reoccur for almost 250 years.
Jupiter first
There are two reasons why scientists want to get there as soon as possible. The first has to do with its atmosphere.
Since 1989, Pluto has been moving farther from the Sun and as it gets colder its atmosphere will freeze out, so researchers want to arrive while there is a chance to see it.
The second reason is to map as much of Pluto and Charon as possible. The longer we wait, the more of Pluto and Charon will be shadowed for decades impeding the spacecraft's ability to take pictures in reflected sunlight.
Celestial mechanics say that an opportunity to launch to Pluto by way of Jupiter, which gives it a gravity kick, occurs in January 2006.
But given the uncertainty about the money that do not provide much time to get a probe designed and built. But if it does get off, scientists know what they want to do.
From Earth, the spacecraft will head to Jupiter, arriving just over a year later. Passing the Jovian system at 80,500 km per hour (50,000 mph) it will move on a trajectory that will arrive at Pluto and Charon as early as 2015.
The cameras on the spacecraft will start taking data on Pluto and Charon a year before it arrives and about three months from the closest approach - when Pluto and Charon are about 160,000 kilometres (100,000 miles) away - the spacecraft can make the first maps.
One day only
The busiest part of the Pluto-Charon flyby lasts a full Earth day. On the way in, the spacecraft will make the best global maps of Pluto and Charon in green, blue, red, and a special wavelength that is sensitive to methane frost on the surface.
The spacecraft will get as close as about 9,600 kilometres (6,000 miles) from Pluto and about 27,000 kilometres (17,000 miles) from Charon. During the half hour when the spacecraft is closest to Pluto or its moon, it will take close-up pictures in both visible and near-infrared wavelengths. The best pictures of Pluto will depict surface features as small as 60 meters (about 200 feet) across.
But even when it has sailed past Pluto the spacecrafts scientific life is far from over.
After passing Pluto it will retarget itself for an encounter with a Kuiper Belt Object (KBO) - one of the many large chunks of rock and ice that have been found in the cold outer reaches of the solar system in the past decade.
The team has not yet identified their target KBO, but scientists expect to find one or more the spacecraft can reach that are 50-100 kilometres (about 30-60 miles) across.
With so much pioneering science that such a probe could do researchers know they can make a case for the Pluto probe. They just hope that the politicians are listening.
Despite their proximity, Pluto and Charon are covered with bright frosts of differing compositions.
Water ice covers Charon, while Pluto's surface is predominantly nitrogen frost with traces of methane and carbon monoxide ices.
The Pluto/Charon system has a highly elliptical orbit around the sun. In 1989, Pluto was as close to the Sun as it gets during its long year - less than 30 astronomical units (AU), or 30 times the distance between Earth and the Sun. That distance nearly doubles just half a Pluto year later, to 50 AU in 2123.
As Pluto recedes from the Sun, much of its thin nitrogen atmosphere will condense as frost on the surface. This periodic reappearance of fresh frost takes place every Pluto year (248 Earth years) and is the reason that Pluto's is one of the most reflective surfaces in the solar system.
"The House and Senate ultimately went against NASA and Bush administration wishes by including $30 million for the Pluto Kuiper Express mission."
Looks like it is up to Congress. I'm not an advocate of the Pluto-Kuiper Mission; Pluto is not going to be important to space exploration for a long time to come, even if now is an opportunity to explore the planet before its atmosphere freezes once again. The next opportunity will be in a couple of centuries. Pluto can wait.
Uh....some of us are just dumb Joes who love this stuff.....I revel in your knowledge....even tho it will take me 3 or 4 hours to try and understand it.
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No one has seen the face of Pluto before Hubble's historic images. Maps derived from Hubble data shaow that Pluto has the highest contrast between light and dark regions of any planet except Earth. |
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The use of parametric cost estimation is helping engineers at NASA's Marshall Space Flight Center (MSFC) make early cost estimates for a proposed mission to Pluto. Cost estimates are critical in the early phases of projects in order to obtain budgetary approval and evaluate various approaches early in the life of the proposed program when they can have the most impact on its cost. MSFC uses a cost model developed by the government especially for aerospace program costs but it works at a very high level so it often isn't very useful for comparing alternative approaches at the subsystem level and below. In recent years, MSFC has supplemented these estimates with those provided by a commercial software package that offers the ability to create a model that is as detailed as desired and provides an extensive database that quickly generates system, subsystem and component cost estimates based on real-world experience. This approach proved very useful in providing early estimates of the cost of making the first flyby of the last unexplored planet as well as the Kuiper Belt, which lies beyond it and hasn't changed much since the solar system was created.
Pluto is the only planet in our Solar System not yet viewed close-up by spacecraft, and given its great distance and tiny size, study of the planet continues to challenge and extend the skills of planetary astronomers. Most of what we know about Pluto we have learned since the late 1970s. Many of the key questions about Pluto and its satellite Charon await the close-up observation of a space flight mission. Beyond Pluto lies the recently-discovered Kuiper Belt of "ice dwarfs" or minor planets. NASA originally planned to launch the Pluto-Kuiper Express in 2004 to conduct the first reconnaissance of Pluto and its large moon Charon with low mass flyby spacecraft, using advanced technologies to serve as a pathfinder for low cost exploration of the outer Solar System. The scientific goals of the mission were to 1) characterize the global geology and geomorphology of Pluto and Charon, imaging both sides of each 2) map the surface composition and 3) characterize Pluto's neutral atmosphere, including composition, thermal structure, and aerosol particles.
Need for a lower cost approach
Missions to the outer Solar System are by nature complex and expensive and it soon became clear that the funding was inadequate to launch the series of missions NASA had hoped for during the next decade. Last fall, NASA Headquarters announced that - because both the Pluto-Kuiper Express Mission and the Europa Orbiter mission to follow it were now certain to cost almost twice as much as the Jet Propulsion Laboratory had first suggested - the 2004 Pluto mission would be cancelled, to ensure that there were enough funds to launch the Europa mission in 2007. Europa is the subject of great scientific interest because of the possibility that it may hold life, but the Pluto cancellation nevertheless disappointed the planetary science community. They pointed out that if the 2004 launch opportunity is missed there can be no gravity-assist flyby of Jupiter to catapult them out to Pluto and that the Europa mission, on the other hand, could tolerate a launch delay without any loss of science. As a result, NASA Headquarters began soliciting proposals for a simpler, less expensive Pluto-Kuiper Belt mission, ideally one that could be flown for under $500 million.
As the request for proposals put it: "Every aspect of the investigation must reflect a commitment to mission success while keeping total costs as low as possible. Consequently, the investigation should be designed to emphasize mission success within the specified cost and schedule constraints by incorporating sufficient cost, schedule, and design margins, reserves, and content resiliency." MSFC with partners Teledyne Brown Engineering (TBE), Los Alamos National Laboratory (LANL), and NASA Glenn Research Center (GRC) put together a team of engineers from the disciplines involved, including structural, thermal control, propulsion, and avionics, in an effort to meet this challenge. These engineers developed rough order of magnitude subsystem level design specifications, in many cases developing multiple alternative designs. The MSFC/TBE/LANL/GRC design efforts resulted in a Pluto Orbiter which far surpassed the original specification for a flyby mission. Their work was turned over to the engineering cost group, the group that is responsible for developing cost estimates of various proposals for accomplishing this mission. NASA has used parametric costing methods for about three decades. One tool that they used on this project is the NASA/Air Force Cost Model (NAFCOM96) which is an innovative tool for developing a high level estimate of aerospace program costs.
SEER-H has approximately 40 knowledge bases for electronic elements and for mechanical. While SEER-H is primarily focused on the development process, it also includes manufacturing cost estimation capabilities for low volume production. The program is sensitive to the difference between mechanical and electrical elements and between labor and materials costs. It also bases the price of individual PCBs on their number of components rather than their weight, an approach that usually provides more realistic results. SEER-H allows the user to choose the probability level of estimates, and set different levels for each portion of the project. It also provides detailed sensitivity analysis features that make it possible to determine the impact of adjusting specific project factors. This feature, for instance, makes it possible to quickly estimate the impact on cost if a project schedule is compressed by two months. This software package reduces the learning curve by avoiding the use of less-than-obvious adjustments in order to present the estimating objective more clearly.
Along the same line are those that believe our sun has a companion star, Death Star, that drops by every few thousand years and disrupts the oort cloud and sends asteroids crashing into earth.
I thought that's where comets are spawned.
I though JPL was pretty good at that type of driving...
From what we know about asteroids and comets, what would be the difference except that comets have a greater percentage of volatiles for a while and wild orbits?
Oops! You are correct. I was referring to the asteroid belt between Mars and Jupiter. (Jeez...I have a 2fx3f picture of the whole system here above my desk) Hmmmm.
You can generally see comets coming for a couple of years. You never know when an asteroid is going to get ponged out
of the belt, let alone see it, track it, whatever.
Its my favorite for resetting the progress of humanity on the planet, but I don't lose any sleep over it.
Geez, you're quite the masochist. The envirowhackos complain about the internal combustion engine.
Mention "nuke" and all bets are off.
Here's how they spot incoming asteroids:
The process of discovering one of these rocks is akin to looking for a very tiny needle in a stadium-sized haystack that -- just to keep things interesting -- is very far away. Every night, Pravdo and his team aim their powerful electronic cameras at a small patch of the sky. They take three different pictures of the same spot, each one at a different time.
Then the three images are overlaid over each other, and the team uses a computer to see whether any of the objects appear to have moved over time. These moving objects are possible asteroids.
I wonder if scientists will plan a Goofy flyby?
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