quarta-feira, 28 de novembro de 2007

NASA apresenta planos para missão tripulada a Marte

Quem segue estas questões da exploração do espaço sabe que planos nunca faltam, por isso estes planos poderão parecer apenas isso - apenas planos. Têm de significativo, no entanto, virem da própria NASA, o que lhes poderá conferir alguma credibilidade. No entanto ainda fazem referência a tecnologias muito futuristas e não testadas, como a propulsão nuclear.

Note-se também o prazo alargadíssimo de uma possível missão a Marte - 2031, ou seja, a 24 anos de distância. Muitos de nós não veremos homens a caminhar em Marte, mesmo que a NASA, por uma vez na sua existência, pudesse cumprir os prazos definidos nos seus planos.

Mas vale a pena a leitura da apresentação oficial.

Fonte: Flight Global

NASA manned Mars mission details emerge
Rob Coppinger

A 400,000kg (880,000lb) Marship would be assembled in orbit using the Ares V cargo launch vehicle for a 900-day mission to the red planet, according to details that have emerged about NASA's new Constellation programme's manned Mars mission.

The spacecraft would take a "minimal crew" to Mars in six to seven months, with the crew spending up to 550 days on the surface, according to the programme's design reference architecture 5.0, currently in development.

Each of the three to four Ares V rockets used to launch the Marship elements into low Earth orbit would need a 125,000kg payload capacity and use a 10m (32.7ft) fairing.

Crews would be sent every 26 months, will need up to 50,000kg of cargo, use an aerodynamic and powered descent method and the 40min communications delay between Earth and Mars would require autonomy or at least asynchronous operation with mission control.

Notionally launched in February 2031, the first crew's flight would be preceded by the cargo lander and surface habitat being sent in December 2028 and January 2029, respectively using two Ares V launches.

The lander will arrive around October 2029 and the habitat November the same year. Nuclear power is the preferred surface energy source. The crew will arrive in August 2031.

A second mission's habitat and lander will be launched by two Ares Vs in late 2030/early 2031 to reach Mars at the same time as the first crew. In the first quarter of 2033, the second mission's crew will leave Earth to arrive at Mars by December, while the first crew leaves Mars in January 2033 after a 17-month stay, to reach Earth by September.

The details were included in a presentation at "Enabling Exploration: The Lunar Outpost and Beyond", the October meeting of NASA's Lunar exploration analysis group.

It also states, "Conjunction class missions (long-stay) [have] fast inter-planetary transits. Successive missions provide functional overlap of mission assets," referring to the presence of a following mission's habitat and cargo lander being on Mars when its preceding mission's crew are there already.

quinta-feira, 15 de novembro de 2007

O Cometa Holmes é agora maior do que o Sol!

Imagem à escala.
Clique para aumentar.

Tem agora um diâmetro de 1.4 milhões de quilómetros, sendo assim o maior objecto do Sistema Solar! É visível a olho nú.

Fonte: David Jewitt

Spectacular outbursting comet 17P/Holmes exploded in size and brightness on October 24. It continues to expand and is now the largest single object in the Solar system, being bigger than the Sun (see Figure).

The diameter of the tenuous dust atmosphere of the comet was measured at 1.4 million kilometers (0.9 million miles) on 2007 November 9 by Rachel Stevenson, Jan Kleyna and Pedro Lacerda of the University of Hawaii Institute for Astronomy. They used observations from a wide-field camera on the Canada-France-Hawaii Telescope (CFHT), one of the few professional instruments still capable of capturing the whole comet in one image.

Other astronomers involved in the UH program to study the comet include Bin Yang, Nuno Peixinho and David Jewitt. The present eruption of comet Holmes was first reported on October 24 and has continued at a steady 0.5 km/sec (1100 mph) ever since.

The comet is an unprecedented half a million times brighter than before the eruption began. This amazing eruption of the comet is produced by dust ejected from a tiny solid nucleus made of ice and rock, only 3.6 km (roughly 2.2 miles) in diameter.

The new image also shows the growth of a tail on comet Holmes (the fuzzy region to the lower right in the comet picture), caused by the pressure of sunlight acting on dust grains in the coma. Over the next few weeks and months, the coma and tail are expected to expand even more while the comet will fade as the dust disperses.

Comet Holmes showed a double outburst in November 1892 and January 1893. It is not known if the present activity in the comet will follow the pattern from 1892, but continued observations from Mauna Kea are planned to watch for a second outburst. Most comets show small fluctuations in brightness and some have distinct outbursts.

The huge event on-going in comet Holmes is unprecedented, however.
The orbit period of comet Holmes is about 6 years, putting it in the class of Jupiter Family Comets whose orbits are strongly influenced by Jupiter. These objects are thought to have spent most of the last 4.5 billion years orbiting the Sun beyond Neptune, in a region known as the Kuiper Belt. Holmes probably was deflected into its present orbit within the last few thousand years and is losing mass as it evaporates in the heat of the Sun. In another few thousand years it is likely either to hit the Sun or a planet, be ejected from the Solar system, or simply die by running out of gas.

Contacts Rachel Stevenson [rach@ifa.hawaii.edu 808-956-6680] David Jewitt [jewitt@ifa.hawaii.edu 808-956-7682]

David Jewitt. Last updated 09 Nov 2007

quarta-feira, 14 de novembro de 2007

Space Shuttle Atlantis deslocado para a torre de lançamento

Em preparação da missão STS-122, que com alguma sorte poderá ser lançada ainda no início de Dezembro, o que revela um ritmo de lançamentos bastante alto para a NASA!

A NASA pretende lançar o Atlantis no início de Dezembro para evitar problemas de ordem informática com uma estadia em órbita durante a passagem de ano, apesar de já terem sido feitos testes, com resultados positivos, acerca destes possíveis problemas.

Será mais uma missão de montagem da Estação Espacial Internacional ISS, em que será montado o módulo Colombus, da Agência Espacial Internacional (ESA).

Sinto alguma pena em ver que, agora que foram resolvidos diversos problemas graves do Shuttle, e se tenha alcançado esta eficiência, se vá desistir do programa Shuttle, para voltar atrás 50 anos e voltar a usar tecnologias dos anos 60!

terça-feira, 13 de novembro de 2007

Primeiras imagens de alta resolução obtidas da órbita da Lua

Imagens obtidas pela sonda japonesa Kaguya / Selene. Filme disponível aqui (recomendado).

Fonte: JAXA

sexta-feira, 9 de novembro de 2007

Mulheres, lancem-se ao espaço!

É a mensagem de Peggy A. Whitson, comandante da Estação Espacial Internacional ISS, e de Pamela Melroy, Comandante do Space Shuttle durante a sua última missão. Foi a primeira vez que o espaço foi 'comandado por mulheres'. E a nota foi alta!

Fonte: MSNBC

Female space pioneers tell girls to aim high
Women make history in orbit as young audience attends aerospace forum
By Marcia Dunn
The Associated Press
updated 4:26 p.m. ET Nov. 2, 2007

CAPE CANAVERAL, Fla. - As two women circled overhead in charge of their respective spacecraft, the first female shuttle commander, the first female space tourist and other female trailblazers gathered Friday to encourage girls to aim high.

Peggy A. Whitson, left, is the international space station's
first female skipper and Pamela Melroy is the space shuttle Discovery
commander. The joint mission marks the first time both spacecraft have been
commanded by females simultaneously.

"It's just not a crazy thing anymore to have women flying in space," said retired astronaut Eileen Collins, who commanded two shuttle flights. "It's just normal and it's accepted."

Discovery's commander, Pamela Melroy, and the international space station's first female skipper, Peggy Whitson, are the first women to be in charge of two spacecraft at the same time.

Melroy and Whitson are showing it does not matter whether someone is male or female, "it's how you do the job and your dedication to the mission," Collins said.

"I'd fly with them any day," she added.

Nearly 400 girls packed an IMAX theater at the Kennedy Space Center Visitor Complex for the pioneering women of aerospace forum, part of an expo celebrating NASA's 50th birthday in just under a year.

Joining Collins on the stage was Kathryn Sullivan, NASA's first female spacewalker; Iran-born businesswoman Anousheh Ansari, who paid a reported $20 million for a Russian rocket ride to the space station last year; the first female pilot for the Air Force Thunderbirds and the first female solo pilot for the air-demonstration squadron; and a high-ranking Federal Aviation Administration official.

Sullivan told the young audience — a sea of green vests decorated with scouting patches — to ignore the inevitable naysayers in the ever-present peanut gallery.

She recalled that when she was graduating from high school, some of her friends told her that when they were younger they would deliberately switch the conversation to baby dolls every time she mentioned airplanes.

"They thought they'd eventually get me over it," Sullivan said with a smile.

Collins said she never told anyone she wanted to be an astronaut when she was young.

"I was afraid they were going to say, 'You can't do that, you're a girl,' " she said. "So I just never told anybody and, in my own plan, I went out and did it."

The six panelists talked about how they set their sights early on, sometimes stumbled onto their interests, and overcame stereotyping and adversity. The two Thunderbird pilots, performing at the weekend expo, provided a glimpse into their jobs.

"What's really neat is in 3 1/2 hours I'm going to be going 500 mph three feet away from some other people," said Air Force Maj. Nicole Malachowski.

terça-feira, 6 de novembro de 2007

Cometa 'explosivo' visível a olho nú.

Foi designado Cometa 17P/Holmes.

Trata-se de um cometa que explodiu recentemente, tornando-se maior do que o planeta Júpiter (o maior do nosso sistema solar!). Agora é visível a olho nú, após o pôr do Sol, no hemisfério Norte. Aqui fica o mapa para auxiliar a localização:

Clique para aumentar.

Clique para aumentar.

Comet’s fame keeps growing, and growing ...
Holmes attracts increased interest; celestial show could last for weeks
The Associated Press
updated 9:37 a.m. ET Nov. 5, 2007

KNOXVILLE, Tenn. - A comet that has unexpectedly brightened in the past couple of weeks and now is visible to the naked eye is attracting professional and amateur interest.

Paul Lewis, director of astronomy outreach at the University of Tennessee, is drawing students to the roof of Nielsen Physics Building for special viewings of Comet 17P/Holmes.

The comet is exploding and its coma, a cloud of gas and dust illuminated by the sun, has grown to be bigger than the planet Jupiter.

The comet lacks the tail usually associated with such celestial bodies but can be seen in the northern sky, in the constellation Perseus, as a fuzzy spot of light about as bright as the stars in the Big Dipper.

"This is truly a celestial surprise," Lewis said. "Absolutely amazing."

Until Oct. 23, the comet had been visible to modern astronomers only with a telescope, but that night it suddenly erupted and expanded.

A similar burst in 1892 led to the comet's discovery by Edwin Holmes.

"This is a once-in-a-lifetime event to witness, along the lines of when Comet Shoemaker-Levy 9 smashed into Jupiter back in 1994," Lewis said.

Scientists speculate the comet has exploded because there are sinkholes in its nucleus, giving it a honeycomblike structure. The collapse exposed comet ice to the sun, which transformed the ice into gas.

"What comets do when they are near the sun is very unpredictable," Lewis said. "We expect to see a coma cloud and a tail, but this is more like an explosion, and we are seeing the bubble of gas and dust as it expands away from the center of the blast."

Experts aren't sure how long the comet's show will last, but estimate it could be weeks — if not months. Using a telescope or binoculars help bring the comet's details into view, they said.

Skywatchers marvel at surprise comet
Cosmic fuzzball should be visible to naked eye for next few weeks

By Joe Rao
Skywatching columnist
updated 7:26 p.m. ET Oct. 30, 2007

Skywatchers throughout the Northern Hemisphere report the newly visible Comet Holmes is a remarkable sight even under city lights. The comet, described in glowing terms by many observers, should continue to be visible to the naked eye for at least the next few weeks.

Only a couple comets each decade are this easy to see.

Holmes is actually an old comet. First seen in November 1892 by British observer Edwin Holmes, it has since made 16 circuits around the sun and should have fizzled out a long time ago. It made its closest approach to the sun last May, yet never came closer to it than 191 million miles (307 million kilometers). The comet is actually moving away from the sun now, almost midway between the orbits of Mars and Jupiter. Not exactly a recipe for an outburst, since solar heating is typically what triggers comets to brighten.

But sometime late last Tuesday, this comet underwent an explosive outburst and within just 24 hours increased its brightness almost a millionfold. Since then, Holmes has been putting on a unique display, looking very different than any other comet of our generation: It has yet to sprout a noticeable tail, while its head — called the coma — appears like a round, yellowish fuzzball in the constellation Perseus, and is visible for most of the night.

Since its outburst, Holmes has shone almost consistently between magnitudes 2 and 3, making it similar in brightness to the stars that make up the famous Big Dipper. (On this astronomer's scale, smaller numbers represent brighter objects.)

Use the ‘W’ as a guide
You can find Comet Holmes by using the "W" of Cassiopeia as your guide. The five stars in a conspicuous zigzag pattern are high in the northeast sky during midevening.

Draw an imaginary line from the star Gamma Cass down to Delta Cass (known also as Ruchbah). Extend the line downward about five times the distance between these two stars and you'll come very close to where Comet Holmes is. The comet itself forms a triangle with Alpha Persei (known also as "Mirfak") and Delta Persei.

If you have binoculars, you'll know the comet immediately when you see it: a small, albeit distinct, circular lemon-yellow cloud of light. A small telescope will help bring out the fuzzy details.

The moon, which was full on Oct. 26 and whose brilliant light hindered comet viewing to a degree, is now diminishing in phase and rising later in the night, allowing viewers an increasing window of dark sky before the moon interferes. The moon is one day before last quarter on Wednesday and rises just after 11 p.m.. But by Nov. 4, after the switch to standard time, it will be rising around 1:20 a.m., having shrunk to a crescent and leaving more than half of the night dark for comet watchers.

Reports from around the world
Bryan Bradley, an amateur observer from Long Island, N.Y., writes: "I went out the past two nights and observed the comet from my driveway observatory. Very interesting how bright it has become. My daughters also saw it with me and commented that it looked like a big fuzzy ball, but where is the tail?"

Percy Mui photographed the comet from Illinois, capturing the fuzzball appearance reported by many.

Another Long Island amateur observer, Rich Tyson, relates that "my wife Antoinette described Comet Holmes as looking like a 'fried egg.' Can we call it the 'Fried Egg Comet'?"

Well-known comet observer John Bortle of Stormville, N.Y., has carefully scrutinized the comet on a number of nights with a variety of different instruments. He saw the comet on Sunday evening without the glaring moon in the sky. "So much info was recorded I can't begin to report more than a fragment of it here. A double envelope feature surrounding the comet is truly spectacular in the darker sky."

Similar raves were coming in from other places around the globe.

Eddie Guscott from Essex, England, had been trying to see Comet Holmes since it exploded into view, but "the weather here has been dire: 100 percent cloud. So it was a great surprise to finally get an hour of clear weather enabling me to observe this wonderful sight. I have never seen anything like it before."

Robert McNaught, discoverer earlier this year of a spectacular daylight comet that bears his name, observed Comet Holmes from Siding Spring, Australia.

"The comet was a surprisingly easy naked-eye object despite the near-full moon sitting above it," McNaught said of Comet Holmes. "Lovely views in the Uppsala's 6-inch finderscope at 80x showing the faint stellar condensation ... within the large 'planetary nebula'-like coma. Very impressive."

Also during the night of Oct. 28, there was a brief flurry of excitement as many observers thought they had seen the comet's nucleus split in two. What actually happened, however, was that the comet passed very near to a faint background star with virtually the same brightness as the inner coma, giving the impression that a splitting had occurred. As of this writing, the entire comet remains intact.

What caused the outburst?
More than a week after Comet Holmes erupted, astronomers are still debating what caused it.

Some think it might be due to a rich vein of volatile ices on the comet's nucleus that was suddenly exposed to sunlight. This is actually the second time that Holmes has flared up in this manner, the last time coming in its discovery year of 1892.

Bortle suggested the nucleus of Comet Holmes might consist of low-density material that, over time and through outgassing, develops a large region with a very tenuous structure, perhaps like a honeycomb.

"Cometary nuclei being irregular in shape, rotation or perhaps even the minute gravity of the nucleus itself will create increasing shear forces if the area is remote from the center of rotation," Bortle said. "At some point, the highly fragile bonds connecting the honeycomb of material will reach the failing point and a collapse, or more likely a sudden crushing/consolidating event on a grand scale perhaps covering several square kilometers wide and deep, will occur. This crushing collapse would expel a truly gigantic volume of dust in the process."

Another outburst possible?
The show could have a reprise later this year.

"Those who are familiar with terrestrial structural collapse situations are aware that the primary event often leaves a large amount of instability in the material involved," Bortle said. "This remaining instability will only remain for a short time before a further adjustment toward stability occurs, resulting in a major second collapse, with an outward physical appearance very similar to that of the initial event."

Back in 1892, Comet Holmes underwent a second outburst about 75 days after the first.

Will there be a "cosmic aftershock" that will again cause the comet's brightness to again spike a similar number of days after the big Oct. 23 outburst this year? Bortle thinks it's a possibility.

"I would urge everyone to watch very carefully for a possible repeat of this secondary event about the turn of the year," he said.