quinta-feira, 20 de dezembro de 2007

Mãe de astronauta a bordo da ISS falece em acidente de viação.

A mãe de um dos astronautas actualmente a bordo da Estação Espacial Internacional ISS, Dan Tani, faleceu ontem num acidente de viação.

Se a missão do Space Shuttle tivesse sido lançada como previsto, no início deste mês, Tani estaria já na Terra, mas assim terá de esperar pelo lançamento, que será em Janeiro, na melhor das hipóteses. Não há forma de o fazer regressar antes.

Uma situação difícil e inédita para um astronauta da NASA.

Fonte: Email da CBS Space News

Tani's mother killed in car-train collision

Space station astronaut Dan Tani's 90-year-old mother, Rose, was killed today when her car was struck by a train in Lombard, Ill., a suburb of Chicago, police said.

In a statement, the Lombard Police Department said a preliminary investigation showed Rose Tani went around a school bus that was stopped at a railroad crossing, "going past the downed crossing gate at which time the westbound train struck the passenger side of the vehicle."

She was transported to Good Samaritan Hospital where she was pronounced dead, police said.

Launched to the international space station aboard the shuttle Discovery Oct. 23, Dan Tani was originally scheduled to return to Earth this week aboard the shuttle Atlantis. Liftoff originally was planned for Dec. 6, which would have resulted in a landing today. But Atlantis was grounded twice by suspect fuel sensors and the flight is now on hold until Jan. 10 at the earliest.

Tani and his two station crewmates - Expedition 16 commander Peggy Whitson and flight engineer Yuri Malenchenko - can return to Earth aboard a Russian Soyuz capsule in a life-threatening emergency, but that is not an option for the death of a friend or family member.

"This is something we consider," former astronaut Jim Voss told CBS Radio. "NASA understands there is a possibility of things like this happening while someone is on orbit. And they actually get the crew member's permission to either tell them or not tell them when something happens like this."

Most astronauts, Voss said, choose to be informed.

"It's particularly difficult to have a loss like that when you're in orbit because you're kind of helpless, you can't do anything, you can't be there to be with the family, you feel very, very isolated," Voss said. "And I think for Dan, this will be just a very, very difficult thing because of the closeness of the family member and not being able to return.

"Even in the military, when people are very isolated and far away, they make every effort possible when there's a death in the family to return the service member to be back with their family. And that probably is not a possibility in this case. You just can't do that. It's something you just have to endure."

Tani has trained with Whitson and Malenchenko for years and Voss said the closeness of the crew will be a comfort.

"And of course, NASA will offer any assistance that they can," he said. "They have flight surgeons who have worked very closely with the crew and know them extremely well and they're trained to assist in cases like this. ... It'll just be a very hard time for him for a while on orbit."

Tani's father, Henry N. Tani, is deceased, according to Dan Tani's NASA biography. Rose Tani lived in Lombard. During World War 2, Tani's parents and a brother were forced to leave their home and move to a California internment camp. They were U.S. citizens, but like 100,000 other Japanese-Americans, they had no choice.

In an interview with CBS radio station WBBM-AM before Tani's launch aboard Atlantis, Rose said she was proud of her son, adding "he was lucky to be picked as an astronaut."

terça-feira, 18 de dezembro de 2007

Senador Norte Americano propõe prolongar o programa Space Shuttle para além de 2010.

Para tal propõe um aumento de 10 biliões de dólares ao orçamento da NASA, o que permitirá, na sua opinião, realizar mais algumas (5 ou 6) missões do Shuttle, e evitar o recurso da NASA a naves russas, até às naves Orion estarem operacionais, por volta de 2015. No entanto, o administrador da NASA afirma que esse volume de fundos é irrealista para o número de missões que seriam necessárias, além de reafirmar o risco que é voar com o Shuttle para além de 2010.

É a minha opinião, porém, que o risco existirá sempre, e missões deste tipo serão sempre extremamente caras, mesmo com as futuras naves Orion. Acho que a NASA está a fazer um trabalho satisfatório no controlo dos riscos inerentes à operação do Shuttle, e deveria considerar sériamente esta possibilidade.

Fonte: MSNBC

Lawmaker wants space shuttle extension
Weldon proposes $10 billion to keep ships flying past 2010
By Irene Klotz
updated 7:55 p.m. ET Dec. 17, 2007

CAPE CANAVERAL, Fla. - The United States should keep flying the space shuttles past their 2010 retirement date to avoid depending on Russia to fly astronauts to the international space station, a Florida congressman said Monday.

U.S. Rep. Dave Weldon, a Republican whose Florida district includes NASA's Kennedy Space Center, proposed extending the shuttles’ lifetime to close the gap until their replacement ships, called Orion, are ready for their first manned flights in 2015.

His proposal, which would cost about $10 billion, would have the shuttles make six or seven additional flights between 2010 and 2013 and speed up development of the Orion ships to be ready by then.

A second proposal would keep the shuttles flying until 2015 and leave Orion’s schedule alone.

“This is an issue of priorities,” said Weldon, who announced his plan at the Kennedy Space Center Visitors Center on Monday.

The board investigating the 2003 Columbia accident recommended that the shuttle fleet be retired in 2010 unless the fleet was completely recertified, a process that NASA said would be too time-consuming and expensive to attempt.

President George W. Bush accepted the recommendation and ordered the shuttles’ retirement. He also directed NASA to complete construction of the space station and develop new spaceships and rockets that could travel to the station as well as to the moon and other destinations in the solar system as part of a program called Constellation.

“The 2010 date was really an arbitrary date that was really picked more by OMB [the U.S. Office of Management and Budget] than NASA,” said Weldon spokesman Jeremy Steffens.

“The risk [of flying the shuttle] does not increase overnight. Obviously there’s risk, and NASA is doing its best to mitigate it. The risk is worth the goals we set out,” Steffens said.

As the shuttles’ 2010 retirement nears, NASA planned on getting exemptions to a congressional ban that prohibits purchases of Russian Soyuz rockets. The ban was imposed to curb the spread of nuclear weapons technology to Iran, which Russia is accused of helping.

Steffens said that paying the Russians to ferry U.S. astronauts back and forth may not be a viable option either.

NASA hopes that U.S. commercial launch vehicles may be developed to transport cargo and perhaps eventually astronauts to the station.

Congress already rejected a proposed $1 billion boost to NASA’s 2008 budget to keep Orion’s development on schedule.

NASA says, however, it is unsafe, expensive and counterproductive to keep flying the shuttle past 2010.

“Flying the space shuttle past 2010 would carry significant risks, particularly to our efforts to build and purchase new transportation systems that are less complex, less expensive to operate, and better suited to serving both [the space station] and exploration missions to the moon, Mars and beyond,” NASA administrator Michael Griffin told a congressional oversight committee last month.

Griffin said it would cost $2.5 billion to $4 billion per year to keep the shuttles flying past 2010.

sábado, 15 de dezembro de 2007

Space Shuttle Atlantis atacado por aranha gigantesca!

Pelo menos era o que parecia na NASA TV! Uma aranhita andou por momentos na objectiva de uma das cameras que irá cobrir o lançamento da próxima missão do Atlantis, adiada para 10 de Janeiro, na melhor das hipóteses, devido a vários problemas nos sensores de combustível do grande tanque externo.

sexta-feira, 14 de dezembro de 2007

NASA divulga mais emails sobre o caso de Lisa Nowak

Já há algum tempo que não tínhamos notícias da astronauta Lisa Nowak, cujo julgamento continua marcado para o primeiro trimestre de 2008.

A NASA divulgou agora, de forma bastante discreta, um conjunto de cerca de 200 páginas de emails entre Bill Oefelein, Lisa Nowak e Colleen Shipman.

Fonte: ABC News

NASA Releases Documents, E-mails in Nowak Case

Arrested Ex-Astronaut Was on Good Terms With Boyfriend Days Before Her Arrest


Dec. 13, 2007 - Newly released e-mails between former NASA astronauts Lisa Nowak and Bill Oefelein indicate Nowak may have been unaware that she had competition for Oefelein's affections until a few days before she confronted the other women in a Florida airport parking lot. Following the encounter Nowak was arrested and later dismissed by NASA.

The documents, which NASA posted online quietly overnight, were released 10 months after ABC News requested them under the Freedom of Information Act. NASA released e-mails between Nowak and Oefelein since 2004 and e-mails written by Oefelein to his girlfriend, Air Force Capt. Colleen Shipman. Messages that NASA deemed to be of a personal nature were excluded.

Nowak was arrested in February after allegedly confronting Shipman in Florida. Police documents say Nowak stalked Shipman at the Orlando airport and tried to get into her car, then attacked her with pepper spray. Shipman was able to drive away, and report the attack to police, who tracked down Nowak nearby and arrested her. Police didn't know until much later that she was an astronaut.

Nowak is charged with attempted kidnapping and burglary with assault which can be punishable by life in prison.

As late as Jan. 25, just a couple of weeks before Nowak's arrest on Feb. 8 in Florida, Nowak and Oefelein were still exchanging friendly e-mails and chatting about training, working out and going on bike rides together. There is no hint that she is aware of his relationship with Shipman, a woman he had met three months before while training for his shuttle mission.

In the e-mails, Oefelein asked Nowak's advice about what shirts to order for his space shuttle flight. He asked what did she think about the food he ordered to take into space during his shuttle mission? There is a lengthy discussion about whole wheat tortillas and granola bars, plus personal appearances at baseball games.

The e-mails between Nowak and Oefelein are neither romantic nor suggestive. They do portray a friendly, but on the surface, professional relationship.

When discussing a happy-hour party to celebrate a shuttle mission, Oefelein e-mailed Nowak on Wednesday Jan. 3, 2007 to ask, "Are you going to this?"

"Only if u r [sic]," she replies.

A week later, Jan. 31, Oefelein e-mailed Shipman about a junket to Alaska, his home state. The tone was more romantic.

"They want your size for the arctic gear for the snow machine outing. I think I can figure that out ... sexy and athletic," Oefelein wrote. ABC News also requested information from NASA on the space agency's policy for granting leave to its employees. And the documents they gave ABC News apparently show the agency did not have a policy about what to do if an astronaut was arrested.

NASA's leave policy covers sick leave, family responsibilities, military duty and jury duty. The policy does not contain a word about what to do if an astronaut is arrested and charged with a felony.

A month after Nowak's arrest, she was terminated as an astronaut by NASA. Months later, her former boyfriend, Oefelein was also let go. Nowak is now working on flight software for the Navy, and keeping a very low profile. She is still scheduled to go to trial in April, 2008.

The documents also detail some of NASA's response to the February attack. The day Nowak was arrested; Johnson Space Center Director Michael Coats briefed reporters on NASA's budget, but said nothing about the arrest of one of their astronauts, earlier in the day.

Behind the scenes, the NASA press office was scrambling to figure out what to do. Astronaut Steve Lindsey, who commanded Nowak's shuttle flight, flew to Orlando to see what he could do, along with shuttle pilot Chris Ferguson. Lindsey escorted Nowak back to Houston after she was released on bond.

"Steve, you are handling an incredibly difficult task very extremely well," Michael Coats wrote in an e-mail, also released by NASA "Let us know whatever you need. Thank you for a job well done."

It was important to many in the astronaut corps who wanted to make sure that one of their own was not abandoned, while they struggled to understand what happened to Lisa Nowak. Ten months later, despite the release of hundreds of pages of evidence, videotapes, photos and cell phone records, there are still more questions than answers.

During the legal proceedings since Nowak's arrest, Oefelein has made it a point to appear by Shipman's side. Nowak has been bolstered by a devoted circle of family and friends.

In the two weeks between chatty e-mails and the incident in the Orlando parking lot, Nowak separated from her husband, and discovered that she would not be assigned to a shuttle mission. The job went to someone else when colleagues said Nowak was "not a team player," according to documents released by the courts earlier this year.

Nowak has spoken publicly only once, outside the courtroom following a hearing.

"The past six months have been very difficult for me, my family, and others close to me," Nowak said. "I know that it must have been very hard for Colleen Shipman, and I would like her to know how very sorry I am about having frightened her in any way and the subsequent public harassment that has besieged all of us."

Nowak won a huge legal victory earlier this year week when Judge Marc Lubet granted motions to suppress her 72-page statement to police the night she was arrested and to toss out the evidence seized from her car.

The evidence seized from Nowak's BMW in a motel parking lot included maps to alleged victim Colleen Shipman's home, e-mails between Shipman and Oefelein, large garbage bags, latex gloves and some used diapers.

Nowak's defense team repeatedly denies she ever wore diapers to avoid stopping during her drive from Houston, but the detective who took her statement said Nowak told him she had done so.

Despite the suppression of her statement, authorities still have evidence against Nowak. At the time, she carried a duffel bag with a steel mallet, a buck knife, a BB gun resembling a 9mm handgun, gloves and six feet of rubber tubing.

Imagem detalhada de um dos 'buracos' em Marte

Clique para aumentar.
Já falei destes buracos aqui e aqui. Esta nova imagem é muito mais detalhada e mostra bastantes detalhes no interior do 'buraco'.

Parece tratar-se de uma entrada para uma gruta, do lado direito, mas pode ser apenas um efeito da sombra.

Como este 'buraco' está localizado num lado de um vulcão, é possível que tenha sido criado quando um túnel de magma abateu.

Fonte: Bad Astronomy (ver nº 9)

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!

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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.

quarta-feira, 31 de outubro de 2007

Envie uma mensagem aos astronautas da STS-120

Vá a http://spacecenter.org/message.asp, e a sua mensagem será incluída num CD que será entregue aos astronautas da missão STS 120, após o seu regresso.

Ò diabo! Danos graves num painel solar da ISS!

Clique para ver em alta definição.
Infelizmente esta missão de montagem da Estação Espacial Internacional está a sofrer alguns percalços razoavelmente graves. Primeiro foi a descoberta de alguns pedaços de metal numa plataforma que girava os painéis solares de um dos extremos da Estação, e agora, muito mais grave, foi este rasgo impressionante, que ocorreu quando os astronautas estavam a desdobrar um novo painel solar.

A NASA está agora a ponderar possibilidades de reparação deste painel (que continua a gerar electricidade apesar do dano) no próximo Sábado.

Estes problemas são tão mais graves porque afectam os próximos passos da montagem da ISS, durante as próximas missões do Space Shuttle, com prazos apertados - quanto a mim desnecessariamente - pela data marcada para a reforma dos Shuttles em 2010.

Em minha opinião dever-se-ia considerar concluida a montagem da ISS quando esta estiver concluída, e não forçar a NASA a lançar missões a contra-relógio apenas para respeitar uma data arbitrária fixada pelo Presidente George Bush. Claro que isto irá, forçosamente, custar mais dinheiro, mas pelo menos poderemos tentar evitar mais um desastre terrível como os do Challenger e Columbia. Não podemos sucumbir de novo à 'febre de lançar' que condenou 14 astronautas e dois shuttles no passado bem recente.

quarta-feira, 24 de outubro de 2007

Vídeo do lançamento, ontem, do Space Shuttle Discovery

Esta será provavelmente a missão mais complexa de sempre. Será montado um novo módulo na Estação Espacial Internacional, e o tipo de trabalho que terá de ser feito é bastante intenso e complexo.

Durante a contagem decrescente houve vários problemas, e mesmo dúvidas acerca do lançamento, devido nomeadamente ao tempo que estava a piorar bastante próximo do momento do lançamento, e à detecção de gelo numa das condutas que alimentam o Shuttle de combustível - este problema tendo sido considerado MUITO GRAVE pela NASA. No entanto, a análise feita levou os responsáveis a concluir que não haveria perigo para o Shuttle durante o lançamento.

A missão está a correr bem, não tendo havido quase nenhuma queda de gelo a partir do grande tanque externo (côr de laranja), como infelizmente é costume nestas missões.

É a primeira vez que um Shuttle comandado por uma mulher vai ao encontro de uma Estação Espacial também comandada por uma mulher.

Outra curiosidade é a hora do lançamento ter coincidido exactamente com a hora de lançamento da última missão do Challenger.

Shuttle Discovery launched
02:30 PM, 10/23/07, Update:
(UPDATED at 3 p.m. with post-launch news conference; quotes and details; correcting time of docking)

The shuttle Discovery, carrying seven astronauts and a critical connecting module for the international space station, roared to life and rocketed into orbit today, kicking off a high-stakes five-spacewalk mission considered by many the most complex orbital construction work ever attempted.

"I don't think there's ever been an astronaut who doesn't consider their flight the most dramatic, exciting, complex mission ever," lead spacewalker Scott Parazynski said before launch. "But ours is!"

With its three hydrogen-fueled main engines roaring at full throttle, Discovery's twin solid-fuel boosters ignited with a rush of fire and thunder at 11:38:19 a.m., instantly pushing the huge spacecraft away from pad 39A.

Seconds later, Discovery's flight computers sent commands to the booster steering system, rolling the spacecraft about its vertical axis to put the crew in a heads down orientation as the spaceplane arced out over the Atlantic Ocean on a trajectory paralleling the East Coast of the United States.

NASA managers were worried early today about an ice buildup on an umbilical on the lower section of the shuttle's external fuel tank and by threatening weather. But as the morning wore on, the anticipated cloud development held off, engineers decided the ice would most likely shake off at launch and Discovery was cleared for flight.

"OK, Pambo, on behalf of your KSC family, I'd like to wish you good luck, Godspeed, have a little fun up there," Launch Director Mike Leinbach radioed the crew a few minutes before launch.

"Copy that, Mike," replied Melroy, the second woman to command a space shuttle. "We feel a tremendous amount of pride in the 10A and Discovery team and a lot of gratitude for the hard work to get us here. And we're ready to take Harmony to her new home."

Joining Melroy on Discovery's flight deck were Marine Corps pilot George Zamka, flight engineer Stephanie Wilson and Doug Wheelock, an Army helicopter pilot. Strapped in on the orbiter's lower deck were physician-astronaut Parazynski, Italian astronaut Paolo Nespoli and Dan Tani, a space station crew member hitching a ride to the lab complex aboard Discovery. Tani will replace station engineer Clay Anderson, who will return to Earth aboard the shuttle.

Television views from a camera mounted on Discovery's external fuel tank provided spectacular views of the Florida spaceport dropping away and then the limb of the Earth as the ship headed for orbit. Bill Gerstenmaier, chief of space flight operations for NASA, said a quick look at the video indicated about a half-dozen small pieces of foam insulation fell away from the shuttle's external tank during the climb to space.

But in all cases, Gerstenmaier said, the debris separated after Discovery's solid-fuel boosters were jettisoned and well beyond the regime in which the denser lower atmosphere can slow lightweight foam enough to cause impact damage when the shuttle runs into it at a high relative velocity.

"We took a quick look at the video and we saw probably six instances of foam loss off the tank and they were all after solid rocket booster separation," Gerstenmaier said. "So in that sense, they're not a concern from a damage-to-the-orbiter standpoint. ... We'll see when we get some good pictures of the external tank here later today or tomorrow."

While Gerstenmaier was addressing reporters at a post-launch news conference, astronaut Terry Virts in mission control at the Johnson Space Center in Houston, radioed Melroy with a debris update.

"Pam, there were several events noted during ascent," he said. "They occurred after the critical transport mach number. We will continue to look at it. This is just preliminary only, but it did look like a clean ascent. Also there was some ice on the aft LH2 (liquid hydrogen) lines on the tank, we saw that pre launch and it cleared right at T-0 as expected."

The astronauts photographed the tank shortly after it separated from the shuttle in orbit and Parazynski reported "no visible, at least to the naked eye, loss of big pieces of foam."

The crew will carry out a detailed inspection of the shuttle's nose cap and wing leading edge panels using a laser scanner and high-resolution camera on Wednesday while engineers on the ground continue analysis of long-range tracking camera and launch pad footage. In the meantime, NASA managers were thrilled with today 's launching.

"This is a great start to a very challenging mission in front of us," Gerstenmaier said. "If I look at this mission and what's coming up for us, we're combining, effectively, activities we've done on at least four other missions, all into one mission. So this is a pretty exciting mission. We're going to do a solar array deploy, a radiator deploy, a pressurized module addition, just a tremendous series of challenges in front of us.

"I think the teams are ready, really prepared for any eventualilty. ... I can't think of a better start to this mission than what we got today. So again, hats off to the KSC folks and the orbiter folks who gave us a great vehicle and a great ride to start a great mission."

Discovery took off at roughly the moment Earth's rotation carried the launch pad into the plane of the space station's orbit. If all goes well, Melroy will manually guide the shuttle to a linkup with the station around 8:35 a.m. Thursday.

Discovery's docking and the usual welcome aboard ceremony will have an unusual flavor this time around as Expedition 16 commander Peggy Whitson, the station's first female commander, welcomes Melroy, probably the final woman to command a shuttle before the program is retired in 2010. Both women flew together in 2002 when Whitson served as flight engineer of the fifth station expedition and Melroy visited as pilot of the shuttle Atlantis during mission STS-112.

"One of the moments I'm looking forward to the most is when the hatch opens and I see Peggy's face on the other side and we reach through for the traditional handshake," Melroy said in an interview. "That will be a really special moment for me."

Whitson said the timing of their flights was a coincidence, "but I do think it is special, not only special just for Pam and I because, you know, we have flown in space before, but the experience of having two women up there at the same time will hopefully be an inspiration to somebody."

"I was inspired when I was young by the Apollo era astronauts and in particular, I was motivated to become an astronaut when they selected the first female astronauts," she said. "I would hope that we could be a role model like that."

The day after docking, the astronauts will use the station's robot arm to pull the 31,500-pound Harmony module from Discovery's cargo bay as part of the first of the mission's five spacewalks.

Harmony will be temporarily mounted on the left side of the station's central Unity module. After the shuttle departs, Whitson, flight engineer Yuri Malenchenko and Tani will detach the station's main shuttle docking port, known as pressurized mating adapter No. 2, mount it on Harmony and then use the station's robot arm to move both components on the front end of the Destiny laboratory module.

Whitson and Tani plan to stage two spacewalks in November to connect Harmony to the station's cooling system and power grid to clear the way for launch of the European Space Agency's Columbus research lab aboard the shuttle Atlantis in December. Columbus will be attached to Harmony's right-side port while Japan's Kibo lab module will be connected to Harmony's left hatch next year.

"Harmony has six different ports that we can add modules onto to build the station," said Whitson. "So it's, it's our next big connecting piece in our puzzle of putting this huge station together on orbit."

Attaching a new pressurized module would have been the highlight of many past assembly missions. But for Discovery's crew, it is just the beginning. The second major objective of the flight is the disconnection and relocation of a huge set of solar arrays known as P6. Designed as the sixth and final segment of the port, or left, side of the station's main power truss, P6 was mounted at the center of the station in December 2000 to provide power to the U.S. segment during the initial stages of assembly.

Now, with identical solar panels in place on the left and right sides of the main power truss, NASA needs to move P6 to its permanent position on the far left end of the beam. The 35,000-pound segment's huge arrays, stretching 240 feet from tip to tip, were stowed during shuttle missions last December and June. Power and cooling lines were disconnected during an August flight, setting the stage for the massive truss's detachment, relocation and re-extension during Discovery's mission.

The station's robot arm cannot reach far enough on its own to make the move. So the station arm, after handing P6 off to the shuttle's space crane, will be moved by the station's mobile transporter to the far end of the power truss. At that point, the shuttle arm will hand the truss segment back to the station arm and Parazynski and Wheelock, making their third spacewalk by that point, will oversee its attachment to the P5 truss segment.

"Moving the P6 solar array will be a major activity," Melroy said in a NASA interview. "On our second spacewalk - our first spacewalk is all about (Harmony) - we'll be using the robotic arm in one location to actually reach around and pull P6 off ... with the assistance of our spacewalkers.

"Once the P6 has been detached from the space station, then the robotic arm will move it around to the port side of the shuttle, at which point it will be handed off to the shuttle arm. The shuttle robotic arm will take control of the P6 truss while the space station robotic arm is reconfigured and rolled out on the mobile transporter, the mobile platform, all the way to the far end of the port truss. And then, we'll use the station arm to take it back and install it in its final location.

"This is pretty nearly the design-limiting case for the robotic arm of the space station, so it's out at its full extension, trying to get that truss out there," Melroy said. "We'll have the help of the spacewalkers on the third spacewalk to do that. So, all these activities will actually span three days, three full days, two spacewalks with robotics in the middle."

Discovery is scheduled to land back at the Kennedy Space Center on Nov. 6.

quarta-feira, 17 de outubro de 2007

Lançamento do Space Shuttle Discovery aprovado para 23 de Outubro

Apesar de algumas preocupações com telhas de protecção térmica numa das asas do Shuttle, a NASA aprovou o lançamento sem reparar este problema, considerando não ser suficientemente grave para adiar o lançamento.

A terem de ser reparadas, o shuttle teria de ser de novo levado para o Vehicle Assembly Building - VAB - o que implicaria forçosamente um adiamento no lançamento de pelo menos um mês.

Fonte: Email da CBS Space News

Update: Discovery cleared for launch Oct. 23; Hale confident suspect wing panels safe
11:45 PM, 10/16/07

Senior NASA managers today cleared the shuttle Discovery for launch Oct. 23 on a critical space station assembly mission, concluding concern about the integrity of a protective coating on three of 44 wing leading edge panels did not warrant a lengthy delay. While there were no official dissenting opinions, NASA's chief engineer opted to write down his concerns about the decision to proceed with flight and a NASA engineering panel stuck to an earlier recommendation to replace the panels in question.

In a worst-case failure, one in which some unknown mechanism caused the protective coating to somehow come off after the crew's normal heat-shield inspections in orbit and before peak heating during re-entry, the shuttle could suffer a catastrophic leading edge burn through. Replacing the panels in question would eliminate the threat but the work would delay launch for two months or more.

NASA is attempting to complete the international space station and retire the shuttle by the end of fiscal 2010. At a news conference late Tuesday, Hale did not address how the prospect of a long delay might have played into the launch decision. But he made it clear he believes it is safe to proceed with Discovery's flight while testing continues, saying there is no engineering data to support the worst-case scenario.

"We certainly explored it in a great deal of depth," Hale said. "Everybody got to ask questions, everybody got to give their understanding of it down to the working-troop level. And at the end of the day, the flight readiness review board decided we were in an acceptable risk posture to go fly. Which is not to say we completely and perfectly understand the problem that's been laid out. We're going to continue to work very hard on it as the data comes in. We will continually re-evaluate our position from flight to flight and if the risk grows to an unacceptable level, we will take action, whether that's to change some hardware or to delay some flights while we do testing or what have you.

"I really think this was a credit to the lessons that we learned since Challenger and Columbia to be able to listen to all the opinions, to think very clearly about what they mean, apply some critical thought processes and, I trust, come to a good decision that provides us with an acceptable reason to go fly. We have a very important mission ahead of us and the crew is going to have a very intense time on orbit. We need to focus on what they are getting ready to do ... because it's absolutely critical to the next stage of building the international space station which is, after all, the reason for which we're flying the space shuttle."

Discovery's crew - commander Pam Melroy, pilot George Zamka, Scott Parazynski, flight engineer Stephanie Wilson, Doug Wheelock, Italian astronaut Paolo Nespoli and space station crew member Dan Tani - is scheduled to fly to the Kennedy Space Center Friday for the start of the shuttle's countdown Saturday afternoon. Launch is targeted for 11:38 a.m. Tuesday.

Bill Gerstenmaier, NASA's chief of space flight operations, said the crew, represented by the astronaut office at the Johnson Space Center in Houston, agreed with the decision to press ahead with launch. So did NASA's new chief engineer, Michael Ryschkewitsch, although he apparently had reservations. Gerstenmaier said Ryschkewitsch wanted to write down his concerns as part of a process that allows managers to go beyond a simple yes-no vote.

The primary goal of Discovery's mission is to deliver a new multi-hatch module called Harmony that will serve as the connecting point for European and Japanese research modules scheduled for launch in December and early next year. The astronauts also plan to move a stowed set of solar arrays to its permanent mounting point on the far left end of the station's main power truss and stage a recently added spacewalk to test heat shield repair techniques.

Discovery's flight is the first to use a new management approval process, splitting up the traditional flight readiness review into separate program- and headquarters-level meetings. The idea behind the change was to make it easier for mid-level managers and engineers to express their views and opinions, part of NASA's on-going drive to improve communications between engineers and managers.

The program-level review was held Oct. 10 and during that meeting, shuttle project and wing leading edge subsystem engineers recommended launching Discovery on time despite concern raised by the NASA Engineering and Safety Center - NESC - that the coating on three reinforced carbon carbon (RCC) wing leading edge panels might be susceptible to failure.

The issue involves a protective silicon-carbide coating on the shuttle's RCC nose cap and wing leading edge panels. The nose cap and 44 RCC leading edge panels - 22 on each wing - protect the shuttle from the most extreme heating during re-entry when temperatures exceed 3,000 degrees Fahrenheit. A breach in Columbia's left wing leading edge, caused by the impact of foam debris from the ship's external tank, led to the shuttle's destruction in 2003.

Since then, NASA and contractor engineers have paid close attention to the RCC panels and nose cap, devising sophisticated non-destructive tests to assess the health of the critical carbon composite material before each flight. One of those new techniques is called thermography, which measures how heat dissipates in the carbon composite material. The technique can show areas where the protective coating on the panels might be degrading.

"Before Columbia there were two instances where we landed and some of this coating, visibly little amounts ... was off the vehicle when it landed," Hale said. "Nothing bad had happened, the vehicle survived. There was a theory as to why this happened, we developed a screening technique that we thought would detect the problem before it became critical, before it became a safety-of-flight issue."

After the first post-Columbia mission, however, thermography revealed an area of concern on an RCC panel from the shuttle's right wing. The panel - 8R - was removed and returned to the vendor, Lockheed Martin, for refurbishment. In the course of post-flight inspections, Hale said, engineers discovered "there was more sub-surface damage than we would have expected on that panel."

"That kicked off this whole concern and starting in about May, we have been trying to understand do we really have a flight safety concern?" Hale said. "Because we don't know that we do. There are some hypothesized, proposed failure modes that would say you potentially could have a safety-of-flight issue. So we're working through that engineering data.

"Now that's not a simple sound bite," he said. "There is disagreement over the interpretation of results from this panel, which we have now taken and cut little slices of and looked at under a microscope and compared that back with what the thermography readings were before. What does all this mean to us? It's a very complicated problem, it's a very complicated system and we absolutely need to make sure it works right and I can tell you right now, today, there is some question whether or not all these panels will work right. And the question is, do we stop and wait until we completely understand this problem, do we remove three or four or five of these panels and try to replace them with newer and potentially better panels? What do we do? That's what we've been grappling with, that's the issue."

The area of concern is near the apex of the curved RCC panels where they join together with so-called T-seals. Three panels on Discovery - RCC panels 9 right, 13 right and 12 left - were known to have small areas of degraded coating.

Until recently, the leading theory for the cause of such coating degradation was a slow process of oxidation, one that would not be expected to lead to a sudden loss of protection. The areas of concern on the three panels aboard Discovery had not shown any signs of worsening after three flights.

But the NASA Engineering and Safety Center, an independent review group set up after the 2003 Columbia disaster, concluded ongoing analysis of test data did not support the presumed root cause of the coating degradation and that as a result, engineers could not predict how the damage might evolve over time or accurately assess the danger it might pose. The NESC recommended replacing all three panels.

But Hale said there is no actual test or flight data that would suggest a sudden coating failure is a credible scenario. If any such loss did occur during launch or the crew's orbital operations, it would be detected by now-standard post-Columbia heat shield inspections. If any such damage was detected, it could be repaired, in theory at least, by spacewalking astronauts. For severe damage, the crew could take refuge aboard the space station and await rescue by another shuttle.

But if something caused a coating loss after the crew's normal inspections, the shuttle could re-enter with an undetected, potentially catastrophic heat shield defect. The problem for NASA is the recent conclusion that the previously held oxidation explanation may not be valid and as such, engineers do not understand the underlying causes of coating degradation or how that degradation might change over time.

"I would love to be in the position of saying we understand all our problems completely and we have resolved them all and there is nothing that's worrying anybody," Hale said. "The fact of the matter is this is a very complicated vehicle, it's an old vehicle and there are a lot of loose ends out there. We fly every time without having solved every one of our problems, found a root cause of every one of our issues.

"This is an absolutely critical subsystem for the safety of flight and the potential is a catastrophic loss of vehicle. So therefore, we have to pay particularly close attention to it. And we are committed to (finding) a root cause. ... The question you have to ask yourself is do we have sufficient understanding and sufficient mitigation - and in this case, mitigation is things like inspection and repair - to go proceed to fly while we're proceeding to work root cause?"

Gerstenmaier said the question comes down to "where is that line, when is the right time to ... take some remedial action or when is it not a problem? And frankly, we don't know and that's what the teams are struggling with."

"Without an underlying cause mechanism, you can go in one direction that says you ought to (replace the panels) at this value, another direction at a different value. When we thought we had oxidation as a root cause it was clear then we had margin to go fly for an extended period of time. Now, because we don't know what that failure mode is, depending on which failure mode we hypothesize, we may not have as much margin as we like. Then we have to go look at other mitigating circumstances."

Asked how NASA could proceed with flight with major unknowns about a potentially critical failure mode, Hale said "I don't know what else to say other than what we've told you."

"We have a new technique to inspect these panels," he said. "It's showing us some interesting things, we're trying to understand what that means. In the process of understanding, some folks that I highly respect, who are good engineers, have hypothesized this could lead to a very bad situation. We haven't demonstrated that, we have a test program to go out and understand all of that.

"So you ask yourself, should we quit flying? Should we do some minor repairs on these piece parts? What should we do? You look at the mitigations. If it happens during the launch phase, we can detect it on orbit and repair it. And we think if it happens late in entry it won't be a problem. If it happens early in entry, we've done an awful lot of work and calculations and it probably, to a fairly high degree, won't be a problem although it could be. That's the kind of logic we go through."

Said Gerstenmaier: "We would have to lose the coating sometime prior to peak heating to have this potential problem during entry based on our conservative entry tools. So when you factor all those things together, even though you have all these unknowns, even if you extrapolate those unknowns to the worst case, we have enough rationale that says we're OK to continue to fly while we continue to aggressively investigate this."