Endeavour's crew performed some early morning robotic calisthenics on Saturday, stretching both the International Space Station's and orbiter's arms to inspect a small gouge found on the space shuttle's heat shield tile-covered underbelly.
The "focused inspection" was expected to give mission managers on the ground the additional data needed to clear the damaged "area of interest" as safe for Endeavour to return through Earth's atmosphere at the end of its on-going 16-day, STS-134 final mission.
"There is nothing alarming here and we're really not concerned," NASA's chair of the shuttle mission management team LeRoy Cain said Friday. "This is one that we feel pretty confident we're going to be able to clear once we get some higher fidelity data."
To perform the inspection and clear the surrounding station complex, the astronauts needed to first use both the station's and shuttle's Canadian built robot arms to hand-off a 50-foot extension boom tipped with sensors and cameras flown on the shuttle for just such damage surveys.
Once grasped by the shuttle's own Canadarm, the boom was extended underneath Endeavour and positioned about seven feet from the 3.22 by 2.49 inch divot, which straddles two heat shield tiles located between the orbiter's right main landing gear door and an external tank feed line port.
The couple of hours required for the inspection was mostly consumed by the time needed to position the arms and boom; the actual scans of the damaged area, which began at 2:25 a.m. CDT and included five different angled-views, took about just a minute to perform each.
STS-134 pilot Greg H. Johnson oversaw the computer-controlled boom movements and data collection. Assisting him positioning the arms were mission specialists Mike Fincke, Andrew Feustel, and European Space Agency astronaut Roberto Vittori.
The images collected by the inspection were downlinked in real time to Mission Control in Houston, Texas, where imagery experts will analyze the data for how deep the gouge is and what effects it might have to the integrity of the orbiter's thermal protection when heated during reentry.
The small gouge was one of seven debris-damaged areas first revealed earlier in the week through photographs taken as Endeavour approached the space station to dock. Four of the dings were considered very minor and were quickly cleared as safe by engineers. Of the remaining three, two were able to be analyzed using the available imagery. The third was "kind of fuzzy" in the available photos, leading managers to order today's focused inspection.
The survey came on a day of relatively light work for the six Endeavour astronauts. The crew woke at 8:26 p.m. on Friday to the song "In View" performed by the band Tragically Hip for Feustel. He and his crew mates have several hours of off-duty time scheduled before they are to start setting up for Sunday's spacewalk, the second of four scheduled during the STS-134 mission.
The shuttle and station crews are scheduled to take a special call from The Vatican to speak with Pope Benedict XVI at 6:11 a.m. The papal call will mark the first time His Holiness the Pope has spoken with astronauts in space.
In a first for The Vatican, Pope Benedict XVI called to the heavens on Saturday, but instead of reaching God, he spoke to two Italian astronauts and their 10 colleagues working on board the International Space Station (ISS).
"Dear astronauts, I am very happy to have this extraordinary opportunity to converse with you during your mission and especially grateful to be able to speak to so many of you as both crews are present on the space station at this time," said the Pope, reading from prepared remarks.
The video call, which began at 6:11 a.m. CDT, originated from the Foconi Room of the Vatican Library in Rome. It was organized by the European Space Agency, whose astronauts Paolo Nespoli and Roberto Vittori are currently working in space.
The conversation marked the first time that the Pope has spoken with astronauts in orbit.
"This conversation gives me the chance to express my own admiration and appreciation to you and all those collaborating making your mission possible and offer my heartfelt encouragement to bring it to a safe and successful conclusion," said the Pope.
Joining the two Italians for the space-to-ground conversation were the U.S. and Russian crew members of space shuttle Endeavour's STS-134 mission and the space station's Expedition 27.
ESA astronaut Thomas Reiter, who like Pope Benedict XVI is German, joined His Holiness in The Vatican together with the president of the Italian Space Agency Enrico Saggese and General Giuseppe Bernardis with the Italian Air Force.
An adventure of the human spirit
After a brief introduction, the Pope asked the astronauts and cosmonauts questions concerning their unique vantage point in space and how it affected their view on a variety of subjects ranging from the violence experienced between countries to protecting the Earth's environment to their personal connection to God.
"Space exploration is a fascinating scientific adventure. I know you have been studying your equipment to further scientific research and to study radiation coming from outer space. But I think it is also an adventure of the human spirit. A powerful stimulus to reflect on the origins and on the destiny of the universe and humanity," said the Pope.
"In the midst of your intense work and research, do you ever stop and reflect like this, perhaps even pray to the creator? Or will it be easier for you to think about these things once you have returned to Earth?" he asked.
"When we have a moment to look down [at Earth], the beauty is the three-dimensional effect and the beauty of the planet is capturing our heart... capturing my heart," replied Vittori. "And I do pray. I do pray for me, for our families, for our future."
The Pope, speaking in Italian, also addressed Nespoli about the recent death of his mother, mentioning that he had prayed for her.
"Holy father, I felt your prayers and everyone's prayers arriving up here, where outside the world we orbit and we have a vantage point to look at the Earth and we feel everything around us," replied Nespoli. "I felt very far but also very close and the thought of feeling all of you near me at this time has been a great relief."
Tell me of your experiences and your reflections
Turning to the subject of practical concerns, the Pope asked the crew members about the absurdity of violence between men, specifically citing the assassination attempt on the wife of Endeavour's commander Mark Kelly, Congresswoman Gabrielle Giffords.
"I know that Mark Kelly's wife was a victim of an attack and I hope her health continues to improve," he said. "When you are contemplating the Earth from up there, do you ever wonder about the way nations and people live together down here and about how science can contribute to the cause of peace?"
"Thank you the kind words, your holiness, and thank you for mentioning my wife Gabby," replied Kelly. "It is a very good question. We fly over most of the world and you don't see borders. But at the same time, we realize that people fight with each other and there's a lot of violence in this world and it is really an unfortunate thing."
"On Earth, often people fight for energy. In space, we use solar power and we have fuel cells on the space shuttle, but on the space station, it's the science and technology that we put in to the space station to develop a solar power capability [that] gives us pretty much unlimited amount of energy. And if those technologies could be adapted more on Earth, we could possibly reduce some of that violence," Kelly said.
The Pope also asked the astronauts if they saw "signs of phenomena" that we need to be more attentive to protecting the Earth's environment.
"On the one hand, we can see how indescribably beautiful the planet that we have been is, but on the other hand, we can really, clearly see how fragile it is," replied Ron Garan, a NASA astronaut serving as a flight engineer on the space station.
"The atmosphere for instance," Garan continued. "The atmosphere when viewed from space is paper thin, and to think that this paper thin layer is all that separates every living thing from the vacuum of space and all that protects us is really a sobering thought."
Asked by the Pope what the most important message the astronauts could convey on their return, Endeavour mission specialist Mike Fincke stressed exploration and cooperation.
"We can look down and see our beautiful planet that God has made and it is the most beautiful planet in the whole solar system. However, if we look up, we can see the rest of the universe. And the rest of the universe is out there for us to go and explore. The International Space Station is just one symbol, one example of what human beings can do when we work together constructively," said Fincke.
"So our message I think, one of our many messages, but I think one of our most important messages is to let the children of the planet, the young people know, that there is a whole universe for us to go explore. And when we do it together, there is nothing we cannot accomplish," he said.
Vittori, who launched with Endeavour on its 16-day final mission, carried to space a silver medal with donated by the Pope.
"We are struck by the mystery of His Greatness," said the Pope. "That is why the medal I gave Robert as a sign of my own participation in your mission represents the creation of man as painted by Michelangelo in the Sistine Chapel."
Vittori displayed the medal during the video conversation, letting it float in front of him.
"I allow this coin to float in front of me to demonstrate microgravity. I shall thank you very much for this opportunity and I would like to allow this coin to float to my friend and colleague Paolo. He will make return on Earth on the Soyuz. I brought it with me to space and he will take down on Earth to then give back to you," said Vittori.
The Pope thanked the crew members for this "wonderful opportunity" to talk with them.
"Humanity is experiencing a period of extremely rapid progress in the fields of scientific knowledge and technical applications. In a sense, you are our representatives spearheading humanity's exploration of new spaces and possibilities for our future, going beyond the limitations of our everyday existence," he said.
"You have helped me and many other people to reflect together on important issues which regard the future of humanity. I wish you the very best for your work and for the success of your great mission in the service of science, international collaboration, authentic progress and for peace in the world. I will continue to follow you in my thoughts and prayers and in bidding I impart my apostolic blessing."
Shuttle Endeavour's heat shield has been deemed safe for the ship's last landing thanks to images taken by its astronauts and sent down for study on Saturday.
"We are essentially clearing the vehicle for reentry at this point," NASA's shuttle mission management team chair LeRoy Cain said.
Earlier this week, engineers and mission managers were able to clear six of the seven areas of minor debris damage they had found dotting the right-side of Endeavour's tile-covered underbelly.
"Fuzzy" photographs of the seventh gouge, which straddled two thermal protection system (TPS) tiles, couldn't be analyzed to the same degree so the shuttle's astronauts were tasked with using cameras and sensors mounted at the end of a robotic arm inspection boom to get a close-up look at the site early on Saturday morning.
By Saturday afternoon, engineers at the NASA Johnson Space Center in Houston, Texas had processed the newly-downlinked data, even creating a physical 3D model of the divot.
Focused inspection view of the heat shield tile damage cleared on Saturday.
"The analyses team went back and essentially what they did was verify how much of the tile was still in the cavity, because of course, it is more important what remains than it is what is gone," said Cain. "What we are interested in is protecting the structure underneath the tile."
The team found the damage was well within the margins of safety and so recommended that the shutlte was cleared to return to Earth. Endeavour, flying its 25th and final spaceflight, is scheduled to make its last landing from space on June 1, weather permitting.
"With that we've cleared the TPS," said Cain. "The vehicle is otherwise in great shape as well. It continues to perform outstanding."