Without question, the riskiest and most specialized job that an astronaut can do in space is space walking, otherwise known as EVA or Extra Vehicular Activity. Over the course of the last decade and a half, NASA has made four trips to the Hubble Telescope, the first of which was to deploy the giant telescope which has given us an abundance of information about so many aspects of space science.
When astronaut Dr. John Grunsfeld was preparing for space walks prior to the first walks he did to repair the Hubble Telescope, he spent two years during which he trained in one of NASA's 11 million gallon pools. There, they can train with life size replicas of the Hubble. They practice repairs on other types of virtual reality replicas.
Astronauts wear a space suit that is called an EMU when they go on space walks. EMU is short for Extra-Vehicular Mobility Unit. The EMU is like a self contained space suit. The astronauts must spend time preparing these suits before they can go outside. Each suit will contain:
*Batteries for power
*A lithium hydroxide cartridge to take the carbon dioxide out of the air inside the suit
*Bottles of oxygen,
*A UHF Communication system that makes it possible for astronauts to talk to one another while on a space walk, to the rest of the crew, and to mission control.
*A canteen of water
One of the things that the astronauts must do before they embark on a space walk is reduce the cabin pressure. They reduce it to the equivalent of a 10,000 foot mountain. This is essential because if it were not done, the astronauts would be in danger of suffering from decompression sickness.
Astronauts will spend several hours the day before a space walk preparing the suits and testing all of the equipment to make sure it is in good working order.
When astronauts went up on one of the early Hubble repair mission, they had to replace the gyroscopes that had failed. Without the functioning gyroscopes, the Hubble was no longer capable of performing observations and send that data back to earth. On that mission, the astronauts also replaced a reel to reel recorder with a digital one, and they replaced the telescope's on board computers.
On a second space walk, they had to replace the guidance sensors that are housed in a box that is roughly the size of a refrigerator. These guidance sensors are the component that allows Hubble to point to astronomical objects. They also had to replace the telescope's central computer with a 486 upgrade. Additionally, they removed and replaced a faulty radio transmitter, upgraded the tape recorders so that they had a solid state memory as opposed to the old reel to reel configuration, and they had to replace some of the thermal insulation that is on the telescope's electronic bays.
Grunsfeld is about to go up on another Hubble repair mission, and this one will be the last. Sadly, one of the things they will need to do on this mission is install a mechanism on the Hubble that will make it possible for a spacecraft to capture it when it is time to remove Hubble from space.
The list of repairs for this forthcoming mission are extensive.
*They will replace the wide field camera.
*They will replace the science data processing computer.
*They will change three boxes, each of which contain two of Hubble's six gyroscopes and three batteries.
*They will install a Cosmic Origins Spectrograph. (Spectrography is the science of breaking light up into all of its individual components.)
*They will repair the telescope's advanced camera for surveys. It has suffered from power failures in the past, but now, two of the camera's three observing channels aren't working.
*They will also repair and upgrade the STIS (Space Telescope Imaging Spectrograph) because it hasn't worked since 2004 due to power failures.
*They will install stainless steel blankets on the outside of the telescope. These blankets are designed to provide the telescope's equipement bays with ome added thermal protection.
*Time has caused the current multi layer of insulation to degrade, so that will be replaced on this forthcoming mission.
*They will also install and replace the final set of batteries.
*They will replace the sensor that makes it possible for the telescope to point at precise targets.
*Their last task will be to cover the exterior of the telescope with yet another blanket.
When medical doctors go on Shuttle missions, they might study the effects of microgravity on human bone and tissue. Experiments with protein crystals that are grown in space teach researchers on earth about how to make stronger and safer medications. Plants grown in space teach scientists how to grow stronger and healthier plants on earth.
The International Space Station (ISS) was built to be a permanent orbiting research station. Astronauts on the ISS spend their time doing important research that can only be done in an environment of microgravity. They also do medical experiments to learn about how well their bodies are holding up to living in a zero gravity environment for long periods of time.
Astronauts on both vehicles also have to spend time doing maintenance and upkeep, just as one does on their own home. The astronauts are living in these facilities while they are in space. Maintaining all of the equipment and facilities ensures that their work is done properly and that their living conditions are as comfortable as they can be given the circumstances.
Astronauts sometimes release satellites, but they may also take pictures with high tech cameras that are made to capture very specialized pictures. Sometimes astronauts go on space walks. They may be doing work on the Shuttle itself, or on other things, as is the case when Hubble telescope repair missions are sent up.
Sometimes astronauts will talk to school children while they are in space. They will answer questions, teach children about all of the features on the Space Shuttle, or show them neat tricks about weightlessness. Astronauts may send reports back to Earth so that people who are interested in the Space program can learn about what is happening on specific missions.
The things that astronauts do in space is highly varied. A lot depends on their expertise, what they have been training for before the mission, and how much time they will have on the mission. The International Space Station is the real scientific research center. That isn't to say that astronauts on the Shuttle don't do research. It just means that the purpose of the ISS is for research.