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Astrophysics Science Division | Sciences and Exploration

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 Frequently Asked Questions (FAQ)

Why the name "3B"?
Servicing Mission 3B is actually the fourth visit to Hubble. NASA split the original Servicing Mission 3 into two parts and conducted 3A in December of 1999.

How long will the mission take? What is the timetable?
The crew of Space Shuttle Columbia will conduct Servicing Mission 3B in early 2002 and perform five spacewalks over an 11-day mission. Click here for the mission timeline.

Why do we have to service?
As new technology becomes available, space-walking astronauts fit the telescope with the latest, high performance equipment. They also replace components that would otherwise wear out and limit Hubble's life. Each time astronauts visit the Hubble Space Telescope, they leave it newer and better than they found it.

What is the biggest improvement/change?
The biggest improvement will be the installation of the Advanced Camera for Surverys (ACS) - it will effectively increase Hubble's discovery efficiency by 10 times. Hubble will also receive a new look with its smaller, rigid solar arrays.

How noticeable will the improvements be?
By being able to collect data 10x faster with ACS, conceivably, 10x the amount of discoveries can be made. In terms of image quality, it is akin to upgrading a digital camera. A difference will be noticable, but a person may have to know what to look for. Also, images taken with by ACS will not have the "missing" corner squares typical of the ones taken by Wide Field Planetary Camera 2.

How do astronauts get close to Hubble to work on it?
Astronauts fly up to Hubble in a space shuttle, grapple it, and pull it in so it stands within the shuttle's open bay. They then leave the shuttle in their space suits during Extra Vehicular Activities (EVA) - or spacewalks - to work on Hubble up close.

How many astronauts are on the mission? - what are their jobs?
There are 7 astronauts on the mission - A mission commander, pilot, payload commander/mission specialist, and 4 more additional mission specialists. Click here to find out more about the crew.

How are the astronauts trained?
Not including their extensive backgrounds in science, the airforce, the space program, etc... the crew are trained in the Neutral Buoyancy Lab at Johnson Space Center in Houston, where zero-gravity conditions are simulated underwater. They also get hands-on training with the actual Hubble parts and instruments that they will install, at Goddard Space Flight Center in MD.

How many servicing missions remain? When is the next?
One more after SM3B. On SM4 in 2004, we will be installing the Cosmic Origins Spectrograph (COS), the most sensitive ultraviolet spectrograph ever flown on Hubble, and the Wide Field Camera 3 (WFC3), the first truly panchromatic camera (sensitive to a wide range of colors) on Hubble.

General Questions about Hubble...

When is the end of Hubble's mission?
The current plan is to operate Hubble until 2010. We anticipate a mission to Hubble will be required in 2010 either to return it to the ground, or to raise it to a higher orbit (possibly with the aid of an attached booster) where it cannot fall back to Earth.

Where can I find images taken by Hubble?
The archive of Hubble images is maintained by the Space Telescope Science Institute.

What Does Hubble weigh and how big is it?
Hubble weighs about 11000 kg (24000 lbs) on Earth. More exactly, it weighs 11065 kg (24395 lbs) pre-SM3B, and will weigh 11864 kg (26155 lbs) post-SM3B. It is about the size of a big tractor-trailer truck. To be more precise: The length is 13.2 meters (43.5 ft.) and the maximum diatemer is 4.2 meters (14 ft.)

You can compare this to a car, which weighs around one or two tons (or roughly 1000 to 2000 kg). Thus, Hubble weighs as much as 6 to 12 cars (depending on their size). It is not phenomenally heavy. To get really heavy stuff, look at big aircraft carriers and monster skyscrapers!

How fast does Hubble travel?
At its current altitude, Hubble orbits the earth about every 96 minutes, with a speed of approximately 17,000 mi/hr or 27,200 km/hr.

How high up is Hubble?
The Hubble Space Telescope is a low earth orbiting (LEO) satellite. It is located about 320 nautical miles (360 statute miles, 600 km) above the surface of the earth.

How can I see Hubble pass over my area?
Check for Hubble sightings in your area at NASA Sky Watch.

What are the main objectives of the Hubble Program?
The Announcement of Opportunity for The Hubble Space Telescope, dated March 1977, cites that the main scientific objectives for Hubble are to determine:

A. The constitution, physical characteristics, and dynamics of celestial bodies.

B. The nature of processes which occur in the extreme physical conditions existing in and between astronomical objects.

C. The history and evolution of the universe.

D. Whether the laws of nature are universal in the space-time continuum.

Who was Edwin Hubble?
Hubble, Edwin Powell 1889-1953, American astronomer, was born in Marshfield, Mo. As a staff member (from 1919) at Mt. Wilson Observatory, Hubble used the 100-in. (254-cm) telescope there to discover that there are large-scale galaxies beyond the Milky Way and that they are distributed almost uniformly in all directions.

In what is now known as Hubble's Law, he was the first to offer observational evidence supporting the theory of the expanding universe.

What is Hubble's Law?
Hubble's law is a statement that the greater the distance between any two galaxies, the greater is their relative speed of separation. In other words, the universe is expanding roughly uniformly. This empirical finding is more consistent with the Big Bang theory of the universe's origin than with the steady state theory.

The law was first proposed in 1929 by Edwin Hubble, who observed that the more distant a galaxy, the greater its redshift, and hence its velocity relative to our Galaxy.


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