Waching daily May 4 2018

In 1923, Hermann Oberth, a German scientist, in a book entitled The Rocket Into Interplanetary

Space, put forward a dream.

If we could look at the heavens with an astronomical telescope in orbit, unhindered by the shielding

sea of atmosphere that blankets the Earth, think of the discovers we would make, the

clear vision of the universe we would have in quiet space.

The telescope, an instrument for collecting more light than would normally enter the human

eye.

For over 300 years, light, optics, and the human imagination have sculptured our perception

of the universe.

Today, large telescopes such as those at Palomar Mountain and Kitt Peak carry out detailed

investigations of very faint objects at the limits of perception.

The naked eye has been replaced by spectroscopes,

photographic plates,

computers.

Yet, a fundamental challenge, a length between past and present, remains ever constant:

the quest for more light, to see fainter and more distant objects, to construct better

light collectors.

"This is a photograph of the galaxy Messier 33, a nearby galaxy, a rather common type,

and quite illustrative of the type of image that we obtain with telescopes that are based

on the surface of the Earth.

This type of information, together with spectra like the plate that I am holding here, form

the largest part of the information obtained and used by ground-based astronomers.

It's quite god, but nowhere as good as it might be.

Astronomers themselves, and many in the lay public, don't appreciate, at times, the

enormous distances that they're dealing with.

When we look at the photograph of a cluster of galaxies like this, it's hard to appreciate

that these images that we obtain now are from galaxies that are probably a billion lightyears

away.

With the space telescope, we'll be able to look to much great distances and therefore

much further back into time.

In fact, much closer to the creation of the universe itself.

In order to understand how the Space Telescope works, we really need to understand how the

astronomer and the astrophysicists work with light."

Almost all the information we have about the universe reaches us in the form of electromagnetic

radiation, which objects either radiate, absorb, or reflect.

The spectrum disperses this radiation into its separate colors, visible light, infrared

radiation, radio waves at one end to X-rays and gamma rays at the other.

Now, each element in nature has a characteristic spectral signature, a fingerprint of light,

if you will.

Because common Earthly elements have been found in the Sun and stars, we can determine

through a star's own unique stellar spectrum the speed of an object, its temperature, density,

chemical composition.

Each band of light becomes a window unto the universe with a unique view.

But many wavelengths are permanently inaccessible to astronomers using Earth-bound telescopes.

Due to the Earth's atmosphere, which in shielding us from most of the biologically

harmful radiations, allows only visible light and varying amounts of ultraviolet, infrared,

and radio to reach the ground.

We are given a very incomplete picture of the universe in these wavelengths.

Our stellar fingerprint is difficult to analyze.

The atmosphere also frustrates ground-based optical observations.

One hundred miles deep, it is filled with dust particles, water vapor, and other obscuring

materials.

Constantly shifting layers of air of different densities bend light back and forth.

Atmospheric turbulence imposes a fundamental limitation on a telescope's ability to see

clearly two objects close together in the sky.

At times of bad seeing, stellar images waver like candle flames in a gentle breeze.

The space telescope will be out where the images are completely quiet, where the full

spatial and wavelength resolution powers of the telescope can be used.

It will peer far into the ultraviolet and infrared regions of the spectrum.

A galaxy seen through the Earth's atmosphere as a big shimmering fuzz ball in space will

be brought into sharp, clear, and steady view for study and analysis.

We will see it ten times clearer than we see it now.

We will see fifty time further into the universe than the best ground-based telescopes can

see.

All this from a telescope no different in principle than the reflecting telescope of

Newton and his descendants.

"Every optical telescope operates in essentially the same manner.

It gathers a part of a light produced by or reflected from an object, concentrates this

light in a single area, a focal plane, and then magnifies the image formed there."

So, in space, as on Earth, we must begin with a mirror.

In this case, polished within one half a millionth of an inch of accuracy.

As light enters from space, something must catch the reflection of our primary mirror.

A secondary mirror is set into place.

An image must now be fed into a variety of auxiliary instruments, so we provide a package

of five major scientific instruments which will convert telescope images into useful

data.

The scientific instruments and optical assembly must then be encased in a shell, which protects

them from dangers in the space environment such as stray light or micrometeoroids.

To power our telescope, we turn to the Sun for energy and attach solar array panels.

In the Earth's shadow, we will power our telescope by batteries.

Finally, we must have a means of communicating with our telescope, so we obtain two high

gain antennas.

Data which these antennas beam back to Earth will be converted to pictures.

"Two earliest telescopes here at Palomar in California is only about twice as big as

the space telescope will be, yet it is very much more massive because, of course, it has

to work in the Earth's gravity.

However, all telescopes, including this one and Space Telescope, are essentially the same.

They gather light so we can analyze it with various instruments.

The space telescope will have five such instruments.

There will be two wide field cameras which take pictures of the sky, one over a wide

region and another over a smaller region.

The smaller region camera will have a much higher resolution than the other.

There will also be two spectrographs aboard Space Telescope, one will be used on fairly

bright objects and take the highest resolution spectra, the other will be used for quite

faint objects such as galaxies and far away quasi-stellar sources.

There will also be on Space Telescope an instrument that utilizes the fine guidance system of

the telescope.

This is the system that keeps the telescope pointed quite accurately at the stars during

an exposure.

This instrument will allow us to measure the distance between stars quite accurately on

the sky and also their motions over a short period of time."

The space telescope, due to be launched in the 1980s, will be hoisted into orbit some

500 miles above the Earth by the space shuttle.

Fitting into the shuttle's cargo bay, the telescope will be latched to a tilting mechanism

and rotated into a ninety degree position for checkout.

It will then be placed in a vertical angle, released, and its power and communication

systems deployed.

The periodic revisit of the shuttle will allow for the replacement of components and routine

maintenance.

Every five years, the telescope will be returned to Earth for major ground refurbishment.

This ability to service the telescope through human care will extend its lifespan up to

twenty years.

"It will orbit above our murky atmosphere and obtain images of objects that are incredible

distances away, perhaps of galaxies fourteen billion lightyears distance.

So far away that when the light first set out towards us, there was no Earth, no Sun,

no Milky Way galaxy.

We will be probing the time of the earliest history of the universe.

Space Telescope is, in a way, a little like Galileo's first telescope.

Wherever Galileo pointed his telescope, he made major new discoveries.

Look at the Moon, you find mountains and craters.

Look at Saturn, you find rings.

Look at the Milky Way, you find it is littered and composed of stars.

Every one of these discoveries, things that people had not known before.

I think it's going to be very similar with the space telescope, yet will illuminate celestial

objects that we know about.

It will discover celestial objects never before guessed.

It will provide insights into the most important questions such as stellar evolution, such

as the search for planets going around other stars, and the grandest cosmological questions

of the origin, nature, and fate of the universe.

Space Telescope is a kind of grand intellectual adventure for all of us, which will cast light

not just on the cosmos, but also on ourselves."

"It's impossible to predict what Space Telescope will bring in terms of its results,

but we do know the results will be exciting.

When the first radio telescopes were built, we did not know that we'd find quasars and

pulsars.

Or when the first X-ray telescopes were built, we did not know that we would discover X-ray

stars.

With Space Telescope, we will find many new things, we'll find exciting things."

Stretching the mind of humankind to the very beginning and end of space and time, the space

telescope may tell us at last whether the universe will expand forever or whether that

expansion is slowing.

It may help us learn more about the violent events of the universe,

pulsars,

quasars,

the gravitational implosions that produce black holes.

It may also tell us how the universe began and how it will end.

Ultimately, as is the case with all voyages of discovery, it's greatest contribution

will be the unexpected breakthrough that brings completely new knowledge.

But with the space telescope, we will shake loose of the Earth, of its murky and oblique

atmosphere, and in the never-ending quest for light, we will soar.