NASA studies space railway to explore origins of planets, stars,and galaxies (Forwarded)

Bill Steigerwald
NASA Goddard Space Flight Center, Greenbelt, MD
301-286-5017

October 5, 2004

Release 04-056

NASA STUDIES SPACE RAILWAY TO EXPLORE ORIGINS OF PLANETS, STARS, AND GALAXIES

A NASA-led team is studying the construction of a railway in space for a pair of
telescopes that will provide views of planet, star, and galaxy formation in
unprecedented detail. The proposed Space Infrared Interferometric Telescope
(SPIRIT) mission will also examine the atmospheric chemistry of giant planets
around other stars.

SPIRIT will consist of two telescopes at opposite ends of a 120-foot (40-meter)
beam. The telescopes will move along the beam like cars on a railway, combing
their images using the techniques of interferometry to achieve the resolving
power of a single giant telescope 120 feet across.

NASA's Goddard Space Flight Center, Greenbelt, Md., will lead a
NASA/university/industry team to develop a preliminary design for SPIRIT. The
team will evaluate various mission concepts, create a roadmap of the technology
development required for the mission, and generate independent cost assessments.

The study was commissioned in July 2004 by NASA Headquarters, Washington, D.C.,
as one of nine proposals that will help strategic planning for NASA's Origins
Space Science research theme. NASA's Origins program seeks to answer the
fundamental questions about the universe, such as where we came from and whether
or not we are alone. The team will report to the Origins Roadmap Committee in
early January, 2005, and a final report is due three months later.

"I'm delighted that SPIRIT was chosen for study," said Dr. David Leisawitz of
NASA Goddard, Principal Investigator for the proposed mission. "We're going to
give NASA a chance to build a telescope that will dazzle the world with crisp,
clear infrared pictures of the universe."

"These images will help us to answer some very profound questions. How did we
living critters wind up on a rocky planet bathed in light from the Sun, one of a
hundred billion stellar denizens of the magnificently spiral-shaped Milky Way
galaxy? Perhaps even more tantalizing, we should expect the unexpected, as
that's what we find whenever a big step is taken to improve the scientific
community's tools. SPIRIT will use techniques pioneered a century ago by Nobel
Laureate Albert A. Michelson, so we know it can be done, and I think it's an
excellent match to the Origins mission class envisioned in NASA's call for
proposals,” said Leisawitz.

SPIRIT will examine the universe in the far-infrared and sub-millimeter
wavelengths of light. This light is invisible to the human eye, but some types
of infrared light are perceived as heat.

The processes that build planets, stars, and galaxies are most readily visible
in these kinds of light. For example, stars are born when massive interstellar
clouds collapse under their own gravity. The collapse generates heat, causing
the central star-forming region of the cloud to glow in infrared. Newborn stars
are frequently surrounded by disks of dust and gas, which also collapse under
their own gravity to form planets. While the planets are too small to be seen
directly, their gravity disturbs the dust disk, forming ripples and lumps.
Warmed by the central star, the dust glows in infrared light, revealing the
dusty structures to SPIRIT and divulging the locations and sizes of previously
unknown planets.

Looking farther into space is equivalent to seeing back in time, because the
speed of light is finite, and it takes light a significant amount of time to
traverse immense cosmic distances. We see the nearest large galaxy (Andromeda)
as it appeared about two million years ago, because that's how long it took for
its light to reach us. We cast our gaze back billions of years by looking toward
the limit of the observable universe, and thus can watch galaxies as they
evolve. However, since the universe is expanding, light emitted by remote
galaxies has been stretched by the expansion of space to infrared and
sub-millimeter wavelengths, so we need telescopes highly sensitive to these
types of light to observe distant galaxy formation.

Many of these objects appear too small, or shine too faintly at their remote
distances for existing telescopes to observe in great detail. To accomplish such
ambitious observations, SPIRIT will have 100 times the angular resolution
(ability to see fine detail) than existing infrared telescopes, complemented
with a matching improvement in sensitivity.

Technical challenges to overcome include keeping the telescope mirrors extremely
cold (about 4 degrees Kelvin or minus 452 degrees Fahrenheit) so their own heat
does not obscure the faint infrared light they are trying to collect. The
detectors also need to have greater sensitivity and more pixels. The
Goddard/industry team is up to the challenge: "Our engineers love working on
this project; there's a lot of room for creative thought, and everyone
understands that this is an opportunity to take a giant leap forward
scientifically while inspiring the next generation of explorers." says Leisawitz.

If approved, SPIRIT could be ready for launch in 2014, on board a large
expendable rocket. SPIRIT would travel to the L2 libration point one million
miles from Earth where it will automatically unfold its beam and deploy the
telescopes. The Goddard-led team includes collaborators from Caltech, Cornell,
the Harvard-Smithsonian Center for Astrophysics, the University of Maryland, the
Massachusetts Institute of Technology, the Naval Research Laboratory, Princeton,
the University of California, Los Angeles, the University of Wisconsin, and
NASA's Jet Propulsion Laboratory and Marshall Space Flight Center. The industry
team includes Ball Aerospace, Boeing, Lockheed-Martin, and Northrop-Grumman. For
an image and more information, refer to:
http://www.gsfc.nasa.gov/topstory/2004/0915spirit.html

In message , Andrew Yee
writes
Bill Steigerwald
NASA Goddard Space Flight Center, Greenbelt, MD
301-286-5017

October 5, 2004

Release 04-056

NASA STUDIES SPACE RAILWAY TO EXPLORE ORIGINS OF PLANETS, STARS, AND GALAXIES

A NASA-led team is studying the construction of a railway in space for
a pair of telescopes that will provide views of planet, star, and
galaxy formation in unprecedented detail. The proposed Space Infrared
Interferometric Telescope (SPIRIT) mission will also examine the
atmospheric chemistry of giant planets around other stars.

SPIRIT will consist of two telescopes at opposite ends of a 120-foot
(40-meter) beam. The telescopes will move along the beam like cars on a
railway, combing their images using the techniques of interferometry to
achieve the resolving power of a single giant telescope 120 feet across.


Don't you need at least three mirrors for imaging?

"JS" == Jonathan Silverlight writes:

NASA STUDIES SPACE RAILWAY TO EXPLORE ORIGINS OF PLANETS, STARS,
AND GALAXIES

A NASA-led team is studying the construction of a railway in space
for a pair of telescopes that will provide views of planet, star,
and galaxy formation in unprecedented detail. The proposed Space
Infrared Interferometric Telescope (SPIRIT) mission will also
examine the atmospheric chemistry of giant planets around other
stars.

SPIRIT will consist of two telescopes at opposite ends of a
[40-meter] beam. The telescopes will move along the beam like cars
on a railway, combing their images using the techniques of
interferometry to achieve the resolving power of a single giant
telescope [40 meters] across.

JS Don't you need at least three mirrors for imaging?

Not necessarily. The important aspect is Fourier plane coverage.
SPIRIT could obtain this by allowing the beam to rotate and taking
"snapshots." Each snapshot, with the beam at a slightly different
angle and with the telescopes at slightly different positions along
the beam, provides effectively a different interferometer pair.
Combining all of the different effective interferometer pairs, one can
then make an image.

In the case of radio interferometers, we (often) use the rotation of
the Earth to provide different effective interferometer pairs. In the
early days of radio interferometry, though, a process similar to what
is planned for SPIRIT was used. Some early interferometers contained
a moveable antenna. So an observation was conducted, the antenna
moved, another observation conducted, etc. Even today, some of the
highest "precision" images (more precisely, highest dynamic range
images) are obtained using multiple configurations of the VLA. In
other words, one makes an observation with the VLA in one
configuration, waits for the antennas to be moved to a new
configuration, makes a new observation, and then combines the data
from the different configurations.

Obviously, a key assumption in all of this is that the structure of
the source does not change appreciably in the time it takes to move
the antenna(s).

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