From: "Mel Bartels" 
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Reply-To: "Mel Bartels" 




Global Network of Astronomical Telescopes (GNAT) Tucson, Arizona

Contacts:
Dr. Eric R. Craine, 520-325-4505, craine{at}gnat.org

Embargoed until 27 May 2003, 12:30 p.m. CDT

AUTOMATED TELESCOPE ARRAY DISCOVERIES MOUNT

Astronomers are announcing today early results of a prototype,
three-telescope array of automated astronomical imagers. These have been
used to discover new Solar System objects, as well as to discover and
monitor the time variable brightness of stars, especially those potentially
harboring extrasolar planets. The report is being presented today by Dr.
Eric R. Craine of the Global Network of Astronomical Telescopes (GNAT),
Tucson, Arizona to the American Astronomical Society meeting in Nashville,
Tennessee. The system is of special interest because of its very low cost,
extremely high data output and application to myriad astronomical
observations.

This array is named the Moving Object and Transient Event Search System
(MOTESS). It was designed by Roy A. Tucker of Goodricke-Pigott Observatory
(GPO), Tucson, Arizona. It was originally implemented for discovery and
astrometric measurement of asteroids, but it is also used as a large-scale,
cost-effective photometric monitoring instrument with large volume data
handling techniques developed under direction of Dr. Eric R. Craine and
Mark S. Giampapa of the National Solar Observatory (NSO), Tucson, Arizona.
The prototype automated MOTESS observatory, located in Tucson, is a
proof-of-principle system for a 48-telescope, globally distributed network
planned by GNAT. During its first two years of automatic operation, MOTESS
has yielded valuable observations of asteroids as well as stellar
variability.

The MOTESS system is both cost-effective and productive. Costs for the
telescope hardware are minimized through "scan-mode" operation,
whereby each telescope in the array is pointed at a specific position in
the sky with respect to the Earth. The view of the sky seen by each
telescope changes by virtue of the rotation of the Earth, thereby scanning
the sky across the field of view of each instrument. With no moving parts
in the hardware system, costs of the prototype system were held at under
$20,000, a fraction of the cost of more traditional, comparable
telescopes. The telescopes make their observations automatically and
continuously throughout the night, and hence remain unattended by human
operators during that time. Since the cameras make one long, uninterrupted
exposure throughout the night, there is no deadtime for moving the
telescopes to new positions or inactivating camera recording while
individual images are read out. Each image has a width nearly twice the
full Moons diameter, and about 10-12 hours of time long, thus typically
covering about 200 square degrees on the sky per night, per telescope in
the array. During the course of a year, the system typically makes several
observations per night of approximately 1.5 million stars, as well as
hundreds of asteroids and transient events.

Asteroid searches with the MOTESS system involve acquisition of triplets of
images of select regions of the sky, each telescope contributing one of the
images of the triplet each night. These images are aligned with respect to
one another and they are alternately displayed in software such that moving
objects are visually distinguished from the fixed background stars.
Detection of asteroids as faint as 20-21 magnitude is possible with this
system. During the first year of observation, 290 newly discovered
asteroids were measured. Naming rights for over 180 new asteroids have
accrued to the program. Experience with this system is leading to data
handling software which is expected to provide automated detection of such
asteroids.

The MOTESS system is presently accumulating a catalog of three brightness
observations per night of the 1.5 million stars in its current observing
list. These observations are repeated nightly throughout the year, enabling
the creation of long-term light curves for each of these stars. In the
region of the sky along the celestial equator presently monitored, there
are 179 known variable stars, all of which have been observed. In addition,
examination of the light curves in this database indicate that there are
approximately 55,000 newly discovered variable star candidates. These
include stars that vary periodically, either due to eclipses by companion
stars or by intrinsic internal pulsations, as well as stars which vary
irregularly over long periods of time.

The MOTESS system is a pioneering complement to other planned major survey
instruments, and it is a valuable test-bed for developing techniques of
handling large volumes of specialized astronomical images. Combined
discovery rates of asteroids as well as varyiable stars of many different
types provides analysis opportunities which could occupy hundreds of
students and researchers for many years to come. The flow of MOTESS data
will triple by Spring of 2004 with the implementation of six more
telescopes in the emerging network of scan-mode systems. GNAT is actively
seeking collaborators interested in studying and analyzing these
interesting new objects.

For more information, see:
http://www.gnat.org/~ida/gnat/index.html

IMAGE CAPTION:
[http://www.gnat.org/~ida/gnat/pr/MOTESS-PR1.JPG]
The MOTESS prototype system produces continuous images during the course of
each night of observation which, when reproduced with a 30-inch width,
stretch for over 180 yards in length. The inset shows the size of the Full
Moon in one of the images. These images are currently produced three times
during each night of observation and contain images of nearly 1.5 million
stars during the course of a year.

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