Press Release

Automated Telescope Array Discoveries Mount

By SpaceRef Editor
May 28, 2003
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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 Moon s 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:

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.

SpaceRef staff editor.