TA-57 Brief Description

March 1998 2 0 8 TA and Facilities Descriptions
4.33.1 Site Description

TA-57 [Figure 4-33 (index map of TA-57)] is located about 28 mi (45 km) west of Los Alamos on
the southern edge of the Valles Caldera in the Jemez Mountains. The 15-acre (6-ha) site lies on
land leased from the US Forest Service, and the Laboratory’s use of the land is governed by a
memorandum of understanding between the Laboratory and the Forest Service. The site includes
the main area; a 2-acre (0.81-ha), 5-million-gallon (18,927,060-L) pond and two smaller
ponds; and a housing area shared with the Forest Service. TA-57 is the location of environmental
research, including the Laboratory’s Hot Dry Rock Geothermal Project and the Milagro Project,
which investigates astronomical events.
Fenton Hill was originally developed to study the use of hot dry rocks to generate geothermal energy.
The Geothermal Project has been completed, and the site is now being proposed as the
location for an astrophysics observatory. The proposed observatory would be dedicated to observations
of objects that brighten in the night sky then quickly fade away. These objects include
supernovae, flare stars, and brief, very-high-energy flashes from space called gamma-ray bursts.
The proposed facility may also contribute to catalogs of near-Earth objects, including potential
Earth-crossing comets and asteroids.
The instruments planned for the Fenton Hill site are designed specifically to observe and record
ephemeral flickers and flashes. As envisioned, the site will be home to a suite of telescopes dedicated
to optical observations set for short time scales—from fractions of a second to hours. The
short-time-scale exposures will allow broad searches of the sky and a chance to catch transient
optical events before they vanish.
The first optical telescope planned for Fenton Hill will be the Research and Education Automatically
Controlled Telescope (REACT). REACT will be an automatic and robotic telescope that allows
astronomers and astronomy students to search the sky from their computer terminals. REACT will
have a narrow, one-half-degree field of view with high resolution. In its event-alert mode, REACT
will automatically swing around to take a series of 1-min exposures to catch any optical signals coinciding
with gamma-ray transients seen by other sky-watching instruments. REACT will be housed
in a weather-sensing dome that will automatically close in the rain.
The next instrument proposed for the site will be the Robotic Optical Transient Search Experiment
(ROTSE I), a four-barreled system with 200-mm, wide-field lenses on electronic cameras. It
will have an intermediate 15° field of view. ROTSE will use telemetry data from the National Aeronautics
and Space Administration’s (NASA’s) Compton Gamma-Ray Observatory to direct its array
of cameras toward burst events as they occur. Alerts will come from the fast-alert system developed
by NASA at Goddard Space Flight Center. ROTSE will respond within 10 s of a burst onset.
ROTSE will probably respond to alerts from BACODINE about once a week. The rest of the time
ROTSE will spend its time watching comets. If a comet in the Kuiper Belt beyond Neptune happens
to pass in front of our view of a star, ROTSE will record the tenth-of-a-second dip in light intensity
from that star. The data may help detect and track comets long before they can be spotted
from their own optical emissions.
The new telescopes will stand beside an unusual observatory already in place at Fenton Hill called
Milagro (the Milagro Project). Using more than 700 sensitive light detectors submerged in a 5-million-
gallon (18,927,060-L) artificial pond, plus another 200 detectors arrayed around the pond,
Milagro will record signals from high-energy cosmic emissions, including gamma-ray bursts. Milagro
will stare continuously at the sky from horizon to horizon, day and night, acting like a camera
whose shutter is always open. When Milagro alerts ROTSE, it will be watching the same piece of
the sky, increasing the odds of capturing transient flashes.
The water in the main pond is filtered to maintain its purity for use in environmental research.


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