The APO 3.5-meter
remote observing program-2002 and beyond
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Bruce Gillespie
Site Operations Manager, Apache Point
Observatory
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Abstract
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The Apache Point Observatory 3.5-meter telescope
is a working model of a modern mid-sized telescope used primarily on
a shared-night, remote-observing basis. After a decade of successful
remote operation and scientific accomplishments, the Astrophysical
Research Consortium, builder and owner of the telescope, is examining
the role by which this university-owned instrument can best serve its
constituency and astronomy at large in the coming years. Various
"niche" scientific capabilities are described for the telescope,
including fast-response observations of transient phenomena, synoptic
observing programs, reactive queue-scheduled observations, temporal
study programs, plus being a capable test bed for new instruments.
While specialized uses of the telescope offer potential for major
scientific discoveries, traditional observing capabilities need to be
sustained for the ongoing and future research programs for the
majority of the consortium astronomers and students, a large and
diverse community. Finding an appropriate balance between the "unique
and specialized" versus the "bread-and-butter" observing models is
discussed, as is the role hands-on remote observing can serve to
support the various operational models.
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Keywords:Astrophysical
Research Consortium, Apache Point Observatory, 3.5-meter telescope,
remote observing
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1. background
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<![if
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The
Astrophysical Research Consortium (ARC or 'consortium'
hereafter) was established in 1984 to build and
operate Apache Point Observatory (APO) at Apache Point, New Mexico,
for the shared use and benefit of consortium astronomers and
students. Two major ARC projects at the site are the 3.5-meter
telescope, which has been in routine operation since 1994, and the
2.5-meter Sloan Digital Sky Survey (SDSS) telescope, in operation
since 1998. The following ARC member institutions
currently fund the operation and capital improvement projects for the
3.5-meter telescope: the University of Chicago, the University of
Colorado, Johns Hopkins University, New Mexico State University,
Princeton University, and the University of Washington. Telescope
time is allocated to these institutions in proportion to their
project contributions, and the telescope has a diverse and
geographically widespread user community of more than 200 astronomers
and students.
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<![if
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telescope and instrument description
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The 3.5-meter telescope has an f/10 Nasmyth
optical design with a 30-arcminute field-of-view, a lightweight
spun-cast 3.5-meter primary mirror, and lightweight secondary and
tertiary mirrors. Rotating the tertiary mirror provides access to
nine parfocal instrument ports. Direct friction drives enable precise
pointing and tracking. The telescope structure and enclosure have low
mass and are kept close to isothermal (at ambient temperature) by
wind and fan-forced air. The secondary mirror is actively controlled
to effect focus and tilt compensation, and the transformation between
the alt-az telescope mount and celestial coordinates is derived from
observational pointing models, while collimation is periodically
adjusted using a Shack-Hartmann wavefront sensor. The telescope has
excellent blind pointing performance, frequently provides
sub-arcsecond images in the visible, and requires unscheduled repairs
less than 2% of the time. Further telescope information is found at
http://www.apo.nmsu.edu/Telescopes/eng.papers/eng.papers.html.
An interior view of the telescope is shown in Figure 1.
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Figure 1.The 3.5-meter telescope from
inside enclosure, photograph by Dan Long
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Several
facility-class instruments are available for routine use on the
telescope, including an infrared imager and grism spectrometer, a
medium-resolution visible-light spectrograph and imager, a
high-resolution visible-light CCD imager, and an echelle
spectrograph. Also, a number of specialized visitor-supplied
instruments have been successfully used with the telescope, some for
limited observing runs and others on a continuing basis. Projects to
upgrade existing instruments and for acquiring next-generation
instruments have either been completed, are well underway, or are at
the proposal stage. These include a detector upgrade to new low-noise
CCDs for the medium-resolution visible-light spectrograph and imager
(completed in 2002), a new IR imager with a medium field detector and
Fabry-Perot etalon (under construction), a near-IR spectrograph
(under construction), a new medium-field visible CCD imager (being
designed), and a low-noise detector upgrade to the echelle
spectrograph (proposed). Continued use of more specialized "visiting"
instrumentation is expected and welcome, which include a Fabry-Perot
tunable narrow-band visible imager, a laser lunar ranging experiment,
and a Fourier Transform Spectrometer, among others. Additional
information on most of the existing and future instruments can be
found at http://www.apo.nmsu.edu/Instruments/.
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<![if
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overview
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The telescope systems were designed and built
for real-time remote operation through the Internet. Most (about three-quarters) of all observing is done
remotely, with in-person visits to the site by astronomers being
mainly for installation and testing of new instruments or for
training purposes. Multiple independent science programs
share the telescope in turn on the same night, often using more than
one scientific instrument. Remote users also collaboratively use the
telescope simultaneously from different off-site locations. Synoptic
observing programs and rapid-response observations are frequently
accommodated.
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The manner in which observatories support users
ranges from "help-yourself" to "full-service." The APO user support
model is somewhere in the middle, and is often described as an equal
partnership between the consortium astronomers and the observatory
staff. User support is helped by easy telescope access afforded by
the remote observing capability and on-line user information systems.
Operational costs are kept low by allowing and encouraging the direct
involvement of the astronomers in the operations and engineering
projects. Also, consortium astronomers have first-hand involvement
with the data acquisition process and can more readily understand and
appreciate the quality of their data. The APO remote observing
systems promote this hands-on observing approach while enabling
flexible and semi-reactive telescope use, which saves a significant
amount of astronomers' time (and funds) by greatly reducing the
amount of travel necessary to observe. While Principal Investigators
of the science programs are from ARC-affiliate institutions,
collaborations with scientists and students from outside the
consortium institutions are welcome and numerous.
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The telescope is scheduled by quarters using
proposals solicited and prioritized within each of the consortium
institutions. Except for brief synoptic observations and target of
opportunity programs, each night is typically divided into halves.
These half-night blocks provide adequate on-target and calibration
time, plus simplify the manual scheduling process. Se