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Observatories and Instruments

Apache Point Observatory

Ground-Based Optical Observatories

An astronomical observatory in the Sacramento Mountains at Sunspot, New Mexico, operated by the Astrophysical Research Consortium. Construction began in 1985 and full operations started in November 1994; the site hosts the 2.5-meter Sloan Foundation Telescope used for the Sloan Digital Sky Survey since 2000 and the 3.5-meter ARC telescope, and it houses the APOLLO lunar laser ranging experiment, operational since 2005, which measures the Earth-Moon distance to millimeter precision.

Facts
Observatory Type
Ground-based optical observatory 2
Location
Sunspot, New Mexico, United States 2
Operational
from 1994 2
Measures
Visible-light imaging and spectroscopy for wide-field sky surveys, precision astrometry, and millimeter-precision lunar laser ranging. 2
Operating Principle
Hosts multiple telescopes, including the 3.5-meter ARC Ritchey-Chretien reflector on an alt-azimuth mount and the 2.5-meter Sloan Foundation Telescope; the APOLLO laser ranging station fires laser pulses at retroreflectors left on the Moon by Apollo astronauts. 2
Classification
Observing Band
Infrared 1
Observing Band
Optical / Visible 1
FAQs

How does the APOLLO experiment at Apache Point measure the distance to the Moon so precisely?

It times laser pulses bounced off lunar reflectors to a few picoseconds, about one millimeter of range precision.

APOLLO, the Apache Point Observatory Lunar Laser-ranging Operation, fires laser pulses from the observatory's 3.5-meter telescope at reflectors left on the Moon and times the round trip. It measures that travel time to a few picoseconds, which corresponds to about one millimeter of precision in the range to the Moon. The telescope's large aperture and the good atmospheric seeing at the site let it record multiple returned laser photons per pulse, whereas earlier lunar ranging facilities averaged only 0.01 photon per pulse.
Connections

Operated By

Source Apache Point Observatory (Wikipedia)
Source Apache Point Observatory (Wikipedia)
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Located In

Also in Geography Atlas: where this subject is located.

Sources
1. Apache Point Observatory (Wikipedia)
  • Lead section
    The Apache Point Observatory (APO; obs. code: 705) is an astronomical observatory located in the Sacramento Mountains in Sunspot, New Mexico, United States, approximately 18 miles (29 km) south of Cloudcroft.
  • Article text: band optical
    a variety of optical and near-infrared instruments
  • Article text: band infrared
    a variety of optical and near-infrared instruments
  • In Group: Optical Observatories of the Americas, Lead sentence
    code: 705) is an astronomical observatory located in the Sacramento Mountains in Sunspot, New Mexico, United States, approximately 18 miles (29 km) south of Cloudcroft.
  • Operated By: New Mexico State University, Article text: operator
    The observatory is operated by New Mexico State University (NMSU) and owned by the Astrophysical Research Consortium (ARC).
  • Operated By: Astrophysical Research Consortium, Article text: operator
    The observatory is operated by New Mexico State University (NMSU) and owned by the Astrophysical Research Consortium (ARC).
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2. Wikipedia (space and spaceflight articles)
Wikimedia Foundation
  • Wikipedia: Apache Point Observatory, history section
    Construction of the building began in 1985, but full operations of the telescope were delayed until November 1994
  • Wikipedia: Apache Point Observatory, instruments section
    The SDSS 2.5 m telescope is used for the Sloan Digital Sky Survey, and began operating in 2000
  • Wikipedia: Apache Point Observatory, telescopes section
    The ARC 3.5 m telescope is a Ritchey-Chretien reflector on an alt-azimuth mount with instruments attached at several focal points
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