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Navy Precision Optical Interferometer

November 23, 2023

The Navy Precision Optical Interferometer (NPOI) is an American astronomical interferometer, with the world's largest baselines, operated by the Naval Observatory Flagstaff Station (NOFS) in collaboration with the Naval Research Laboratory (NRL) and Lowell Observatory. The NPOI primarily produces space imagery and astrometry, the latter a major component required for the safe position and navigation of all manner of vehicles for the DoD. The facility is located at Lowell's Anderson Mesa Station on Anderson Mesa about 25 kilometers (16 mi) southeast of Flagstaff, Arizona (US). Until November 2011, the facility was known as the Navy Prototype Optical Interferometer (NPOI). Subsequently, the instrument was temporarily renamed the Navy Optical Interferometer, and now permanently, the Kenneth J. Johnston Navy Precision Optical Interferometer (NPOI) – reflecting both the operational maturity of the facility, and paying tribute to its principal driver and retired founder, Kenneth J. Johnston.[1][2]

Navy Precision Optical Interferometer
Navy Precision Optical Precision Interferometer at the Anderson Mesa Station of Lowell Observatory.
Alternative namesNPOI
Part ofUnited States Naval Observatory Flagstaff Station 
Location(s)Arizona
Coordinates35°05′45″N 111°32′02″W / 35.0959°N 111.534°W / 35.0959; -111.534
OrganizationLowell Observatory
United States Naval Observatory Flagstaff Station
United States Naval Observatory
United States Naval Research Laboratory 
Altitude2,163 m (7,096 ft)
Built1992–1994 (1992–1994)
First light1994 
Telescope styleastronomical interferometer
Michelson interferometer 
Websitelowell.edu/research/research-facilities/npoi/
Location of Navy Precision Optical Interferometer
  Related media on Commons
[edit on Wikidata]

The NPOI project was initiated by the United States Naval Observatory (USNO) in 1987.[3] Lowell joined the project the following year when the USNO decided to build the NPOI at Anderson Mesa.[4] The first phase of construction was completed in 1994, which allowed the interferometer to see its first fringes, or light combined from multiple sources, that year.[5] The Navy began regular science operations in 1997.[6] The NPOI has been continuously upgraded and expanded since then, and has been operational for a decade. The workings of NPOI as a classic interferometer, are described at Scholarpedia,[7] and at the NPOI site.[8]

Description edit

The NPOI is an astronomical interferometer laid out in a three-arm "Y" configuration, with each equally-spaced arm measuring 250 meters (820 ft) long. There are two types of stations that can be used in the NPOI. Astrometric stations, used to measure the positions of celestial objects very accurately, are fixed units placed 21 meters (69 ft) apart, with one on each arm and one at the center. Imaging stations can be moved to one of nine positions on each arm, and up to six can be used at one time to perform standard observing. Light from either type of station is first directed into the feed system, which consists of long pipes which have been evacuated of all air. They lead to a switchyard of mirrors, where the light is directed into the six Long Delay Lines, which is another set of long pipes that compensate for the different distances to each station. The light is then sent into the Beam Combining Facility, where it enters the Fast Delay Lines. This third set of evacuated pipes contains mechanisms that move mirrors back and forth with a very high degree of accuracy. These compensate for the movement of the mirrors as they track an object across the sky, and for other effects. Finally, the light leaves the pipes inside the BCF and goes to the Beam Combining Table, where the light is combined in a way that allows images to be formed.[3]

 
Navy Precision Optical Interferometer layout.

Both types of station have three elements: a siderostat, a Wide Angle Star Acquisition (WASA) camera, and a Narrow Angle Tracking (NAT) mirror. The first is a precisely-ground flat mirror 50 cm (20 in) in diameter. The WASA cameras control the aiming of the mirror at the celestial target. The reflected light from the siderostat is directed through a telescope which narrows the beam down to the diameter of the pipes, which is 12 cm (4.7 in). The light then hits the mirror of the NAT, which compensates for atmospheric effects and directs the light into the feed system.[3]

In 2009 NOFS began final plans for NPOI to incorporate four 1.8 m (71 in) aperture optical-infrared telescopes into the array, which were accepted by the Navy in 2010,[9][10] and assigned to the Naval Observatory Flagstaff Station.[11] They were originally intended to be "outrigger" telescopes for the W. M. Keck Observatory in Hawaii, but were never installed and incorporated into Keck's interferometer. Three telescopes are being prepared for near-immediate installation,[12][13] while the fourth is currently at Mount Stromlo Observatory in Australia and will be incorporated at some point in the future.[11] The new telescopes will help with faint object imaging and improved absolute astrometry, due to their greater light-gathering abilities than the existing siderostats.[11]

NOFS operates and leads the science for the Navy Precision Optical Interferometer,[14][15] as noted, in collaboration with Lowell Observatory and the Naval Research Laboratory at Anderson Mesa. NOFS funds all principal operations, and from this contracts Lowell Observatory to maintain the Anderson Mesa facility and make the observations for NOFS to conduct the primary astrometry. The Naval Research Laboratory (NRL) also provides funds to contract Lowell Observatory's and NRL's implementation of additional, long-baseline siderostat stations, facilitating NRL's primary scientific work, synthetic imaging (both celestial and of orbital satellites). When complete by 2013, NPOI will run the longest baseline interferometer in the world. The three institutions – USNO,[16][17] NRL,[18] and Lowell[19] – each provide an executive to sit on an Operational Advisory Panel (OAP), which collectively guides the science and operations of the interferometer. The OAP commissioned the chief scientist and director of the NPOI to effect the science and operations for the Panel; this manager is a senior member of the NOFS staff and reports to the NOFS Director.[20]

NPOI is an example of the Michelson Interferometer design, with the principal science managed by NOFS. Lowell Observatory and NRL join in the scientific efforts through their fractions of time to use the interferometer; science time is 85% Navy (NOFS and NRL); and 15% Lowell. NPOI is one of the few major instruments globally which can conduct optical interferometry.[21][22] See an illustration of its layout, at bottom. NOFS has used NPOI to conduct a wide and diverse series of scientific studies, beyond just the study of absolute astrometric positions of stars,;[23] additional NOFS science at NPOI includes the study of binary stars, Be Stars, Oblate stars, rapidly rotating stars, those with starspots, and the imaging of stellar disks (the first in history) and flare stars.[24] In 2007–2008, NRL with NOFS used NPOI to obtain first-ever closure phase image precursors of satellites orbiting in geostationary orbit.[25][26]

Installation plans for a 1m Array have been developed by NRL and Lowell Observatory, based on the funded science performed.

Discussion edit

Optical interferometers are extremely complex, unfilled aperture photon-collecting telescopes in the visual (sometimes the near infrared, too), which produce synthesized images and fringe data "on the fly" (unlike radio interferometers which are privileged to record the data for later synthesis), essentially by taking an inverse Fourier transform of the incoming data. Astrometry is understood by precisely measuring delay line additions while fringing, to match the light path differences from baseline ends. Using essentially trigonometry the angle and position of where the array is 'pointed' can be determined, thus inferring a precise position on the sphere of the sky.

Only a few exist that can be considered operational. To date NPOI has produced the highest resolution optical images of any astronomical instrument, though this may change when the CHARA array and Magdalena Ridge Observatory Interferometer begin optical-band operations.[27] The first astronomical object imaged (resolved) by NPOI was Mizar, and since, a significant amount of astrometry, reference tie frame, rapid rotator star, and Be stellar disk study has been performed.[28] NPOI is capable of determining positions of celestial objects to a few milli-arcsecond, in part due to the optical anchoring of its components using a complex metrology array of lasers that connect main optical elements to each other and to bedrock.

Many specialized lasers are also used to align the long train of optics. The current NPOI siderostat array remains the world's only long-baseline (437-meter) optical interferometer that can simultaneously co-phase six elements.[29] NPOI is expected to grow significantly in capability with the pending addition of four 1.8-meter aperture IR/Optical telescopes into the current array.[11] The enhanced array will also employ adaptive optics techniques. This layout and increased sparse aperture will permit significant improvements to the science capability, from a tenfold increase in measuring ever-fainter wide-angle astrometry targets, to improved positional determination for numerous binary and flare stars. When the 1.8m telescope addition are complete, NPOI also will undertake additional studies of dust and proto-planetary disks, and planetary systems and their formation.[30]

See also edit

References edit

  1. ^ . Lowell Observatory. Archived from the original on 2012-01-31. Retrieved 2012-01-04.
  2. ^ . Archived from the original on 2013-10-04. Retrieved 2013-01-25.{{cite web}}: CS1 maint: archived copy as title (link)
  3. ^ a b c Armstrong, J. T.; Mozurkewich, D.; Rickard, L. J.; Hutter, D. J.; Benson, J. A.; Bowers, P. F.; Elias, N. M.; Hummel, C. A.; Johnston, K. J.; Buscher, D. F.; Clark Iii, J. H.; Ha, L.; Ling, L.‐C.; White, N. M.; Simon, R. S. (1998). "The Navy Prototype Optical Interferometer". Astrophysical Journal. 496 (1): 550–571. Bibcode:1998ApJ...496..550A. doi:10.1086/305365. S2CID 120515684.
  4. ^ Hutter, D. J.; Elias, N. M.; Peterson, E. R.; Weaver, W. B.; Weaver, G.; Mozurkewich, D.; Vrba, F. J.; Simon, R. S.; Buscher, D. F.; Hummel, C. A. (1997). "Seeing Tests at Four Sites in Support of the NPOI Project". Astronomical Journal. 114: 2822. Bibcode:1997AJ....114.2822H. doi:10.1086/118690.
  5. ^ Hutter, Donald J. (1995). "Current Status of the Navy Prototype Optical Interferometer". Bulletin of the American Astronomical Society. 27: 1452. Bibcode:1995AAS...18712102H.
  6. ^ Armstrong, J. T.; Mozurkewich, D.; Pauls, T. A.; Rickard, L. J.; Benson, J. A.; Dyck, H. M.; Elias, N. M.; Hajian, A. R.; Hummel, C. A.; et al. (1997). "The Navy Prototype Optical Interferometer (NPOI) is Operational". Bulletin of the American Astronomical Society. 29: 1234. Bibcode:1997AAS...191.1603A.
  7. ^ Hutter, Donald (2012). "Ground-based optical interferometry". Scholarpedia. 7 (6): 10586. Bibcode:2012SchpJ...710586H. doi:10.4249/scholarpedia.10586.
  8. ^ . Archived from the original on 2010-05-27.
  9. ^ (PDF). Archived from the original (PDF) on 2016-12-27. Retrieved 2012-02-05.{{cite web}}: CS1 maint: archived copy as title (link)
  10. ^ (PDF). Archived from the original (PDF) on 2012-03-12. Retrieved 2012-04-25.{{cite web}}: CS1 maint: archived copy as title (link)
  11. ^ a b c d Divittorio, Michael; Hutter, Donald J.; Kelley, Michael (2008). Schöller (ed.). "Plans for utilizing the Keck Outrigger Telescopes at NPOI". Optical and Infrared Interferometry. 7013: 87. Bibcode:2008SPIE.7013E..2UD. doi:10.1117/12.787635. S2CID 122637531.
  12. ^ (PDF). United States Navy. 2010-11-03. Archived from the original (PDF) on 2016-12-27. Retrieved 2012-01-04.
  13. ^ Hutter, Don (2011-03-01). "NPOI Update" (PDF). United States Naval Observatory. Retrieved 2012-01-05.[permanent dead link]
  14. ^ . Archived from the original on 2009-12-15.
  15. ^ Plans for utilizing the Keck Outrigger Telescopes at NPOI | Publications. SPIE. Retrieved on 18 October 2011.
  16. ^ . Archived from the original on 2010-10-21.
  17. ^ (PDF). Archived from the original (PDF) on 2013-01-29. Retrieved 2012-07-06.{{cite web}}: CS1 maint: archived copy as title (link)
  18. ^ (PDF). Archived from the original (PDF) on 2013-01-29. Retrieved 2012-07-06.{{cite web}}: CS1 maint: archived copy as title (link)
  19. ^ . Archived from the original on 2012-08-17. Retrieved 2012-07-06.
  20. ^ (PDF). Archived from the original (PDF) on 2012-05-15. Retrieved 2012-07-06.{{cite web}}: CS1 maint: archived copy as title (link)
  21. ^ (PDF). Archived from the original (PDF) on 2012-03-23. Retrieved 2012-04-25.{{cite web}}: CS1 maint: archived copy as title (link)
  22. ^ (PDF). frank.harvard.edu. Archived from the original (PDF) on 20 July 2011. Retrieved 30 June 2022.{{cite web}}: CS1 maint: archived copy as title (link)
  23. ^ Large-Angle Astrometry at the Navy Prototype Optical Interferometer (NPOI). Adsabs.harvard.edu. Retrieved on 18 October 2011.
  24. ^ . Archived from the original on 2010-05-27. Retrieved 2012-07-01.
  25. ^ Satellite Imaging and Characterization with Optical Interferometry amostech.com
  26. ^ Observations of a Geosynchronous Satellite with Optical Interferometry dtic.mil
  27. ^ Armstrong, J. T.; Clark Iii, James H.; Gilbreath, G. C.; Hindsley, Robert B.; Hutter, Donald J.; Mozurkewich, David; Pauls, Thomas A. (2004). "Proceedings of SPIE – Precision narrow-angle astrometry of binary stars with the Navy Prototype Optical Interferometer". New Frontiers in Stellar Interferometry. 5491: 1700. doi:10.1117/12.553062. S2CID 42997726.
  28. ^ "The U.S. Naval Observatory Preprint Library (2011)". United States Naval Observatory. 2011-03-01. Retrieved 2012-01-05.
  29. ^ Hutter, Donald J.; Benson, James A.; Buschmann, Tim; Divittorio, Michael; Zavala, Robert T.; Johnston, Kenneth J.; Armstrong, J. Thomas; Hindsley, Robert B.; Schmitt, Henrique R.; Clark Iii, James H.; Restaino, Sergio R.; Tycner, Christopher; Jorgensen, Anders M.; Davis, Sam (2008). "Proceedings of SPIE – NPOI: recent progress and future prospects". Optical and Infrared Interferometry. 7013: 701306. doi:10.1117/12.787486. S2CID 122096561.
  30. ^ Shankland, Paul D.; Divittorio, M. E.; Hutter, D. J.; Benson, J. A.; Zavala, R. T.; Johnston, K. J. (2010). "The Science with Four 1.8-m Telescopes at the Navy Prototype Optical Interferometer". Bulletin of the American Astronomical Society. 42: 402. Bibcode:2010AAS...21544112S.

External links edit

  • Additional USNOFS Information
  • Lowell Observatory NPOI site

November 23, 2023
navy, precision, optical, interferometer, npoi, american, astronomical, interferometer, with, world, largest, baselines, operated, naval, observatory, flagstaff, station, nofs, collaboration, with, naval, research, laboratory, lowell, observatory, npoi, primar. The Navy Precision Optical Interferometer NPOI is an American astronomical interferometer with the world s largest baselines operated by the Naval Observatory Flagstaff Station NOFS in collaboration with the Naval Research Laboratory NRL and Lowell Observatory The NPOI primarily produces space imagery and astrometry the latter a major component required for the safe position and navigation of all manner of vehicles for the DoD The facility is located at Lowell s Anderson Mesa Station on Anderson Mesa about 25 kilometers 16 mi southeast of Flagstaff Arizona US Until November 2011 the facility was known as the Navy Prototype Optical Interferometer NPOI Subsequently the instrument was temporarily renamed the Navy Optical Interferometer and now permanently the Kenneth J Johnston Navy Precision Optical Interferometer NPOI reflecting both the operational maturity of the facility and paying tribute to its principal driver and retired founder Kenneth J Johnston 1 2 Navy Precision Optical InterferometerNavy Precision Optical Precision Interferometer at the Anderson Mesa Station of Lowell Observatory Alternative namesNPOIPart ofUnited States Naval Observatory Flagstaff Station Location s ArizonaCoordinates35 05 45 N 111 32 02 W 35 0959 N 111 534 W 35 0959 111 534OrganizationLowell ObservatoryUnited States Naval Observatory Flagstaff StationUnited States Naval ObservatoryUnited States Naval Research Laboratory Altitude2 163 m 7 096 ft Built1992 1994 1992 1994 First light1994 Telescope styleastronomical interferometerMichelson interferometer Websitelowell wbr edu wbr research wbr research facilities wbr npoi wbr Location of Navy Precision Optical Interferometer Related media on Commons edit on Wikidata The NPOI project was initiated by the United States Naval Observatory USNO in 1987 3 Lowell joined the project the following year when the USNO decided to build the NPOI at Anderson Mesa 4 The first phase of construction was completed in 1994 which allowed the interferometer to see its first fringes or light combined from multiple sources that year 5 The Navy began regular science operations in 1997 6 The NPOI has been continuously upgraded and expanded since then and has been operational for a decade The workings of NPOI as a classic interferometer are described at Scholarpedia 7 and at the NPOI site 8 Contents 1 Description 2 Discussion 3 See also 4 References 5 External linksDescription editThe NPOI is an astronomical interferometer laid out in a three arm Y configuration with each equally spaced arm measuring 250 meters 820 ft long There are two types of stations that can be used in the NPOI Astrometric stations used to measure the positions of celestial objects very accurately are fixed units placed 21 meters 69 ft apart with one on each arm and one at the center Imaging stations can be moved to one of nine positions on each arm and up to six can be used at one time to perform standard observing Light from either type of station is first directed into the feed system which consists of long pipes which have been evacuated of all air They lead to a switchyard of mirrors where the light is directed into the six Long Delay Lines which is another set of long pipes that compensate for the different distances to each station The light is then sent into the Beam Combining Facility where it enters the Fast Delay Lines This third set of evacuated pipes contains mechanisms that move mirrors back and forth with a very high degree of accuracy These compensate for the movement of the mirrors as they track an object across the sky and for other effects Finally the light leaves the pipes inside the BCF and goes to the Beam Combining Table where the light is combined in a way that allows images to be formed 3 nbsp Navy Precision Optical Interferometer layout Both types of station have three elements a siderostat a Wide Angle Star Acquisition WASA camera and a Narrow Angle Tracking NAT mirror The first is a precisely ground flat mirror 50 cm 20 in in diameter The WASA cameras control the aiming of the mirror at the celestial target The reflected light from the siderostat is directed through a telescope which narrows the beam down to the diameter of the pipes which is 12 cm 4 7 in The light then hits the mirror of the NAT which compensates for atmospheric effects and directs the light into the feed system 3 In 2009 NOFS began final plans for NPOI to incorporate four 1 8 m 71 in aperture optical infrared telescopes into the array which were accepted by the Navy in 2010 9 10 and assigned to the Naval Observatory Flagstaff Station 11 They were originally intended to be outrigger telescopes for the W M Keck Observatory in Hawaii but were never installed and incorporated into Keck s interferometer Three telescopes are being prepared for near immediate installation 12 13 while the fourth is currently at Mount Stromlo Observatory in Australia and will be incorporated at some point in the future 11 The new telescopes will help with faint object imaging and improved absolute astrometry due to their greater light gathering abilities than the existing siderostats 11 NOFS operates and leads the science for the Navy Precision Optical Interferometer 14 15 as noted in collaboration with Lowell Observatory and the Naval Research Laboratory at Anderson Mesa NOFS funds all principal operations and from this contracts Lowell Observatory to maintain the Anderson Mesa facility and make the observations for NOFS to conduct the primary astrometry The Naval Research Laboratory NRL also provides funds to contract Lowell Observatory s and NRL s implementation of additional long baseline siderostat stations facilitating NRL s primary scientific work synthetic imaging both celestial and of orbital satellites When complete by 2013 NPOI will run the longest baseline interferometer in the world The three institutions USNO 16 17 NRL 18 and Lowell 19 each provide an executive to sit on an Operational Advisory Panel OAP which collectively guides the science and operations of the interferometer The OAP commissioned the chief scientist and director of the NPOI to effect the science and operations for the Panel this manager is a senior member of the NOFS staff and reports to the NOFS Director 20 NPOI is an example of the Michelson Interferometer design with the principal science managed by NOFS Lowell Observatory and NRL join in the scientific efforts through their fractions of time to use the interferometer science time is 85 Navy NOFS and NRL and 15 Lowell NPOI is one of the few major instruments globally which can conduct optical interferometry 21 22 See an illustration of its layout at bottom NOFS has used NPOI to conduct a wide and diverse series of scientific studies beyond just the study of absolute astrometric positions of stars 23 additional NOFS science at NPOI includes the study of binary stars Be Stars Oblate stars rapidly rotating stars those with starspots and the imaging of stellar disks the first in history and flare stars 24 In 2007 2008 NRL with NOFS used NPOI to obtain first ever closure phase image precursors of satellites orbiting in geostationary orbit 25 26 Installation plans for a 1m Array have been developed by NRL and Lowell Observatory based on the funded science performed Discussion editOptical interferometers are extremely complex unfilled aperture photon collecting telescopes in the visual sometimes the near infrared too which produce synthesized images and fringe data on the fly unlike radio interferometers which are privileged to record the data for later synthesis essentially by taking an inverse Fourier transform of the incoming data Astrometry is understood by precisely measuring delay line additions while fringing to match the light path differences from baseline ends Using essentially trigonometry the angle and position of where the array is pointed can be determined thus inferring a precise position on the sphere of the sky Only a few exist that can be considered operational To date NPOI has produced the highest resolution optical images of any astronomical instrument though this may change when the CHARA array and Magdalena Ridge Observatory Interferometer begin optical band operations 27 The first astronomical object imaged resolved by NPOI was Mizar and since a significant amount of astrometry reference tie frame rapid rotator star and Be stellar disk study has been performed 28 NPOI is capable of determining positions of celestial objects to a few milli arcsecond in part due to the optical anchoring of its components using a complex metrology array of lasers that connect main optical elements to each other and to bedrock Many specialized lasers are also used to align the long train of optics The current NPOI siderostat array remains the world s only long baseline 437 meter optical interferometer that can simultaneously co phase six elements 29 NPOI is expected to grow significantly in capability with the pending addition of four 1 8 meter aperture IR Optical telescopes into the current array 11 The enhanced array will also employ adaptive optics techniques This layout and increased sparse aperture will permit significant improvements to the science capability from a tenfold increase in measuring ever fainter wide angle astrometry targets to improved positional determination for numerous binary and flare stars When the 1 8m telescope addition are complete NPOI also will undertake additional studies of dust and proto planetary disks and planetary systems and their formation 30 See also editList of astronomical interferometers at visible and infrared wavelengths List of telescope typesReferences edit NPOI renamed to reflect its evolving role in research Lowell Observatory Archived from the original on 2012 01 31 Retrieved 2012 01 04 Archived copy Archived from the original on 2013 10 04 Retrieved 2013 01 25 a href Template Cite web html title Template Cite web cite web a CS1 maint archived copy as title link a b c Armstrong J T Mozurkewich D Rickard L J Hutter D J Benson J A Bowers P F Elias N M Hummel C A Johnston K J Buscher D F Clark Iii J H Ha L Ling L C White N M Simon R S 1998 The Navy Prototype Optical Interferometer Astrophysical Journal 496 1 550 571 Bibcode 1998ApJ 496 550A doi 10 1086 305365 S2CID 120515684 Hutter D J Elias N M Peterson E R Weaver W B Weaver G Mozurkewich D Vrba F J Simon R S Buscher D F Hummel C A 1997 Seeing Tests at Four Sites in Support of the NPOI Project Astronomical Journal 114 2822 Bibcode 1997AJ 114 2822H doi 10 1086 118690 Hutter Donald J 1995 Current Status of the Navy Prototype Optical Interferometer Bulletin of the American Astronomical Society 27 1452 Bibcode 1995AAS 18712102H Armstrong J T Mozurkewich D Pauls T A Rickard L J Benson J A Dyck H M Elias N M Hajian A R Hummel C A et al 1997 The Navy Prototype Optical Interferometer NPOI is Operational Bulletin of the American Astronomical Society 29 1234 Bibcode 1997AAS 191 1603A Hutter Donald 2012 Ground based optical interferometry Scholarpedia 7 6 10586 Bibcode 2012SchpJ 710586H doi 10 4249 scholarpedia 10586 NPOI Navy Prototype Optical Interferometer Archived from the original on 2010 05 27 Archived copy PDF Archived from the original PDF on 2016 12 27 Retrieved 2012 02 05 a href Template Cite web html title Template Cite web cite web a CS1 maint archived copy as title link Archived copy PDF Archived from the original PDF on 2012 03 12 Retrieved 2012 04 25 a href Template Cite web html title Template Cite web cite web a CS1 maint archived copy as title link a b c d Divittorio Michael Hutter Donald J Kelley Michael 2008 Scholler ed Plans for utilizing the Keck Outrigger Telescopes at NPOI Optical and Infrared Interferometry 7013 87 Bibcode 2008SPIE 7013E 2UD doi 10 1117 12 787635 S2CID 122637531 Acceptance of Gift of Telescopes PDF United States Navy 2010 11 03 Archived from the original PDF on 2016 12 27 Retrieved 2012 01 04 Hutter Don 2011 03 01 NPOI Update PDF United States Naval Observatory Retrieved 2012 01 05 permanent dead link NPOI Navy Prototype Optical Interferometer Archived from the original on 2009 12 15 Plans for utilizing the Keck Outrigger Telescopes at NPOI Publications SPIE Retrieved on 18 October 2011 Scientific Director USNO Naval Oceanography Portal Archived from the original on 2010 10 21 Archived copy PDF Archived from the original PDF on 2013 01 29 Retrieved 2012 07 06 a href Template Cite web html title Template Cite web cite web a CS1 maint archived copy as title link Archived copy PDF Archived from the original PDF on 2013 01 29 Retrieved 2012 07 06 a href Template Cite web html title Template Cite web cite web a CS1 maint archived copy as title link Curiosity Archived from the original on 2012 08 17 Retrieved 2012 07 06 Archived copy PDF Archived from the original PDF on 2012 05 15 Retrieved 2012 07 06 a href Template Cite web html title Template Cite web cite web a CS1 maint archived copy as title link Archived copy PDF Archived from the original PDF on 2012 03 23 Retrieved 2012 04 25 a href Template Cite web html title Template Cite web cite web a CS1 maint archived copy as title link Archived copy PDF frank harvard edu Archived from the original PDF on 20 July 2011 Retrieved 30 June 2022 a href Template Cite web html title Template Cite web cite web a CS1 maint archived copy as title link Large Angle Astrometry at the Navy Prototype Optical Interferometer NPOI Adsabs harvard edu Retrieved on 18 October 2011 NPOI Navy Prototype Optical Interferometer Archived from the original on 2010 05 27 Retrieved 2012 07 01 Satellite Imaging and Characterization with Optical Interferometry amostech com Observations of a Geosynchronous Satellite with Optical Interferometry dtic mil Armstrong J T Clark Iii James H Gilbreath G C Hindsley Robert B Hutter Donald J Mozurkewich David Pauls Thomas A 2004 Proceedings of SPIE Precision narrow angle astrometry of binary stars with the Navy Prototype Optical Interferometer New Frontiers in Stellar Interferometry 5491 1700 doi 10 1117 12 553062 S2CID 42997726 The U S Naval Observatory Preprint Library 2011 United States Naval Observatory 2011 03 01 Retrieved 2012 01 05 Hutter Donald J Benson James A Buschmann Tim Divittorio Michael Zavala Robert T Johnston Kenneth J Armstrong J Thomas Hindsley Robert B Schmitt Henrique R Clark Iii James H Restaino Sergio R Tycner Christopher Jorgensen Anders M Davis Sam 2008 Proceedings of SPIE NPOI recent progress and future prospects Optical and Infrared Interferometry 7013 701306 doi 10 1117 12 787486 S2CID 122096561 Shankland Paul D Divittorio M E Hutter D J Benson J A Zavala R T Johnston K J 2010 The Science with Four 1 8 m Telescopes at the Navy Prototype Optical Interferometer Bulletin of the American Astronomical Society 42 402 Bibcode 2010AAS 21544112S External links editUnited States Naval Observatory Flagstaff Station Additional USNOFS Information Lowell Observatory NPOI sitePortals nbsp Astronomy nbsp Stars nbsp Spaceflight nbsp Outer space nbsp Solar System Retrieved from https en wikipedia org w index php title Navy Precision Optical Interferometer amp oldid 1172172704, wikipedia, wiki, book, books, library,

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