ALMA high performance nutating subreflector

Victor L. Gasho, Simon J E Radford, Jeffrey S Kingsley

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Citations (Scopus)

Abstract

For the international ALMA project's prototype antennas, we have developed a high performance, reactionless nutating subreflector (chopping secondary mirror). This single axis mechanism can switch the antenna's optical axis by ±1.5′ within 10 ms or ±5′ within 20 ms and maintains pointing stability within the antenna's 0.6″ error budget. The light weight 75 cm diameter subreflector is made of carbon fiber composite to achieve a low moment of inertia, < 0.25 kg m2. Its reflecting surface was formed in a compression mold. Carbon fiber is also used together with Invar in the supporting structure for thermal stability. Both the subreflector and the moving coil motors are mounted on flex pivots and the motor magnets counter rotate to absorb the nutation reaction force. Auxiliary motors provide active damping of external disturbances, such as wind gusts. Non contacting optical sensors measure the positions of the subreflector and the motor rocker. The principle mechanical resonance around 20 Hz is compensated with a digital PID servo loop that provides a closed loop bandwidth near 100 Hz. Shaped transitions are used to avoid overstressing mechanical links.

Original languageEnglish (US)
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
EditorsJ.M. Oschmann, L.M. Stepp
Pages430-437
Number of pages8
Volume4837
Edition1
DOIs
StatePublished - 2002
EventLarge Ground-based Telescopes - Waikoloa, HI, United States
Duration: Aug 22 2002Aug 26 2002

Other

OtherLarge Ground-based Telescopes
CountryUnited States
CityWaikoloa, HI
Period8/22/028/26/02

Fingerprint

subreflectors
antennas
Antennas
carbon fibers
Carbon fibers
gusts
pivots
resonant vibration
nutation
fiber composites
Optical sensors
moments of inertia
optical measuring instruments
budgets
Magnets
counters
Mirrors
Thermodynamic stability
thermal stability
disturbances

Keywords

  • Carbon fiber composites
  • Cassegrain optics
  • Chopping secondary systems
  • Millimeter waves
  • Mirrors
  • Optical switching
  • Subreflectors
  • Telescopes

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Condensed Matter Physics

Cite this

Gasho, V. L., Radford, S. J. E., & Kingsley, J. S. (2002). ALMA high performance nutating subreflector. In J. M. Oschmann, & L. M. Stepp (Eds.), Proceedings of SPIE - The International Society for Optical Engineering (1 ed., Vol. 4837, pp. 430-437) https://doi.org/10.1117/12.457911

ALMA high performance nutating subreflector. / Gasho, Victor L.; Radford, Simon J E; Kingsley, Jeffrey S.

Proceedings of SPIE - The International Society for Optical Engineering. ed. / J.M. Oschmann; L.M. Stepp. Vol. 4837 1. ed. 2002. p. 430-437.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Gasho, VL, Radford, SJE & Kingsley, JS 2002, ALMA high performance nutating subreflector. in JM Oschmann & LM Stepp (eds), Proceedings of SPIE - The International Society for Optical Engineering. 1 edn, vol. 4837, pp. 430-437, Large Ground-based Telescopes, Waikoloa, HI, United States, 8/22/02. https://doi.org/10.1117/12.457911
Gasho VL, Radford SJE, Kingsley JS. ALMA high performance nutating subreflector. In Oschmann JM, Stepp LM, editors, Proceedings of SPIE - The International Society for Optical Engineering. 1 ed. Vol. 4837. 2002. p. 430-437 https://doi.org/10.1117/12.457911
Gasho, Victor L. ; Radford, Simon J E ; Kingsley, Jeffrey S. / ALMA high performance nutating subreflector. Proceedings of SPIE - The International Society for Optical Engineering. editor / J.M. Oschmann ; L.M. Stepp. Vol. 4837 1. ed. 2002. pp. 430-437
@inproceedings{9330cf1c7f174d26b1aefb4f15780407,
title = "ALMA high performance nutating subreflector",
abstract = "For the international ALMA project's prototype antennas, we have developed a high performance, reactionless nutating subreflector (chopping secondary mirror). This single axis mechanism can switch the antenna's optical axis by ±1.5′ within 10 ms or ±5′ within 20 ms and maintains pointing stability within the antenna's 0.6″ error budget. The light weight 75 cm diameter subreflector is made of carbon fiber composite to achieve a low moment of inertia, < 0.25 kg m2. Its reflecting surface was formed in a compression mold. Carbon fiber is also used together with Invar in the supporting structure for thermal stability. Both the subreflector and the moving coil motors are mounted on flex pivots and the motor magnets counter rotate to absorb the nutation reaction force. Auxiliary motors provide active damping of external disturbances, such as wind gusts. Non contacting optical sensors measure the positions of the subreflector and the motor rocker. The principle mechanical resonance around 20 Hz is compensated with a digital PID servo loop that provides a closed loop bandwidth near 100 Hz. Shaped transitions are used to avoid overstressing mechanical links.",
keywords = "Carbon fiber composites, Cassegrain optics, Chopping secondary systems, Millimeter waves, Mirrors, Optical switching, Subreflectors, Telescopes",
author = "Gasho, {Victor L.} and Radford, {Simon J E} and Kingsley, {Jeffrey S}",
year = "2002",
doi = "10.1117/12.457911",
language = "English (US)",
volume = "4837",
pages = "430--437",
editor = "J.M. Oschmann and L.M. Stepp",
booktitle = "Proceedings of SPIE - The International Society for Optical Engineering",
edition = "1",

}

TY - GEN

T1 - ALMA high performance nutating subreflector

AU - Gasho, Victor L.

AU - Radford, Simon J E

AU - Kingsley, Jeffrey S

PY - 2002

Y1 - 2002

N2 - For the international ALMA project's prototype antennas, we have developed a high performance, reactionless nutating subreflector (chopping secondary mirror). This single axis mechanism can switch the antenna's optical axis by ±1.5′ within 10 ms or ±5′ within 20 ms and maintains pointing stability within the antenna's 0.6″ error budget. The light weight 75 cm diameter subreflector is made of carbon fiber composite to achieve a low moment of inertia, < 0.25 kg m2. Its reflecting surface was formed in a compression mold. Carbon fiber is also used together with Invar in the supporting structure for thermal stability. Both the subreflector and the moving coil motors are mounted on flex pivots and the motor magnets counter rotate to absorb the nutation reaction force. Auxiliary motors provide active damping of external disturbances, such as wind gusts. Non contacting optical sensors measure the positions of the subreflector and the motor rocker. The principle mechanical resonance around 20 Hz is compensated with a digital PID servo loop that provides a closed loop bandwidth near 100 Hz. Shaped transitions are used to avoid overstressing mechanical links.

AB - For the international ALMA project's prototype antennas, we have developed a high performance, reactionless nutating subreflector (chopping secondary mirror). This single axis mechanism can switch the antenna's optical axis by ±1.5′ within 10 ms or ±5′ within 20 ms and maintains pointing stability within the antenna's 0.6″ error budget. The light weight 75 cm diameter subreflector is made of carbon fiber composite to achieve a low moment of inertia, < 0.25 kg m2. Its reflecting surface was formed in a compression mold. Carbon fiber is also used together with Invar in the supporting structure for thermal stability. Both the subreflector and the moving coil motors are mounted on flex pivots and the motor magnets counter rotate to absorb the nutation reaction force. Auxiliary motors provide active damping of external disturbances, such as wind gusts. Non contacting optical sensors measure the positions of the subreflector and the motor rocker. The principle mechanical resonance around 20 Hz is compensated with a digital PID servo loop that provides a closed loop bandwidth near 100 Hz. Shaped transitions are used to avoid overstressing mechanical links.

KW - Carbon fiber composites

KW - Cassegrain optics

KW - Chopping secondary systems

KW - Millimeter waves

KW - Mirrors

KW - Optical switching

KW - Subreflectors

KW - Telescopes

UR - http://www.scopus.com/inward/record.url?scp=0038636059&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0038636059&partnerID=8YFLogxK

U2 - 10.1117/12.457911

DO - 10.1117/12.457911

M3 - Conference contribution

AN - SCOPUS:0038636059

VL - 4837

SP - 430

EP - 437

BT - Proceedings of SPIE - The International Society for Optical Engineering

A2 - Oschmann, J.M.

A2 - Stepp, L.M.

ER -