Far sidelobes measurement of the Atacama Cosmology Telescope

Rolando Dünner, Patricio Gallardo, Ed Wollack, Fernando Henriquez, Carlos Jerez-Hanckes

Resultado de la investigación: Capítulo del libro/informe/acta de congresoContribución a la conferenciarevisión exhaustiva

Resumen

The Atacama Cosmology Telescope (ACT) is a 6m telescope designed to map the Cosmic Microwave Background (CMB) simultaneously at 145GHz, 220 GHz and 280 GHz. Its off-axis Gregorian design is intended to minimize and control the off-axis sidelobe response, which is critical for scientific purposes. The expected sidelobe level for this kind of design is less than -50 dB and can be challenging to measure. Here we present a measurement of the 145GHz far sidelobes of ACT done on the near-field of the telescope. We used a 1mW microwave source placed 13 meters away from the telescope and a chopper wheel to produce a varying signal that could be detected by the camera for different orientations of the telescope. The source feed was designed to produce a wide beam profile. Given that the coupling is expected to be dominated by diffraction over the telescope shielding structure, when combined with a measurements of the main beam far field response, these measurement can be used to validate elements of optical design and constrain the level of spurious coupling at large angles. Our results show that the diffractive coupling beyond the ground screen is consistently below -75 dB, satisfying the design expectations.

Idioma originalInglés
Título de la publicación alojadaMillimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VI
DOI
EstadoPublicada - 2012
Publicado de forma externa
EventoMillimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VI - Amsterdam, Países Bajos
Duración: 3 jul. 20126 jul. 2012

Serie de la publicación

NombreProceedings of SPIE - The International Society for Optical Engineering
Volumen8452
ISSN (versión impresa)0277-786X

Conferencia

ConferenciaMillimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VI
País/TerritorioPaíses Bajos
CiudadAmsterdam
Período3/07/126/07/12

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