The SAO phasing prototype visits MagAO

“Without phasing, there’s no real reason to build the GMT.”
-Andrew Szentgyorgyi

The biggest optical/infrared telescope in world will be the Giant Magellan Telescope, which will be built on a nearby mountain peak within sight of the Clay and Baade telescopes at Las Campanas.  The telescope will have 7 primary mirror segments and 7 adaptive secondary mirrors, similar to the Magellan AO system.

The 25 meter diameter Giant Magellan Telescope
The 25.5 meter diameter Giant Magellan Telescope
Photograph of the GMT site from the Magellan footpath.
Photograph of the GMT site from the Magellan footpath.

If we could build any optic we wanted for the primary of the GMT, we would probably build a monolithic 30 meter diameter (or larger) mirror made of a single piece of glass, with a thin face sheet and a honeycomb lightweight structure on back.  However, at the moment, the largest mirrors in the world are built in the Steward Observatory Mirror lab under the bleachers of the football stadium at the University of Arizona and are limited to a diameter of 8.4 meters.  Depending on who you ask, this 8.4 meter limit comes from either the distance between the columns underneath the stadium bleachers, or the size of an underpass on the highway leading from Tucson.

An 8.4 meter mirror being polished in the Steward Observatory mirror lab underneath the football stadium bleachers.  Making mirrors larger than this will require a larger football stadium.
An 8.4 meter mirror being polished in the Steward Observatory mirror lab underneath the football stadium bleachers. Making mirrors larger than this will require a larger football stadium.

Because of this limit, the GMT is designed to take 7 of the largest mirrors that can be made and combine them to form one giant 25.5 meter primary.  For this to be possible, the seven 8.4 meter segments must be “phased” to a fraction of a wavelength.  That is to say, they must be aligned to each other so that they act as if they are one large continuous mirror.

To achieve the phasing of the GMT segments using off-axis natural guide stars, SAO and our collaborators at GMTO and Flat Wavefronts have designed a sensor that creates dispersed interference fringes using subapertures spanning the 12 segment boundaries.  Phase shifts across the segment boundaries manifest themselves as tilts in the fringes.

Segment boundary subapertures for the dispersed fringe phasing sensor.
Segment boundary subapertures for the dispersed fringe phasing sensor.
Simulated fringes from one subaperture showing 0 piston phase difference (left) and 10 microns (right).
Simulated fringes from one subaperture showing 0 piston phase difference (left) and 10 microns (right).

To test this sensor technology, SAO has built a phasing prototype that simulates 6 of the GMT segment boundaries working in conjunction with the Magellan AO system.  Our three nights at the end of the MagAO run turned out to be a success.

Six sets of fringes as seen by the SAO phasing prototype working in conjunction with the MagAO system.
Six sets of fringes as seen by the SAO phasing prototype working in conjunction with the MagAO system.
The SAO phasing prototype team.  Clockwise from top left: Derek Kopon, Alan Conder, Ken McCracken, Jared Males, Laird Close, Dan Catropa, Brian McLeod, Bill Podgorski.
The SAO phasing prototype team. Clockwise from top left: Derek Kopon, Alan Conder, Ken McCracken, Jared Males, Laird Close, Dan Catropa, Brian McLeod, Bill Podgorski.

We obtained phasing data both on-axis and off-axis, with AO on and off, and at two different wavelength bands (I and J).  This data, and data that we gather during another run possibly in February, will inform the design of the GMT phasing sensor, scheduled for first light in the next decade.

Lastly, a “song of the run:”  Phazing, by Dirty South:

https://www.youtube.com/watch?v=031hzipvnTY

2015B Summary

We made it back home! The strike ended the day we flew out so we didn’t end up riding the bus from La Serena to Santiago, but thanks to Nelda for arranging that so that we were sure to get there either way. And thanks to Juan Gallardo and the rest of the crew for their careful work removing the ASM and the Nas from the Clay in 1 day so that we could get home in time for the holidays! After 32 hours of travel and 4 airplanes, 2 buses, 5 taxis, and 1 tram, we are happy to be safe and sound in Tucson. And here’s what I got to enjoy after jump-starting my car, eating, showering, and napping:

Cats are doing well

We had 25 nights of MagAO+VisAO+Clio and 3 nights of MagAO+VisAO+PhaseCam. It was a good run for the 25 MagAO+VisAO+Clio nights which involved planets, disks, and other exciting science; and fun for us to see a new instrument mounted behind MagAO and playing well with VisAO for the 3 nights testing the GMT AGWS prototype PhaseCam. Amali Vaz and Kim Ward-Duong came from Arizona and ASU to help out, and we had observers from Arizona, Carnegie, Chile, Harvard, Michigan, and Stanford.

A lot happened this run! Amali won the first MagAO blog prize; Our paper by Sallum, Follette, et al. on the discovery of hydrogen accretion onto proto-planet LkCa 15 b was published; Our paper Morzinski et al. on the first empirical measurement of the energy of young super-Jupiter beta Pic b went from accepted to proofs to published; MagAO results were featured on the home page of the NASA Exoplanet Science Institute; Jared’s new collaborators came for a visit (more on that later); and we managed to stay happy and healthy thanks to the great staff at LCO and El Pino!

For the song of the day, we started with You’ll Never Leave Harlan Alive:

and ended with Pequeña serenata nocturna de Mozart, primer movimiento (Allegro):

Thanks to all our great bloggers this run for playing the song-of-the-day game!

And finally, thanks to NSF, NASA, NExScI Sagan, and UA for supporting our instrument and work, and all our family and friends at home who help take care of our Tucson-side lives while we are away for 5+ weeks at a time. Happy holidays and best wishes for 2016.

2015B Día 34: Última noche en LCO.

He revisado las Reglas del Blog y nada dice sobre el idioma que debe utilizarse. Por eso, lo haré en español, una licencia para el último día del equipo MagAO en el Observatorio Las Campanas.

Aún no se sabe si viajarán a Santiago en bus o avión, la huelga terminó esta tarde.

Durante las 33 noches de observaciones más las noches previas y posteriores nos deja muchas satisfacciones, como Operador de Telescopios Magallanes hemos podido vivir los avances que se lograron día a día (osea noche a noche), superando dificultades técnicas, sufriendo el clima y obteniendo datos de alto nivel científico.

Este run hemos apreciado fotos muy variadas y novedosas, flora, fauna, Luna, telescopio, instrumentos nuevos, astronomía, clima, comida, paisajes desde el Observatorio.

Difícil competir con algunas imágenes pues mis fotos son de un iPhone 3, igual me atrevo a compartirlas con Ustedes. Les he puesto nombre para identificarlas.

1. Naturaleza y tecnología. El brillo que se aprecia al medio de la foto (algunos milímetros) son un array de paneles solares.

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2. Naturaleza y tecnología. Aquí tenemos la Luna, cóndor chileno y la tecnología de un camión-grúa.

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3. Naturaleza y tecnología. La Luna desde el interior de la cúpula del Baade.

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4. Naturaleza pura. Cóndor chileno.

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Me preparé varias veces para elegir la canción del día, basándome en la de la noche anterior.

Comencé con la confusión que siempre tengo entre Ella Fitzgerald y Aretha Franklin, cierto que los nombres no se parecen pero igual me confunden.

Considerando Stars Wars y La marcha Imperial pensé en “Starman” de David Bowie, además que me recuerda a mi adolescencia y los sueños con el futuro, qué había más allá.

Ya no está relacionada con la noche previa pero igual la incluyo porque es un clásico.

Brian ha elegido “Modest Mussorgsky’s Night on Bald Mountain. Es una canción de la película Fantasía de Walt Disney. Me gusta también por los recuerdos de infancia.

Considerando que un antiguo Operador de Telescopio ha pasado por todos los estilos musicales que nos traen los Astrónomos, he pensado en seleccionar música clásica, si me permiten.

Pequeña serenata nocturna de Mozart, primer movimiento (Allegro). Me parece que es el más conocido.

Nos vemos el próximo año: 2016A

That’s all Folks!