Binospec and future MMT optical spectroscopy

Binospec and future MMT optical spectroscopy

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Daniel Fabricant

Wednesday, May 19, 2010

Binospec Design Goal

Build the most powerful spectrograph for deep optical surveys on an 8 meter class telescope

Power calculated by

P = Telescope Area · Throughput · FOV


Binospec in a Nutshell

• 3900-10000 Å wavelength range for imaging (g r i z) and spectroscopy

• 0.24″ pixel sampling• 200 mm collimated beam diameter – all refractive optics• Two identical beams observing adjacent 8′ by 15′ fields

• Continuous wavefront sensing maximizes image quality• Active flexure and focus control


Scientific Goals for Binospec

Three major themes have emerged:

(1)Near-Field Cosmology: Deep Studies of the Nearby Universe

(2) The High-Redshift Universe

(3) Transients and Transient Hosts


Binospec Operations

• Queue scheduling like the Hectos

• Full implementation of “piggy-back” projects to use all of the available slits and coordination of survey projects


Binospec Dual-Beam Optical Layout

Slit maskPeriscope fold mirrors

CollimatorCamera

Filter

Third Fold MirrorCCD

Grating


Binospec Spectroscopic ModesGrating Ruling

Order SpectralCoverage

(Å)

DispersionÅ/ pixel

Pixelsfor 1″slit

Resolutionfor 1″ slit

270 1 3900-9240 1.30 3.75 1340

600 1 4500-6960 0.60 3.47 2740

600 1 6000-8480 0.61 3.32 3590

600 1 7255-9750 0.61 3.20 4360

632 2 6405-7590 0.29 2.56 9427


Imaging Spectrographs and Fiber-Fed Spectrographs

• Imaging spectrographs (Binospec) preserve spatial information perpendicular to the dispersion

– Offer high fidelity sky subtraction– Small-scale kinematic information available– Operate as imagers– Offer the highest throughput

• Fiber-spectrographs (Hectospec) address the largest possible FOV


Binospec Offers Spatially Resolved Spectroscopy


Binospec’s Very Large FOV

15′ (150 mm)

8′ (80 mm)

1.33′ (13 mm)

1.26′ (13 mm)

1.68′ (17 mm)

Wave Front Sensor

X

Y

Guide strips


Binospec Aperture Mask

Up to 300 slitlets each 6″ long

Channel 1 Channel 2

15′

8′


Binospec’s Camera Optics

Lens 1

Lens2

Lens3

Lens4

Lens5

Lens6

Lens7

Lens8

Lens9

Binospec (2008)

Big optics allow:

Huge field of viewHigher resolution

Calcium fluoride lenses

Aspheric lens

360 mm


Binospec Offers Very High Throughput

Binospec

Hectospec

Telescope/Corrector optics included


Future of the MMT – before GMT

The 6.5 meter telescopes must provide our access to faint object spectroscopy

– Binospec will be the workhorse dark time instrument, combining spectroscopy and imaging to support observation of transients in the standard queue (fewer instrument changes)

– Binospec will be simpler to maintain than Hectospec, minimizing operations costs


Binospec Interior View

Filter Cassette

Optical Bench

Mounting Flange

Focal Plane Bench

Slit Exchange Cassette

A-frame Strut


Binospec Optical Bench

Dewar

CCD HousingGrating on Turntable

Grating Storage

Third Collimator Fold Mirror

Camera


Slit Mask Assembly


Grating Assembly


Oil-Coupled Doublet Prototype


Binospec Status

• Aiming for delivery early 2013 – contingent on funding

• Optics complete by end of 2010, high risk aspherics and CaF2 lenses already in hand. Major mechanisms and optical mounts prototyped and tested

• Main structure out for bid mid-June

• Major mechanisms completed: grating assembly, slit mask. Wavefront sensor under construction followed by single object guider. Main electronics assembly under construction

• Optical alignment equipment fully developed and tested on prototype optics, used for MMIRS


Binospec allows MMT scientists to lead in fields now dominated by DEIMOS/Keck

• Binospec gathers 65% of the light that DEIMOS collects per unit time

• Binospec has twice the slit length and three times the field of view of DEIMOS

• Power of Binospec = 1.3 to 2.0 Power of DEIMOS


The end

BK7 Entrance Window

Insulated Cover

Handling Cart


Binospec Exterior View

BK7 Entrance Window

Insulated Cover

Handling Cart


December 2007 Final Design Review

Chaired by Steve Shectman

“The design of the spectrograph in general impressed the committee to a very high degree”


Binospec uses all of the MMT’s available instrument volume and all of its weight carrying capacity to maximize throughput and FOV

3.26

156.80

Telescope Pivot


Large Calcium Fluoride Lenses

The closest approach to a perfect lens


Binospec Design Elements

• Large optics for large FOV, high resolution, wide spectral coverage

• Few glass-air surfaces with the best possible coatings• Very efficient detectors

• Robust mechanisms enhance reliability• Active flexure control for maximum data quality


Binospec and future MMT optical spectroscopy

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