WNEW A 2.4 Meter TMA Survey Telescope Concept

Rodger ThompsonUniversity of ArizonaSteward Observatory

WNEW CHARACTERISTICS2.4 meter 3 mirror anastigmat telescope utilizing the NRO telescope components.Dichroic splitting of the optical paths to produce 4 fields of view, each of which images 0.25 sq. degrees.WNEW contains 8 filters in two sets of four that can be viewed simultaneously.The plate scale is 0.11” per pixel.WNEW also contains 8 grisms for low resolution spectroscopy

WNEW ADVANTAGESFour fold dichroic multiplexing optimizes the very large field of view to maximize the scientific return.WNEW is based on a previously funded Origins Probe study, the Galaxy Evolution Probe, with a very well studied and mature design.WNEW achieves all of the WFIRST DRM science in approximately 1/3 of the time in twice as many filters.The WNEW capabilities enable science significantly beyond the scope of WFIRST.

Use of the NRO Telescope as part of a Three Mirror Anastigmat System

NRO Provided Component

Four Focal Plane Optical Schematic

Each array of detectors has two filters and two grisms to provide 8 photometric bands.Each dichroic assembly has two dichroics.

Dichroic Wheel Filter Wheel

Eight Equal Filters

Two Exposures Produce Eight Images

POSITION 1, 4 IMAGES

POSITION 2, 4 IMAGES

REPRESENTATIVE PERFORMANCE CHARTS

IMPLEMENTING WFIRST SCIENCE WITH WNEW

WNEW can implement all of the WFIRST DRM2 programs in less time with twice as many photometric bands.The 8 WNEW photometric bands greatly enhances the scientific productivity of the WFIRST DRM2 programs.The reduced time to implement the DRM2 programs provides extra time for innovative programs not envisioned for WFIRST.

WFIRST Survey ProgramsSurvey of 3400 sq. degrees to ABmag=26 WFIRST: 429 days for 4 filters WNEW: 122 days for 8 filters

Survey of 3400 sq.deg R=600 ABmag=22.5 per pixel WFIRST: 284 days WNEW: 61 days

Survey of Gal. Plane 1240 sq. deg. ABmag =25.1 WFIRST: 160 days for 4 filters WNEW: 15 days for 8 filters

EXO-PLANET MICROLENSING

Monitor >2 sq. degrees for J=20.5 star with S/N=100 for 250 total days.Cadence < 15 MinutesTime for WNEW to reach S/N=100 for J=20.5 in 4 filters is 224 seconds = 3.75 minutes.Better than 0.4” resolutionWNEW has 0.11” pixelsAutomatic color information in at least 4 bands Automatic guard against chromatic false

positives

WNEW AS WFIRSTWNEW easily meets all of the WFIRST DRM requirements in far less time than WFIRST.WNEW easily meets all of the WFIRST DRM requirements in twice as many filters than WFIRSTWNEW can exceed all of the WFIRST DRM requirements and still have time for additional science goals.

AN ADDITIONAL SCIENCE EXAMPLE

Very deep imaging in 4 fields of 1 square degree for 1 year.Fields separated by ~90 degrees on sky4000 second integrations8 integrations to cover 1 sq. degree in all filters223 integrations at each position in one year with 10% overhead

4 Sq. Degree 5 AB mag per PixelFilter F86W F98W F113W F129W F148W F170W F198W F224W

ABmag 32.28 32.19 32.07 31.92 31.75 31.54 31.30 30.54

8 Bands provide excellent photometric redshifts for high z objects

4 Square degrees and separation greatly reduces errors due tolarge scale structure.

High spatial resolution avoids confusion limit.

Technical ReadinessThe WNEW concept was developed during two funded studies as an origins probe. As such it has a very mature design.WNEW simplifies the original concept by retaining only infrared bands and restricting the focal plane to a single detector type.Many components already have preliminary or in some cases a mature design.

Dichroic Design in Place

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Visible/NIR Dichroic Transmittance

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300to850_35_a_o7: Reflectance

47 layer dielectric multilayer results in reasonable VIS/NIR wavelength separation at 35 degree incidence angle

Need to adapt previous telescope design to NEW components

Redesigned optics

NEW Telescope

DetectorsFour focal planes utilizing 16 H4RG detectors (4kx4k) each.

Guiding arrays on one focal plane only

Science 4x4 array

Spacecraft Based on GEP DesignIn drift away or L2 orbit the mirrorsinstrument and detector systems areradiatively cooled with no cryogenicsrequired.Data transmission requires only 5 hoursof DSN reception per day on a moderate size receiver equivalent to the Univ. of AZ 12m dish on Kitt Peak.

CONCLUSIONWNEW provides a greatly enhanced platform for carrying out the proposed WFIRST science program at higher sensitivity, in less time and with twice as many photometric bands.WNEW provides new science capabilities to go beyond the proposed WFIRST program.WNEW could start tomorrow.