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WNEW A 2.4 Meter TMA Survey
Telescope Concept
Rodger Thompson
University of Arizona
Steward Observatory
WNEW CHARACTERISTICS
2.4 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 ADVANTAGES
Four 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 Dl/l 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 Programs
Survey 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 Minutes
Time for WNEW to reach S/N=100 for J=20.5 in 4
filters is 224 seconds = 3.75 minutes.
Better than 0.4” resolution
WNEW has 0.11” pixels
Automatic color information in at least 4 bands
 Automatic guard against chromatic false positives
WNEW AS WFIRST
WNEW 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
WFIRST
WNEW 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 sky
4000 second integrations
8 integrations to cover 1 sq. degree in
all filters
223 integrations at each position in one
year with 10% overhead
4 Sq. Degree 5s AB mag per
Pixel
Filter
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 to
large scale structure.
High spatial resolution avoids confusion limit.
Technical Readiness
The 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
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
NEW Telescope
Redesigned
optics
Detectors
Four focal planes utilizing 16 H4RG detectors
(4kx4k) each.
Science 4x4 array
Guiding arrays on
one focal plane only
Spacecraft Based on GEP Design
In drift away or L2 orbit the mirrors
instrument and detector systems are
radiatively cooled with no cryogenics
required.
Data transmission requires only 5 hours
of DSN reception per day on a moderate
size receiver equivalent to the Univ. of AZ
12m dish on Kitt Peak.
CONCLUSION
WNEW 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.