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dotardhousesΜηχανική

18 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

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Export or re
-
export of information contained herein
may be subject to restrictions and requirements of

U.S. export laws and regulations and may require
advance authorization from the U.S. Government.

NWO Science Telescope

25 Aug 2008

2

Where Next with Space Missions for Exoplanets?



There Has Been Stunning Progress in Study of Exoplanets


It takes 10 to 20 years to launch a space observatory


14 years ago this field didn’t exist


where will it be in 20 years with or without space????


A Space Exoplanet Mission Must Have A


Dramatic Leap In Sensitivity and Inner Working Angle


High Quality Spectroscopy


Capability WAAAAAY Beyond What We have Seen So Far


Otherwise the Mission Will Be Rendered Mundane


In Short We Need High Quality Spectroscopy of Earth
-
twins


And broad capability to study planetary systems in detail


Anything less would be a gamble

NWO Science Telescope

25 Aug 2008

3

NWO Team Membership:

Organizations, Roles and Leads



Team consist of 43 active members


9 organizations are participating


Additional involvement is provided from each organization and includes technical area experts
and graduate/undergraduate students



Organizations, Roles and Leads:


Colorado University
: PI, Science, Optical Design, and Systems Analysis:
Webster Cash


Northrop Grumman:

Deputy PI and Starshade Development:
Amy Lo


Ball Aerospace Technology Corporation
: Telescope Development:
Charley Noecker


USNO:

Astrometry:
Ralph Gaume


NASA GRC
: Occulter (Starshade) Propulsion:
Scott Benson


KinetX:

Mission Design and Navigation:
Bobby Williams


GSI:

Lead Scientist:
Maggie Turnbull


University College of London
: Exoplanet Spectra Modeling:
Giovanna Tinetti


NASA GSFC
: Study Management:
Kate Hartman


Space Telescope Science Institute
: JWST Interface:
Remi Soummer

NWO Science Telescope

25 Aug 2008

4

Stars are very bright and their glare
makes it difficult to see fainter objects
near them

NWO Science Telescope

25 Aug 2008

5

Starshade prevents starlight from entering the telescope


The telescope is shaded from the star by the starshade


Besides the vanishingly small residual signal, the starlight does
not

enter the
telescope

Starshade

100% of the planet light is reaches the telescope

NWO Science Telescope

25 Aug 2008

6

Fly the Telescope into the Shadow

NWO Science Telescope

25 Aug 2008

7

Dropping It In

Note: No Outer Working Angle

NWO Science Telescope

25 Aug 2008

8

Extinguishing The Spot of Arago


Occulters Have Very Poor Diffraction Performance


The 1818 Prediction of Fresnel led to the famous episode of:


Spot of Arago (variously Poission’s Spot)


Occulters Often Concentrate Light!



Must satisfy Fresnel Equation, Not Just the Fraunhoffer Equation



Must Create a Zone That Is:


Deep

Below 10
-
10

diffraction


Wide

A couple meters minimum


Broad

Suppress across at least one octave of spectrum



Must Be Practical


Binary

Non
-
transmitting to avoid scatter


Size

Below 150m Diameter


Tolerance

Insensitive to microscopic errors

NWO Science Telescope

25 Aug 2008

9

NWO has an Opaque Starshade


Opaque Starshade

Offset Hypergaussian function

Apodization Function

exp
n
r a
T
b
 

 
 
 
 
 
 
 

Apodizing Function

Radius

Transmission

Parameter

Occulter inner radius

a

Petal 1/e length

b

Hypergaussian order

n

Distance to telescope

z

Number of petals

P

NWO Science Telescope

25 Aug 2008

10

Performance

A 50m diameter occulter at 80,000km can reveal Earths at over 20pc

NWO Science Telescope

25 Aug 2008

11

Target Stars: Exo
-
zodiacal Light

From P. Oakley

1.5m

2.4m

4m

10m

4m Case

NWO Science Telescope

25 Aug 2008

12

Map Planetary Systems


Prime Goal is Exploration
of the Solar
Neighborhood


NWO will allow us to
make maps of over 100
nearby planetary systems
from the habitable zone
outward


Detect and classify all
major planets

Jupiter

Saturn

Uranus

Neptune

Zodiacal Light

Galaxies

10 arcseconds

NWO Science Telescope

25 Aug 2008

13

Four Color Photometry


Molecules!!

Export Control Notice

Export or re
-
export of information contained herein
may be subject to restrictions and requirements of

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Simulated Image of Earth

with starshade and JWST

NWO Science Telescope

25 Aug 2008

15

Planet Finding with Starshades

Five Random Systems from Raymond Database


The higher resolution of ATLAST brings weak signals out of the noise

ATLAST

JWST

NWO Science Telescope

25 Aug 2008

16


Confusion from dust structure


“Is that a planet or a dust clump?”


Can we tell by its color before
wasting time on a spectrum?





Greaves et al. (2005)

Epsilon Eridani

Other Exozodi Issues


Maybe …


Solar System zodi has
red scattered light color


Known debris disks show
red, grey, & blue colors




AU Mic

Blue

HD 92945

Neutral

Beta Pic

Red

NWO Science Telescope

25 Aug 2008

17

Target Stars: Exposure Times

i

= 60˚

From A. Roberge

NWO Science Telescope

25 Aug 2008

18

Where to Look for ExoEarths?


Entire habitable zone : ~ 110 stars


Half of habitable zone : ~280 stars



NWO blue IWA

40 mas

Contrast ~ 10
-
11

NWO red IWA

65 mas

NWO Science Telescope

25 Aug 2008

19

Importance of Inner Working Angle

Once you can study all the stars with correctly
-
sized Habitable Zones, there is no
further advantage in being able to study more. New Worlds can do this.

NWO Science Telescope

25 Aug 2008

20

Study Exoplanets


NWO will perform spectroscopy of discovered planets


This will reveal their true natures

O
2

H
2
O

CH
4

NH
3

NWO Science Telescope

25 Aug 2008

21

Spectroscopy of Earths

JWST

ATLAST

ATLAST @ High Resolution

Fine Structure!

NWO Science Telescope

25 Aug 2008

22

Characterizing Planets: Photometric Variability

From P. Oakley

NWO Science Telescope

25 Aug 2008

23

70% of Time Available for Other Astrophysics

1.
The “NWO Deep Field”

2.
Galaxy interactions and evolution

3.
Stellar evolution

4.
The Solar System


KBO UB313

NWO Science Telescope

25 Aug 2008

24

NWO Flagship Mission


ASMCS Study

Starshade and Telescope on
single EELV

Stacked
configuration

Starshade and
telescope deploy

~50 m
starshade

72,000 km

4 m telescope

Earth to L2 = 1.5 million km

Suppression

10
-
10

IWA

55
-

65 mas

Wavelength

120


900 nm

Total pointings

90
-

140

Slewing time

9
-
13 days

Observation time

1
-

10 days

Simulation from E. Shindhelm, CU

NWO Science Telescope

25 Aug 2008

25

Tall Poles



Deployment of 50m shade to cm class tolerances




Acquiring and holding line of sight




Fuel usage, orbits and number of targets




Stray Light


particularly solar


NWO Science Telescope

25 Aug 2008

26

Starshade Critical Technology

Enabling Technologies

Precision Shape Control



Maintain edge position


Maintain structure shape

Precision Deployment



Minimize jitter


Maintain petal location

Opaque Membrane


Maintain opacity


Lightweight

2 Axes Formation Flying


Maintain 1m alignment


Minimize jitter

Enhancing Technologies

Solar Electric Propulsion


NEXT engine


Increase observable targets


Reduce propellant mass

Lightweight S/C Structures


Increase observable targets


Reduce overall mass

Thin Edge Treatment


Maintain edge stability


Minimize stray light

NWO Science Telescope

25 Aug 2008

27

Lab Studies

NWO Science Telescope

25 Aug 2008

28

NGS Starshade with HID source, 1000s integration

Total suppression within 200 pixel radius = 8.8e
-
006

wire

wire

wire

Wire

3.9e
-
7

wire

Wire

4.3e
-
7

(Chamber door open)

Chamber door closed

NWO Science Telescope

25 Aug 2008

29

CU/NIST starshade, 200s

200 micron entrance pinhole, iris=10mm, 4/24/09 data

Total suppression within 200 pixel radius = 3.0e
-
006

1.53e
-
006

1.49e
-
006

1.47e
-
006

Contrast at points

where mount wires

cross petal edges

NWO Science Telescope

25 Aug 2008

30

5.05e
-
010

6/19/07 Image27
-

600sec

NWO Science Telescope

25 Aug 2008

31

Conclusion

By 2025

O
2

H
2
O

By 2013

Demonstration Program 2009
-
2012

Study Earths with JWST 2015

Lifefinder 2022

Planet Imager


2030?