Transcript The OWL and the penguin Why we should build an in Antarctica

The OWL and the penguin
Why we should build an
Extremely Large Telescope
in Antarctica
John W.V. Storey
Images: Michael Ashley & GSMT project
A wise thought from the owl:
Sometimes it’s easier to do two hard
things than one hard thing.
Outline
• You can’t be serious...
• Orientation
• What makes a good observing
site
• Additional requirements of an
ELT
• Sub-millimetre thoughts
• The real disadvantages &
challenges
• Why Australia should do this
• The way forward
Image: Patrik Kaufmann
Top four myths about Antarctica
1. It’s completely inaccessible
2. Your telescope will blow
away
3. The conditions make it
impossible to work
4. The polar bears will eat
you
Image: Karim Agabi
Image:
Australian Antarctic Division
ESO data
Valenziano & Dall’Oglio
1999, PASA 16, 167
Dome C 50% = 1.0 m/s
Myth #3: The conditions make
it impossible to work....
Dome C.
Pressure altitude: 3600 m
temperature: -30oC
Image: Patrik Kaufmann
Image: Camillo Calvaresi
Image: Camillo Calvaresi
Image: Camillo Calvaresi
Image: Karim Agabi
Image: Geanpiero Venturi
Image: Camillo Calvaresi
Image: John Storey
Orientation
Image: Patrik Kaufmann
Antarctica is very large;
USGS image
Geosciences
Australia image
roughly twice the area of Australia.
Contour map of Antarctica
Mount Kosciusko: 2,228 m
USGS image
Potential observatory sites
• South
Pole
• Dome A
• Vostok
• Dome C
USGS image
Dome C is a French/Italian station that will be
open year-round from 2005
Dome C
• Casey
• Hobart
• Mawson
• Davis
Image:
Australian Antarctic Division
South Pole Station
Dome Concordia
Latitude
Longitude
90º S
-
75º 06 S
123º 06 E
Altitude (m asl)
Average pressure (mb)
Minimum Temperature (ºC)
Average Temperature (ºC)
2,835
680
-82
-49
3,205
644
-87
-50.7
Average wind speed (m s-1)
Period of activity
5.8
Since 1957
2.8
Summer: since 1997
Expected first winterover: 2005
What makes a good
observing site?
•
•
•
•
•
•
•
•
•
Cloud-free
High
Dry
Cold
Dark, and radio-quiet
Low integrated turbulence
Low high-altitude turbulence
Low wind at all altitudes
Accessible
Image: Karim Agabi
Icecam and COBBER – two
micro-power instruments to
measure cloud cover.
Image: John Storey
Icecam
COBBER
The two experiments require no
heat, run on a lithium battery pack,
and send data out via the ARGOS
satellite network.
Image: John Storey
ICECAM
Calibration LED
First winter-time stellar observations from Dome C
ICECAM
Winter-time 2001 at Dome C: data look encouraging!
Clouds
2003 Icecam and
COBBER data
Aircraft contrails across Europe
http://www.eso.org/gen-fac/pubs/astclim/contrails/NOAA-AVHRR-trail.jpg
http://www.lightpollution.it/dmsp/
The infrared sky is extremely dark
• Kdark sky spectral
brightness:
Percentage of bins
100
220 Jy. arcsec-2 (mean)
120 Jy. arcsec-2
(median)
50
• This is 1-2 orders of
magnitude lower than found
at typical mid-latitude sites
0
0
200
400
600
800
1000
1200
-2
Sky Spectral Brightness (Jy.arcsec )
Lawrence et al, PASA (2002)
South Pole is 20 ~ 100 times darker than Siding Spring
Phillips et al 1999
Mid-infrared
Comparison between South Pole and other sites
Chamberlain et al 2000
This would be a good place
Image: NASA
Vol 186
189
Vol
Dome C
(Dec 2000)
Altitude (Km)
Altitude (Km)
Altitude (Km)
Wind Speed Profiles (University of Nice)
Vol 43
Paranal ESO Chile
(1992)
Vol
Vol 116
121
Gemini NOAO Chile
(1998)
Agabi and Fossat (2003)
Atmospheric turbulence
100000
The absence of high-altitude
turbulence above the Antarctic
plateau is of profound
importance.
Marks et al, A&A Supp (1998)
Marks et al, A&A Supp (1999)
Log Altitude Altitude (m)
10000
MK
1000
SP
100
SP25
10
1
1E-19 1E-18 1E-17 1E-16 1E-15 1E-14
2
Turbulence
CN
The effect of eliminating high-altitude
turbulence
Turbulent layer high
 narrow field
Turbulent layer low
 wide field
10 ~ 100 times improvement in isoplanatic angle,
scintillation noise, and astrometric error.
The effect of reducing high-altitude
wind
Turbulent layer
moves slowly
• Phase coherence
times increased
• Required adaptive
optics bandwidth
decreases
10 ~ 100 times improvement in sensitivity of
interferometers and AO sensors.
Sample
SODAR
data
900 m
0
June 24 - 27, 2000
Vertical
wind speed
Wind
direction
Horizontal
wind speed
CT 2
Time
Summary of the global oceanic aerosol pattern detected by
polar-orbiting satellites between July 1989 and June 1991
Movie: European Southern Observatory
Additional requirements for ELTs
Image: Patrik Kaufmann
A Nest for OWL
Additional Requirements for ELTs
• Low Seismic Activity
An ELT cannot be made stiff enough to survive
earthquakes
• Low Wind at ground level
An ELT is more sensitive to wind shake during tracking
• Low Wind at high altitude
Longer atmospheric time constant for AO
• Climate Stability
Marc Sarazin, ESO
Peak Ground Acceleration up to
5m/s²: 10% probability of
exceedance in 50 years
Source: http://www.seismo.ethz.ch/GSHAP/
ESO data
Valenziano & Dall’Oglio
1999, PASA 16, 167
Sub-millimetre thoughts
Image: Patrik Kaufmann
CARA has carried out very
successful mm and sub-mm work at
South Pole for over a decade.
Image: Tony Stark
Quartiles of PWV at three Sites
At each site, the year
is divided into the
best and worst 6 month periods.
Bars show quartiles
of the PWV
distribution at each
site.
Lane, ASP Conference Series 141, 1998
Sky Noise and opacity
measurements at
350µm from three sites
Peterson, Radford et al (in press).
Summer 2000 – 01 at
Dome C & South Pole
Opacity at 350 m
Calisse et al 2003, PASA (submitted).
Summary of site conditions
Clear
Low surface wind
High
Low wind throughout
atmosphere
Dry
No high level turbulence
Cold
Low seismic activity
Clean
Very accessible
Dark
Continuous observing
possible
Stable climate
Image: Patrik Kaufmann
SPIREX, the South Pole
Infrared Explorer, was a 60
cm telescope with 1024 x
1024 InSb detector array.
SPIREX demonstrated the
viability of IR astronomy
from Antarctica.
SPIREX was a collaboration
between CARA, Ohio State
University, NOAO,
Rochester I.T. and UNSW.
Image: UNSW
SPIREX image of starformation in NGC6334
Burton et al, Astrophysical
Journal, 542, 359, (2000)
The real disadvantages and
challenges
• “Diamond dust”
• Altitude
• Winter isolation
•
•
•
•
See less of sky
Less true “dark time”
Aurora?
Ecliptic always at low
elevation
Image: Michael Ashley
Why Australia should do this
Image: Patrik Kaufmann
Astronomy is one of the sciences in which
Australia’s international reputation is highest:
• Over 160 professional
astronomers employed at
universities, observatories
and CSIRO
• Citation rates amongst the
highest in Australian science
• Nine astronomers amongst
top 33 “citation laureates”
• Several world-class
observatories in Australia
• International links to top
institutions
World class facilities in
Australia include:
However, our Southern Hemisphere
“natural advantage” has been eroded.
• Australia has only a 5% share of Gemini (→ 6.5%?).
• We have no high mountains. All future major
developments in IR/optical astronomy will be off-shore.
• We have no sub-mm or far-infrared (THz) capability.
Radioastronomy may
have a rosier outlook,
particularly if LOFAR
and/or the SKA is built
in Australia.
Image: ATNF
Australia is uniquely placed to benefit
from Antarctic astronomy.
• Geographic proximity.
• Tradition of Antarctic exploration.
• On-going, major, national Antarctic program.
• No national participation in SOFIA, SIRTF etc.
• The “Antarctic advantage” means cutting edge
science can be done at an affordable price.
• Experience with SPIREX/Abu and site testing
demonstrates technological leadership.
Logistic support of Dome C is via Hobart.
Image: John Storey
L’Astrolabe brings heavy items from Hobart
to Dumont d’Urville in 6 days...
Image: John Storey
...thence by tractor-traverse to Dome C.
Image: Patrik Kaufmann
The tractor-traverse takes 11 days to get from the coast
to Dome C.
• Three traverses/year (currently)
• Each traverse delivers ~150 tonnes
• Fuel consumption 600 litres/tonne
• Twelve-metre sleds – essentially no size or weight restrictions
Dome C is particularly attractive to Australia
(compared to South Pole)
because:
• The logistic support is via Tasmania
• Dome C is at a similar longitude to the
ATNF CA, Mopra, and AAT.
• Geostationary satellite communications
are possible (eg AUSSAT?)
Image: Karim Agabi
The way forward
• Completion of site testing
• The DMT
Image: Patrik Kaufmann
The AASTINO at Dome C, 2003
Image: Camillo Calvaresi
The AASTINO
Instrumentation (on roof)
Solar panels
Heat exchangers
Electronics and
work area
Iridium antenna
1200 litre fuel tanks
Stirling engines
Image: John Storey
Image: Geanpiero Venturi
Image: Geanpiero Venturi
Image: Camillo Calvaresi
Image: Camillo Calvaresi
Image: UNSW AASTINO webcam
The AASTINO has operated
robotically, without human
presence, since February 7,
2003.
CamilloAASTINO
Calvaresi webcam
Image: UNSW
14 May,
2003.
Images
spaced
every
30 mins.
Image: UNSW
AASTINO
webcam
SODAR
Image: Geanpiero Venturi
SODAR data
South Pole 2001
Dome C 2003
(so far...)
Travouillon et al, in prep.
SUb MilliMetre Tipper
(SUMMIT)
• Differential flux measurement
at 350 m
• Calibrated to hot and cold
blackbodies
• Opacity and brightness
temperature
• Dome C summer 2000/2001
• South Pole winter 2001 &
2002
Image: UNSW
Opacity (tau) at 350 m
Calisse et al, in prep.
MASS – Multi-Aperture Scintillation Sensor
• Sensitive measurement of
the vertical distribution of
turbulence
• A collaboration between
CTIO, JPL and UNSW
• To be deployed to Dome C
November 2003
Image: Andrei Tokovinin
The Douglas Mawson Telescope
• A 2-metre infrared
telescope for Dome C.
• Proposed to MNRF II as
an Australian/French/Italian
collaboration in 2001.
• Not funded in that round,
but support is still strong
from all partners.
• Important to find new
funding options soon.
Image: EOST
Conclusions
Conditions at Dome C are
unique, and extremely
favourable.
A medium-size telescope or
interferometer could do groundbreaking science.
A very large telescope at Dome
C would be unbeatable.
The opportunity awaits!
Image: Patrik Kaufmann
Myth #4: the polar bears will eat you
To deal with the polar bears, we pour water on the ground...
...which freezes into ice...
...and all the bears fall over.
Image: www.dandennis.com
Acknowledgements
IPEV - Institut Polaire Emile Victor
JACARA - Joint Australian Centre for
Astrophysical Research in Antarctica
ARC - Australian Research Council
Italian Programma Nazionale di
Ricerche in Antartide
NSF- National Science Foundation
CARA - Center for Astrophysical
Research in Antarctica
AAD - Australian Antarctic Division
IAU2003 General Assembly
Sydney, July 13 – 26 2003
– Special Session 2, ASTRONOMY IN ANTARCTICA, July 18
– “Future Visions for Antarctic Astronomy”, Taronga Zoo, July 19
Michael Ashley
Michael Burton
Paolo Calisse
Jessica Dempsey
Jon Everett
Jon Lawrence
Caroline Santamaria
John Storey
Tony Travouillon
http://www.astronomy2003.com