plato: a third-generation site-testing observatory for · pdf fileimage: li yuansheng plato: a...
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Image: Li Yuansheng
PLATO: a third-generation site-testing observatory for Dome A
John StoreyJon LawrenceMichael Ashley
Daniel Luong-VanShane Hengst
Lifan Wang
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Outline
• Where is Antarctica?• South Pole
– AASTO• Dome C
– AASTINO• Dome A
– PLATO
Image: Patrik Kaufmann
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Outline
• Where is Antarctica?• South Pole
– AASTO• Dome C
– AASTINO• Dome A
– PLATO
Image: Patrik Kaufmann
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Antarctica is conveniently located (if you live in Sydney...)
Hobart ●
Sydney ●
Dome C ●
Image: Australian Antarctic Division
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Contour map of Antarctica
USGS image
Dome C
South Pole
Dome A
Dome F
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What makes a good observing site?
Clear
High
Dry
Cold
Clean
Dark
Low precipitation
No lightning
No forest fires
Low surface wind
Low wind throughout atmosphere
No high level turbulence
Low seismic activity
Accessible
Continuous observing possible
Stable climate
Image: Anna Moore
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Outline
• Where is Antarctica?• South Pole
– AASTO• Dome C
– AASTINO• Dome A
– PLATO
Image: Patrik Kaufmann
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South Pole
South Pole 2835 m altitude
Site testing summer/ winter 1995-2000(CARA, UNSW, U Nice)
Ground level seeing poor (1.8 arcsec) Free atmosphere > 300 m very good (ε0=0.4 as, θ0=3 as, τ0=2 ms)Extremely low IR sky backgroundExcellent transmission and stability in sub-mmPoor cloud statistics (50% cloud free)
Antarctic wind field Courtesy A. Monaghan, Byrd Polar Research Centre
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The AASTO• Evolved from the US “AGO”• 2.4 x 2.4 x 4.8 metre fibreglass shelter• Shirt-sleeves environment • Liquid propane fuelled TEG• Electrical power: 50 watts• On-site data recording for one year• House keeping via Argos satellite• 12-month autonomous operation
Image: Seth White
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Image: Seth White
The South Pole is a thriving international observatory
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Image: Bob Spotz
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Image: Bob Spotz
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Outline
• Where is Antarctica?• South Pole
– AASTO• Dome C
– AASTINO• Dome A
– PLATO
Image: Patrik Kaufmann
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Dome C
Dome C3250 m altitude
Ground level seeing poor (1.2 arcsec) Free atmosphere > 30 m very good (ε0=0.3 as, θ0=6 as, τ0=8 ms)Extremely low IR sky backgroundExcellent transmission and stability in sub-mmExcellent cloud statistics (~90% cloud free)
Site testing summer/ winter 2000-(U Nice, UNSW, Arcetri, U Rome, CTIO, JPL, U Idaho, U Cardiff)
Antarctic wind field Courtesy A. Monaghan, Byrd Polar Research Centre
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Dome C
The best observing site on earth?
Image: Jon Lawrence
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Dome C is 15o from the South Pole.
Image: Guillaume Dargaud
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Dome C versus conventional sites
Seeing (above 30 m) 2 – 3x betterIsoplanatic angle 2 – 3x largerCoherence time 2.5x longerScintillation 3 – 4x lessIR background 20 – 100x lessAerosols up to 50x lower
Image: Paolo Calisse
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Image: Karim Agabi
The real disadvantages: • See less of sky
• Less “dark time” (?)
• Ecliptic always low
• Physical isolation in winter
• Difficult to work outside in winter
• “Diamond dust”close to ground
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ESO data
Aristidi et al 2005, A&A Dome C 50% = 2.8 m/s
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January 2003November 2003Dome C
Image: John Storey
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Ice core taken in 1978
Annual precipitation: 35 g/cm2
ie, ~40 mm/year of ice.
Site testing with nuclear weapons...
J.F. Pinglot & M. Pourchet, 1981
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Witness Mirror Reflectivity
80
81
82
83
84
85
86
87
88
89
90
400 450 500 550 600 650 700 750 800Wavelength (nm)
Ref
lect
ivity
(%)
InitialAfter 36 Months
Credit: Jon Everett et al 2007
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Difference in Reflectivity
-3
-2.5
-2
-1.5
-1
-0.5
0400 450 500 550 600 650 700 750 800
Wavelength (nm)
Ref
lect
ivity
(%)
Credit: Jon Everett et al 2007
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The AASTINO
Stirling engines
Heat exchangers
1200 litre fuel tanks
Instrumentation (on roof)
Electronics and work area
Iridium antenna
Solar panels
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Image: Camillo Calvaresi
AASTINO
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Image: Geanpiero Venturi
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The Whispertech
Stirling engine
• 800 watts at sea level
• 6.5 kW of heat
• Runs on liquid or gaseous fuel
• Fully remote controlled
• Very low pollution
• Quiet
Image: Geanpiero Venturi
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Image: John Storey
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0
20
40
60
80
100
0.0 0.2 0.4 0.6 0.8 1.00
100
200
300
CPMK
N
umbe
r of m
easu
rem
ents
Total atmospheric seeing (arcsec)
DC
Cum
ulat
ive
prob
abilit
y
Lawrence, Ashley, Tokovinin, and Travouillon, Nature, 431, 278, (2004)
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Seeing from ground level, measured with DIMM by Eric Aristidi(LUAN) in 2006
0.09 arcseconds
0.14 arcseconds
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Estimates of the boundary layer thickness at Dome C
“Thin”. Gillingham 1991, Schwerdtfeger plus AWS
< 30 m Lawrence et al 2004, SODAR
> 20 m Agabi et al 2006, DIMM
36 ± 19 m Agabi et al 2006, Balloon μthermal
27 m median Swain & Gallee 2006, modelling
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What we know
• Surface temperature and snow precipitation rate
• Wind speed and direction, atmospheric pressure
• IR sky brightness (upper limit)
• Precipitable water vapour (approximately)
• Turbulence profile (some)• Practicalities
Image: Paolo Calisse
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Site testing: still need to knowBasic surface layer parameters!Isopistonic angleOuter scale[Clear-sky statistics]Temporal spectrum (not just
coherence time)Surface layer height and
variabilityKolmogorov?Better statistics on all parameters!
Image: Paolo Calisse
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What might surprise us
• Cloud cover• Near-ground turbulence• Intrusion of jet-stream
• IR and sub-mm transmission• “Best” conditions might be
super superb
Image: Paolo Calisse
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PILOT
Pathfinder for an International Large Optical Telescope
Image: EOST
Strawman design:• 2.4 metre primary• Dual Nasmyth f/10• Brushless direct drive• Fast tip-tilt
secondary
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PILOT, 2.4 metres, 2009
LAPCAT, 8 metres, 2014GMTA, 24 metres, 2020
Towards an Antarctic ELT
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Outline
• Where is Antarctica?• South Pole
– AASTO• Dome C
– AASTINO• Dome A
– PLATO
Image: Patrik Kaufmann
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Elevated Telescopes
~18 m~21 m~27 m
Swain & Gallee, 2006
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PILOT weighs 27 tonnes
30 m “Hammerschlag” tower weighs 100 tonnes
Deflection under maximum wind gusts at Dome C is less than 100 milli arcsec(Lanford et al 2006)
Image: Robert Hammerschlag et al, 2006
Is a tower required?
Dutch Open Telescope, La Palma
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Dome A
Precipitable water vapour
Swain, 2007
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Image: Li Yuansheng
Dome A
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Dome A
Courtesy A. Monaghan, Byrd Polar Research Centre
The annual vector mean winds from Polar MM5Dome A
4100 altitude
highest driestcoldest calmest
Wind speed (m/s)
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E60
10001500
2000
2500
500
3000
3500
40004200
80 75 70
E70
E80
The Amery ice shelf
The prince checks the mountain of 尔斯
ZhongshanZhongshanSmall forest mountain
Dome A
Mawson
White land of the 伊丽莎 of princess
Gulf of Prydz
Davis
MGA
Dome A traverse lineDome A traverse line
2004/20052004/2005
about 1300
kilometers
Image: Polar Research Institute of China
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Images courtesy Li Yuansheng, PRIC
• Polar Research Institute China tractor traverse:– January 2005– 13 member team– 30 days: Zhongshan → Dome A– 2 weeks: Dome A– Ice radar, ice core, AWS,
skycam
Dome A Traverse 2004 – 5
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Image: Li Yuansheng
UNSW experiment currently at Dome A
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SastrugiDome CDome C
Dome ADome A
Dome ADome A
coastalcoastal
inlandinland
Images courtesy Li Yuansheng, Xiao Cunde, PRIC, CAMS
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AWS data
• Wind speeds Dome A– Mean 2.5 m/s– Median 1.8 m/s– Max 14 m/s
• Dome C (same period)– Mean 3.6 m/s– Max 19 m/s
• Dome C (10 years)– Mean 2.9 m/s– Max 20 m/s
Data courtesy PRIC, AAD 0 2 4 6 8 10 12 14
0
500
1000
Cou
nts
Wind speed (m/s)
Dome A 2005 Dome C 2005
J J F M A M J J A S O N D0
2
4
6
8
10
12
14
Win
d S
peed
(m/s
)
Date, 2005
1 m 2 m 4 m
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Dome A AWS data
Wind speedsMean 2.5 m/sMedian 1.8 m/sMax 14 m/scf Dome C (10 year) mean 2.7 m/scf Dome C (same period) mean 3.6cf Dome C max 19 m/s
Temperatures Mean air temp -52.6° C at 2 mcf Dome C (10 year) mean -50.8° Ccf Dome C (same period) mean -49.8° C
Relative humidityAverage 42 %Similar values to SP and DC
Data courtesy PRIC, AAD
J J F M A M J J A S O N D0
2
4
6
8
10
12
14
Win
d S
peed
(m/s
)
Date, 2005
1 m 2 m 4 m
J J F M A M J J A S O N D-90
-80
-70
-60
-50
-40
-30
-20
-10
Air
Tem
pera
ture
(deg
rees
C)
Date, 2005
airT 1m airT 2m airT 4m
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Image: Geanpiero Venturi
PLATO: Plateau Observatory
PLATO is the “next generation” AASTINO PLATO is a collaboration between PRIC, NOAC and UNSWPLATO will be deployed to Dome A in January 2007PLATO will not look like this
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Well insulated enclosure
“AASTINO-style”thermal mangement
Six 1.5kW diesel generators
3,500 litres of Jet A1 fuel250 Farad ultra-capacitor bank (for engine starting)
PLATO power module
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PLATO power
• 6 x Hatz diesel engines– Air-cooled 4-stroke single-
cylinder; 350 cc– Jet A1 aviation fuel ~3000 litres– 1500 W @ 2,000 rpm, 0.5 atm
• Solar panels – 8 x 150 W with MPPT
• Ultra-capacitor bank for engine starting
• 200 Ahr 24V gel-cell battery
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Engine test rig
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PLATO instruments• Turbulence:
– Boundary layer: height, distribution and variability – High altitude: evidence of jet stream
• Sky emission and opacity:– Visible: auroral intensity and distribution, sky background
versus sun/moon elevation – Near/mid infrared: airglow (NIR), and thermal (MIR)
background and stability– Sub-millimetre: transparency and noise in long wave windows
• Meteorology:– Cloud cover: night and day– Precipitation: rates of snowfall and accumulation– Temp, pressure and wind vector at ground level
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PLATO instrument module
Well insulated enclosure
MASS
CSTARNigel
PreHEAT
Gattini
Web camera
200 Ahr 24V gel-cells
Spare optical ports
Plus: Acoustic radar and tower microthermals
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Image: Jon Lawrence
Image: Andrei Tokovinin
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Turbulence
Sonics (tower mounted anemometers)
Applied Technologies #SX anemometer (x3)
Mounted on NRG systems 30 m TallTower
Measures wind speed vector and temperature, hence CN2
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SNODAR (Surface layer NOn Doppler Acoustic Radar)
Aim: to measure boundary layer turbulence at ~1 m resolution
Baseline design uses 37 element array of high frequency piezo-electric horns OR single dish with parabolic reflector
Simple, cheap, robust, winterisable
Turbulence
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SNODAR (Surface-layer NOn Doppler Acoustic Radar)
Dual operating modes:Low spatial resolution up to 500 m using f = 1–2 kHz
High spatial resolution in the near surface layer using f=10–15 kHz
Low temperatures enhance signal relative to most sites
Turbulence
0 1 2 3 4 5 6 7 8 9 100.0
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etur
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ower
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height = 20 m height = 40 m height = 100 m height = 200 m
-80 -60 -40 -20 00.0
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10 kHz
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4 kHz
Tran
smis
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r 200
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Temp
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Supervisor node A
IRIDIUM
SWW
PC104
IRIDIUM
SWW
PC104
IRIDIUM
SWW
PC104
Supervisor node B Supervisor node C
24V 24V 24V
ADCDIO
USB HUB
HDN
HD2
powerdistribution
USBmultiplexer
HD1
Ethernethub
Instrument N
Instrument 1
Instrument 2
RS232multiplexer
24V
Thermal control
Engine control
Solar control
Housekeeping
PLATO control
CAN bus
24 VDC
Computer Nodes:• PC104 computer system• Iridium L-band transceiver• Super wakey-wakey PCB
Supervisor Hub:• 3 independent Nodes• CAN bus communication
Power control:• individual units for engine, solar power, thermal, and housekeeping data• linked via CAN bus ADC/DIO
Instrument control:• data storage on networked USB HD• comms via RS232 and Ethernet• power supply via CAN bus
RS232
Ethernet
USB
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Dome A Traverse
Dome C
Dome A
Zhongshan
The Polar Research Institute of China will deploy PLATO to Dome A by tractor traverse in January 2008,as part of the “PANDA” IPY program.
Images courtesy Li Yuansheng, PRIC
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UNSW team: Michael Ashley, Colin Bonner, Tui Britton, Michael Burton, Jessie Christiansen, Jon Everett, Shane Hengst, Balt Indermuehle, Suzanne Kenyon, Jon Lawrence, Daniel Luong-Van, John Storey.
Image: Colin Bonner