plato: a third-generation site-testing observatory for · pdf fileimage: li yuansheng plato: a...

Image: Li Yuansheng

PLATO: a third-generation site-testing observatory for Dome A

John StoreyJon LawrenceMichael Ashley

Daniel Luong-VanShane Hengst

Lifan Wang

Outline

• Where is Antarctica?• South Pole

– AASTO• Dome C

– AASTINO• Dome A

– PLATO

Image: Patrik Kaufmann

Antarctica is conveniently located (if you live in Sydney...)

Hobart ●

Sydney ●

Dome C ●

Image: Australian Antarctic Division

Contour map of Antarctica

USGS image

Dome C

South Pole

Dome A

Dome F

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

Outline


– AASTO• Dome C


– PLATO


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

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

Image: Seth White

The South Pole is a thriving international observatory

Image: Bob Spotz

Outline


– AASTO• Dome C


– PLATO


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

Dome C

The best observing site on earth?

Image: Jon Lawrence

Dome C is 15o from the South Pole.

Image: Guillaume Dargaud

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

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

ESO data

Aristidi et al 2005, A&A Dome C 50% = 2.8 m/s

January 2003November 2003Dome C

Image: John Storey

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

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

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

The AASTINO

Stirling engines

Heat exchangers

1200 litre fuel tanks

Instrumentation (on roof)

Electronics and work area

Iridium antenna

Solar panels

Image: Camillo Calvaresi

AASTINO

Image: Geanpiero Venturi

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: John Storey

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)

Seeing from ground level, measured with DIMM by Eric Aristidi(LUAN) in 2006

0.09 arcseconds

0.14 arcseconds

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

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


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!


What might surprise us

• Cloud cover• Near-ground turbulence• Intrusion of jet-stream

• IR and sub-mm transmission• “Best” conditions might be

super superb


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

PILOT, 2.4 metres, 2009

LAPCAT, 8 metres, 2014GMTA, 24 metres, 2020

Towards an Antarctic ELT

Outline


– AASTO• Dome C


– PLATO


Elevated Telescopes

~18 m~21 m~27 m

Swain & Gallee, 2006

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

Dome A

Precipitable water vapour

Swain, 2007

Image: Li Yuansheng

Dome A

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)

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

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

Image: Li Yuansheng

UNSW experiment currently at Dome A

SastrugiDome CDome C

Dome ADome A

Dome ADome A

coastalcoastal

inlandinland

Images courtesy Li Yuansheng, Xiao Cunde, PRIC, CAMS

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

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


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

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

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

Engine test rig

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

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

Image: Jon Lawrence

Image: Andrei Tokovinin

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

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

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

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Rel

ativ

e R

etur

n P

ower

Frequency (GHz)

height = 20 m height = 40 m height = 100 m height = 200 m

-80 -60 -40 -20 00.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

10 kHz

2 kHz

8 kHz

6 kHz

4 kHz

Tran

smis

sion

ove

r 200

m

Temp

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

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

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

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