january 11, 2007 workshop 3e zone, nantes. leslie young pluto occultation 2006 june 12 from...

January 11, 2007 Workshop 3e Zone, Nantes. Leslie Young

Pluto occultation 2006 June 12from Australia & New Zealand

Leslie Young, Eliot Young, Catherine Ruhland, Catherine Olkin (SwRI)

Richard French (Wellesley College)Marc Buie (Lowell Observatory)Jeff Regester (Greensboro Day School, NC)Kevin Shoemaker (Shoemaker Labs, Longmont CO)Martin George (Launceston Planetarium, Tasmania)John Broughton (Reedy Creek, Australia)Grant Christie,Tim Natusch (Auckland Observatory)Ross Dickie, Peter Jaquiery, Graham Blow (RASNZ)Dave Gault (Hawkesbury Heights, Australia)Blair Lade (Stockport Observatory, Australia)


Occultation Overview

Temperature PressureExtinction

Refractivity Bending

angle=>

Flux Position in shadow

=>=>


Occultation:Reconstructed Shadow Path


Reedy Creek 0.51 m (20")John Broughton


Anglo-Australian Telescope 4-m (163 ")Dick French, Kevin Shoemaker


Hawkesbury Heights 0.25 m (10")Dave Gault


Stockport Observatory 0.51 m (20")Blair Lade


Longford Farm 0.36 m (14")Eliot Young, Jeff Register


Auckland Observatory 0.36 m (14")Grant Christie, Tim Natusch


Carter Observatory 0.41 m (16")Marc Buie, Trina Ruhland


Farm near Wanaka, 0.36 m (14")Leslie Young, Cathy Olkin, Peter Jaquirey, Ross Dickie


Geometric Solution


Change in Shadow Radius:1988 to 2002: 2.74 ± 1.36 km/yr (increase)

2002 to 2006: 1.17 ± 4.31 km/yr (consistent with no change)


Frame Rate: 10 Hz

SNR per point: 62

SNR per 60 km: 331

GPS-based absolute timing accuracy better than 100 µsecond.

Spikes are resolved, differ in detail between ingress/egress


T0

2006 AAT 2006 AAT 2006 AAT 1988 KAOIngress Egress Avg Avg

T0 (K) 100.0±4.2 106.4±4.6 103.9±3.2 104.0±7.3

P0 (µbar) 1.76±0.14 1.95±0.15 1.86±0.10 0.83±0.11

dT0/dr (K/km) -0.113±0.045 -0.082±0.051 -0.086±0.033 -0.040±0.052

r1 (km) 1286.8±10.6 1287.1±37.1 1273.6±7.1 1215.8±1.3

κ2 (1000xkm-1) 2.7±0.5 3.0±0.5 3.0±0.4 4.1±0.3

Hτ216.6±1.7 15.9±1.8 15.9±1.1 24.6±4.2


Lower Atmosphere Inversion(Ref: Elliot, Person and Qu 2003)

• Small Planet Case• No Ray Crossing• Geometric Optics• Clear Atmosphere


Immersion

R (km) v. T (K) R (km) v. dT/dr (K/km)

dry adiabat


Emersion

R (km) v. T (K) R (km) v. dT/dr (K/km)

dry adiabat


Monte Carlo-Based Error Estimates

• Monte Carlo errors based on 100 simulated lightcurves with appropriate noise.

• The Temperature Inversions: Similar overall shape, similar wiggles, but largest errors (up to ±18 K) above the temperature inversion at 1240 km.

R (km) v. T (K)- Nominal Case- 1-sigma env.


Effects of an example haze layer

• Haze dramatically changes the lower temperature profile.

• Brings dT/dr closer to a dry adiabat.

Consider the effects of sudden haze onset at 1263 km with a scale height of 15 km.

R (km) v. T (K)

R (km) v. dT/dr (K/km)dry adiabat


Conclusions• Pluto's bulk atmosphere (geometry):

– 1988 to 2006, pressure has increased by 0.98 ± 0.09 µbar, a factor of 2.17±0.21

– For N2 surface vapor pressure equilibrium, this implies an increase in surface temperature of 1.2-1.7 K.

– Pressures consistant between 2002 and 2006

• Pluto’s upper atmosphere (model fit): – Non-isothermal. dT/dr = -0.127±0.028 K/km– Average (103.9±3.2 K) same as 2002 (104±2 K, isothermal fit),

and 1988 (104.0±7.3 K). – 99.4±3.1 K (ingress, 30.0 S, summer), 105.5±3.5 K (egress, 53.2 N, winter)

dispite ~1500 less insolation averaged over the winter latitude, so not tied to insolation (in a straightforward way)

• Pluto’s lower atm, clear assumption (inversion):– As in 1988 & 2002, not isothermal. – Temperature inversion around 1210 - 1220 km.– Ingress & Egress are qualitatively similar, but the density perturbations differ in detail.

• Pluto’s lower atm, haze assumption (inversion, removing haze from model fit)– Top of haze poorly constrained.– Temperature purturbations qualitatively similar to those seen on Earth, Jupiter, Titan

january 11, 2007 workshop 3e zone, nantes. leslie young pluto occultation 2006 june 12 from...

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