ATMOSPHERIC WINDOWS TO IMAGE THE SURFACE FROM BENEATH THE CLOUD DECK ON THE NIGHT SIDE OF VENUS

J. J. Knicely, R.R. HerrickUniversity of Alaska FairbanksVEXAG 2018, Laurel Maryland

Acknowledgements• Giada Arney• Lori Glaze• Franz Meyer• Sebastian Lebonnois

Introduction• Study the surface of Venus• Searched for surface viewing

atmospheric windows▫ Beneath the cloud deck ▫ Emission only – night side

• Explored 4 variables▫ Sensor altitude▫ Surface emissivity▫ Surface elevation▫ Regional temperature variations

Methods• 1D radiative transfer problem

!" # = !%&' exp −,-

./" #0 1#′ +

,-

./" #0 4" 5 #0 exp −,

.6

./" #00 1#′′ 1#′

Surface signal Decay through atmo

Atmo signal

Methods (2)• Surface viewing atmospheric

window▫ !"#$ ≥ &

' !()(*+• Assumptions▫ 1D radiative transfer problem▫ Constant surface emissivities▫ Thermo-dynamic equilibrium▫ Lambertian surface▫ Plane-parallel and homogenous

slab layers

• Emission

!"#$ = - ."#$ /, 1 = - 2ℎ4'

/51

exp ℎ4/:;1 − 1

• Parameters▫ Sensor altitude – 10 to 100 km, ∆ℎ=10 km▫ Emissivity – 1.0, 0.95, 0.86, 0.7▫ Surface elevation – 0 & 11 km▫ Regional temperature - +20 K

Data• Total extinction coefficients▫ Lebonnois et al. [2015]� HITRAN2008 & HITEMP2010▫ Underprediction of opacity from

1.10-1.18 microns• Temperature profile of Seiff et al.

[1985]▫ Pioneer Probes/Oribter▫ Venera 10, 12, & 13 landers

Figure ALPHA. Adapted from Lebonnois et al. [2015]. Total extinction coefficients as a function of altitude in linear scale and wavelength in log scale.

Results• Atmospheric window - !"#$ ≥ &

' !()(*+

Results (2)

Results (3)

Discussion• Identified Windows▫ Expanded satellite windows

• Parameter effects▫ Sensor altitude - weak▫ Surface emissivity – strong▫ Surface elevation – strong▫ Regional temperature – weak

• Basic rock segmentation• Redox state of Venus

Figure 5. Emissivity for various rock types at known Venus atmospheric windows and surface temperatures. Taken from Helbert et al. [2018].

Discussion (2)• Very simple modeling• HITEMP 2010 underpredicts CO2 opacity from 1.10-1.18

microns• Low data quality▫ Total extinction coefficients

Conclusions• Expanded spectroscopic

abilities beneath cloud deck• 0.9-1.2 !" & 1.27 !"▫ Possible error from 1.1-1.18 !"

• Potential uses▫ Basic rock segmentation▫ Redox state▫ Search for active volcanism

• Need improved ancillary data

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