skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Titan Imagery with Keck AO during and after Probe Entry

Abstract

We present adaptive optics data from the 10-m W.M. Keck telescope that were taken during the time the Huygens probe descended through Titan's atmosphere, and on the days following touch-down. The spatial resolution of the images is typically {approx}0.04-inch, or {approx}240 km on Titan (60 km/pixel). No probe entry signal was detected at levels exceeding 0.8 {micro}Jy (3-{sigma}) per pixel (0.01-inch), which although within the range of predicted flux levels, cannot constrain any models. We present data on Titan's surface, troposphere and stratosphere during the days following probe entry, when the solar phase angle varied from 0.05{sup o} up to 0.8{sup o}, with the Sun in the West. Contrary to expectation, the data often showed the East side to be brightest. Adding data obtained with Keck and Gemini over the past few years reveals that the East-West asymmetry can be explained by a combination of the solar phase angle effect together with a general preponderance of haze on Titan's East or morning hemisphere. The troposphere was characterized by quiescent weather; only a few small clouds were present near the south pole, at typical altitudes of 30-40 km. While stratospheric haze was prominent over the northern hemisphere, tropospheric haze dominated themore » south, from the S. pole up to latitudes of {approx} -45{sup o}. An intriguing observation is that obtained at 1.22 {micro}m, which revealed haze in the form of a collar at -60{sup o}, in contrast to the polar haze cap as usually seen. A comparison of narrow band JHK images of Titan's surface with that obtained by Cassini ISS shows a striking resemblance in small-scale features. After a decent attempt to remove the atmosphere from the images, the surface contrast between dark and bright areas may be larger at 2 {micro}m than at 1.6 and 1.3 {micro}m. If true, this could imply that the dark areas on Titan's surface are covered by a coarser grained frost than the bright areas, and/or that there are more absorbers, such as NH{sub 3}/NH{sub 4}SH frost, in these dark areas.« less

Authors:
; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
957175
Report Number(s):
UCRL-JRNL-218795
TRN: US201007%%595
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Journal Article
Journal Name:
Geophysical Research Planets, vol. 111, E7, June 1, 2006, pp. 5-7
Additional Journal Information:
Journal Volume: 111; Journal Issue: E7
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUMM MECHANICS, GENERAL PHYSICS; CLOUDS; EAST-WEST ASYMMETRY; FROST; NORTHERN HEMISPHERE; OPTICS; PROBES; SPATIAL RESOLUTION; STRATOSPHERE; SUN; TELESCOPES; TROPOSPHERE; WEATHER

Citation Formats

de Pater, I, Adamkovics, M, Bouchez, A H, Brown, M E, Gibbard, S G, Marchis, F, Roe, H G, Schaller, E L, and Young, E. Titan Imagery with Keck AO during and after Probe Entry. United States: N. p., 2006. Web.
de Pater, I, Adamkovics, M, Bouchez, A H, Brown, M E, Gibbard, S G, Marchis, F, Roe, H G, Schaller, E L, & Young, E. Titan Imagery with Keck AO during and after Probe Entry. United States.
de Pater, I, Adamkovics, M, Bouchez, A H, Brown, M E, Gibbard, S G, Marchis, F, Roe, H G, Schaller, E L, and Young, E. 2006. "Titan Imagery with Keck AO during and after Probe Entry". United States. https://www.osti.gov/servlets/purl/957175.
@article{osti_957175,
title = {Titan Imagery with Keck AO during and after Probe Entry},
author = {de Pater, I and Adamkovics, M and Bouchez, A H and Brown, M E and Gibbard, S G and Marchis, F and Roe, H G and Schaller, E L and Young, E},
abstractNote = {We present adaptive optics data from the 10-m W.M. Keck telescope that were taken during the time the Huygens probe descended through Titan's atmosphere, and on the days following touch-down. The spatial resolution of the images is typically {approx}0.04-inch, or {approx}240 km on Titan (60 km/pixel). No probe entry signal was detected at levels exceeding 0.8 {micro}Jy (3-{sigma}) per pixel (0.01-inch), which although within the range of predicted flux levels, cannot constrain any models. We present data on Titan's surface, troposphere and stratosphere during the days following probe entry, when the solar phase angle varied from 0.05{sup o} up to 0.8{sup o}, with the Sun in the West. Contrary to expectation, the data often showed the East side to be brightest. Adding data obtained with Keck and Gemini over the past few years reveals that the East-West asymmetry can be explained by a combination of the solar phase angle effect together with a general preponderance of haze on Titan's East or morning hemisphere. The troposphere was characterized by quiescent weather; only a few small clouds were present near the south pole, at typical altitudes of 30-40 km. While stratospheric haze was prominent over the northern hemisphere, tropospheric haze dominated the south, from the S. pole up to latitudes of {approx} -45{sup o}. An intriguing observation is that obtained at 1.22 {micro}m, which revealed haze in the form of a collar at -60{sup o}, in contrast to the polar haze cap as usually seen. A comparison of narrow band JHK images of Titan's surface with that obtained by Cassini ISS shows a striking resemblance in small-scale features. After a decent attempt to remove the atmosphere from the images, the surface contrast between dark and bright areas may be larger at 2 {micro}m than at 1.6 and 1.3 {micro}m. If true, this could imply that the dark areas on Titan's surface are covered by a coarser grained frost than the bright areas, and/or that there are more absorbers, such as NH{sub 3}/NH{sub 4}SH frost, in these dark areas.},
doi = {},
url = {https://www.osti.gov/biblio/957175}, journal = {Geophysical Research Planets, vol. 111, E7, June 1, 2006, pp. 5-7},
number = E7,
volume = 111,
place = {United States},
year = {2006},
month = {2}
}