Near infrared observations of Venus' nightside hemisphere are performed in a collaboration between globally distributed observatories, enabling tracking of cloud features over a long temporal baseline. The observations, mainly in the 2.1 mum K-band, will allow a study of the atmospheric circulation pattern and heat transport, partly to support the European Space Agency Venus Xpress mission.
Participating observatories include the 2.6-m Nordic Optical Telescope at the Roque de Los Muchachos Observatory, La Palma, Canary Islands, Spain, the 2-m Himalayan Chandra Telescope at Mt. Saraswati, Hanle, Indian Astronomical Observatory, the 1.2-m Mt Abu Telescope of the Physical Research Observatory, the Sacramento Peak Observatory, National Solar Observatory, New Mexico, USA, and the 3.6-m NASA Infrared Telescope Facility, Mauna Kea, Hawaii, USA.
The images below are obtained with NOTCam infrared imager/spectrograph on the Nordic Optical Telescope in High Resolution mode (0.08"/pix) using the following NOT filters: K cont #10 2.26 mum, CH4 #24 1.70 mum, Br gamma #9 2.16 mum.
Exposures are in the range 300-500 ms, giving delta DN values of about 500-900 between the brightest and darkest cloud features on the unilluminated hemisphere.
Scattered light is a problem, especially in the CH4 filter, with an enlarged inverted ghost image of the crescent appearing in the field, as well as a demagnified one.
All images shown are RAW -- no flatfielding, sky subtraction etc. of any kind has been applied. Click the images to show them at 50% nominal resolution.
This research is funded by the Swedish Research Council.
Cu clouds and high humidity forced a late opening of the dome and closure of the dome at one point. Some data obtained between 2130 and 2200 UT of Venus and HD 43583, in K and CH4 filters. The derotator was incorrectly positioned.
K band 2141 UT, 300 ms K band 2144 UT, 500 ms CH4 band 2147 UT, 500 ms
Clear weather, perfect conditions. However, problems in obtaining adequate sky frames.
K band 2059 UT, 300 ms CH4 band 2105 UT, 300 ms K band 2134 UT, 300 ms
Cloudy skies, 7/8 Cirrus, sometimes thick, poor seeing. All scripts worked excellently, though tnight one of the filter wheels was stuck enabling use of only the K filter. Tests with cont filter at 1.57 mum and 1.004 mum narrowband filter showed no cloud structure.
K band 2033 UT, 300 ms K band 2055 UT, 300 ms K band 2126 UT, 300 ms
Photometric sky. Still able to use K filter only.
K band 2025 UT, 300 ms K band 2113 UT, 300 ms
Due to the problems with NOTCam filter wheel 2, the instrument was replaced with the visible imager/spectrograph ALFOSC in the morning. The idea is to image Venus with Bessel U #7 and 1020 nm SII #26 NOT filters. No Venus observations due to clouds, however.
Last night, no Venus observations due to clouds.
Johan Warell
Department of Astronomy and Space Physics
Uppsala University
Box 515
SE-751 20 Uppsala
Sweden
E-mail: johan.warell@astro.uu.se
Phone: +46 18 471 5970
Fax: +46 18 471 5999
