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Venus Observations with SCIAMACHY

Manfred Gottwald(1), Eckhart Krieg(1), Sander Slijkhuis(1), Franz Schreier(1), Günter Lichtenberg(1), Mayte Vasquez(1), Ralph Snel(2), Daphne Stam(2) and Remco de Kok(2)

(1) German Aerospace Center (DLR), Oberpfaffenhofen, 82234 Wessling, Germany
(2) SRON, Sorbonnelaan 2, 3584 CA Utrecht, Netherlands

Abstract

SCIAMACHY (Scanning Imaging Spectrometer for Atmospheric Chartography) onboard ENVISAT successfully captured visible and near-infrared spectra of sunlight scattered and reflected off Venus’ atmosphere. This occurred while executing a sequence of calibration measurements aiming at determining the slit width in elevation with high precision. Venus is well suited for such measurements since our solar system neighbour appears almost pointlike from an Earth’s distance and its brightness ensures a sufficiently high signal-to noise ratio. What we undertook with SCIAMACHY is the opposite approach to ESA’s Venus Express mission, when the Earth is occasionally observed from an orbit around Venus.

Planning of the Venus observation required careful analysis of the viewing conditions from ENVISAT’s orbit. Only when the planet was rising above the Earth’s limb the line-of-sight geometry allowed to observe Venus. In March 2009 Venus was already close to passing right between the Earth and the Sun, i.e. inferior conjunction. During this phase we mainly saw the backside of Venus and only a very small part of the planet’s atmosphere lit by sunlight. Thus observing conditions mimicked a limb geometry.

We present a summary of how we planned and executed these measurements together with the results obtained. Additionally SCIAMACHY’s capabilities for further planetary observations are outlined.