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Focal lengths of Venus Monitoring Camera from limb locations

Limaye, S, S. and Markiewicz, W. J. and Krauss, R. and Ignatiev, N.I. and Roatsch, Thomas and Matz, Klaus-Dieter (2015) Focal lengths of Venus Monitoring Camera from limb locations. Planetary and Space Science, 113-11, pp. 169-183. Elsevier. DOI: 10.1016/j.pss.2015.01.010 ISSN 0032-0633

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The Venus Monitoring Camera (VMC) carried by European Space Agency’s Venus Express orbiter (Svedhem et al., 2007) consists of four optical units, each with a separate filter casting an image on a single CCD (Markiewicz et al., 2007a, 2007b). The desire to capture as much of the planet in a single frame during the spacecraft’s 24 h, 0.84 eccentricity orbit led to optics with 181 field of view. Analysis of Venus images obtained by the VMC indicated that the computed limb radius and altitude of haze layers were somewhat inconsistent with prior knowledge and expectations. Possible causes include errors in the knowledge of image geometry, misalignment of the optic axis from the pointing direction, and optical distortion. These were explored and eliminated, leaving only deviations from the ground and pre- solar damage estimate of the focal length lengths as the most likely reason. We use the location of planet’s limb to estimate the focal length of each camera using images of the planet when the orbiter was more than 20,000 km from planet center. The method relies on the limb radius to be constant at least over a small range of solar zenith angles. We were able to achieve better estimates for the focal lengths for all four cameras and also estimate small offsets to the boresight alignment. An outcome of this analysis is the finding that the slant unit optical depth varies more rapidly with solar zenith angle in the afternoon as compared to morning, with lowest values at local noon. A variation of this level is also observed with latitude. Both are indicative of the presence of overlying haze above the clouds, and the morning afternoon asymmetry suggests different photochemical processes in destruction and production of the haze.

Item URL in elib:https://elib.dlr.de/96977/
Document Type:Article
Title:Focal lengths of Venus Monitoring Camera from limb locations
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Limaye, S, S.Univ. of WisconsinUNSPECIFIED
Markiewicz, W. J.Max-Planck-Institut für Sonnensystemforschung, Katlenburg-LindauUNSPECIFIED
Krauss, R.Univ. of WisconsinUNSPECIFIED
Ignatiev, N.I.Max-Planck-Institut für Sonnensystemforschung, Max-Planck-Straße 2, 37191 Katlenburg-Lindau, GermanyUNSPECIFIED
Roatsch, Thomasthomas.roatsch (at) dlr.deUNSPECIFIED
Matz, Klaus-Dieterklaus-dieter.matz (at) dlr.deUNSPECIFIED
Date:June 2015
Journal or Publication Title:Planetary and Space Science
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:Yes
DOI :10.1016/j.pss.2015.01.010
Page Range:pp. 169-183
Keywords:Venus Express, Venus Monitoring Camera, Venus limb radius
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Science and Exploration
DLR - Research area:Raumfahrt
DLR - Program:R EW - Erforschung des Weltraums
DLR - Research theme (Project):R - Vorhaben Venus Express Kamera (old)
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Planetary Research > Planetary Geology
Deposited By: Roatsch, Dr.rer.nat. Thomas
Deposited On:04 Sep 2015 07:53
Last Modified:08 Mar 2018 18:48

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