The Mercury Dual Imaging System on the MESSENGER Spacecraft

Abstract

The Mercury Dual Imaging System (MDIS) on the MESSENGER spacecraft will provide critical measurements tracing Mercury's origin and evolution. MDIS consists of a monochrome narrow-angle camera (NAC) and a multispectral wide-angle camera (WAC). The NAC is a 1.5°field-of-view (FOV) off-axis reflector, coaligned with the WAC, a fourelement refractor with a 10.5°FOV and 12-color filter wheel. The focal plane electronics of each camera are identical and use a 1,024 × 1,024 Atmel (Thomson) TH7888A chargecoupled device detector. Only one camera operates at a time, allowing them to share a common set of control electronics. The NAC and the WAC are mounted on a pivoting platform that provides a 90°field-of-regard, extending 40°sunward and 50°anti-sunward from the spacecraft +Z-axis-the boresight direction of most of MESSENGER's instruments. Onboard data compression provides capabilities for pixel binning, remapping of 12-bit data into 8 bits, and lossless or lossy compression. MDIS will acquire four main data sets at Mercury during three flybys and the two-Mercury-solar-day nominal mission: a monochrome global image mosaic at near-zero emission angles and moderate incidence angles, a stereocomplement map at off-nadir geometry and near-identical lighting, multicolor images at low incidence angles, and targeted high-resolution images of key surface features. These data will be used to construct a global image base map, a digital terrain model, global maps of color properties, and mosaics of high-resolution image strips. Analysis of these data will provide information on Mercury's impact history, tectonic processes, the composition and emplacement history of volcanic materials, and the thickness distribution and compositional variations of crustal materials. This paper summarizes MDIS's science objectives and technical design, including the common payload design of the MDIS data processing units, as well as detailed results from ground and early flight calibrations and plans for Mercury image products to be generated from MDIS data.

Stereo topographic models of Mercury after three MESSENGER flybys

“…MESSENGER's Mercury Dual Imaging System (MDIS) consists of two framing cameras, a wide-angle camera (WAC) and a narrow-angle camera (NAC), co-aligned on a pivot platform and equipped with identical 1024 Â 1024-pixel charge-coupled device (CCD) sensors (Hawkins et al, 2007). NAC, the principal tool for stereo analysis in this paper, consists of a compact off-axis optical system that has been geometrically calibrated using laboratory as well as in-flight stellar observations (Hawkins et al, 2007(Hawkins et al, , 2009 …”

“…NAC, the principal tool for stereo analysis in this paper, consists of a compact off-axis optical system that has been geometrically calibrated using laboratory as well as in-flight stellar observations (Hawkins et al, 2007(Hawkins et al, , 2009 …”

“…The spacecraft is equipped with a well-calibrated imaging system (Hawkins et al, 2007(Hawkins et al, , 2009, and data obtained during three Mercury flybys in included images that allowed stereo topographic reconstructions for a substantial portion of the planet not covered by Mariner 10. The stereo analysis in this paper constitutes an important test case for MESSENGER's orbital mission phase, to begin in March 2011, when dedicated stereo mapping sequences will be obtained at near-global coverage.…”

The tectonics of Mercury: The view after MESSENGER's first flyby

“…The Mercury Dual Imaging System (MDIS) (Hawkins et al, 2007) obtained images on approach to and departure from Mercury during the MESSENGER flyby of 14 January 2008. The highest-resolution images were obtained with the MDIS narrow-angle camera (NAC).…”

Emplacement and tectonic deformation of smooth plains in the Caloris basin, Mercury

“…The Mercury Dual Imaging System (MDIS) (Hawkins et al, 2007), a co-articulated multispectral wide-angle camera (WAC) and monochromatic narrow-angle camera (NAC), obtained more than 1200 images of Mercury during the flyby. MDIS images were calibrated to radiance factor (or I/F, the observed radiance divided by solar irradiance) and photometrically corrected to standard viewing geometry (30°solar incidence and 0°emission angles) ).…”