The Europa Imaging System (EIS) combines a Narrow-Angle Camera (NAC) and a Wide-Angle Camera (WAC) to explore Jupiter’s Icy moon Europa. EIS is designed to address high-priority geology, composition, ice shell and ocean science objectives with the challenges of imaging in a wide range of scenarios spanning fast, low-altitude flybys with rapidly changing geometry and illumination to high-altitude imaging of faint scenes. Images for both EIS cameras are taken with a 10-μm pixel-pitch, 4096×2048 frontside illuminated CMOS image sensor. To perform color pushbroom imaging, the NAC and WAC both have six 32-row broadband stripe filters. The WAC is an F/5.75, 46-mm focal length, 8- lens refractive telescope with a 48° × 24° FOV and an IFOV of 218-μrad, achieving 11-m pixel scale from a 50-km altitude over a 44-km-wide swath. The along-track FOV provides 3-line (forward, nadir, and aft) pushbroom stereo swaths enabling digital topographic models with 32-m spatial scale and 4-m vertical precision. In order to perform over a 400- 1050 nm bandwidth in the extreme radiation environment surrounding Europa, the design contains 4 different materials: fused silica, CaF2, and two radiation resistant glasses. Each lens, except the exposed front surface of Lens 1 (L1), is coated with a proprietary antireflective (AR) coating, which has been tested for durability and performance in varying temperature and radiation environments. The 25-mm thick fused silica L1 plays dual roles in the WAC telescope design to also protect the CMOS sensor from the intense radiation of the Jovian environment. The optomechanical design maintained the optical alignment through thermal and vibration environmental testing. The WAC was delivered to NASA’s Jet Propulsion Laboratory (JPL) and integrated to the Europa Clipper spacecraft in summer 2022.
S. Edward Hawkins, Scott Murchie, Kris Becker, Christina Selby, F. Scott Turner, Matthew Noble, Nancy Chabot, Teck Choo, Edward Darlington, Brett Denevi, Deborah Domingue, Carolyn Ernst, Gregory Holsclaw, Nori Laslo, William McClintock, Louise Prockter, Mark Robinson, Sean Solomon, Raymond Sterner
The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, launched in
August 2004 and planned for insertion into orbit around Mercury in 2011, has already completed two flybys of the
innermost planet. The Mercury Dual Imaging System (MDIS) acquired nearly 2500 images from the first two flybys and
viewed portions of Mercury's surface not viewed by Mariner 10 in 1974-1975. Mercury's proximity to the Sun and its
slow rotation present challenges to the thermal design for a camera on an orbital mission around Mercury. In addition,
strict limitations on spacecraft pointing and the highly elliptical orbit create challenges in attaining coverage at desired
geometries and relatively uniform spatial resolution. The instrument designed to meet these challenges consists of dual
imagers, a monochrome narrow-angle camera (NAC) with a 1.5° field of view (FOV) and a multispectral wide-angle
camera (WAC) with a 10.5° FOV, co-aligned on a pivoting platform. The focal-plane electronics of each camera are
identical and use a 1024×1024 charge-coupled device detector. The cameras are passively cooled but use diode heat
pipes and phase-change-material thermal reservoirs to maintain the thermal configuration during the hot portions of the
orbit. Here we present an overview of the instrument design and how the design meets its technical challenges. We also
review results from the first two flybys, discuss the quality of MDIS data from the initial periods of data acquisition and
how that compares with requirements, and summarize how in-flight tests are being used to improve the quality of the
instrument calibration.
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