Turtle E P, McEwen A S, Patterson G W, Ernst C M, Elder C M, Slack K A, Hawkins S E, McDermott J, Meyer H, DeMajistre R, Espiritu R, Seifert H, Niewola J, Bland M, Becker M, Centurelli J, Collins G C, Corlies P, Darlington H, Daubar I J, Derr C, Detelich C, Donald E, Edens W, Fletcher L, Gardner C, Graham F, Hansen C J, Haslebacher C, Hayes A G, Humm D, Hurford T A, Kirk R L, Kutsop N, Lees W J, Lewis D, London S, Magner A, Mills M, Barr Mlinar A C, Morgan F, Nimmo F, Ocasio Milanes A, Osterman S, Phillips C B, Pommerol A, Prockter L, Quick L C, Robbins G, Soderblom J M, Stewart B, Stickle A, Sutton S S, Thomas N, Torres I, Tucker O J, Van Auken R B, Wilk K A
Johns Hopkins Applied Physics Laboratory, Laurel, MD USA.
University of Arizona, Tucson, AZ USA.
Space Sci Rev. 2024;220(8):91. doi: 10.1007/s11214-024-01115-9. Epub 2024 Dec 4.
The Europa Imaging System (EIS) consists of a Narrow-Angle Camera (NAC) and a Wide-Angle Camera (WAC) that are designed to work together to address high-priority science objectives regarding Europa's geology, composition, and the nature of its ice shell. EIS accommodates variable geometry and illumination during rapid, low-altitude flybys with both framing and pushbroom imaging capability using rapid-readout, 8-megapixel (4k × 2k) detectors. Color observations are acquired using pushbroom imaging with up to six broadband filters. The data processing units (DPUs) perform digital time delay integration (TDI) to enhance signal-to-noise ratios and use readout strategies to measure and correct spacecraft jitter. The NAC has a 2.3° × 1.2° field of view (FOV) with a 10-μrad instantaneous FOV (IFOV), thus achieving 0.5-m pixel scale over a swath that is 2 km wide and several km long from a range of 50 km. The NAC is mounted on a 2-axis gimbal, ±30° cross- and along-track, that enables independent targeting and near-global (≥90%) mapping of Europa at ≤100-m pixel scale (to date, only ∼15% of Europa has been imaged at ≤900 m/pixel), as well as stereo imaging from as close as 50-km altitude to generate digital terrain models (DTMs) with ≤4-m ground sample distance (GSD) and ≤0.5-m vertical precision. The NAC will also perform observations at long range to search for potential erupting plumes, achieving 10-km pixel scale at a distance of one million kilometers. The WAC has a 48° × 24° FOV with a 218-μrad IFOV, achieving 11-m pixel scale at the center of a 44-km-wide swath from a range of 50 km, and generating DTMs with 32-m GSD and ≤4-m vertical precision. The WAC is designed to acquire three-line pushbroom stereo and color swaths along flyby ground-tracks.
欧罗巴成像系统(EIS)由一台窄角相机(NAC)和一台广角相机(WAC)组成,它们被设计为协同工作,以实现与欧罗巴的地质、成分及其冰壳性质相关的高优先级科学目标。EIS在快速低空飞越期间适应可变的几何形状和光照条件,具备帧成像和推扫成像能力,采用快速读出的800万像素(4k×2k)探测器。彩色观测通过使用多达六个宽带滤光片的推扫成像来获取。数据处理单元(DPU)执行数字时间延迟积分(TDI)以提高信噪比,并使用读出策略来测量和校正航天器抖动。NAC的视场(FOV)为2.3°×1.2°,瞬时视场(IFOV)为10微弧度(μrad),因此在距离50千米处,在2千米宽、数千米长的条带内实现了0.5米的像素分辨率。NAC安装在一个两轴万向节上,横滚和沿轨方向均为±30°,这使得能够以≤100米的像素分辨率独立进行目标定位和对欧罗巴进行近全球(≥90%)测绘(到目前为止,只有约15%的欧罗巴区域以≤900米/像素的分辨率成像),以及从低至50千米的高度进行立体成像,以生成地面采样距离(GSD)≤4米、垂直精度≤0.5米的数字地形模型(DTM)。NAC还将在远距离进行观测,以搜索潜在的喷发羽流,在100万千米的距离处实现10千米的像素分辨率。WAC的视场为48°×24°,IFOV为218微弧度,在距离50千米处,在44千米宽条带的中心实现了11米的像素分辨率,并生成GSD为32米、垂直精度≤4米的DTM。WAC旨在沿着飞越地面轨迹获取三线推扫立体和彩色条带。