WISE 3-Band Cryo Single Exposure (L1b) Frame Metadata Table

The WISE 3-Band Cryo Data Release products are comprised of data taken during the mission's 3-Band Cryo survey phase. This phase covers the time following the exhaustion of solid hydrogen in the WISE payload outer cryogen tank, while the detectors and telescope were still cooled by the inner cryogen tank. During this time, WISE's W1, W2 and W3 bands were operational and continued to acquire useful data, but the W4 detector was saturated by thermal emission from the warming telescope. The sensitivity achieved in the W1 and W2 bands was similar to that during the full cryogenic mission phase. The W3 measurement sensitivity was degraded and decreased steadily during the 3-Band Cryo phase because of the increasing telescope temperature and decreasing exposure times. WISE scanned approximately 30% of the sky during the 3-Band Cryo survey phase continuing with the same strategy that was used during the full cryogenic survey. The following table contains brief descriptions of all metadata information that is relevant to the processing of Single-exposure (level 1) images and the extraction of sources from the corresponding Single-exposure images. The table contains the unique scan ID for a specific scan frame and the reconstructed right ascension and declination of the level 1b frame center. Much of the information in this table is processing-specific, and may not be of interest to general users (e.g. flags indicating whether frames have been processed or not, and the date and time for starting of the pipeline, etc.). The metadata table also contains some characterization and derived statistics of the Single-expsoure image frames, basic photometric parameters used for photometry and derived statistics for extracted sources and artifacts. For example, it contains median pixel values of the coadded sky coverage map, the number of sources with profile-fit photometry Signal-to-Noise (SNR) greater than 3, and the total number of real sources affected by artifacts such as electronic ghosts, etc. This dataset or service is made available by the Infrared Science Archive (IRSA) at IPAC, which is operated by the California Institute of Technology under contract with the National Aeronautics and Space Administration.

WISE三波段低温阶段数据发布产品（WISE 3-Band Cryo Data Release products）由该任务三波段低温巡天阶段获取的观测数据构成。该阶段始于WISE载荷外部低温储罐内固态氢耗尽之时，此时探测器与望远镜仍可通过内部低温储罐维持冷却。在此期间，WISE的W1、W2与W3波段均处于工作状态，持续获取有效观测数据，但W4探测器因升温望远镜的热辐射而出现信号饱和。W1与W2波段的观测灵敏度与全低温任务阶段基本一致；由于望远镜温度持续升高、曝光时间不断缩短，W3波段的测量灵敏度在三波段低温阶段中持续退化并下降。WISE在三波段低温巡天阶段沿用全低温巡天的观测策略，完成了约30%天区的扫描工作。下表简要说明了与单帧（Single-exposure, level 1）图像处理及从对应单帧图像中提取天体源相关的全部元数据信息：该表包含特定扫描帧的唯一扫描标识（scan ID），以及level 1b帧中心的重构赤经与赤纬。表中多数信息为处理流程专属内容，普通用户可能无需关注（例如标记帧是否已完成处理的状态标志、流水线启动的日期与时间等）。该元数据表还包含单帧图像的部分特征表征与衍生统计量、用于天体测光的基本光度参数，以及提取的天体源与观测伪影的衍生统计量。例如，该表包含叠加天区覆盖图的像素中值、轮廓拟合测光信噪比（Signal-to-Noise, SNR）大于3的天体源数量，以及受电子鬼影等伪影影响的真实天体源总数量。本数据集或服务由加州理工学院根据与美国国家航空航天局签订的合同运营的IPAC下属的红外科学档案馆（Infrared Science Archive, IRSA）提供。