Heat Capacity Mapping Mission Digital Source: 1978-1980

NASA's Heat Capacity Mapping Mission (HCMM) project collected Earth data in the visible and thermal bands between April 1978 and September 1980. This was an experimental satellite program which observed day and night thermal conditions of Earth's surface. The black and white scenes cover large areas (approximately 500,000 square km at a resolution of 500 meters for the visible channel and 600 meters for the thermal channel. The scale of the imagery is 1:400,000. Areas covered include parts of the United States, western Canada, western Europe, northern Africa, and eastern Australia.

The HCMM Digital Source dataset includes approximately 2400 scenes of recovered digital data with a resolution of 100 dpi. The original scenes are 715 km wide and vary in length from 715 to 3,000 km. The file size is 3-13 MB depending on the length of the scene and is stored in a TIFF format.

The HCMR transmitted analog data in real time to selected receiving stations. The radiometer was similar to the surface composition mapping radiometer (SCMR) of Nimbus 5 (72-097A). The HCMR had a small instantaneous geometric field of view of 0.83 mrad, high radiometric accuracy, and a wide 716-km swath coverage on the ground so that selected areas were covered within the 12-h period corresponding to the maximum and minimum of temperature observed. The spacecraft was spin stabilized at a rate of 14 rpm. The HCMM circular sun-synchronous orbit allowed the spacecraft to sense surface temperatures near the maximum and minimum of the diurnal cycle.

美国国家航空航天局（NASA）热容量制图任务（Heat Capacity Mapping Mission, HCMM）项目于1978年4月至1980年9月间，采集了可见光与热波段的地球观测数据。该项目为实验性卫星计划，用于昼夜监测地球表面的热环境状态。其黑白影像覆盖大片区域：可见光通道分辨率为500米时，单景覆盖面积约50万平方公里；热通道分辨率为600米，影像比例尺为1:400000。观测区域涵盖美国本土部分区域、加拿大西部、西欧、北非以及澳大利亚东部。

HCMM数字源数据集包含约2400景经恢复的数字数据影像，分辨率为100dpi。原始影像幅宽为715公里，长度介于715至3000公里之间。文件大小依影像长度不同在3至13MB范围内浮动，采用TIFF格式存储。

HCMM搭载的辐射计（HCMR）实时向选定的接收站传输模拟数据。该辐射计与雨云5号（Nimbus 5，72-097A）的表面成分制图辐射计（Surface Composition Mapping Radiometer, SCMR）结构相近。HCMR具备0.83毫弧度的小瞬时几何视场，辐射测量精度极高，且地面扫描幅宽达716公里，可在对应地表温度日变化极值的12小时周期内完成选定区域的覆盖。卫星采用14转每分钟的自旋稳定模式。HCMM的圆形太阳同步轨道可使卫星获取接近日循环最高与最低温度时刻的地表温度观测数据。