6.11 Media for Data Recording, Storage and Distribution

6.11 Media for Data Recording, Storage and Distribution

Generally satellite data received at a ground station are recorded in real time into HDDT (high density digital tape) with 14 or 28 tracks. Depending on the requests, HDDT data will be transferred to CCT (computer compatible tape) with 9 tracks and/or other media for distribution. Recently optical disks for examples, WORM (write once read many ), MO disk (magneto-optical disk with erasable function ) and CD-ROM (compact disk - read only memory ) are becoming popular.

These media are characterized by the following factors.

a. Memory capacity: total memory in byte
b. Cost: cost of media, reader and unit data volume (cost per 1 MB)
c. Compatibility: for data formats and computer systems
d. Portability: size and weight e. Durability: years of life

The type of media should be selected depending on the purpose, in consideration of the above items. Table 6.11.1 shows the characteristics of major media used in remote sensing.

For use in data centers the factors of data storage, portability, cost and durability are more important than compatibility. Recently DAT (digital audio tape) or 8 mm cartridge tape is replacing HDDT and CCT because of its compact size.

For distribution to public users, compatibility is most important, which makes CCT and floppy disk more popular. CD-ROM is very convenient and also low cost as mass media, similar to a music record disk. Optical disks such as MO and WORM are very attractive, though standardization and compatibility are not yet fully implemented. However the optical disk has the big advantages of low cost of both media and driver, and a large memory capacity, especially as a large auxiliary supplementary memory for personal computers or work stations.