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Suggested Citation:"LST DATA HANDLING ." National Research Council. 1976. An International Discussion of Space Observatories: Report of a Conference Held at Williamsburg, Virginia, January 26-29, 1976. Washington, DC: The National Academies Press. doi: 10.17226/12381.
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Suggested Citation:"LST DATA HANDLING ." National Research Council. 1976. An International Discussion of Space Observatories: Report of a Conference Held at Williamsburg, Virginia, January 26-29, 1976. Washington, DC: The National Academies Press. doi: 10.17226/12381.
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Page 13

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5. LST DATA HANDLING The conference considered the magnitude of the LST data now as presently estimated. While not large compared with that of current earth resources projects, it is large enough to require careful consideration of data handling and distribution procedures. The conference was not able to consider in detail the ways in which the various LST instruments will generate data; such a consideration must be based on a detailed study of various typical missions. These conclusions are based, therefore, on quite elementary estimates of the data-generation rate. Oat> Generotion In its first Oight the LST will be able to generate data from five instruments, and there will be additional positional and housekeeping data. Of the five instruments, the data rate from the SEC Vidicon (if it is selected for use) of the Focal Plane Camera (FPC) will dominate and therefore is the only neces- sary consideration here. The FPC pictures will be made up of 2000 X 2000 pixels, the intensity of each being dlgjtlzed asa 12-bit number and read out twice to minimize errors. In each earth day some 20 pictures of lo" bits each will be transmitted, gjving a total of 2 X 109 bits per day. Data Transmission No great dlfncullies should be encountered in returning data from the LST. Data rates of a few mepblts per second will be easily handled by the proposed Tracking Data Relay Satellite System (ToRss) or by the existing STADAN net. Data Storage on the Ground II seems probable that users wiD wish to store all their raw data for many months; therefore, considerable data.storage capacity on the ground will be necessary. One day's worth of SEC Vidicon data would require something 12

like I 0,000 ft of 9-track 1600 BPI tape. Undoubtedly, hJaber-<lenslty packing will be available In the mid-1980s,_,and the extent of increase in density wUI determine the physical storage requirements. In later stqes of t.he LST project, uxrs may find it poss1"ble to overlay suc""ssive pictures In the spate· craft or otherwbe to red""" the data volume in orbit, further reducin& the ground storage needs. Oau Monipubtion It is in this area that the need for detaUed information is areotest. " Manlpula· tion" includes everything from simple linearization, calibration, and over· laying of a few tens of pictures to the full treatment recent planetary pictures have received at tlte Jet Propulsion Laboratory. A certain first requirement will be for quick-look pictures. At Its simplest this might involve picture linearization, cah"bration, and distortion removal. It is not a difficult task, and an IBM 360-50 would not be overloaded In keep- in& up with the LST output. Further analysis of data·handlin& procedures requires detailed study, but it is clear that a system for the transmission of data to experimenters over terml- nals will be required, so that the data can be analyzed further on a variety of devices. Conclusions • The data·transmission rates to be generated by the LST are already well within the capabilities of exist in& systems. • Titc provision of quick·look pictures that have been linearized, call· bra ted, and freed from distortion will be well within the capablllty of a large computer. • The storage or raw data in archives over months or years may require special provision, depending somewhat upon technical developments over the next few yean. • The maanitude of the full data-manipulation task requires detailed study to establish the level of manpower and equipment that will be required at an LST science institute and at the u.sen· own instituUons. 13

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