The U.S. Global Change Research Program An Assessment of the FY 1991 Plans (1990) / Chapter Skim
Currently Skimming:
6. Simultaneity of Data Collection
6. Simultaneity of Data Collection
Pages 50-60
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 50... ...
The arguments, which do not apply to all the measurements that NASA proposes to make with EOS, depend primarily on the importance of studying the interactions within natural processes occurring on short time scales and on the interdependence of certain pairs or small sets of measurements for precise quantitative interpretation. For measurements critical to two high priority areas of research in the USGCRP, the needs for several small sets of instruments to make simultaneous measurements lead to a set of interwoven requirements for a suite of ten instruments that should be flown on the same satellite.
|
From page 51... ...
In the current context, we take "simultaneous" to mean "within a few seconds." There is a more stringent requirement in several instances for "at the same time through the same atmospheric path," i.e., essentially "bore-sighted." There are also some special requirements for "at nearly the same time but through different view paths, i.e., different look angles." Given the above, observations taken within a few seconds of the same area on the surface through the same view path are termed `'congruent"; those acquired at the same time of the same area but through different view paths are termed C`simultaneous"; those acquired within a few minutes of the same area are termed 'Cclose sequential." Observations of a common area obtained at intervals greater than about ten minutes are termed``sequential.'' The most stringent requirement would be for C`congruent" obse~vations, the least stringent for `'sequential." But there are some special situations that require specifically 'Cclose sequential" observations made through different view paths. Several specific remote sensing studies illustrate the differences in
|
From page 52... ...
Third, merging sequential data streams can place additional technical and financial burdens on ground-based data management and computational systems that might not be present if the data were taken simultaneously. Fourth, engineering considerations-such as the availability of launch vehicles, onboard electrical power, viewing angles, and data transmission capabilities-affect decisions on spacecraft size, complexity, reliability, and cost.
|
From page 53... ...
Many surface materials such as crops, scrub brush, flowering plants and trees, and suspended sediments in surface waters can change character significantly over time periods that are short relative to the repeat cycles of a single spacecraft. Further, the spectral signatures of the sensed objects often vary with the angle of the sun, or the angle of observation of the instrument.
|
From page 54... ...
To Facilitate Data Management Merging sequential data streams places technical and financial burdens on ground-based data management and computational systems in addition to those that would be present if the data were taken simultaneously. For instance, co-location of pixels from the NOAA Geostationary Operational Environmental Satellite (GOES)
|
From page 55... ...
Historical measurements of stratospheric ozone, sea surface temperature, and atmospheric temperature are three examples. One way to calibrate optical instruments is to compare instruments flown at the same time looking at the same dark or bright scene on the surface.
|
From page 56... ...
The PAP concludes that overall consistency among the cloud properties, humidity, temperature, and radiance measurements requires that the 8 instruments make essentially simultaneous measurements. Because of their larger pixel size, HIMSS and AIRS/AMSU-A and -B can be separated by as much as ten minutes.
|
From page 57... ...
AIRS AMSU H IMSS C o CERES-IN U D S MODIS-N & MODIS-T HIRIS EOSP C M A T MISR E ALT STIKSCAT FIGURE 2 Simultaneity for observations calf the role of clouds in climate and of the biogeochemical dynamics of tmce gases based on the PAP analysis. the several instruments listed above for clouds and climate studies (see the upper right side of Figure 2)
|
From page 58... ...
This complement of research instruments, with the support instruments for communications and positioning (e.g., COMM and GGI) , if selected for flight, would constitute a payload comparable to that envisaged for EOS-N We are not aware of any similar discussion of the currently proposed payload for the science objectives of the EOS-B satellite, although the positioning instruments, and perhaps others, may require some coordination to correct for atmospheric water vapor.
|
From page 59... ...
These include a detailed analysis of facility-class instruments, a detailed analysis of PI instruments, a briefing on NASA:s `'Science Plan" for EOS, and two draft letter reports to NASA from the Payload Advisory Panel of the EOS Investigators Working Group. The analyses of the instruments contain a wealth of detailed arguments for simultaneous measurements related to individual scientific objectives.
|
From page 60... ...
None identified Potentially strong. Physics Systems Data Management FIGURE 3 Summary assessment of arguments for a large platform for research on the role of clouds in climate and on the fluxes of trace gases.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.