The U.S. Global Change Research Program An Assessment of the FY 1991 Plans (1990) / Chapter Skim
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7. EOS Platforms
7. EOS Platforms
Pages 61-71
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From page 61... ...
Dividing the proposed instruments for these measurements among several smaller satellites and flying them in close formation is technically feasible, but the smallest coherent set of instruments for one of the smaller satellites is still sufficiently large to require a launch vehicle larger than the Delta rocket. The scientific requirements for continuity in data sets has led the community of researchers and NASA to plan for a long time-series of measurements.
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From page 62... ...
and foreign research and operational satellite missions, including the proposed Earth Probes series, prior to the scheduled first launch of EOS in 1998. Some of the EOS instruments are intended to continue monitoring certain environmental parameters so that the precursor missions that fly similar instruments will be prerequisites, not substitutes.
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From page 63... ...
Launch Vehicles Space missions are constrained by the availabilities and capabilities of the launch vehicles available for the purpose. NASA, in its analysis, considered a large number of factors, including cost, mass, power, data rate, launch vehicle, the ability of the launch option to satisfy the mission requirements, the number of spacecraft required, launch schedule, production schedule, operational complexity, data processing requirements, ability to fit the instruments on existing spacecraft, and direct data downlink and broadcast requirements.
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From page 64... ...
The experience in the NOAA TIROS series has been that half of the tape drives fail on orbit before the end of the mission and usually early in the mission. Providing extra tape decks, which is NASA:s current plan, will require extra space on the spacecraft, but it can be supplied with the larger platform.
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From page 65... ...
An interruption in the time series of this magnitude would seriously disrupt USGCRP research objectives. The second type of failure is of the platform itself, once it is in orbit.
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From page 66... ...
A third approach, which might also apply in the event that an instrument is not ready at the scheduled time for launching, would be to use existing instruments on the platform to provide backup. In a working document entitled EOS Instnument Standard Data Products, NASA is assembling backup strategies for each data product in the event of loss of an instrument or channel in an instrument.
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From page 67... ...
The data continuity issue is so important that it deserves continuing careful financial analysis and consideration. NASA s analysis indicates that the large platform approach gives the better overall reliability.
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From page 68... ...
With the Atlas and mixed ELV scenarios, additional costs will have to be met to sustain a dedicated launch capability at the Western Test Range. Obviously, the costs for integration and testing increase with the number of spacecraft.
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From page 69... ...
........... T Optimistic Conservative Optimistic Conservative Optimism Conservative BASELINE MIXED ATLAS DELTA Note: Direct downlink communication aysteme not induded in the mixed, Atlas, or Delta options FIGURE 4 NASA estimates of relative costs of alternative mission configurations with identical instrument payloads.
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From page 70... ...
Satellite series like the NOAA polar orbiters and the satellites of other nations can provide opportunities for modest instruments. The flight of the SBUV instrument on the NOAA polar orbiting series and the planned flight of the TOMS instrument on a Soviet meteorological spacecraft are instructive examples.
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From page 71... ...
operational systems supply both interim data and a continuing contribution to global change research. They include the NOAA polar orbiting and geostationary meteorological satellites, the Defense Meteorological Satellite Program (DMSP)
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