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An alternative derivation of the nimbus 7 total solar irradiance variations
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Hoyt, Douglas V. Kyle, H. Lee |
| Copyright Year | 1990 |
| Description | Nimbus 7 solar irradiance values have been made available to the scientific community through the open literature (e.g., Hickey et al., 1988) and through NASA data centers. A comparison of these measurements to the Solar Maximum Mission/Active Cavity Radiometer Irradiance Monitor (SSM/ACRIM) time series indicated differences which might be caused in part by the method of converting the Nimbus 7 raw data counts to solar irradiance values. In an effort to see if the derivation of the solar irradiance could be improved, the raw counts were extracted from the tapes and analyzed to see how a new algorithm could be constructed. The basic form of the calibration remains the same as in the previous solar irradiance derivations. However, the input values to the equation differ from what was used before. In particular, improved values of the Earth-sun distance are incorporated and new temperature sensitivities were derived. Several problems with the instrument were uncovered which previously had not been noticed. The sun did not appear to cross the center of field of the radiometer but was systematically off by 1.5 to 2.5 degrees. The analog to digital convertor changed its properties in July 1980. The gain of the electronics apparently increased by 0.03 percent in September 1987. Applying these and other changes in the processing, the day to day variations appear much more like the SMM observations. In fact, the Nimbus 7 observations are sufficiently stable that a problem with the SSM observations in the spin mode period of 1981 to 1984 can be detected when the two time series are compared. |
| File Size | 371716 |
| Page Count | 8 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_19910003183 |
| Archival Resource Key | ark:/13960/t7hq8v87z |
| Language | English |
| Publisher Date | 1990-08-01 |
| Access Restriction | Open |
| Subject Keyword | Solar Physics Radiometers Stability Time Series Analysis Calibrating Solar Activity Effects Variations Irradiance Solar Maximum Mission Sun Algorithms Nimbus 7 Satellite Monitors Solar Radiation Analog To Digital Converters Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Article |
