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Abstract:
Discrete inverse theory (DIT) forms the basis of new techniques for extracting dayside O(+) number density profiles from the 834 A airglow, as measured by a limb-scanning system on an orbiting satellite. Our tests of this method assume observations from an altitude of 850 km with scans from 10 deg to 26.5 deg below horizontal, consistent with future multiyear missions. The retrieval code computes an iterative, maximum likelihood solution by comparing observations to estimates calculated with a new forward model. The model includes multiple resonant scattering and pure absorption. To generate synthetic data for tests, we represent the true O(+) distribution as a Chapman layer and compute an intensity profile with the forward model, adding simulated noise. We present detailed studies of convergence properties of the retrieval techniques and of uncertainties in the retrieved parameters. For this baseline (Chapman layer) case, the method is robust, converging to an accurate solution for a wide variation in synthetic data. We include a brief preview of recent studies showing the following: (1) for future missions, the DIT method can correctly distinguish between distinctly different Chapman layers that produce nearly identical intensity profiles and (2) the retrieval of an additional parameter that scales the model intensity profile can compensate for inaccuracies in the instrument sensitivity or in the magnitude of the initial volume excitation rate. (AN)
| Limitations: |
 APPROVED FOR PUBLIC RELEASE |
| Description: |
Memorandum rept. 1 Oct 91-1 Jul 95 |
| Pages: |
38 |
| Report Date: |
01 SEP 95 |
| Report Number: |
A829892 |
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