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The
Thermospheric and Ionospheric Physics (TIP) division
of the Naval Research Laboratory
(NRL) is developing two Computer Software Configuration Items
(CSCIs) for the United
States Air Force (USAF) to process and display the collected
sensor data. These are the Mission Algorithm (MA) and the Mission
User Interface (MUI).
The GDAS Mission Algorithm The Mission Algorithm (MA) consists primarily of three atmospheric algorithms that generate Environmental Data Records (EDRs) from SSULI observational limb scan data. A Data Preprocessing Algorithm (DPA) is applied to calibrate the SSULI prepfile and generate spectra. The brightness of emission components are found by deconvoluting the spectra using multiple linear regression (MLR). Intensity profiles are then fed to three atmospheric inversion algorithms that use nonlinear Discrete Inverse Theory (DIT) to determine the electron and neutral density composition of the upper atmosphere. Data products (see the table below) include N2, O2, O, O+ and temperature profiles, model parameters and Total Electron Count (TEC). The MA also generates two types of Sensor Data Records (SDRs). The first type, SDR1s, consists of normalized sensor data for all of the wavelength bins in the instrument. The second type, SDR2s, contains similar sensor data, but extracted for one of six particular spectral features: 834 Angstroms (Å), 911 Å, 1304 Å, 1356 Å, and Lyman-Birge-Hopfield Bands 1 and 2 (LBH1 and LBH2). SDR and EDR record types are stored in the ASCII format for ease of use and portability. The MA generates files that include a SSULI Prep File, SSULI Sensor Data Record files (SDFs), and SSULI Environmental Data Record files (EDFs). Prepfiles contain raw sensor data that has been sorted chronologically and reformatted into 32-bit words. The SDFs are orbit-sized files that have been calibrated with the background subtracted. The EDFs are derived from the SDFs by the three algorithms.
The GDAS Mission User Interface The MUI is a graphical user interface written in PV-WAVE that is designed to retrieve and display the SSULI Data Files . Numerous map projections are available for the display of the satellite ground tracks. Scan locations are marked with unique plot symbols that denote the latitude, longitude, SZA, maximum density (EDF) or maximum intensity (SDF) value, and altitude at peak value for each scan. Additional information such as a model representation of the equatorial boundary of the auroral oval, ground-based operational sites, and geomagnetic grids (provided by 55th Weather Squadron), may be overlaid. Individual or multiple scans and orbits can be selected for display in greater detail. The difference between orbit files and individual scans can be found and analyzed graphically. An animation tool allows orbit-sized atmospheric images to be played back sequentially. |
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In the main interactive data mode, called Track Mode, limb scans are plotted over an Cylindrical Equidistant projection of the earth. Daytime, nighttime and terminator scans are easily identified by a unique symbol. In each of the interactive modes, the scan nearest to the user's cursor is highlighted in yellow. Individual scans can be selected for further analysis by clicking on the left mouse button. Scans that have been selected are plotted in bright red. The scanlist of selected scans is accumulated in the lower, right-hand text window of the GUI. During each run of the GDAS, a printable journal is automatically generated in the lower, left-hand area of the GUI. The user can add comments to the journal interactively via a text input area located just above the journal window. Click on the image to view a full-size, 173KB version. |
Interactive Track Mode Cylindrical Equidistant Projection |
| Other Track Mode Projections: | |||
Albers Equal-Area Conic (166 KB) |
Mollweide (154 KB) |
North Polar Azimuthal (123 KB) |
South Polar Azimuthal (128 KB) |
Interactive Image Mode |
Image Mode can be used interactively to identify density variations as a function of both altitude and latitude. As the user holds down the left mouse button while in the EDR image area, both the vertical and horizontal profiles are updated in realtime. The user can then click on the center mouse button to overplot a profile (it will remain selected while the user interactively plots other profiles.) Multiple profiles are shown with varying line styles and colors. The user can deselect all selected scans by clicking on the right mouse button. Click on the image to view a full-size, 80KB version. |
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Interactive Line Mode shows a complete orbit of each scan's density and peak altitude using a polar plot around the earth. Density values are denoted by a color bar in the MUI status area and the altitude of each scan's peak value is denoted by the plot symbol's radial distance from the image of the earth. Click on the image to view a full-size, 38KB version. |
Interactive Line Mode |
Interactive Radial Mode |
SDR1 Display |
| The Radial Mode interactive mode shows a graphical interpretation of the 68 individual SSULI limb scans around the earth, where a color bar is used to correspond colors with density values. Click on the image for a full-size, 58KB version. | The SDR1 Display shows the user the spectral intensity as a function of vertical scan angle. A color bar is used to correspond colors with intensity values. Click on the image for a full-size, 32KB version. |
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On the right-hand side of the MUI is a Status Area that gives detailed information about the data set currently displayed in the main draw window. The status area includes general information such as the file type, file name and orbit number, as well as more detailed information such as local and Zulu time, data type, Hmax, Zmax, convergence information, a data quality flag, and the latitude and longitude of both the cursor and the nearest scan location. Uncertainties are also included for the data density or intensity value and the altitude at peak value. A user-definable color bar is used to display the range of intensities or densities. Click on the image for a full-size, 10KB version. |
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