DMSP F17 successfully launched on November 4, 2006 at 05:53 Pacific time.
The Naval Research Laboratory (NRL) has developed five
ultraviolet remote sensing instruments for the Air
Force Defense Meteorological Satellite Program (DMSP).
These instruments known as SSULI (Special Sensor Ultraviolet Limb Imager) will launch aboard the DMSP block of
5D3 satellites, which started in 2003. SSULI measures vertical profiles of the natural airglow radiation from
atoms, molecules and ions in the upper atmosphere and ionosphere by viewing the Earth's limb at a tangent
altitude of approximately 50 km to 750 km. The second SSULI flight was launched on November 4th, 2006. The
remaining sensors are scheduled for launch approximately every 24 months.
Measurements are made from the extreme ultraviolet (EUV) to the far ultraviolet (FUV) over the wavelength range of 80 nm to 170 nm, with 1.8 nm resolution. The satellites will be launched in a near-polar, sun-synchronous orbit at an altitude of approximately 830 km. The Low Resolution Airglow and Auroral Spectrograph (LORAAS) , a SSULI prototype, was launched onboard the Advanced Research and Global Observation Satellite (ARGOS) on February 23, 1999. LORAAS data is being used to validate SSULI algorithms that convert raw measurements (Figure 2) into useful environmental parameters that characterize the upper atmosphere.
An extensive operational data processing system has been developed to generate environmental data products from SSULI spectral data. Spectral data from the LORAAS instrument is shown to the left. This system, known as the Ground Data Analysis Software (GDAS) , includes operational data reduction software using advanced science algorithms also developed at NRL , a customized graphical user interface (GUI), and comprehensive validation techniques. Programs are designed to generate a SSULI Prep file from multiple data sources including Raw Sensor Data Records (RSDR) at the Air Force Weather Agency (AFWA), HIRAAS real-time data assembled at US Space Command, and an extensive HIRAAS infobase on site at NRL.
The SSULI GDAS is composed of two operational Computer Software Configuration Items (CSCI), the Mission Algorithms (MA) and the Mission User Interface (MUI). The GDAS MA consists of three algorithms that generate Environmental Data Records (EDRs) from SSULI observational prepfile 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 retrieve density profiles from the airglow. Data products 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, SDR1, consists of normalized sensor data for all of the wavelength bins in the instrument. The second type, SDR2, 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 files are stored in the ASCII format for ease of use and portability.
SSULI concept of operations.
Read about SSULI measurements and about the instrument itself.
SSULI Hardware Development
A description of the major hardware components that make up the SSULI instrument.
SSULI Data Files
Detailed descriptions of the format of SSULI files, from the binary prepfiles that are ingested by the Mission Algorithm to the final data prodcuts that are generated for use with the Mission User Interface. A description of validation sources is included.
Ground Data Analysis Software (GDAS)
Read about the Mission Algorithms and Mission User Interface that are used to process and display SSULI sensor data.
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