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SSUSI:Special Sensor Ultraviolet Spectrographic Imager Dr. Larry J. Paxton SSUSI Principal Investigator The Johns Hopkins University Applied Physics Laboratory Laurel, MD 20723 SSUSI Supports Operational and Basic Research Communities SSUSI is designed to remotely sense ionospheric, atmospheric, and auroral environmental parameters on a global basis. SSUSI obtains FUV spectrographic observations of the atmosphere and aurora and visible light photometric measurements of the aurora and nightglow. The radiance observations will be used to produce: • Electron Density Profiles (day and night) • Neutral Density Profiles(day) • Auroral Energy Deposition Rate (day and night) • Auroral Oval Location (day and night) and provide a unique database for the production of environmental parameters, validation of operational models, and extend the validity of the "nowcast". SSUSI was launched on October 18, 2003. - There will be four more DMSP flights with a SSUSI Roadmap From 1989 to First Launch The SSUSI program started in 1989 when DMSP solicited proposals from AFRL and APL to build a follow-on to the Polar BEAR AIRS and HiLat AIM sensors. In 1992 we were asked to design automated data processing software for the SSUSI data stream. Software was delivered in 1996. By 1994 the first SSUSI (SN01) had been built and delivered. The last (SN05) was delivered in 1996. SSUSI and the SSUSI Ground Data Analysis System (GDAS) were designed to meet DMSP needs for near-realtime ionospheric specification and auroral imagery. What We Are Doing and Where We Are Going SSUSI was launched on DMSP F16 on October 18, 2003 • What is SSUSI? • How does it work? • How do we get information out of the data stream? • How is the user supported? SSUSI on S20 Spacecraft The first SSUSI to be launched was installed on the S20 spacecraft. • DMSP spacecraft are numbered as they are constructed. • Currently numbers 16 through 20 have been built. • Only S20 has been flown. Once the spacecraft is launched the flight is given a number, the most recent launch was the F16 spacecraft. The current schedule and past experience indicate that launches should occur every 1 ½ to 2 years. • The last SSUSI should be launched in 2009 to 2011. • With a 3 year design lifetime there will be 3 operating SSUSIs during most of this decade. SSUSI is the Next Generation of Remote Sensing Instrument Nadir imagery of the Earth’s upper atmosphere is best done in the Far Ultraviolet or FUV (115 to 180 nm) • sunlight doesn’t penetrate the atmosphere below about 80 km • proven concept • simple and relatively low-cost sensors can be flown Mission/Instrument Operational Dates Instrument Type HILAT/AIM 1983 Single color imaging Polar BEAR/AIRS 1986-1987 2 color imaging Delta 180 1985 Imagers and spectrometers Delta 181 1987 Spectrographs and imagers Delta 183 1989-1991 Imagers MSX/UVISI 1996-2000 Spectrographic imagers and imagers DMSP/SSUSI 2003-2012 Scanning imaging spectrograph TIMED/GUVI 2002-2007 Scanning imaging spectrograph Hyperspectral Imagers Panchromatic imagers Sunshade Filter Wheel Drive motor combine all the light they Telescope receive into a single image. white light from scene 2D detector Multispectral sensors sample light in several non-adjacent to detector electronics color bands. to detector electronics 2D detector imagers sort the Collimating Mirror incoming light into a Grating hundred or more mutually white light from scene exclusive and complete bins. Telescope Filter/slit mechanism Telescope sunshade Mirror SSUSI Provides Required Environmental Data Records and Parameters MJCS 154-86 Ranking Environmental Parameter 5 Electron Density Profile 12 Neutral Number Density Profile 16 Solar Radiation (UV integrated flux) 18 Auroral Emissions and Airglow 24 Precipitating Electrons and Ions 26 Electric Fields (low latitude) 31 Ionospheric Scintillation SSUSI meets or exceeds SESS Sensor Requirements Specifications for the NPOESS sensors (see SESS Sensor Requirements Document; 1999). SSUSI is not, however, slated for flight on NPOESS. SSUSI Consists of a Hyperspectral Imager and a Photometer System The Spectrographic Imaging Spectrograph (SIS)can obtain an horizon-to-horizon images • in five "colors" in the wavelength range 110nm to 180nm - by using a scan mirror (IMAGING MODE) or it can operate with the mirror in a fixed position (SPECTROGRAPH MODE). • Three slits are available to optimize the combination of spatial, spectral, and altitude resolution. The Nadir Photometer System is optimized for observations of the nightside ionosphere and detection of the auroral boundary. • 630nm photometer to observe the O(1D) radiation field • 629nm photometer to deduce the background at 6300Å • 428nm photometer to observe the N2+ 1Neg band at 4278Å SSUSI 630 and 629 nm Photometers 428 nm Photometer Hyperspectral Imager – the Scanning Imaging Spectrograph (SIS) SSUSI on S20 The SSUSI SIS and NPS are visible as mounted on the Earth-facing panel of the DMSP spacecraft. SIS (with cover closed for launch) NPS (covered by a bag) GLOB (a sun shield for the OLS) SSUSI NPS The SSUSI NPS is the first flight of a system that allows one to accurately remove the effects of the planetary albedo (reflections from clouds) from the measurement of the 630 nm signal. • This enables the more accurate measurement of the height of the nightside ionosphere. The SSUSI NPS also allows us to use the 630 and 428 nm photometers to locate the auroral boundary, independent of the SIS. SSUSI A Novel Hyperspectral Imager Details of the SSUSI Scan Geometry Scan Mirror Detector n 160 spectral ele ments ca an bS Sc Lim m ck 5k s Tra ls 44 ixel s os ixe 16 spatial elements 8p ° Cr 24 p 9.6 +Y 11 .8 ° FOV Along Track Motion –Z 148 km/22 sec 10 Km x 10 Km resolution 153 Km 16 pixels 124.8° Cross Track Scan 156 pixels (h orizon to horizon) +Z SSUSI Spectrograph Design is Optimized for the DMSP Mission nadir slit mechanism telescope mirror SSUSI design is simple cross track scan range and robust. • An off-axis parabaloid telescope feeds a simple, 180nm Rowland circle, 140nm spectrograph. scan mirror 115nm • Minimizes the number of reflections toroidal grating secondary detector primary detector - FUV reflectivity is low Two detectors are implemented to meet lifetime requirements. We’re not worried about failure so much as our ability to characterize changes in performance. SSUSI “Color” Definitions SSUSI produces monochromatic multispectral images by extracting “colors” from the observed spectrum. • Indicated by highlighted areas • preserves the science content for EDRs • data rate reduced by factor of 30. Scanning Imaging Spectrograph Data Has a High Information Content Use of data in an operational environment requires that higher level data products be produced and that the user have an interface to all levels of the data. The interface has to convey the information about required parameters while reducing the user workload. Sample image from GUVI See: guvi.jhuapl.edu SSUSI Images the Earth SSUSI will routinely provide intensity maps and environmental parameters to AFWA. Day Night Aurora O/N2 on disk Total Electron Content (TEC) Q,E0 images O, N2, O2 on limb Height of Peak in F region Height of Peak in E (HmF2) region (HmE) EDP Qeuv Number Density of Electrons at Number Density of F-region Peak (NmF2) Electrons at E-region Peak (NmE) Cross-hatched area indicates SSUSI coverage on one orbit - over 10,000 ionospheric observations per orbit. SSUSI Data are Monitored and Evaluated at APL and Used at AFWA SSUSI data recorded on S/C and downlinked Data reformatted for processing Calibration applied to convert from counts to radiance Each pixel is located on the Earth Radiance data are regridded into superpixels - Sensor Data Records (SDR) Pixels are separated by region: Day, Night, and Aurora Each regions data are processed to produce the Environmental Data Records (EDR) SSUSI data are ingested by models to produce higher level forecast and nowcast products SSUSI scans are recorded in key wavelength bands and downlinked and calibrated, geolocated and gridded to form Sensor Data Records. SSUSI observes spectra. SSUSI downlinks scan images. SDRs are formed at AFWA. SSUSI SDRs are processed to form Environmental Data Records (EDRs) that support the warfighter. AFWA provides value-added processing to support specific customer requirements. User Interface Supported Through PVWave The SSUSI User Interface was designed over 10 years ago. At that time the AF chose PVWave as the language for coding. The current user interface allows the user to interact with the data by cjhoosing color table, product, map projection, contouring, etc. We are Looking at Enhancing SSUSI’s Utility to AFWA Users AFWA will use SSUSI to predict ionospheric perturbations that impact s/c operations & communications • Provides location of auroral boundary and energy deposition - s/c anomaly resolution - changes in neutral atmosphere composition and density • Indicates probable areas of disruptions or degradation - High frequency communications, precision geopositioning, over-the- horizon radar, predictions from PRISM - Images nightside ionosphere for bubbles and scintillation signatures in the equatorial Scans perpendicular to S/C orbital plane ionosphere and onto the limb SSUSI Software History The SSUSI Ground Data Analysis Software (GDAS) translate data numbers into key parameters: • 32,000 lines of MilSpec 2167A documented Ada code • 28,000 line of 4GL code to drive interactive displays • Software Users Manual and Science Interpretation Manual provided • near real-time processing of data • near real-time display The GDAS was delivered to 55th Weather Squadron. • Displays delivered March 1995. • Algorithms delivered June 1996. The GDAS re-delivery October 2001 at AFWA. • Changes to the software were required in order to meet changes in the platforms and operating environment. Current SSUSI GDAS Accommodates Differences Between AFWA and 55th Raw DMSP AFSFC Data System AFSFC Data Reformatter System Access User Algorithms Interface Data Product Algorithms User Data Tables Data Products Preferences SSUSI GDAS Components Have Varied Requirements The SSUSI GDAS consists of three elements • “Data Reformatter” ingests - the raw SSUSI sensor data and DMSP satellite ephemeris data currently formulated as an RSDR - indices from the Air Force solar & geomagnetic databases • “Data Product Algorithms” generates SSUSI data products - Sensor Data Records (SDRs) - Environmental Data Records (EDRs) • “User Interface” ingests the SDRs and EDRs and displays them through a tailorable graphical user interface. - The operator interface is menu driven and has built in help SSUSI GDAS is Supported by APL on the Same Type of Platform The APL plan has always been that the SSUSI algorithms will be run here at APL on the same platform and same environment as that at the host site (AFWA). The approach ensures • better support for the user - we will have most of the same operating environment dependencies • faster and cheaper upgrades - work can be done and tested here then installed at AFWA • proven bug fixes are produced, tested, and delivered - nothing is worse than a bug fix that doesn’t work - except a new bug • that we can test and evaluate enhancements to the SSUSI code without impacting AFWA operations and still be assured that it will work SSUSI Software Ready to Produce Standard Products SSUSI data are produced as Sensor Data Records (SDRs) and Environmental Data Records (EDRs). • SDRs are strip images in Rayleighs binned to 25 x 25 km2 grid • EDRs are product files binned to 25 x 25 km2 grid for aurora and 100 x 100 km2 for day and night SSUSI swaths are about 6000 km across. • And produce over 10,000 values/orbit or 150,000/day. Standard SSUSI EDRs Day Night Aurora O/N2 on disk Total Electron Content (TEC) Q,E0 images O, N2, O2 on limb Height of Peak in F region Height of Peak in E (HmF2) region (HmE) EDP Qeuv Number Density of Electrons at Number Density of F-region Peak (NmF2) Electrons at E-region Peak (NmE) Block 5D3 Sensors Support SSUSI Observations and Enhanced Data Products Other mission sensors, often referred to as special sensors, provide other meteorological data, depending on the spacecraft configuration. SSIES-3 Thermal Plasma Monitor/ Scintillation Detector SSJ/5 Precipitating Electron/Ion Spectrometer SSM Triaxial Fluxgate Magnetometer SSUSI Special Sensor Ultraviolet Spectrographic Imager SSULI Special Sensor Ultraviolet Limb Imager The other Block 5D3 sensors will contribute data that can be used for on-orbit validation of parts of the SSUSI EDRs. SSJ/5 will provide in situ energetic particle measurements, SSM auroral boundary information, and SSIES ionospheric parameters. SSULI looks in track while SSUSI images the disk and the cross-track limb thus providing a three-dimensional picture of the ionosphere. SSUSI Data and Data Products are Being Calibrated and Validated The SSUSI algorithm approach has been tested using data from the GUVI instrument on TIMED. The SSUSI cal/val period covers the first 13 months of operations. The data will be embargoed until the time that the sponsor agrees that the data and data products are of sufficient quality as to guarantee their utility. The SSUSI data stream and data products are unclassified. GUVI Data Will Contribute to the Validation of SSUSI Products TIMED is the first of NASA’s Solar Terrestrial Probe line. TIMED goals • Determine temperature, density, and wind structure of the MLTI including seasonal and latitudinal variations • Determine the relative importance of the various radiative, chemical, electrodynamical, and dynamical sources and sinks of energy for the thermal structure of the MLTI GUVI emphasis • neutral composition • high latitude energy inputs - conductivities and Joule heating Ground truth and ground-based measurements are an important The STP line provides products that will support SSUSI component of the effort. algorithm validation and enhancement. Concurrent Flight of SSUSI and GUVI Offer Opportunities to Improve Space Weather Products DMSPF16 will also manifest the the SSJ/5 electron and ion energy and flux measurement SSJ/5 will provide an inflight validation of the boundaries, fluxes and energies deduced by SSUSI. TIDI will measure the thermospheric vector wind field • SABER will measure the energy loss terms • SEE will measure the solar inputs During the TIMED mission one may expect more than one SSUSI operating • improved coverage of high latitude inputs • greater local solar time coverage Data from TIMED and from NASA/NSF supported ground sites will help validate SSUSI SDRs and EDRs. APL End-to-End Capability in Space Weather Enhances SSUSI Operational Basic Research Knowledge Transfer System Support System Requirements Measurement Requirement Instrument Instrument Tech Transfer Design Design Operational Software Flight on Flight on Operational Research Satellite Satellite SSUSI is Poised to Take Advantage of Concurrent APL Activities SSUSI hardware is built and awaiting flight. SSUSI SN05 was launched on DMSP S20 on October 18, 2003. • F16 is now in orbit and operating nominally SSUSI GDAS software has been delivered to AFWA. SSUSI cal/val plan is in place. The next step is analyze SSUSI data • evaluate the instrument performance • validate the data products • improve the product Acknowledgements The SSUSI team includes: Bernie Ogorzalek, Daniel Morrison, Michele Weiss, Bill Wood, Yongliang Zhang, Hyosub Kil, Brian Wolven, Jim Eighert, Rob Barnes, Ron Denissen, Ching Meng, Peter Silverglate, John Goldsten, John Boldt, Lloyd Linstrom, Dave Persons, and Dave Humm at APL. Many others at APL have contributed over the years. The SIS was fabricated by SSG, Inc. The SSUSI GDAS was supported by Computational Physics, Inc. : Doug Strickland, Scott Evans, and Kip Wright. The user interface was developed by Tom Spisz and updated by Dan Engfer. Ken Williams and Dave Artis did original GDAS design work along with Margie Hopkins and Geoff Crowley. The cooperation of our colleagues at the Aerospace Corp., especially Paul Straus, is gratefully acknowledged. Jack Heiss and Glen Fountain were earlier program managers for SSUSI.
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