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Space Environment Sensors (SES)
Space Weather Disturbances can result in a variety of system impacts including satellite disorientation & sensor anomalies, radar fake targets & target masking, UHF satellite communication disruption, GPS positioning errors, and space track and missile detection radar errors. The DMSP Space Environment Support System is comprised of both ground and space based sensors to provide data for space weather alerts, warnings, and forecasts for the warfighter. With the addition of SSULI and SSUSI beginning with F-16, there are five sensors in the SES suite aboard DMSP. |
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Special Sensor Auroral Particle Sensor (SSJ-5) provides the user with a time/space vs energy distribution of the charged particle environment in the close proximity to the spacecraft (in situ). By measuring the flux of auroral electrons and ions (0.3-30 keV) precipitating into the atmosphere at high latitudes, it determines the location of daytime auroral oval. SSJ-5 is also used in satellite failure analysis (spacecraft charging). After traversing through charged ion cloud, spacecraft takes on overall charge which can cause arcing and damage circuitry. SSJ-5 is a “new” design for F16; SSJ-4 sensor flew previously. Special Sensor Ion & Electron Sensor (SSIES-3) provides the user with electron and ion data for space operations and in-situ data for space weather model analysis. The sensor measures characteristics of the ionospheric cold-plasma background electron density (ne), electron and ion temperature (Te, Ti) , ion drift velocity (vd), and composition. It also measures strength of geomagnetic activity via high-latitude electric potential derived from vd. SSIES is comprised of:
Special Sensor Magnetometer (SSM) measures geomagnetic fluctuations, the slowly varying components of the geomagnetic field and transients within that field. It is used by navigation/attitude- heading referencing infrastructure of the military services (via updates to a global magnetic model). Began flying with a boom on F15. Special Sensor Ultraviolet Limb Imager (SSULI) provides the user with global electron density and neutral density profiles of the upper atmosphere both day and night through continuous measurement of UV radiation in the 80-170nm range (FUV/EUV). In addition to electron and neutral density profiles, it provides atmospheric temperature and composition. SSULI measures “airglow” in the ram or anti-ram (preferred) direction (F16 sensor views ram). Ionospheric density greatly impacts satellite communications, radar, deep space communications, GPS. The data can be used to determine unsafe conditions for extended space walks and to analyze single event upsets on spacecraft systems (that cause onboard computers to crash). Special Sensor Ultra-violet Spectrographic Imager (SSUSI) provides the user with a best estimate of electron density profiles, plasma transition zones (F-layer heights), auroral boundaries, and energy deposition rates into auroral latitudes. It makes FUV (115-180nm, 430-630nm) spectrographic observations of the airglow and aurora, and visible photometric measurements of the aurora and nightglow. Purpose: It provides information on the changes in Electron density profiles based upon time of day (night vs day). It’s necessary for maintenance of high frequency communication links and assessment of environmental hazards to astronauts. The SES ground based sensors, distributed globally, consist of the Solar Optical Observing Network (SOON) to observe sunspots and flares, the Radio Solar Telescope Network (RSTN) to monitor radio waves emitted by the sun, the legacy Digital Ionospheric Sounder System (DISS), and the newer Ionospheric Measurement System. 
External Variable Effects: Space Weather Seasons - Space weather varies over an 11-year period known as the solar cycle. The number of sunspots rises and falls during the cycle. Though space weather occurs at all times, the number of sunspots often determines how severe the conditions will be. Solar minimum, a period of few sunspots, is where we are right now. The relatively quiet sun normally leads to less severe space weather. Solar maximum, a period when hundreds of sunspots exist, is a 2-4 year period of increased severe space weather expected to occur from 1999 through 2001. The current pattern of activity leads solar experts to believe that the next solar maximum will be the most disruptive in the last 50 years. Occurring throughout the solar cycle and peaking during solar maximum are three types of space weather which affect military operations. Space Weather Types and Impacts - Finally, dense electrically-charged particle clouds may be considered the thunderstorms of the sun. Their energy exceeds that of a hurricane, but their frequency of occurrence and ability to affect operations anywhere resemble a thunderstorm. They radically change the battlespace and cause several types of problems, including SATCOM disruption and spacecraft anomalies, among other effects. These are most common during the 3-4 years of solar maximum, and they often occur after the radiation bursts and high-energy particles just discussed. That means these impact categories occur in succession, and during disruptive solar periods, they occur simultaneously, too. Sample impacts include hundreds of DoD satellite disruptions, and just one case of this weather type resulted in NORAD losing temporary track of space objects, and the loss of power in Canada and the northeast CONUS. To illustrate the frequency of satellite disruptions, the next slide shows the number of satellite anomalies reported during the last 11 years. Ionospheric Effects: 
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