Global Ultra-Violet Ionosphere-Thermosphere Observatory (GUVITO)

UV spectrographic imagers such as SSUSI and GUVI provide measurements of the aurora, ionospheric electron density, ionospheric bubbles, and thermospheric temperature, composition, and density. These imagers have been a key element of the Air Force DMSP program, but to accommodate new satellite concepts and maintain flexibility in the choice of new space systems and launch options, lighter weight and more capable UV instruments are needed to replace the current series of SSUSI sensors. Here we describe a technological alternative to the currently flying SSUSI sensors. It is a spectrographic imaging capability known as the “Global Ultra-Violet Ionosphere-Thermosphere Observatory” (GUVITO) sensor and associated software. GUVITO improves upon current instruments by being smaller in size, weight and power but with improved functionality. The GUVITO sensor represents an upgrade of the SSUSI and GUVI sensors in terms of scan mirror functionality and reliability, sensor functionality, mass, and power requirements. In particular, this improved functionality is expected to lead to enhanced capability in observing ionospheric bubbles, which are thought to cause scintillation and serious technological challenges for communications, navigation and surveillance systems. Initial development and risk reduction activities are currently funded by AFRL through a SBIR Phase II contract. The enhanced reliability and performance of the GUVITO sensor system is achieved with flight heritage components, concepts, software, hardware and is guided by key personnel experienced with both the SSUSI and GUVI hardware, software and operations. GUVITO would meet DoD priority requirements in ionospheric density, scintillation, and satellite drag, meet NPOESS IORD-II requirements for space environment Environmental Data Records (EDRs), maintain current DMSP capability, ensure long-term continuity of space environmental monitoring and leverage new technology development for future operational systems. The existing SSUSI/GUVI design consists of a scanning imaging spectrograph with a cross-track scanning mirror at the input to an off-axis parabaloid telescope which feeds a Rowland Circle spectrograph. A toroidal grating disperses the wavelength and focuses the UV photons onto a two-dimensional photon-counting detector. The detector is effectively divided into a number of spatial elements along the spacecraft track and into a number of spectral bins cross-track over the range of 115 nm to 180 nm. Full spectral information can be collected for each spatial element, but it is sufficient to save and telemeter only the spectral bins associated with selected emission lines and bands. These are mission-selectable. We find that a minimum number of colors is five, corresponding to the most significant key products that we will provide. This presentation will demonstrate and discuss some of the GUVITO capabilities in detail, together with assimilation techniques that could be used for ionospheric specification.