Compact All Sky Interferometric Doppler Imager (CASIDI)

Proposed here is a next generation Compact All Sky Interferometric Doppler Imager (CASIDI) capable of measuring a thermospheric wind field every few minutes, with a precision of 10s of m/s. The ability to measure the wind field two dimensionally over the visible thermosphere will provide greater measurement of gravity waves, energy transport, and interaction between the ionosphere and thermosphere. The proposed sensor addresses key science goals in the Heliophysics Decadal Survey [NRC, 2013]. The first is to Determine the dynamics and coupling of Earths magnetosphere, ionosphere, and atmosphere and their response to solar and terrestrial inputs. The Decadal Survey underscored the importance of the Magnetosphere-Ionosphere-Thermosphere (MIT) system by stating Understanding ionosphere-thermosphere interactions is a major area of inquiry, especially during geomagnetic storms. The ionosphere exhibits significant day-to-day variability, which can seriously degrade important technological systems. Lack of ionospheric data, especially over the oceans, hinders scientific progress, and degrades the quality of existing nowcasting and forecasting systems. Ion-neutral coupling is a fundamental process that drives the evolution of the ionosphere and thermosphere.Recent observations of small-scale irregularities have been linked to neutral wind variability. Variations in neutral winds can drive complex and large-scale variability in the ionosphere. In addition to the sensor, a rapid manufacturing technique for the interferometer itself has been demonstrated. The combination of both the sensor and a vertically integrated manufacturing methodology will allow for lower cost and faster production of these sensors, thus enabling not only deployments in arrays but also on buoys and autonomous sea-going vehicles. Etalons manufactured with this technique will have applications well outside of Heliophysics. In phase I all the elements for constructing a successful phase II Compact ALL Sky Interferometric Doppler Imager (CASIDI) were demonstrated. In addition to the optical design and piezo scanning a novel etalon polishing technique was demonstrated and tested for wind retrieval capability. The test etalons are able to measure neutral winds in the thermosphere. Several etalons and a Doppler Imager will be constructed and tested under field conditions and thermospheric winds and temperatures will be measured. The combination of both the sensor and a vertically integrated manufacturing methodology will allow for lower cost and faster production (50% lower cost, 3x faster delivery) of these sensors, thus enabling not only ground deployments in arrays but also on buoys and autonomous sea-going vehicles, allowing for thermospheric observations in currently under sampled regions. The piezo tuned etalon is applicable to space-based interferometry as well. In phase II, the Compact ALL Sky Interferometric Doppler Imager (CASIDI) will be reduced to practice and fielded near the NCAR Fabry-Perot Interferometer in Boulder, Colorado allowing for instrumental cross comparison. Attaining this objective involves fulfilling three subordinate technical objectives: Use Magnetorheological Finishingtechnology (MHR) to construct 3 polished sets of etalons. Implement the phase I piezo tuning capability designed in Phase I and build two fully tunable piezo etalons. One for CASIDI and one for University of Alaska-Fairbanks (UAF). Measure the spectral stability and spectral uniformity of the etalons The second piezo etalon will be constructed for Mark Conde at UAF, he will test the Orion etalon in his scanning Doppler imager (SDI). Orion will develop a manufacturing and production plan with our TABA partner LARTA and design a production line for etalons, and other plano optics. Proposed Deliverables: Deliverables will include status reports as required by the contract, a final technical feasibility report, data from the CASIDI instrument and a manufacturing plan for future sensors and etalons.
Benefits: The CDI as a standalone sensor can provide thermospheric wind maps that are needed by the Space Weather community. Specifically, CASIDI can aid in understanding the Sun-atmosphere interaction region of Earth and its dynamical response to external and internal influences. Over time, data from CDI will be important in developing a near-real-time predictive capability for quantifying the impact of dynamical processes at the Sun on human activities and in Earth’s ionosphere. Access to global wind maps from one or more CASIDI instruments will significantly improve the specification and forecast of ionospheric responses to solar and geomagnetic disturbances. This improvement provides direct societal benefits due to optimized operation of communication, navigation, and surveillance systems. The data from CASIDI will also provide vital data for scientific studies.