Vincent Realmuto

The advanced spaceborne thermal emission and reflectance radiometer (Aster)

The Advanced Spaceborne Thermal Emission Reflectance Radiometer (ASTER) is the only high‐spatial‐resolution multispectral imager scheduled to fly in Earth orbit on the first platform of NASAs Earth Observation System (EOS‐A). The instrument will nave three bands in the visible near infrared with 15‐m spatial resolution, six bands in the short‐wave infrared with 30‐m spatial resolution and five bands in the thermal infrared with 90‐m spatial resolution. There will be an additional band in the near infrared with 15‐m spatial resolution that will provide same‐orbit stereo data when combined with the corresponding nadir viewing band. The ASTER instrument is being built by the Japanese Government based on the scientific requirements of the ASTER science team. This team consists of Japanese and American scientists, who will also be responsible for the development of algorithms for data reduction and analysis. The ASTER will be able to address a variety of science objectives identified by the EOS global change program. ASTER will provide surface temperatures and emissivity estimates, surface reflected radiances and digital elevation models at a spatial scale that will allow detailed process studies for MODIS and other global monitoring instruments at the subpixel level. Existing aircraft instruments can be used to simulate data that will be provided by ASTER. Examples are shown here of surface temperature mapping, surface compositional mapping, and digital elevation models derived from the NASA Thermal Infrared Multispectral Scanner, the Airborne Visible Infrared Imaging Spectrometer, and aerial photography.

HyTES: Thermal imaging spectrometer development

The Jet Propulsion Laboratory has developed the Hyperspectral Thermal Emission Spectrometer (HyTES).12 It is an airborne pushbroom imaging spectrometer based on the Dyson optical configuration. First low altitude test flights are scheduled for later this year. HyTES uses a compact 7.5–12□m hyperspectral grating spectrometer in combination with a Quantum Well Infrared Photodetector (QWIP) and grating based spectrometer. The Dyson design allows for a very compact and optically fast system (F/1.6). Cooling requirements are minimized due to the single monolithic prism-like grating design. The configuration has the potential to be the optimal science-grade imaging spectroscopy solution for high altitude, lighter-than-air (HAA, LTA) vehicles and unmanned aerial vehicles (UAV) due to its small form factor and relatively low power requirements. The QWIP sensor allows for optimum spatial and spectral uniformity and provides adequate responsivity which allows for near 100mK noise equivalent temperature difference (NEDT) operation across the LWIR passband. The QWIPs repeatability and uniformity will be helpful for data integrity since currently an onboard calibrator is not planned. A calibration will be done before and after eight hour flights to gage any inconsistencies. This has been demonstrated with lab testing. Further test results show adequate NEDT, linearity as well as applicable earth science emissivity target results (Silicates, water) measured in direct sunlight.

In situ observations and sampling of volcanic emissions with NASA and UCR unmanned aircraft, including a case study at Turrialba Volcano, Costa Rica

Abstract Scientific knowledge of transient and difficult-to-access airborne volcanic emissions comes primarily from remote sensing observations, and a few in situ data from sporadic heroic or inadvertent airborne encounters. In the past, patchy knowledge of the composition and behaviour of such plumes from explosive volcanic eruptions, and associated drifting ash and gas clouds, have centrally contributed to unwanted and dangerous aircraft encounters that have put crews at risk and, in some cases, greatly damaged aircraft. Thus, improved knowledge of boundary conditions and plume composition, as inputs to both mass retrieval and predictive models for cloud trajectories, would be of benefit. In this paper, we describe how small robotic unmanned aerial vehicles (sUAVs) can address a variety of measurements that are typically beyond the reach of, and sometimes too dangerous for, manned aircraft. The direct measurements and sampling that can be achieved by sUAVs address serious gaps in knowledge of volcanic processes, and provide important validation data for estimations of volcanogenic ash and gas concentrations gleaned using remote sensing techniques. These data, in turn, constrain key proximal and distal boundary conditions for aerosol and gas transport models on which are based a number of decisions and evaluations by hazard responders and regulatory agencies. We briefly describe a case study from our ongoing field study at Turrialba Volcano in Costa Rica, where we are conducting an international campaign of systematic airborne in situ measurements of volcanogenic SO2 and other gases, as well as aerosols, with sUAVs and aerostats (e.g. tethered balloons and kites), in conjunction with data acquisitions by the Advanced Spaceborne Thermal Emission and Reflection (ASTER) radiometer onboard the NASA Terra Earth orbital platform. To our knowledge, this is the first such systematic in situ UAV- and aerostat-based observation programme for SO2 and particulates in a volcanic plume for correlation with orbital data. We preliminarily report good agreement between our UAV/aerostat and ASTER SO2 retrievals within a 5 km radius of the volcano summit, at altitudes of up to 12 500 ft (c. 3850 m) above sea level (asl) for concentrations within the range of 5–20 ppmv (ppm by volume). Additional work continues.

Field calibration of a broadband compact thermal infrared spectrometer for earth science

We present field results showing excellent performance for a compact earth observing thermal infrared (EOTIR) hyperspectral grating spectrometer using a combination of a Quantum Well Infrared Photodetector (QWIP) and grating based Dyson spectrometer. 12The Dyson design allows for a very compact and optically fast system (F/1.6). Cooling requirements are minimized due to the single monolithic prism-like grating design. The configuration has the potential to be the optimal sciencegrade imaging spectroscopy solution for lighter-than-air (LTA) vehicles and unmanned aerial vehicles (UAV) due to its small form factor and relatively low power requirements. The QWIP allows for optimum spatial and spectral uniformity and provides adequate responsivity to allow for near 100mK noise equivalent temperature difference (NEDT) operation across the EOTIR passband. These tests are in preparation for the deployment of the Hypserspectral Thermal Infrared Spectrometer (HyTES) which is currently being funded under NASAs instrument incubator program (IIP). Test results show NEDT, linearity as well as applicable earth science emissivity target results (silicates, water) measured in direct sunlight. A calibration is also performed to derive direct water temperature using a well calibrated transfer radiometer operating simultaneously.