Snow Ex a NASA airborne campaign leading to
Snow. Ex: a NASA airborne campaign leading to a snow satellite mission Snow. Ex Organizing Committee: Edward Kim, Charles Gatebe, Dorothy Hall, Matthew Sturm, Noah Molotch, Chris Crawford, DK Kang, Eugenia De Marco, with contributions by many others NASA Headquarters Program Manager: Jared Entin June 14, 2016 Snow Watch Columbus, Ohio
Outline • • • Background Sites Instruments & Aircraft Satellite Mission Concept Summary For more information, see http: //snow. nasa. gov 10/30/2020 2
What is Snow. Ex? • A multi-year airborne snow campaign designed to collect multi-sensor aircraft data and ground truth measurements to enable algorithm development and design a future satellite mission • Snow. Ex is all about challenging the sensing techniques and algorithms…. to learn when, where and how each technique works alone, or in synergy with other techniques, and why 10/30/2020 3
Snow. Ex Driving Questions • What is the optimum combination of sensing techniques to measure – regional (global) SWE? – global snow melt/energy balance (where, when, how fast)? The Snow. Ex experiment design must be developed in the context of a future spaceborne measurement system 10/30/2020 4
When is Snow. Ex? • • • Year 1 = 2016/17 fall and winter: campaigns Year 2 = 2017/18 winter: no campaign Year 3 = 2018/19 winter : campaign Year 4 = 2019/20 winter : campaign Year 5 = 2020/21 winter : campaign “Campaign” includes (ideally) • Fall -- no-snow background observations with lidar and radar • Winter -- dry snow observations with full sensor suite 10/30/2020 5
Where will Snow. Ex take place? • In Year 1 the experiment will take place in Western Colorado • Grand Mesa – meets all four Year 1 requirements • Uncompaghre/Senator Beck – good but lacks adequate flat terrain to be the main site • Site selection was primarily based on the requirements needed to achieve Snow. Ex objectives • See snow. nasa. gov for a comparison of sites, and for further details on potential sites 10/30/2020 6
Site Requirements (1) Probability of wet snow is very low (2) Existence of a shallow to deep gradient in snow depths and SWE (3) Snow-covered area with flat terrain that is larger than airborne instrument swath widths (4) Forested stands with variable density and height 10/30/2020 7
Forest-Cover Gradient 10/30/2020 8
Advantages/Strengths Remote Sensing techniques for global snow • Radar (SAR): senses SWE and melt, high resolution through clouds and darkness • Passive MW: senses SWE and melt through clouds and darkness (very long record from satellite data) • Lidar: snow depth, accuracy acceptable for deeper snow, SWE (need density), very high resolution, possibly through forest gaps • Multispectral: MODIS/VIIRS, f. SCA, albedo, grain size, IR, moderate spatial resolution • Hyperspectral: f. SCA, albedo, surface grain size, moderate/high spatial resolution 10/30/2020 9
Instruments • From the 2016 Seattle i. SWGR / Snow. Ex workshop, the core sensor types for Year 1 are: – Lidar – Radar (SAR) – Passive microwave – Passive VIS/IR – Radiometer for sensing BRDF 10/30/2020 10
JPL’s Airborne Snow Observatory (ASO) has been selected by HQ for Year 1 ASO uses a Riegl Q 1560 scanning lidar, which captures the surface topography with <10 cm vertical accuracy. Depth is calculated by subtracting a summer “snow-free” dataset from each winter “snow-on” dataset. The accuracy of these data is dependent upon precise knowledge of the aircraft position during the measurements. An integrated Applanix Inertial Measurement Unit (IMU) and GPS provide aircraft attitude and position information, and this information is combined with error corrections from an existing network of GPS base stations at fixed locations near the survey area. This combined use of the IMU for high-speed attitude information, along with the differential GPS solution for absolute position, yields the sub-decimeter aircraft trajectory accuracy necessary for Li. DAR snow depth measurements. http: //aso. jpl. nasa. gov/ 10/30/2020 11
ESA’s Snow. SAR • Twin frequency [9. 6 and 17. 2 GHz (X- and Ku- bands)] polarimetric Synthetic Aperture Radar • High frequencies will allow the study of both the surface and underlying layers of the snowpack because they have different backscattering properties • ESA commissioned Meta. Sensing, a company based in Noordwijk, The Netherlands, to develop and test the Snow. SAR instrument 10/30/2020 12
The Airborne Earth Science Microwave Imaging Radiometer (AESMIR) • The AESMIR is a passive microwave airborne imager with 6 microwave bands (6, 10, 18, 23, 36, 89 GHz) with 4 -Stokes polarization capability (except at 23 GHz) • 18 & 36 GHz, V &H pols are useful for snow; 10 & 89 GHz are of secondary interest for snow • Programmable scan modes include conical and cross-track scanning • Requires heavy-lift aircraft such as a P-3 aircraft http: //science. gsfc. nasa. gov/sci/index. cfm? fuse. Action=projects. view&project_id=336 10/30/2020 13
Passive VIS/IR • Cloud Absorption Radiometer (CAR) – BRDF capability – Multi-spectral: 14 bands (0. 34 to 2. 29 µm) – Mature • More info at http: //car. gsfc. nasa. gov/ Publication: http: //car. gsfc. nasa. gov/publications/pdf/Gatebe_and_King_2016. pdf 10/30/2020 14
Snow mission concepts • Must address global snow • Therefore must include multiple sensors (community consensus) – Active & passive mw, lidar, multi-spectral VIS/IR • Need mature technology and algorithms – SCLP and Co. Re. H 2 O both suffered on radar algorithms • Satellite mission must avoid high cost – Leverage existing assets (satellite PM and multispectral) – But some satellite assets might go away (PM? ) • International partnering is the key to – Leveraging technology and algorithm development investments – Spreading costs • Some sensors can/should be suborbital – E. g. , Lidar on aircraft and other sensors on satellites • Societal benefits and science return already strong 10/30/2020 15
Summary • Snow. Ex: a NASA airborne campaign leading to a snow satellite mission – Instrument payload designed to determine what combination of sensors provides the optimum results for measuring SWE, BRDF, surface temperature and mass • Snow. Ex Year 1, 2016 -17, will be held in Western Colorado – fall and winter campaigns • Out years (2018 -19, 2019 -20 and 2020 -21) will likely take place in other locations 10/30/2020 16
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