GLIMS colleagues, This letter was sent to USGS/NASA in response to their Request for Information. We have confirmation that the letter is in the hands of the Landsat Next design committee. --Jeff Kargel Letter of support for a stereo capability on Landsat Next We outline here the crucial importance of stereo capabilities to monitor the Earth surface, made more crucial by the lack of a follow-up mission after ASTER, and the unique opportunity possibly provided by the evolving design of the Landsat NEXT (Landsat 10) mission. The stereo capabilities of the two ASTER Band 3 telescopes and the resulting digital elevation models have led to major advances in our understanding of dynamics of the Earth surfaces. Among others, these freely available elevation data were extensively used to map glacier and ice sheet changes and a range of other climate change impacts, and various geohazards such as volcanic activities and landslide dynamics. A new generation of very-high-resolution optical sensors (e.g., WorldView, Pleiades, etc…) now provide stereo capabilities at much higher resolution and precision but have been mainly available for the Polar Regions (Arctic and Antarctic) or restricted to specific targets. Furthermore, these sensors often respond to emergency and commercial requests but do not aim at building a global, freely available archive. Sentinel-2 satellites and their planned successor missions also have a wide swath and good revisit period but no stereo capability. Through this letter, we want to attest that a stereo capability onboard Landsat Next (Landsat 10) would be a game changer for this mission and for the understanding of our constantly evolving Earth surface. Various options could be considered to provide this stereo capability. An obvious option could consist of adding a stereo band pointing forward or backward in the spirit of the ASTER design. Typically, a stereo angle of about 20° is a good compromise, but we suggest a tradeoff study to select the angle. More powerful systems could be designed if Landsat Next would be made as a 2- or 3-platform constellation providing opportunities for higher precision and completeness of the DEMs and also simultaneous imaging and a wealth of new applications, such as in 3-D studies of volcanic eruptions, ocean waves, and clouds. A fallback possibility could be to repurpose, reposition, and repoint Landsats 8 and 9 to fly in a stereo-acquiring constellation with Landsat 10. This repurposing is less desirable, as the acquisition of stereo imaging would halt if the (by-then) aging Landsat 8 and middle-aged Landsat 9 fail. We ask the Landsat Next science and engineering committee to seriously consider these options and not miss a unique opportunity to offer a follow up to the multiple achievements made with ASTER. We are prepared to write a more specific and detailed discussion on this Landsat NEXT augmentation, with a stereophotogrammetric performance tradeoff study, upon request. Glaciers, ice sheets, and snow Jeffrey S. Kargel, Senior Scientist, Planetary Science Institute, USA, jkargel@psi.edu<mailto:jkargel@psi.edu> Bruce Raup, NSIDC, CIRES, University of Colorado, USA; GLIMS Director, braup@nsidc.org<mailto:braup@nsidc.org> Andreas Kääb, University of Oslo, Norway, a.m.kaab@geo.uio.no<mailto:a.m.kaab@geo.uio.no> Etienne Berthier - University of Toulouse / CNRS, France, etienne.berthier@legos.obs-mip.fr<mailto:etienne.berthier@legos.obs-mip.fr> Umesh K. Haritashya, Assoc. Prof., Dept of Geology & Environmental Geosciences, Univ. of Dayton, uharitashya1@udayton.edu<mailto:uharitashya1@udayton.edu> David Shean, Civil and Environmental Engineering, Univ. of Washington, USA dshean@uw.edu<mailto:dshean@uw.edu> Beáta Csathó - University at Buffalo, Buffalo, NY, USA, bcsatho@buffalo.edu<mailto:bcsatho@buffalo.edu> Tobias Bolch, Geography & Sustainable Development, University of St Andrews, Scotland, UK, tobias.bolch@st-andrews.ac.uk<mailto:tobias.bolch@st-andrews.ac.uk> Ted Scambos - Senior Research Scientist, Earth Observation and Science Center, CIRES, University of Colorado Boulder, USA, tascambos@Colorado.EDU<mailto:tascambos@Colorado.EDU> Mike Willis, Assistant Professor, Geodesy and Remote Sensing, CIRES and Department of Geological Sciences, Univ. of Colorado, Boulder, mike.willis@colorado.edu<mailto:mike.willis@colorado.edu> Christopher A. Shuman, Research Associate Professor UMBC JCET at Code 615, NASA GSFC, cshuman@umbc.edu Volcanoes Rick Wessels, U.S. Geological Survey, Volcano Disaster Assistance Program (VDAP), USA, rwessels@usgs.gov Jani Radebaugh, Professor, Geological Sciences, Brigham Young University, USA, janirad@byu.edu<mailto:janirad@byu.edu> Sarah A. Fagents, Hawaii Institute of Geology and Planetology, Univ. of Hawaii at Manoa, USA, fagents@higp.hawaii.edu<mailto:fagents@higp.hawaii.edu> Earthquakes, Tectonics and Landslides Jean-Philippe Malet, University Strasbourg, France - CEOS WG Disaster Landslide Pilot, France, jeanphilippe.malet@unistra.fr<mailto:jeanphilippe.malet@unistra.fr> Pascal Lacroix - University Grenoble Alpes, France, pascal.lacroix@univ-grenoble-alpes.fr<mailto:pascal.lacroix@univ-grenoble-alpes.fr> Dan Shugar, University of Calgary, Canada, dshugar@ucalgary.ca Olivier Dewitte - Royal Museum For Central Africa - Belgium - Olivier.Dewitte@africamuseum.be<mailto:Olivier.Dewitte@africamuseum.be> Eric Fielding, Principal Scientist, Jet Propulsion Laboratory, USA, eric.j.fielding@jpl.nasa.gov<mailto:eric.j.fielding@jpl.nasa.gov> Michael P. Bishop, Dept. of Geography, Texas A&M University, USA, michael.bishop@tamu.edu<mailto:michael.bishop@tamu.edu> Forests Donald Falk, Professor, Natural Resources and the Environment, University of Arizona, dafalk@arizona.edu<mailto:dafalk@arizona.edu> Ocean Lorenzo Corgnati, National Inst. of Marine Science, CNR, Italy, lorenzo.corgnati@sp.ismar.cnr.it<mailto:lorenzo.corgnati@sp.ismar.cnr.it> ASTER Remote Sensing Yasushi Yamaguchi, Japan ASTER Science Team Leader, Professor, Graduate School of Environmental Studies, Nagoya University, Japan, yasushi@nagoya-u.jp<mailto:yasushi@nagoya-u.jp> Michael Abrams, U.S. ASTER Team Leader, NASA/Jet Propulsion Laboratory, Michael.j.jabrams@jpl.nasa.gov