SAR Science Requirements for Ice Sheets

Transcription

1 1 A recommendation to the Polar Space Task Group (PSTG) V1.0 - May 2013 Coordinating Author and Point of Contact for this document: Bernd Scheuchl Associate Project Scientist Department of Earth System Science University of California, Irvine Croul Hall Irvine, CA e- mail: bscheuch@uci.edu (A list of supporters and contributing authors is provided in Appendix H) Executive Summary Following the successful internationally coordinated SAR data acquisitions over ice sheets during the International Polar Year 2007/2008, efforts are undertaken to continue data acquisitions in the spirit of collaboration. The Polar Space Task Group (PSTG) is succeeding the IPY coordinating body of international space agencies, Space Task Group (STG). The PSTG SAR Coordination Working Group was created to address the issue of SAR data acquisitions in the cryosphere. This document outlines the SAR data requirements for the ice sheets of Antarctica and Greenland. The general requirements have been presented at the first SAR Coordination Working Group in November Here, more detailed, sensor specific recommendations on SAR acquisitions are made in response to a SAR Coordination Working Group request. The sensor specific recommendations are summarized in the appendix (A, B, C, and D) and will form the basis for the ongoing discussions of the SAR Coordination Working Group. Relevant areas containing ice caps are mentioned in appendix E, but are not the focus of this document. (V1.0) May 17, 2013

2 2 Table of Contents 1 Introduction Science Requirements... 5 Observation Requirements General Recommendations Current and Upcoming SAR Missions Antarctica General Observation Requirement Reduced Observation Requirement (if sensor capacities require scale down) Science Mission Requirement (assuming no conflicts with other priorities) Specific Considerations - Antarctica Recommendation for X- band High- Resolution Acquisition Super Sites - Antarctica TerraSAR- X specific Recommendation TanDEM- X specific Recommendation COSMO SKYMED specific Recommendation RADARSAT- 2 Recommendations - Antarctica Sentinel- 1 Recommendations - Antarctica ALOS- 2 Recommendations - Antarctica Greenland General Observation Requirement Reduced Observation Requirement (if sensor capacities require scale down) Science Mission Requirement (assuming no conflicts with other priorities) Specific Considerations - Greenland Recommendation for X- band High- Resolution Acquisition Super Sites - Greenland TerraSAR- X Specific Recommendation TanDEM- X Specific Recommendation COSMO SKYMED Specific Recommendation RADARSAT- 1 Recommendations - Greenland Sentinel- 1 Recommendations - Greenland ALOS- 2 Recommendations - Greenland Data Available References Acronyms Appendix A: Summary of Recommendations for RADARSAT- 1 and RADARSAT Antarctica Greenland Appendix B: Summary of Recommendations for High- Resolution X- band Sensors (TerraSAR- X, TanDEM- X, and COSMO- Skymed) (V1.0) May 17, 2013

3 3 9.1 TerraSAR- X specific Recommendation TanDEM- X specific Recommendation COSMO SKYMED specific Recommendation Antarctica Greenland Appendix C: Summary of Recommendations for Sentinel General Recommendations Ramp- up Phase Recommendations (Antarctica and Greenland) Sentinel- 1 Recommendations - Antarctica Sentinel- 1 Recommendations - Greenland Appendix D: Summary of Recommendations for ALOS ALOS- 2 Recommendations - Antarctica ALOS- 2 Recommendations - Greenland Appendix E: Areas Containing Mountain Glaciers and Ice Caps Background and Overview Canadian Arctic General Observation Requirement (ideal case) Reduced Observation Requirement (given sensor capacities) Svalbard and Russian Arctic General Observation Requirement Reduced Observation Requirement (given sensor capacities) Mountainous Glaciers (Andes, Rocky Mountains, Himalaya- Karakoram- TienShan, Patagonia, New Zealand Alps, European Alps, Alaska) General Observation Requirement Appendix F: ALOS- 2 Basic Observation Scenario Appendix G: Ice sheet Requirements Mentioned in the Scientific and Institutional Literature Summary of recommendations of IGOS report EOS Science Plan Global Inter- agency IPY Polar Snapshot Year (GIIPSY) From Cryos Theme Report (2007) GCOS report implementation plan 2010 update GCOS report implementation plan 2011 update supplemental details Fringe ISMASS ESA- CliC- EGU Earth Observation and Cryosphere Science Conference NASA Appendix H: Contributing Authors and Affiliations (V1.0) May 17, 2013

4 4 1 Introduction The International Polar Year 2007/2008 represented an opportunity for international space agencies to coordinate data acquisitions of the cryosphere through the Space Task Group (STG) and through this process to provide a historical data set. The success of the effort led to the formation of the Polar Space Task Group (PSTG) to succeed STG to transform a one- off opportunity into an ongoing effort to collect remote sensing data of the cryosphere. Input from the science community is coordinated with representatives from the science community represented at PSTG meetings. Here, we focus on the science requirements of ice sheets and how they can be met with SAR acquisitions. Ice sheets are acknowledged by WMO and UNFCCC as an Essential Climate Variable (ECV) needed to make significant progress in the generation of global climate products and derived information. The need to monitor the great ice sheets was identified in several prior publications: 1999 EOS Science Plan 2001 Climate and Cryosphere (CliC) Science Coordination Plan 2006 GIIPSY Science Requirements 2007 IGOS Cryosphere Theme Report GCOS Implementation plan for the global observing system for climate in support of the UNFCCC (2010 update) GCOS Systematic observation requirements for satellite- based data products for climate (2011 update) Preliminary scientific needs for Cryosphere Sentinel products (Preparatory material updated after the SEN4SCI workshop March 2011) In addition, the issue was raised at several meetings and workshops: Fringe 2011 (Panel Discussion), Frascati, IT, Sept IPY workshop Montreal (Panel discussion), Montreal QC, Apr PSTG- 2, Geneva, CH, June 2012 SCAR 2012, Portland, OR, July 2012 ISMASS 2012, Portland, OR, July 2012 The PSTG SAR Coordination Group meeting, Frascati, IT, Nov ESA- CliC- EGU Earth Observation and Cryosphere Science Conference, Frascati, IT, Nov AGU 2012 Fall meeting, San Francisco, CA, Dec PARCA 2013, Greenbelt, MD, Jan (V1.0) May 17, 2013

5 5 2 Science Requirements In 2012, an ESA- funded project, ESA ice sheet CCI, conducted a literature review and user survey on ice sheet science requirements. Questionnaire responses were received from 67 scientists and a report was finalized by the Ice Sheet CCI team in August The following is a summary of user requirements and recommendations. It should be noted that the user survey specifically focused on Greenland, though many of the findings can be applied to Antarctica as well. A second user requirement survey specifically focused on Antarctica will be performed in the last half of 2013 as part of a scoping study for an intended future Antarctic CCI project. The results of this study will be made available to the PSTG as soon as they are collected. Summary of user recommendations [Ice Sheet CCI user requirement]: 1. The preferred priority by users is to have low resolution in the interior areas and a high resolution in the margin areas for both Surface Elevation Change (SEC) and Ice Velocity (IV). (other scenarios are also useful). 2. The regions of special interest include glaciers all around the margin of the GrIS, in particular focusing on the major fast- flowing ice streams and glacier systems: Jakobshavn Ice Stream, Helheim Glacier, Petermann Glacier, Kangerlugssuaq, and Nuuk Fjord Glaciers. 3. Open access to data is critical. If not, users will continue using publicly available datasets. 4. High- level datasets are needed, in particular for climate and ice flow modelers who have no special knowledge of satellite- based data. 5. NetCDF (CF- compliant) is by far the most popular choice, in particular by modelers, although there is also a request for simpler file formats. Most users use Matlab or Fortran as their preferred software. 6. Long and continuous records are needed, in particular for SEC. Ensuring long- lasting records, is an important issue and must be taken into account when planning future satellite missions. (V1.0) May 17, 2013

6 6 Table 1 shows a summary of user requirements for ice sheet essential climate variable parameters. These requirements refer to derived products as described. In the case of IV and Grounding Line Location (GLL), requirements for SAR data resolution will be more stringent (i.e. higher resolution required), as spatial averaging is generally performed during product generation. Table 1. User Requirements for Ice Sheet Essential Climate Variable parameters. SEC IV GLL CFL Minimum spatial 1-5 km 100 m 1 km 100 m 1 km 100 m 500 m resolution Optimum spatial < 500 m 50 m 50 m 50 m resolution Minimum temporal annual annual annual annual resolution Optimum temporal monthly monthly monthly monthly resolution Minimum accuracy m/yr - - m/yr Optimum accuracy < 0.1 m/yr 10 m/yr - - What times are observations needed All year All year All year All year SEC Surface Elevation Change IV Ice Velocity GLL Grounding Line Location CFL Calving Front Location (V1.0) May 17, 2013

7 7 Observation Requirements The information provided in the following three chapters came out of a number of discussions within the science community and expertise gained during projects spanning the last 15 to 20 years. 2.1 General Recommendations A set of general recommendations is given below based on a discussion with Ian Joughin and Eric Rignot. Both have many years of expertise in the field and are PIs in current projects dealing with ice velocity mapping of the great ice sheets using spaceborne SAR data. Polarization: Acquisition mode: Incidence angle range: Acquisition strategy: HH preferred Stripmap preferred, (a notable exception is Sentinel- 1 IWS, a TOPS mode. See Sentinel- 1 specific sections for details) Based on experience, 23 to 45 degrees worked fine (even 57 deg. to cover South Pole). Where possible, the same range of incidence angles should be used over individual glaciers and super sites to simplify result comparisons. Regional requirements may lead to specific preferences, specifically on smaller outlet glaciers in mountainous terrain. Acquire at least some long tracks (i.e. coast to coast, rock to rock) to aid processing [4]. The remainder of this document outlines the post- IPY requirements. One aspect to be considered in this respect is the multi- purpose and commercial use of most SAR missions available. Requirements are therefore divided into 3 sections: 1. General Observation Requirements: Based on previous (particularly the IPY) experience, these data requirements should be manageable for space agencies, particularly if acquired in a coordinated fashion. 2. Reduced Observation Requirements: In case competing priorities of the various SAR missions do not allow a fulfillment of the general observation requirements, this set is hopefully manageable (could be enhanced with a prioritized list), while still preserving the science value of the data. 3. Science Mission Requirements: This set of requirements represents the ideal case of a mission with few (or no) competing priorities. (V1.0) May 17, 2013

8 8 2.2 Current and Upcoming SAR Missions Table 1 lists the sensors available or upcoming as of May Chapters 4 and 5 of this document outline sensor specific recommendations; these are summarized in the appendix. The following sections include a recommendation of super sites for high resolution X- band coverage (TerraSAR- X, TanDEM- X and Cosmo- Skymed) and a recommendation for large scale C- band coverage during the winter 2012/2013 (RADARSAT- 1 and - 2). Instrument Table 2. List of currently operating and upcoming SAR missions. Band Mission Duration Space Agency Left looking capability RADARSAT- 1 C CSA No (not operational) Comments Mission ended in late March Included here due to 2013 Greenland acquisitions. RADARSAT- 2 C ongoing CSA Yes Commercial mission (PPP) may affect sensor availability TerraSAR- X / TanDEM- X X ongoing DLR Yes Commercial mission (PPP) may affect sensor availability. 2 satellites acting 2 missions Cosmo- Skymed X ongoing ASI No Commercial mission (PPP) may affect sensor availability RISAT- 1 C ISRO Information Access to science data unclear ongoing not available RISAT- 2 X ongoing ISRO Information Access to science data unclear not available HJ- 1C S ongoing NDRCC/SEPA Information Access to science data unclear not available Sentinel- 1 2 sats. C Launch: ESA / EC No Government mission (PPP) may affect sensor availability ALOS- 2 L Launch: 2013 JAXA Yes Commercial mission (PPP) may affect sensor availability SAOCOM 2 sats L Launch 2014, 2015 CONAE Yes Collaboration with ASI (COSMO- Skymed) RCM 3 sats C Launch CSA No Government mission science access possible DESDynI L Launch: 2021 NASA TBD Full science mission (V1.0) May 17, 2013

9 9 3 Antarctica The IPY effort marks the first time the entire continent was completely covered with interferometric SAR data. The effort led to a reference velocity map [6] as well as an InSAR- based grounding line product [7]. Both products represent measurements of changing geophysical parameters. The coastal regions of Antarctica are undergoing changes, particularly on the West Antarctic Ice Sheet [4,5,9]. Frequent coverage is therefore warranted. Interior regions with little change [10] also benefit from repeat acquisitions to increase the accuracy of measurements particularly in slow moving areas [4]. The size and geographic location of the area of interest requires a combination of left and right looking acquisitions to cover the area. 3.1 General Observation Requirement Annual coverage of all of Antarctica with at least 3 consecutive cycles winter observations. More cycles are considered an asset. More frequent (monthly) observations of critical areas with every possible acquisition of selected tracks (Pine Island / Thwaites Glacier region; Antarctic Peninsula; Totten Glacier; please refer to Table 3 for more information). 3.2 Reduced Observation Requirement (if sensor capacities require scale down) Plan for a full Antarctic coverage at least every 3 years. Provide annual coverage of coastal regions (right looking: all coastal areas; left looking: TAM + Ross and Ronne with their tributaries). More frequent (monthly) observations of critical areas with every possible acquisition of selected tracks 1 3 b 3 a Figure 1. Prioritized coastal regions in Antarctica for a reduced acquisition requirement (1: highest priority, 3: lowest priority). 2 (V1.0) May 17, 2013

10 Science Mission Requirement (assuming no conflicts with other priorities) Ongoing coverage of the visible area with coast- to- coast tracks (right looking: coastal areas; left looking: Central Antarctica). Acquisition of additional tracks covering large outlet glaciers with higher resolution modes Capture seasonal changes over major ice streams 3.4 Specific Considerations - Antarctica Plan for at least some coast- to- coast tracks to facilitate data processing and calibration [4] South of 80 degrees south (i.e. left looking visibility only): It is acknowledged that left looking acquisitions put additional strain on resources (change from right to left looking) and require careful planning and execution. A full coverage per year (3 consecutive cycles) would be considered an asset. L- band: Most critical in coastal zones and WAIS (C- band decorrelation is present for 24 and 35 day repeat orbit, however, 6 and 12- day repeat period of S- 1 should reduce this problem in the future [24]) C- band: Historically most impact in the interior, but coastal coverage is also recommended, particularly for missions with shorter repeat orbits. X- band: Continuation of current approach recommended (example: TerraSAR- X) more frequent coverage of smaller, high impact regions + some limited basin wide coverage of selected regions (e.g. the TerraSAR- X left looking campaign in Antarctica). 3.5 Recommendation for X-band High-Resolution Acquisition Super Sites - Antarctica This section was written in response to a PSTG SAR coordination group information request regarding X- band high- resolution sites for regular monitoring. The sensors addressed include TerraSAR- X, TanDEM- X and the COSMO SKYMED constellation. The PSTG SAR coordination group requested a list of sites recommended for frequent high- resolution observation. The following is a table comprised of existing TerraSAR- X time series resulting from super sites and AOI s of individual PI s augmented by recommendations from the larger community. While the list may seem extensive, it is targeted and the resulting spatial coverage is small. Glacier Names are taken from the following reference: USGS Antarctic Research Atlas ( (V1.0) May 17, 2013

11 11 Table 3. Recommended Sites for X-band high-resolution acquisitions in Antarctica Priority level: 3 (high 6) acquisition every cycle (ongoing acquisitions) 2 (med 6) 3-5 pairs per year (2 winter, 1 summer (or 2 winter, rest evenly spread)) 3 (low 27) 1 pair per year (winter acquisition). # Name Lat Lon DLR Priority Comment (TSX) 1 PIG yes 3 WAIS 2 Thwaites Gl limited 3 WAIS 3 Pope limited 3 WAIS 4 Smith limited 3 WAIS 5 Kohler limited 3 WAIS 6 Institute Ice no 1 WAIS RONNE left stream 7 Rutford Ice no 1 WAIS RONNE left stream 8 Evans ice no 1 WAIS RONNE left stream 9 Ferrigno ice no 1 WAIS RONNE left stream 10 Venable Ice no 1 WAIS shelf 11 DeVicq Gl No InSAR 1 WAIS (Getz) 12 Hull Gl No InSAR 1 WAIS 13 Land Gl No InSAR 1 WAIS 14 Ice stream A/B Yes, one regional InSAR coverage 1 WAIS ROSS left 15 Larsen B glaciers 16 Glaciers feeding into Larsen C 17 Glaciers feeding into George VI Yes (but not regular) Some limited InSAR No for George VI, Yes for Wilkins IS 3 AP (one single coastal coordinate provided; several glaciers to be monitored) 2 AP (single coordinate in the center of the ice shelf provided; several glaciers to be monitored) 2 AP (single coordinate on the ice shelf provided; several glaciers to be monitored) 18 Denman Gl No InSAR 2 EAIS 19 Totten Gl No 2 EAIS 20 Moscow no 2 EAIS University Gl 21 Cook Ice no 2 EAIS Shelf. 22 Foundation/ no 1 EAIS RONNE - left Academy Gl. 23 Recovery Gl. - 81, One 1 EAIS RONNE - left regional coverage 24 Slessor Gl No InSAR 1 EAIS RONNE - left 25 Stancomb Some 1 EAIS Wills Gl. limited InSAR 26 Jutul yes 1 EAIS straumen Gl. 27 Belgium Gl. (big feature No InSAR 1 EAIS (V1.0) May 17, 2013

12 12 # Name Lat Lon DLR Priority Comment (TSX) in QML) 28 Shirase Gl No InSAR 1 EAIS 29 Lambert Gl no 1 EAIS 30 Philippi Gl No InSAR 1 EAIS 31 Holmes Gl no 1 EAIS 32 Frost Gl no 1 EAIS 33 Mertz Gl Yes, one 1 EAIS coverage 34 Ninnis Gl no 1 EAIS 35 David Gl No InSAR 1 EAIS 36 Mulock Gl no 1 EAIS 37 Byrd Gl Yes, full 1 EAIS ROSS - left trunk 38 Nimrod Yes, full 1 EAIS ROSS - left trunk 39 Beardmore Gl Yes, full trunk 1 EAIS ROSS - left Notes: No InSAR: some TerraSAR- X coverage available, but no InSAR pair. Regional coverage: more than one track acquired for larger area coverage. Full trunk: refers to regional coverage of TAM glaciers TerraSAR-X specific Recommendation It is recommended to expand current efforts with an InSAR background mission in Antarctica guided by the information above. Another recommendation is to provide broader access to data (similar to the recent Archive Data AO), without restriction on acquisition date TanDEM-X specific Recommendation The TanDEM- X Science Coordinator has identified a number of super sites where a data plan was prepared for multiple PI s. It is recommended to continue data acquisitions for these super sites as long as the mission is in operation COSMO SKYMED specific Recommendation The COSMO SKYMED constellation allows the collection of one- day interferograms. This capability provides another opportunity for data acquisition with continental impact: Grounding line measurement around the Antarctic continent (or a portion thereof). The grounding line is the boundary, where an ice shelf changes from touching the ground to floating. This boundary has been mapped in the past [7], however, it will change as an ice stream undergoes changes and a repeat mapping campaign is important. It is an important aspect in glacier research and can be measured using differential interferometry. A big issue in this respect is data decorrelation. Data requirement: Two 1 day interferograms for each track (a total of 4 acquisitions). Large area coverage is not required (rather targeted coverage of the coastline guided by the existing grounding line km inland). Options: Data acquisition around the entire coast (V1.0) May 17, 2013

13 13 Data acquisition in specific areas (PIG/Thwaites/Smith/Kohler; Totten/Moscow University; Getz Coast; Lambert; Ferrignot) 3.6 RADARSAT-2 Recommendations - Antarctica Since the end of the ERS- 2, ENVISAT ASAR, and ALOS- PALSAR missions, there has been no large- scale coverage of Antarctica. This data gap is widening and RADARSAT- 2 is currently the only operational C- band sensor with the capability for large area coverage in the region (TerraSAR- X and COSMO- Skymed have limited basin- wide capability, but are better suited for targeted high- resolution super sites). Even with ALOS- 2 and Sentinel- 1 launched on Schedule, required commissioning will cause a data gap of potentially two more winters. The Canadian Space Agency (CSA) together with MDA have expressed their support in trying to minimize the impact of the limited data acquisition capability over the great ice sheets. Following several discussions with CSA and MDA and a better understanding of the priorities and limitations in place, a plan for acquisitions in Antarctica was implemented that includes: 2013 data acquisition in the Pine Island and Thwaites Glacier region on a more frequent basis 2013 data acquisition in the coastal regions of Antarctica with some limited left looking acquisitions to cover areas in the interior that are known to change. Data acquisition is currently underway. The sensor will be in an eclipse during austral winter, which will limit acquisition opportunities. Following the eclipse, acquisitions are planned to resume. 3.7 Sentinel-1 Recommendations - Antarctica The Sentinel- 1 constellation will be capable of large area coverage and is expected to make a significant contribution to ice sheet monitoring. The first of two SAR satellites is scheduled to be launched in late The Sentinel- 1 mission s full operations capacity will be reached with the two- satellite constellation. The second satellite is indicatively planned to be launched 18 months after the 1st unit (full operations capacity is expected by mid 2015). During the ramp- up phase following the launch of the first unit, SAR data will be provided for operations. On Sentinel- 1, the TOPS technique is used both for the Interferometric Wide Swath (IWS) mode and the Extra Wide Swath (EWS) mode. The main goal of the TOPS is to overcome the limitations imposed by a standard ScanSAR mode (variation of SNR (V1.0) May 17, 2013

14 14 and azimuth ambiguity ratio along azimuth, scalloping etc.) by steering the antenna along track in azimuth. The IWS mode has been identified as potential compromise mode between sea ice and ice sheet community s requirements. While the former prefers large area coverage and frequent revisits with less stringent demands on resolution, the latter prefers interferometric acquisitions at high resolution. One issue to resolve is that both communities are interested in the coastal zone. The ice sheet science community has expressed interest in working with S- 1 IWS, however, the mode should be discussed more, pending analysis results for InSAR applications (a recommendation made during FRINGE 2011). The following recommendations are made for the standard operation phase: Four (4) consecutive coverages Stripmap once a year (during austral winter) in coastal areas Crossing orbits (i.e. near- simultaneous ascending AND descending coverage) would be considered an asset. If such data can be provided, they will be used. Frequent coverage using IWS mode (the entire visible area, as often as possible). Crossing orbits (i.e. near- simultaneous ascending AND descending coverage) would be preferred. It is recommended to provide a network of long tracks (coast to coast, TAM to coast) to support velocity calibration. See [4] for further details. During the ramp- up phase following satellite commissioning, the sensor capacity will be reduced. Due to the looming data gap since IPY, an early contribution by Sentinel- 1a would greatly contribute to the post IPY data pool. A recommendation for the ramp- up phase is as follows: 2 consecutive (3 preferred) coverages in IWS mode as soon as possible during the ramp- up phase (considering austral winter). Crossing orbit not required. If coverage of the entire visible area is not possible due to conflicts and or other limitations, the margins shown in Figure 1 should be covered (priority regions 1 and 2). In addition, ice sheet edges (priority regions 3) should be covered. As the mission continues, recommendations below (particularly Stripmap coverage in coastal areas) should be considered even with only a single satellite in orbit. (V1.0) May 17, 2013

15 ALOS-2 Recommendations - Antarctica The ALOS- 2 BOS (ice sheet relevant portions are presented in Appendix F) addresses crucial regions with high- resolution data once per year. The ScanSAR coverages would need to be further evaluated for their utility for ice sheet monitoring. Based on the BOS, the ice sheet science community recommends the following improvement w.r.t. ice sheet monitoring: Ideally, ALOS- 2 would contribute a coverage of the entire coastal area (3 consecutive cycles) with high- resolution data once per year (thus expanding on the current plan to monitor the West Antarctic Ice Sheet once per year) Recognizing that sensor load considerations may not allow the expansion of the coverage to the entire coast, the following recommendation is put forward for consideration: Adding Totten/Moscow University (EAIS) (V1.0) May 17, 2013

16 16 4 Greenland The IPY effort provided high- resolution time series of a number of large outlet glaciers as well as a complete coverage of Greenland [2,8]. The coastal regions of Greenland are undergoing significant changes [3,5]. Frequent coverage is therefore warranted. Unlike Antarctica, right looking imaging provides full coverage for Greenland. The community acknowledges that the sea ice monitoring requirements are not necessarily compatible with ice sheet monitoring requirements. The need to compromise is understood and the sensor specific recommendations were developed with these considerations in mind. 4.1 General Observation Requirement Annual coverage of all of Greenland with at least 3 consecutive cycles Arctic winter observations. More cycles are considered an asset. Time of Year: December to March. A secondary full coverage each year would be an asset (3 cycles). Suggested timing for such a secondary campaign would be July- September. Less correlation can be expected due to summer conditions, but seasonal variability would be captured. More coverages in Arctic winter would also be an important science contribution (to reduce errors). More frequent observations of critical areas with every possible acquisition of selected tracks (see section 5.5). Acquire ascending and descending coverages. This aspect would allow the use of the interferometric phase for improved accuracy. 4.2 Reduced Observation Requirement (if sensor capacities require scale down) Annual coverage of all of coastal Greenland with at least 3 consecutive cycles (Arctic winter acquisitions preferable). Full coverage every second year. Provide additional coverages of coastal regions. (V1.0) May 17, 2013

17 Figure 2. Prioritized coastal regions in Greenland for a reduced acquisition requirement (1: highest priority, 5: lowest priority). 4.3 Science Mission Requirement (assuming no conflicts with other priorities) Ongoing coverage of the entire area (ascending and descending). Acquisition of additional tracks covering large outlet glaciers with higher resolution modes. 4.4 Specific Considerations - Greenland L- band: Most critical in Southern Greenland, specifically SE (C- band decorrelation was encountered when using 35 day repeat orbit data.) Full coverage desired. Long tracks (coast to coast) aid data processing and calibration. C- band: Full coverage desired. Long tracks (coast to coast) aid data processing and calibration. X- band: Continuation of the current approach is recommended more frequent coverage of smaller, high impact regions. (V1.0) May 17, 2013

18 Recommendation for X-band High-Resolution Acquisition Super Sites - Greenland Response to PSTG SAR coordination group information request regarding X- band sites for regular monitoring The PSTG SAR coordination group requested a list of sites recommended for frequent high- resolution observation. The following is a table comprised of existing TerraSAR- X time series resulting from super sites and AOI s of individual PIs (e.g. PI: I. Joughin) augmented by recommendations from the larger community. Glacier Names are taken from [8]. (V1.0) May 17, 2013

19 19 Table 4. Recommended Sites for X-band High-Resolution Acquisitions in Greenland Priority level: 3 (high11) acquisition every cycle (ongoing acquisitions) 2 (med16) 3-5 pairs per year (2 winter, 1 summer (or 2 winter, rest evenly spread)) 3 (low26) 1 pair per year (winter acquisition) # Name Lat Lon DLR (TSX) Priority Comment 1 Kangerlussua q Strip014 asc Rel orb 163 Inc Unnamed Deception O & Unartit Strip012 dsc Rel orb 156 Inc Midgard Gl Strip009 dsc 2 Rel orb 141 Inc Helheim Strip010 asc 3 Rel orb 148 Inc No Name N/A 1 6 Ikertivaq Bay Strip010 dsc Rel orb 50 Inc Koge Bugt Bay Strip008 dsc Rel orb 126 Inc Graulv Gl Strip014 asc Rel orb 42 Inc Gyldenlove Covered by Gl. the above 10 A.P.Bernstorf f Gl., Maelkevejen Gl. 11 Skinfaxe & Rimfaxe Gl Strip009 asc Rel orb133 inc / / Strip012 dsc Rel orb50 inc />>10 12 Heimdal Gl.?? Strip006 asc Rel orbit 133 Inc />10 13 Tingmiarmiut Fjord, Mogens Heinesen Bay Strip009 dsc Rel orb126 inc Puisortoq Gl Strip010 asc Rel orb042 inc (Bay center coordinates provided) 2 Note: one more track available (center between the 2 termini) 2 2 unnamed glacier in Mogens Heinesen Bay 1 15 Unnamed Anorituup Kangerlua N,C,S 16 Kangerluluk Gl. 17 NoName1 SE corner Strip013 asc Rel orb118 Inc N/A N/A 1 (V1.0) May 17, 2013

20 20 # Name Lat Lon DLR (TSX) Priority Comment 18 NoName2 SE N/A 1 corner 19 Qooqqup Sermia and Kiattuut Sermiat Strip007 dsc Rel orb35 inc Qajuuttap Sermia 21 Eqalorutsit Killiit Sermiat Strip013 dsc Rel orb126 inc Strip010 dsc Rel orb35 inc SW 22 Sermilik Brae Strip014 asc 1 End of gap Rel orb103 inc Ukaasorsuaq N/A 1 24 Avannarleq Brae N/A 1 25 Kangiata Nunaata Sermia and Akullersuup Se; Strip006 dsc Rel orb96 inc Narsap Se N/A 3 27 Russel Gletscher Strip013 asc Rel orb 103 Inc Jakobshavn Isbrae Strip008 dsc Rel orb5 inc Include the region SW of this (vel gap in the map) 3 3 Strip014 dsc Rel orb20 inc />10 upstream Strip008 dsc Rel orb5 inc />10 trunk 29 3 GL: Sermeq Kujalleq (middle) Strip013 dsc Rel orb96 inc Store Gl Strip014 dsc Rel orb96 inc Rink Isbrae Strip012 asc Rel orb27 inc Upernavik Isstrom (System of 3 glaciers) 33 Kavifaat Sermiat Strip007 asc Rel orb118 inc Strip009 asc Rel orb27 Inc Ussing Braeer Strip009 asc Rel orb27 Inc Illullip Sermia 36 Hayes Gletscher Strip007 asc Rel orb118 inc Strip009 asc Rel orb 27 Inc Sverdrup Gl Strip010 dsc Rel orb127 inc More tracks available 3 Note: This Region is an ESA ice sheet CCI test AOI and was therefore changed in priority 1 Scene center given 1 Scene center given 2 Scene center given 2 Scene center given 2 (V1.0) May 17, 2013

21 21 # Name Lat Lon DLR (TSX) Priority Comment 38 Nansen Gl Strip 009desc 1 Scene center given Rel orb36 Inc Kong Oscar Gl Strip008 dsc Rel orb112 Inc Rink Gl Strip007 asc Rel orb 27 Inc Morell Gl Strip010 asc Rel orb 12 Inc Carlos Gl Strip011 Rel orb 88 Inc Savissuaq Gl Strip011 asc Rel orb 164 Inc Harald Moltke Brae Strip014 asc Rel orb 149 Inc Heilprin Gl Strip007 asc Rel orb 103 Inc Humboldt Gl Strip 011 dsc Rel orb 82 Inc Peterman Gl Strip012 asc Rel orb42 Inc Ryder Gl Strip014 asc Rel orb72 Inc Academy Gl Strip012 asc Rel orb 147 Inc Hagen Brae Strip009 dsc Rel orb 96 Inc Nioghalvfjerd sfjorden (79 North) 52 Zachariae Isstom 53 Daugaard- Jensen Strip 011 desc Rel orb65 Inc Strip 008 desc Rel orb 141 Inc Strip007 asc Rel orb 117 Inc Scene Center Note: Do not confuse with Rink Isbrae 1 Scene center given Scene center given Note: / Strip009 asc Rel orb 57 Inc Scene center provided This orbit seems to provide slightly better coverage of the trunk, but: fewer scenes in archive (3 only in archive 2010) 1 Scene center given 1 Scene center given 1 Scene center given 3 Scene center given 3 Scene center given (One more pair upstream acquired) 1 Scene center given Note: One pair upstream and one pair terminus also available Note that if the line refers to a specific TerraSAR- X scene, neighboring glaciers that are not named here are also covered by the data. (V1.0) May 17, 2013

22 TerraSAR-X Specific Recommendation It is recommended to expand current efforts with an InSAR background mission in Antarctica guided by the information provided in Table 4. Another recommendation is to provide broader access to data (similar to the recent Archive Data AO), without restriction on acquisition date TanDEM-X Specific Recommendation The TanDEM- X Science Coordinator has identified a number of super sites where a data plan was prepared for multiple PIs. It is recommended to continue data acquisitions for these super sites as long as the mission is in operation COSMO SKYMED Specific Recommendation For COSMO SKYMED it is recommended to acquire near- simultaneous ascending and descending one- day interferograms of selected outlet glaciers for high precision velocity measurements. Table 4 can provide guidance for the selection of sites. 4.6 RADARSAT-1 Recommendations - Greenland Since the end of the ERS- 2, ENVISAT ASAR, and ALOS- PALSAR missions, there has been no large- scale coverage of Greenland. Even with ALOS- 2 and Sentinel- 1 launched on schedule, required commissioning will cause a data gap of potentially two more winters. The Canadian Space Agency (CSA) together with MDA, the Norwegian Space Centre (NSC), and KSAT have worked together to acquire RADARSAT- 1 data over Greenland from January 2013 to the end of the mission in late March. The plan was to carry out a full coverage (3 repeat cycles, fine mode data) of the Greenland ice sheet during the 2012/2013 Arctic winter. While a large portion of the data was acquired, the premature end of the mission in late March 2013 led to some data gaps. It is recommended to close these gaps using other missions between September and December Sentinel-1 Recommendations - Greenland The Sentinel- 1 constellation is described in detail in Section 3.7. The following recommendations are made for the standard operation phase: Four (4) consecutive coverages Stripmap once a year (during Arctic winter) in coastal areas (V1.0) May 17, 2013

23 23 Crossing orbits (i.e. near- simultaneous ascending AND descending coverage) would be considered an asset. If such data can be provided, they will be used. Frequent coverages using IWS mode (the entire visible area, as often as possible). Crossing orbits (i.e. near- simultaneous ascending AND descending coverage) would be preferred. It is recommended to provide long, coast- to- coast tracks to support velocity calibration. See [4] for further details. During the ramp- up phase following satellite commissioning, the sensor capacity will be reduced. Due to the looming data gap since IPY, an early contribution by Sentinel- 1a would greatly contribute to the post IPY data pool. A recommendation for the ramp- up phase is as follows: 2 consecutive (3 preferred) coverages in S1- IWS mode during Arctic winter as soon as possible during the ramp- up phase. Crossing orbit not required. As the mission continues, recommendations below (particularly Stripmap coverage in coastal areas) should be considered even with only a single satellite in orbit. 4.8 ALOS-2 Recommendations - Greenland The ALOS- 2 BOS addresses crucial regions with high- resolution data once per year. The ScanSAR coverages would need to be further evaluated for their utility for ice sheet monitoring. Based on the BOS, the ice sheet science community recommends the following improvement of the BOS w.r.t. ice sheet monitoring: Ideally, ALOS- 2 would contribute a coverage of the entire coastal area (3 consecutive cycles preferably in Arctic winter) with high- resolution data once per year (thus expanding on the current plan to monitor the Northwest Coast of Greenland once per year) Recognizing that sensor load considerations may not allow the expansion of the coverage to the entire coast, the following recommendation is put forward for consideration: Adding the Southeast Coast of Greenland (V1.0) May 17, 2013

24 24 5 Data Available Table 5 provides an overview of currently available InSAR based ice sheet products All data sets are compiled using data from several international SAR missions and are an IPY contribution. Table 5. InSAR based Ice sheet products currently available at NSIDC. Product ID Principal Data Set Title Investigator NSIDC I. Joughin MEaSUREs Greenland Ice Velocity Map from InSAR Data html NSIDC I. Joughin MEaSUREs Greenland Ice Velocity: Selected Glacier Site Velocity Maps from InSAR html NSIDC E. Rignot MEaSUREs InSAR- Based Antarctica Ice Velocity Map html NSIDC E. Rignot MEaSUREs Antarctic Grounding Line from Differential Satellite Radar Interferometry html NSIDC E. Rignot MEaSUREs InSAR- Based Ice Velocity Maps of Central Antarctica: 1997 and html In addition to the above mentioned products, ice velocity products from the RADARSAT Antarctic Mapping Project (RAMP) are available online: Future data sets include Essential Climate Variable (ECV) information from the ESA Ice Sheet Climate Change Initiative (CCI): icesheets- cci.org/ The following references provide details on the data sets: Joughin, I., B. Smith, I. Howat, T. Scambos, and T. Moon Greenland Flow Variability from Ice- Sheet- Wide Velocity Mapping. Journal of Glaciology 56(197): Rignot, E., J. Mouginot, and B. Scheuchl Ice Flow of the Antarctic Ice Sheet. Science 333(6048): Rignot, E., J. Mouginot, and B. Scheuchl Antarctic Grounding Line Mapping from Differential Satellite Radar Interferometry. Geophyical Research Letters 38: L Scheuchl, B., J. Mouginot, and E. Rignot Ice Velocity Changes in the Ross and Ronne Sectors Observed Using Satellite Radar Data from 1997 and The Cryosphere (6): Jezek, K.C The RADARSAT- 1 Antarctic Mapping Project. BPRC Report No., 22, Byrd Polar Research Center, The Ohio State University. Columbus, OH, 64 pages. (V1.0) May 17, 2013

25 25 6 References [1] GIIPSY Science Requirement document (Nov. 3, 2006) last accessed on May 21, 2012 [2] Joughin, I., B. Smith, I. M. Howat, T. Scambos, and T. Moon Greenland Flow Variability from Ice- Sheet- Wide Velocity Mapping. Journal of Glaciology 56 (197), pp [3] Moon, T., I. Joughin, B. Smith, I. Howat st- Century Evolution of Greenland Outlet Glacier Velocities, Science, Vol. 336 (6081): pp doi /science [4] Mouginot J., Scheuchl B., Rignot E. Mapping of Ice Motion in Antarctica Using Synthetic- Aperture Radar Data. Remote Sensing. 2012; 4(9): [5] Pritchard, H. D., Arthern, R. J., Vaughan, D. G., and Edwards, L. A Extensive dynamic thinning on the margins of the Greenland and Antarctic ice sheets, Nature, 461: , doi: /nature08471 [6] Rignot, E., J. Mouginot, and B. Scheuchl Ice Flow of the Antarctic Ice Sheet, Science, Vol. 333(6048): doi /science [7] Rignot, E., J. Mouginot, and B. Scheuchl Antarctic Grounding Line Mapping from Differential Satellite Radar Interferometry, Geophysical Research Letters, 38, L10504, doi: /2011gl [8] Rignot, E. and J. Mouginot Ice flow in Greenland for the International Polar Year , Geophys. Res. Lett., doi: /2012gl051634, in press. [9] Rott, H., Müller, F., Nagler, T., and Floricioiu, D The imbalance of glaciers after disintegration of Larsen- B ice shelf, Antarctic Peninsula, The Cryosphere, 5, , doi: /tc , [10] Scheuchl, B., Mouginot, J., and Rignot, E., Ice velocity changes in the Ross and Ronne sectors observed using satellite radar data from 1997 and 2009, The Cryosphere, 6, , doi: /tc [11] Fringe 2011 Workshop Sorted Recommendations ations_final.pdf (last accessed on May 30, 2012) [12] Gardner, A.S., Moholdt, G., Wouthers, B., Wolken, G.J., Burgess, D.O., Sharp, M.J., Cogley, J.G., Braun, C., Labine, C Sharply Increased Mass Loss from Glaciers and Ice Caps in the Canadian Arctic Archipelago. Nature 473, pp [13] Short, N.H and Gray, A.L Glacier dynamics in the Canadian High Arctic from Radarsat- 1 speckle tracking. Canadian Journal of Remote Sensing 31 (3), pp [14] Van Wychen, W., Copland, L., Gray, L., Burgess, D., Danielson, B., Sharp, M Spatial and Temporal Variation of Ice Motion and Ice Flux from Devon Ice Cap, Nunavut, Canada. Journal of Glaciology 58 (210), pp [15] Hvidberg, C.S., et al., 2012 User Requirements Document for the ice_sheets_cci project of ESA's Climate Change Initiative, version 1.4, 29. May Report: ST- DTU- ESA- ISCCI- URD- 001 (V1.0) May 17, 2013

26 26 [16] Stearns, L. A., Smith, B. E., and Hamilton, G. S Increased flow speed on a large East Antarctic outlet glacier caused by subglacial floods, Nat. Geosci., 1, , [17] IGOS, Integrated Global Observing Strategy Cryosphere Theme Report - For the Monitoring of our Environment from Space and from Earth. Geneva: World Meteorological Organization. WMO/TD- No pp. cryosphere.org/documents.html [18] GCOS, 2010, Implementation plan for the global observing system for climate in support of the UNFCCC (2010 update), GCOS- 138, (GOOS- 184, GTOS- 76, WMO- TD/No. 1523) [19] GCOS, 2011, Systematic observation requirements for satellite- based data products for climate, 2011 update. Supplemental details to the satellite- based component of the Implementation plan for the global observing system for climate in supoort of the UNFCCC (2010 update), GCOS- 154 [20] Allison, I., Barry, R. G., and Goodison, B. E. (Editors), Climate and Cryosphere (CliC) Project. Science and coordination plan, Version 1, WCRP- 114, WMO/TD No [21] A Compilation of Recommendations from the IGOS Cryosphere Theme Report, 10 November [22] Radic, V. and Hock, R., Regionally differentiated contribution of mountain glaciers and ice caps to future sea- level rise. Nature Geoscience, 4, 91 94, doi: /ngeo1052 [23] Dowdeswell, J.A. and Hagen, J.O Arctic ice masses. Chapter 15. In: J.L. Bamber and A.J. Payne (eds.). Mass Balance of the Cryosphere. Cambridge University Press, 712 pp. [24] Hogg, A. E. Shepherd, S. Engdahl, M. Jung, H. S CAFTS: A Coherence and Feature Tracking Study for Sentinel- 1, Earth Observation and Cryosphere Science Conf. Frascati, Italy, November 2012 (ESA SP- 712, May 2013) [25] Fernandez- Prieto et al Earth Observation and Cryosphere Science: The Way Forward, Proc. 'Earth Observation and Cryosphere Science Conf.' Frascati, Italy, November 2012 (ESA SP- 712, May 2013) [26] M.Drinkwater, K. Jezek, E.Sarukhanian, T. Mohr IPY Satellite Observation Program, Chapter 3.1 in "Understandig Earth's Polar Challenges: International Polar Year ", Summary report by IPY Joint Committee, WMO/ICSU, p [27] Jezek, K.C The RADARSAT- 1 Antarctic Mapping Project. BPRC Report No., 22, Byrd Polar Research Center, The Ohio State University. Columbus, OH, 64 pages. (V1.0) May 17, 2013

27 27 7 Acronyms ASI Agenzia Spaziale Italiana (Italy) AGU American Geophysical Union AOI Area of Interest BOS Basic Observation Scenario (ALOS- 2) CCI Climate Change Initiative CFL Calving Front Location CliC Climate and Cryosphere Project CONAE Comisión Nacional de Actividades Espaciales (Argentina) CSA Canadian Space Agency DLR Deutsches Zentrum für Luft- und Raumfahrt (Germany) EAIS East Antarctic Ice Sheet ECV Essential Climate Variable EGU European Geosciences Union EOS Earth Observing System ESA European Space Agency EWS Extra Wide Swath Mode (Sentinel- 1) GCOS Global Climate Observing System GIIPSY Global Inter- agency IPY Polar Snapshot Year GLL Grounding Line Location GMES Global Monitoring for Environment and Security (now Copernicus) HH Horizontal transmit, horizontal receive IASC International Arctic Science Committee IGOS Integrated Global Observing Strategy InSAR Interferometric SAR IPY International Polar Year ISMASS Expert Group on Ice Sheet Mass Balance and Sea Level ISRO Indian Space Research Organisation IV Ice Velocity IWS Interferometric Wide Swath Mode (Sentinel- 1) JAXA Japan Aerospace Exploration Agency KSAT Kongsberg Satellite Services MDA MacDonald, Dettwiler and Associates Ltd. MEaSUREs. Making Earth System Data Records for Use in Research Environments (A NASA program) NASA National Aeronautics and Space Administration NDRCC/SEPA.. National Committee for Disaster Reduction and State Environmental Protection Administration of China NetCDF A set of software libraries and self- describing, machine- independent data formats that support the creation, access, and sharing of array- oriented scientific data NSC Norwegian Space Centre PARCA Program for Regional Climate Assessment PSTG Polar Space Task Group RAMP RADARSAT Antarctic Mapping Program SAR Synthetic Aperture Radar SCAR Scientific Committee on Antarctic Research SEC Surface Elevation Change STG Space Task Group TAM Transantarctic Mountains UNFCCC United Nations Framework Convention on Climate Change USGS United States Geological Survey WAIS West Antarctic Ice Sheet WMO World Meteorological Organization (V1.0) May 17, 2013

28 28 8 Appendix A: Summary of Recommendations for RADARSAT-1 and RADARSAT-2 The Canadian Space Agency (CSA) together with MDA have expressed their support in trying to minimize the impact of the current limited data acquisition capability over the great ice sheets. 8.1 Antarctica Following several discussions with CSA and MDA and a better understanding of the priorities and limitations in place, a plan for acquisitions in Antarctica was implemented that includes: 2013 data acquisition in the Pine Island and Thwaites Glacier region on a more frequent basis data acquisition in the coastal regions of Antarctica with some limited left looking acquisitions to cover areas in the interior that are known to change. Data acquisition is currently underway. The sensor will be in an eclipse during austral winter, which will limit acquisition opportunities. Following the eclipse, acquisitions are planned to resume. 8.2 Greenland Since the end of the ERS- 2, ENVISAT ASAR, and ALOS- PALSAR missions, there has been no large- scale coverage of Greenland. Even with ALOS- 2 and Sentinel- 1 launched on schedule, required commissioning will cause a data gap of potentially two more winters. The Canadian Space Agency (CSA) together with MDA, the Norwegian Space Centre (NSC), and KSAT have worked together to acquire RADARSAT- 1 data over Greenland from January 2013 to the end of the mission in late March. The plan was to carry out a full coverage (3 repeat cycles, fine mode data) of the Greenland ice sheet during the 2012/2013 Arctic winter. While a large portion of the data was acquired, the premature end of the mission in late March 2013 led to some data gaps. It is recommended to close these gaps using other missions between September and December (V1.0) May 17, 2013

29 29 9 Appendix B: Summary of Recommendations for High-Resolution X-band Sensors (TerraSAR-X, TanDEM-X, and COSMO-Skymed) This section was written in response to a PSTG SAR coordination group information request regarding X- band high- resolution sites for regular monitoring. A single track selected at or upstream of the grounding line will provide vital information without requiring large area overage from the sensor in question. The sensors addressed include TerraSAR- X, TanDEM- X and the COSMO SKYMED constellation. Tables 3 and 4 of this document summarize a prioritized set of glaciers in Antarctica and Greenland for regular coverage with a high- resolution X- band sensor. The tables are comprised of existing TerraSAR- X time series resulting from super sites and AOI s of individual PI s augmented by recommendations from the larger community. While the list may seem extensive, it is targeted and the resulting spatial coverage is small. 9.1 TerraSAR-X specific Recommendation It is recommended to expand current efforts with an InSAR background mission in Antarctica guided by the information provided in Table 3. Another recommendation is to provide broader access to data (similar to the recent Archive Data AO), without restriction on acquisition date. 9.2 TanDEM-X specific Recommendation The TanDEM- X Science Coordinator has identified a number of super sites where a data plan was prepared for multiple PIs. It is recommended to continue data acquisitions for these super sites as long as the mission is in operation. 9.3 COSMO SKYMED specific Recommendation The COSMO SKYMED constellation allows the collection of one- day interferograms. This capability provides another opportunity for data acquisition with continental impact Antarctica COSMO SKYMED constellation provides an opportunity for grounding line measurement around the Antarctic continent (or a portion thereof). The grounding line is the boundary, where an ice shelf changes from touching the ground to floating. This boundary has been mapped in the past [7], however, it will change as an ice stream undergoes changes and a repeat mapping campaign is important. It is an important aspect in glacier research and can be measured using differential interferometry. A big issue in this respect is data decorrelation. Data requirement: Two 1- day interferograms for each track (a total of 4 (V1.0) May 17, 2013

30 30 acquisitions). Large area coverage is not required (rather targeted coverage of the coastline guided by the existing grounding line km inland). Options: Data acquisition around the entire coast Data acquisition in specific areas (PIG/Thwaites/Smith/Kohler; Totten/Moscow University; Getz Coast; Lambert; Ferrignot) Greenland For COSMO SKYMED it is recommended to acquire near- simultaneous ascending and descending one- day interferograms of selected Greenland outlet glaciers for high precision velocity measurements. Table 4 provides guidance for the selection of sites. (V1.0) May 17, 2013

31 31 10 Appendix C: Summary of Recommendations for Sentinel-1 The Sentinel- 1 constellation will be capable of large area coverage and is expected to make a significant contribution to ice sheet monitoring. The first of two SAR satellites is scheduled to be launched in late The Sentinel- 1 mission full operations capacity will be reached with the two- satellite constellation. The second satellite is indicatively planned to be launched 18 months after the 1st unit (full operations capacity is expected by mid 2015). During the ramp up phase following the launch of the first unit SAR data will be provided for operations General Recommendations On Sentinel- 1, the TOPS technique is used both for the Interferometric Wide Swath (IWS) mode and the Extra Wide Swath (EWS) mode. The main goal of the TOPS is to overcome the limitations imposed by a standard ScanSAR mode (variation of SNR and azimuth ambiguity ratio along azimuth, scalloping etc.) by steering the antenna along track in azimuth. The IWS mode has been identified as potential compromise mode between sea ice and ice sheet community s requirements. While the former prefers large area coverage and frequent revisit with less stringent demands on resolution, the latter prefers interferometric acquisitions at high resolution. One issue to resolve is that both communities are interested in the coastal zone. The ice sheet science community has expressed interest in working with S- 1 IWS, however, the mode should be discussed more pending analysis results for InSAR applications (a recommendation made during FRINGE 2011) Ramp-up Phase Recommendations (Antarctica and Greenland) During the ramp up phase following satellite commissioning, the sensor capacity will be limited. Due to the looming data gap since IPY, an early contribution by Sentinel- 1a would greatly contribute to the post IPY data pool. A recommendation for the ramp- up phase is as follows (valid for Antarctica and Greenland): 2 consecutive (3 preferred) coverages of the entire ice sheet (i.e. the visible area) in IWS mode as soon as possible during the ramp- up phase. (considering regional winter). Crossing orbit not required. o For Antarctica coverage of the entire visible area may not possible due to conflicts and or other limitations. In this case the margins shown in Figure 1 should be covered (priority regions 1 and 2). In addition, ice sheet edges (priority regions 3) should be covered. As the mission continues, recommendations below (particularly Stripmap coverage in coastal areas) should be considered even with only a single satellite in orbit. (V1.0) May 17, 2013

32 Sentinel-1 Recommendations - Antarctica The following recommendation are made for the standard operation phase: Four (4) consecutive coverages Stripmap once a year (during austral Winter) in coastal areas. o Crossing orbits (i.e. near- simultaneous ascending AND descending coverage) would be considered an asset. If such data can be provided, they will be used. Frequent coverages using IWS mode (the entire visible area, as often as possible). o Crossing orbits (i.e. near- simultaneous ascending AND descending coverage) would be preferred. It is recommended to provide a network of long tracks (coast to coast, TAM to coast) to support velocity calibration. See [4] for further details Sentinel-1 Recommendations - Greenland The following recommendation are made for the standard operation phase: Four (4) consecutive coverages Stripmap once a year (during Arctic winter) in coastal areas. o Crossing orbits (i.e. near- simultaneous ascending AND descending coverage) would be considered an asset. If such data can be provided, they will be used. Frequent coverages using IWS mode (the entire visible area, as often as possible). o Crossing orbits (i.e. near- simultaneous ascending AND descending coverage) would be preferred. It is recommended to provide long, coast- to- coast tracks to support velocity calibration. See [4] for further details. (V1.0) May 17, 2013

33 33 11 Appendix D: Summary of Recommendations for ALOS-2 The ALOS- 2 BOS addresses crucial regions with high- resolution data once per year. ALOS PALSAR data played a crucial role in ice velocity maps of Antarctica and Greenland [2,8]. The ScanSAR coverages would need to be further evaluated for their utility for ice sheet monitoring. The following recommendations for improvement are therefore made for the ALOS- 2 BOS: 11.1 ALOS-2 Recommendations - Antarctica Based on the BOS, the ice sheet science community recommends the following improvement w.r.t ice sheet monitoring: Ideally, ALOS- 2 would contribute a coverage of the entire coastal area (3 consecutive cycles) with high- resolution data once per year (thus expanding on the current plan to monitor the West Antarctic Ice Sheet once per year) Recognizing that sensor load considerations may not allow the expansion of the coverage to the entire coast, the following recommendation is put forward for consideration: Adding Totten/Moscow University (EAIS) 11.2 ALOS-2 Recommendations - Greenland Based on the BOS, the ice sheet science community recommends the following improvement of the BOS w.r.t. ice sheet monitoring: Ideally, ALOS- 2 would contribute a coverage of the entire coastal area (3 consecutive cycles) with high- resolution data once per year (thus expanding on the current plan to monitor the Northwest Coast of Greenland once per year) Recognizing that sensor load considerations may not allow the expansion of the coverage to the entire coast, the following recommendation is put forward for consideration: Adding the Southeast Coast of Greenland (V1.0) May 17, 2013

34 34 12 Appendix E: Areas Containing Mountain Glaciers and Ice Caps 12.1 Background and Overview This main purpose of this document is to provide science and data acquisition requirements for ice sheets. The World Glacier Monitoring Service (WGMS) was represented at the 2012 PSTG meeting in Geneva regarding glacier requirements. Following some discussion during the public review phase of this document it was decided to include other regions than Antarctica and Greenland in this section. These regions include areas containing mountain glaciers and ice caps (in no particular order): Canadian Arctic Svalbard Russian Arctic Iceland (glaciers in the area are affected by sub- glacial volcanism) Himalaya Alaska Patagonia European Alps and Norway Shape files of all glaciers in the world are available from the Randolph Glacier Inventory (RGI) at: The dataset is undergoing improvements but provides an indication where glaciers are located. The following sections provide some general information and recommendations. It should be noted that recommended incidence angle ranges as well as acquisition intervals for velocity mapping depend on various factors (sometimes even within a region). For detailed acquisition planning it is therefore important to obtain region specific requirements. (V1.0) May 17, 2013

35 Canadian Arctic Ice masses located in the Canadian Arctic represent one- third of the global volume of land ice outside of the ice sheets, and have recently been identified as the largest contributor to sea- level rise outside of Greenland and Antarctica [12]. Despite this, relatively little is known about the motion of most of these ice masses, which limits understanding of their flux rates and how these and iceberg calving rates may change in a warming climate. As such, it is essential to continue acquisition of SAR imagery to provide up- to- date ice motion maps of the Canadian Arctic, to refine estimates of mass fluxes, and to aid in the interpretation of mass balance changes. It should be noted that RADARSAT- 2 acquisition plans over the Canadian Arctic are already in place at CSA. Recommendations mentioned here are more general to raise awareness within PSTG General Observation Requirement (ideal case) Ongoing coverage of the entire AOI each year from October to May. RADARSAT- 2 Fine Wide mode (or equivalent), HH polarization is preferred. High resolution (e.g. Radarsat- 2 Ultrafine wide 3 m or equivalent mode) monitoring of 15 target glaciers (tidewater/surge) within the AOI each year from October to May Reduced Observation Requirement (given sensor capacities) Annual coverage (RADARSAT- 2 fide wide beam or equivalent mode) of the entire AOI with at least 4 consecutive cycles January to May. More cycles are considered an asset. Ongoing acquisitions (RADARSAT- 2 Ultrafine wide or equivalent mode) over 15 target glaciers (tidewater/surge) within the AOI from October to May. Specific considerations: For RADARSAT and RADARSAT- 2, expect conflicts for Canadian SAR missions due to other priorities (e.g., Canadian Department of National Defense, Canadian Ice Service). C- Band: Full coverage (RADARSAT- 2 fine wide beam and ultrawide fine beam or equivalent mode) desired as previous studies have shown the utility of C- Band within the Canadian Arctic as well as maintaining continuity with current work [13,14]. (V1.0) May 17, 2013

36 Svalbard and Russian Arctic While much of the focus has been on the Greenland ice sheet, mountain glaciers and ice caps in the Arctic are at present, and will over the present century, be a large source of eustatic sea level change [22]. One of the large issues at present is to improve the knowledge of how the dynamics of ice masses may change due to warming. Svalbard is an Arctic archipelago at around 80 N and Austfonna and Vestfonna are the two major ice- caps on the second largest island (Nordaustlandet). These ice- caps represent one of the largest ice- covered areas in the Eurasian Arctic [23] and were the subject of various past studies on surface ice- velocity. As such, it is essential to continue acquisition of SAR imagery to provide up- to- date ice motion maps of Svalbard, to refine estimates of mass fluxes, and to aid in the interpretation of mass balance changes General Observation Requirement Annual coverage of the entire AOI with at least 4 consecutive cycles January to May. More cycles are considered an asset. Stripmap mode (e.g. RADARSAT- 2 Fine Wide HH polarization or equivalent) preferred. Sentinel- 1 coverages in Stripmap during Arctic winter are preferred Reduced Observation Requirement (given sensor capacities) TOPS mode (ScanSAR like mode, e.g. Sentinel- 1 IWS) annual coverage of the entire AOI with at least 4 consecutive cycles January to May. More cycles are considered an asset. Specific considerations: L- band: Most critical for InSAR (winter time, 2-3 consecutive cycles). Ascending and descending coverage - this aspect would allow the use of the interferometric phase for improved accuracy. C- band: continuous acquisition desired, as an extension of ERS SAR and Envisat ASAR programs. RADARSAT (Standard mode - 25 m or higher resolution), High- resolution Sentinel images. (V1.0) May 17, 2013

37 Mountainous Glaciers (Andes, Rocky Mountains, Himalaya-Karakoram-TienShan, Patagonia, New Zealand Alps, European Alps, Alaska) So- called peripheral glaciers and ice caps are often characterized by very steep topography and comparably small glaciers, limiting the applications of microwave data for surface velocity estimation. However, the increasing resolution of SAR sensors enables mapping of surface flow and velocity changes over time even for smaller mountain glaciers and glaciers surges. ALOS PALSAR 46- day repeat winter imagery, TerraSAR- X 11- day to 5 months interval acquisition and ERS/ENVISAT images with one year time separation have been successfully been applied using intensity feature tracking techniques. Shorter wavelengths are known to perform less in the accumulation area of glaciers where few structures are present. For surface velocity mapping, the optimal time interval is dependent on sensor spatial resolution, sensor frequency, glacier flow velocity as well as observable structures and feature preservation over time. On the other hand, radar sensors are used on mountainous glaciers for improved mapping of debris- covered glaciers using coherence images acquired over a short- repeat period in summer (on the order of days). In the past, ALOS- 1 PALSAR 46- days coherence images were found to have the most suitable contrast. In the future, it is expected that a similar procedure can be applied to Sentinel day image pairs General Observation Requirement Ongoing coverage of mountain glaciers (Andes (incl. Patagonia), Rocky Mountains, Himalaya- Karakoram- TienShan, New Zealand Alps, European Alps, Alaska) during summer months. Stripmap mode is preferred (C- or L- band) or high- resolution X- band data. For surface velocities at least one repeat winter coverage of glaciers Ascending and descending coverage to minimize layover/shadowing effects Specific considerations: For surface velocities of fast Alaskan (e.g. Hubbard, Columbia, Bering) and Patagonian outlet glaciers short repeat intervals (max. 22 to 24 days) and at least 4-5 observations per year are preferred due feature deformation of fast flow and known flow acceleration during summer Annual high- resolution coverage with short observation interval of tidewater glaciers in Alaska (e.g. Stikine and Juneau Icefields) and Patagonia In case of many surging and advancing glaciers in a region (e.g. Karakoram) one very high resolution repeat coverage with 11/12- day repeat has proofed to be suitable Specific acquisitions on demand for other glaciers showing surge type behaviour (e.g. Alaska, Svalbard) It should be noted that for Sentinel- 1 the proposed acquisition strategy is in line with GMES requirements (e.g. hazard assessment related to slope instability). (V1.0) May 17, 2013

38 38 13 Appendix F: ALOS-2 Basic Observation Scenario The two slides shown here were obtained from the following presentation: Ake Rosenqvist, Masanobu Shimada, Shinichi Suzuki, Fumi Ohgushi, Hiroki Nishi, Kaoru Tsuzuku, Tomohiro Watanabe ALOS- 2 Basic Observation Scenario (BOS) (Update ) K&C Science Team meeting KC# Nov 2012 (V1.0) May 17, 2013

39 39 14 Appendix G: Ice sheet Requirements Mentioned in the Scientific and Institutional Literature 14.1 Summary of recommendations of IGOS report Recommendations: Development of Ice Sheet Observations R6.1 Implement a C- band synthetic aperture radar optimized for SAR interferometry and capable of measuring the velocity field of the whole of the Greenland and Antarctic Ice Sheets. Data from this system would also provide new estimates on grounding lines, ice edge and shear margin positions EOS Science Plan 1999 Chapter 6: The Cryosphere (V1.0) May 17, 2013

40 Global Inter- agency IPY Polar Snapshot Year (GIIPSY) In 2006, the Space Task Group identified remote sensing requirements for IPY in the Global Inter- agency IPY Polar Snapshot Year (GIIPSY) Science Requirement document [1]: The primary objective of these plans is to advance polar science by obtaining another critical benchmark of processes in the Arctic and Antarctic during the IPY and to set the stage for acquiring future benchmarks beyond IPY. The technical objective is to coordinate polar observations with spaceborne and in situ instruments and then make the resulting data and derived products available to the international science community. [1] GIIPSY Science Goal: Understand the polar ice sheets sufficiently to predict their response to climate change. [1] GIIPSY Science Objectives: Polar glaciers and ice sheets are rapidly changing. Fast glaciers and ice streams located in Southern Greenland along with fast glacier and ice shelves around West Antarctica and the Antarctic Peninsula are accelerating, thinning and retreating. Satellite data to be collected during the IPY will provide additional benchmark, legacy data sets to document the change. The data sets will also help better understand the climatological and glacial dynamic processes that control rapid changes in flow. Documenting trends and quantifying glaciological processes are important because the phenomena of rapid increases in ice sheet flow are not presently incorporated into global climate models. [1] The SAR observation objectives were identified for IPY [1]: GIIPSY Observation objectives (SAR/InSAR) Satellite data acquisition objectives for Greenland and Antarctica in 2007 and 2008 include: Winter observations (2007 and 2008) of the viewable area at L- band for InSAR mapping (3 consecutive cycles) and seasonal single- cycle SAR observations. Winter Pole to coast InSAR observations (3 consecutive cycles each in 2007 and 2008) at C- band for measuring the surface velocity field. X- band and C- band observations of select fast glaciers for studies based on InSAR, seasonal SAR, and high spatial resolution DEMS [1]. (V1.0) May 17, 2013

41 From Cryos Theme Report (2007) The following table provides current measurement capabilities and observational requirements for ice sheet parameters. In some cases observational requirements are listed separately for satellite and in situ observations because of different applications. Codes are as follows: C = Current Capability, T = Threshold Requirement (Minimum necessary), O= Objective Requirement (Target), L = Low end of measurement range, U = Unit, H = High end of measurement range, V = Value, cl = climate, op = operational. Summary of current/planned capabilities and requirements for ice sheet parameters (excerpt only with focus on SAR and InSAR) (V1.0) May 17, 2013

42 GCOS report implementation plan 2010 update Key Need 3: International and intergovernmental organizations need to incorporate the relevant Actions in this Plan within their own plans and actions. Key Need 5: Parties are encouraged to establish effective institutional responsibilities for oceanographic and terrestrial observations at the national level. Key Need 10: Parties should ensure regular and timely submission of climate data to International Data Centres for all ECVs. Key Need 25: Parties are urged to support the sustained operation of satellite instruments and the sustained generation of the satellite- based products relevant for terrestrial ECVs. Essential Climate Variable (ECV) Ice Sheets: (V1.0) May 17, 2013