Progress Report on activities by

Urs Wegmüller, Tazio Strozzi, Charles Werner

Gamma Remote Sensing AG, Gümligen, Switzerland, http://www.gamma-rs.ch, wegmuller@gamma-rs.ch

Himalayan Glacier Dynamics Project (ID 10302)

This work is supported by ESA under the Dragon 3 Project

- Swiss Corporation - SAR and INSAR competence - Active in research and development projects - Gamma SAR & INSAR Software - Gamma Portable Radar Interferometer (GPRI) - Providing services and products (deformation, biomass, …) Glacier related activities: - ESA GlobGlacier / Glacier_CCI Projects (2007 - 2013) - FP7 - Cryoland Project (2011-2014) - Glacier lake mapping projects - GPRI measurements over glaciers

Gamma Remote Sensing AG http:/ / www.gamma-rs.ch

Part 1: Methodological work Part 2: Production results over Karakorum Part 3: Field trip to Kleine Scheidegg

Contents of presentation

In the beginning of Dragon 3 our focus was on the assessment of Radar based techniques to map glacier dynamics: - Differential SAR Interferometry - SAR image offset tracking - Split-beam interferometry Now the focus is on the assessment of novel Radar sensors to map glacier dynamics using these techniques: - Sentinel-1 (and in particular IWS data) - ALOS PALSAR-2

Methodological work

Sentinel-1 (S1) Interferometric Wide-Swath (IWS )

“TOPS mode”: for each burst the radar beam scans through a wide Doppler spectrum very strong Doppler variation (Doppler ramp on each burst)

- As a consequence interpolation concepts need to be adapted - As a consequence a small azimuth co-registration error results in

an significant phase effect (about 0.1 azimuth pixel error results in a ramp of a full phase cycle in an interferogram of a burst) very high co-registration quality required (0.001 pixel)

S1 IWS SLC DInSAR procedure: 1) Geocoding of multi-look MLI mosaic ( refined geocoding lookup table,

geocoded backscatter, DEM heights in MLI SAR geometry)

2) Calculation of S1 IWS SLC co-registration lookup table (considering terrain topography)

3) Refinement of co-registration using intensity matching procedures

4) Refinement of co-registration using spectral diversity method (considering double difference phase of burst overlap regions)

5) S1 IWS burst SLC resampling to master geometry (considering procedure that takes into account the strong Doppler Centroid variation in azimuth)

6) Generation of mosaic SLC and mosaic MLI

7) Simulation of topographic phase

8) Calculation of differential interferogram

S1 IWS SLC DInSAR example: Nepal

Nepal earthquake: Co-seismic, 20150417_20150429 Color scale: 100mm los displ. / color cycle

PALSAR-2 ScanSAR SLC DInSAR example: Nepal

Nepal earthquake: Co-seismic, 20150405_20150503 Color scale: 100mm los displ. / color cycle

S1 IWS usefulness for glaciers

Feasibility - Differential SAR Interferometry demonstrated - SAR image offset tracking demonstrated - Split-beam interferometry demonstrated Potential - To be further elaborated - Initial results are not too convincing for the mountain glaciers yet - 12-day interval is quite long for InSAR - IWS azimuth resolution is quite low for tracking

Sentinel-1 offset tracking: Svalbard Sentinel-1 EW GRDM

19/31.03.2015 40 m ground-resolution

0 m/yr 2500

Sentinel-1 IW SLC 19/31.01.2015 – 20.01/02.01.2015

10 m ground-resolution

200 km

characteristic azimuth offsets characteristic SBI phase

Ionospheric effects:

Part 2: Production results over Karakorum

Context of work Status

Project Scope: The Glaciers_CCI project will contribute to complete the baseline inventory of glaciers worldwide and by regional change assessments. The project focuses on: - glacier area in the form of detailed glacier inventory data - change assessment for glacier parameters a) length, b) area and c) elevation - ice velocity fields (from optical and SAR sensors) Team: University of Zurich (Switzerland), University of Oslo (Norway), GAMMA Remote Sensing (Switzerland), University of Leeds (UK), ENVEO (Austria) Cooperation: World Glacier Monitoring Service (WGMS) Global Land Ice Measurements from Space (GLIMS - NASA)

ESA Glaciers CCI Project

GAMMA Contribution a) InSAR coherence for debris-covered glaciers (on-demand) b) Global set of velocity products for ice caps and glaciers Take into account already processed regions within other projects (e.g GlobGlacier, CCI Phase 1, EU FP6/FP7 projects, etc.): → 1991-1998 (ERS-1, ERS-1/2, JERS-1) → 2004-2011 (ALOS PALSAR, ENVISAT, ERS-2) Production Year 1 (2014/15): complete historical snap-shots (mainly PALSAR-1) Production Year 2 (2015/16): Sentinel-1 2015 Production Year 3 (2016/17): Sentinel-1 2016 ALOS PALSAR-2 2015/2016 ?

ALOS FBD Summer 46 days coherence

A linear gray scale between 0 (black) and 1 (white) is used

High priority Medium priority Low priority

Mapping of debris-covered glacier parts by using coherence images (20070712_20070827, ALOS PALSAR, FBD-FBD 46 days, 275 m) in the region of Chhota Shigri. The long debris-covered tongue on the eastern part of the image is Bara Shigri glacier. Red lines show the raw glacier outlines resulting from the ETM3/ETM5 ratio, corrected glacier outlines are shown in yellow. a) Shows a false-color composite of the ETM+ scene (RGB 543), b) is a coherence image from two ALOS PALSAR scenes. (Frei et al., 2012)

ALOS FBD Summer 46 days coherence

ALOS 12.07/27.08.2007 Coherence

Phase (left) and coherence (right) image, red are glacier outlines from ETM

Karakoram Summer (ALOS FBD)

0 m/year 300

Karakoram Winter (ALOS FBS)

0 m/year 300

Karakoram Summer (ALOS FBD)

0 m/year 300

Karakoram Winter (ALOS FBS)

0 m/year 300

ASAR 04.04.2004 / 25.04.2005

0 m/year 300

Sentinel-1 28.02.2015 / 12.03.2015

0 m/year 300

Svalbard (Time Series)

0 m/year 300

ERS-1/2 1995/1996 InSAR & offset-tracking

ERS-2 2011 InSAR & offset-tracking

ALOS PALSAR 2008 offset-tracking

JERS-1 1997 offset-tracking

ALOS PALSAR 2010 offset-tracking

Sentinel-1 2015 offset-tracking

Part 3: Field trip to Kleine Scheidegg

Yesterday, we undertook as our team meeting a trip to Kleine Scheidegg, where we set up GAMMA´s terrestrial Radar to measure the velocity of some ten Alpine glaciers.

Part 3: Field trip to Kleine Scheidegg

Part 3: Field trip to Kleine Scheidegg

Glaciers measured

As seen from Kleine Scheidegg (at distances of about 3 to 6 km)

Part 3: Field trip to Kleine Scheidegg

Part 3: Field trip to Kleine Scheidegg

5 km

130 degrees

GPRI backscattering

5 km

12:36 − 12:39

2π ⇔ 8.72 mm @ 17.2 GHz

Interferogram: 3 minutes

5 km

12:08 − 12:39

2π ⇔ 8.72 mm @ 17.2 GHz

Interferogram: 30 minutes

5 km

12:08 − 13:12

2π ⇔ 8.72 mm @ 17.2 GHz

Interferogram: 63 minutes

5 km

12:08 − 14:12

2π ⇔ 8.72 mm @ 17.2 GHz

Interferogram: 123 minutes