ADEN ALOS PALSAR CYCLIC REPORT 09 SEPTEMBER 2008 TO 25 OCTOBER 2008 · 2015. 3. 27. ·...

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PALSAR_CR_22_080909_081025

ADEN ALOS PALSAR CYCLIC REPORT

09 SEPTEMBER 2008 TO 25 OCTOBER 2008

Fine mode PALSAR imagery acquired over Shanghai on the 27th of August 2008, taken from frames 600 and 610 of orbit 13807. The Donghai bridge and large areas of reclaimed land are

visible.

PUBLIC SUMMARY � �� IDEAS SAR Team � �� PALSAR_CR_22_080909_081025 � � � � � �� 1 �� 0 � � �� 07 November 2008 � �� Approved � � � � � � � ��

Technical Note

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A P P R O V A L

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ALOS PALSAR Cyclic Report – Cycle 22 � � � � ��

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IDEAS SAR Team � � ��

07 November 2008

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C H A N G E L O G

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Initial Issue 1 0 07 November 2008

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T A B L E O F C O N T E N T S

1 INTRODUCTION...............................................................................................................5 1.1 Acronyms and Abbreviations ....................................................................................................... 5 1.2 Reference Documents................................................................................................................... 5 1.3 Background Information............................................................................................................... 6

2 SUMMARY........................................................................................................................7

3 SOFTWARE AND AUXILIARY FILE VERSION CONFIGURATION................................9

4 PDS STATUS..................................................................................................................10 4.1 Planned Instrument Unavailability...............................................................................................10 4.2 Unplanned Instrument Unavailability ..........................................................................................10 4.3 Current Platform Status ...............................................................................................................10 4.4 Upcoming Instrument Unavailability ...........................................................................................11 4.5 ADEN PDS Unavailability ..........................................................................................................11 4.6 Periods of missing precision orbit data.........................................................................................11 4.7 Periods of missing precision attitude data ....................................................................................12 4.8 Periods lacking Yaw steering.......................................................................................................12 4.9 JAXA Observation Strategy ........................................................................................................12

5 DATA QUALITY CONTROL...........................................................................................13 5.1 Instrument related anomalies .......................................................................................................13 5.2 Processor related anomalies.........................................................................................................13 5.3 Daily Report Issues .....................................................................................................................13 5.4 User Queries................................................................................................................................13

6 CALIBRATION/VALIDATION ACTIVITIES AND RESULTS..........................................14 6.1 Doppler centroid frequency monitoring .......................................................................................14 6.2 Point Target IRF Analysis ...........................................................................................................15

6.2.1 Ground station analysis........................................................................................................16 6.2.2 Corner reflector PT analysis.................................................................................................18

6.3 Distributed Target Analysis .........................................................................................................19 6.4 Noise Equivalent sigma zero .......................................................................................................19 6.5 Radiometric Resolution and Equivalent Number of Looks...........................................................19 6.6 Elevation Antenna Pattern Monitoring.........................................................................................19

6.6.1 African Rainforest Analysis – Fine Mode ............................................................................20 6.6.2 African Rainforest Analysis – Wideswath Mode..................................................................21

6.7 Localisation Accuracy .................................................................................................................22

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6.8 Ambiguities.................................................................................................................................22 6.9 Dual and Quad Polarisation Calibration.......................................................................................22

6.9.1 Co- registration....................................................................................................................22 6.9.2 Channel coherence, balance and symmetry ..........................................................................22 6.9.3 Cross talk analysis ...............................................................................................................23

6.10 Faraday rotation analysis .............................................................................................................24

7 DISCLAIMERS................................................................................................................26

8 EVENTS..........................................................................................................................27 8.1 Past Events ..................................................................................................................................27

APPENDIX A PALSAR PRODUCT TYPES ............................................................................28

APPENDIX B COHERENCE MEASURES ..............................................................................29

APPENDIX C INSTRUMENT ANOMALIES.............................................................................30

APPENDIX D NATURAL POINT TARGET ANALYSIS...........................................................33

APPENDIX E UNCHANGED ANALYSIS ................................................................................37 E1 African Rainforest Analysis – wideswath mode .............................................................................37 E.2 Corner Reflector PT measurements...............................................................................................38 E3 Radiometric Resolution..................................................................................................................44 E4 Ambiguity measurements...............................................................................................................44

APPENDIX F BEAM NUMBERS.............................................................................................45

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1 INTRODUCTION The PALSAR Cyclic Report is distributed by the PALSAR IDEAS team to keep the PALSAR community informed of any modification regarding instrument performances, the data production chain and the results of calibration and validation campaigns at the end of each ALOS cycle, which represents 671 orbits, or 46 days. The PALSAR instrument is part of the ALOS mission and its products are received and processed via the ADEN ground segment across Europe. A series of quality checks are undertaken in order to assess the ground segment and instrument performance and the product quality. Checks are currently made on a weekly (header parameters, PDS status) or bi-monthly (visual report) basis to have a constant view on the mission status. The cyclic report presents the results of the quality analysis for the different parts of the delivery chain, from satellite to end-product.

1.1 Acronyms and Abbreviations ADEN ALOS Data European Node ALE Absolute Localisation Error ALOS Advanced Land Observing Satellite EO Help Earth Observation Help Desk DN Dynamic Number IDEAS Instrument Data quality Evaluation and Analysis Service IRF Impulse Response Function FR Faraday Rotation LSSR Low rate mission data Solid-State Recorder NRCS Normalised Radar Cross Section OCM Orbit Control Manoeuvre PALSAR Phased Array type L-band Synthetic Aperture Radar PDS Payload Data Segment QC Quality Control SAR Synthetic Aperture Radar SPPA Sensor Performance Products Algorithms SNR Signal to Noise Ratio RCS Radar Cross Section WS Wide Swath

1.2 Reference Documents [1] ALOS PALSAR Product Verification Report, PS-CAL-TN-003, June 2007

[2] Shimada, M., “PALSAR CALVAL Summary and Update 2007”, IGARSS, 2007

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[3] Wright, P., Quegan, S., Wheadon, N. & Hall D., "Faraday Rotation Effects on L-band

Spaceborne SAR Data", IEEE Trans on Geoscience and Remote Sensing, Vol 41, 12, 2003.

[4] Information on ALOS PALSAR Products for ADEN Users, ALOS-GSEG-EOPG-TN-07-0001, April 2007

1.3 Background Information The background information has been extracted from reports issued by ESA during the PALSAR commissioning phase [1]. Information on instrument anomalies and image quality parameters produced during the commissioning phase are quoted here for comparison with the current phase. The PALSAR instrument is a Synthetic Aperture Radar instrument that is part of the ALOS mission built by the Japanese Space Agency (JAXA). The ALOS mission has its data produced and disseminated through geographical nodes. The European node (ADEN) was set up and is operated by ESA through the Tromso, Matera, Maspalomas and Frascati ground stations. As a third party mission (TPM), only the ground segment and data processing are dealt with by ESA, the platform being the responsibility of the owner: JAXA. Each node operates their ground segment independently and shares results with JAXA when required. The ADEN-ALOS team is responsible for the operation and maintenance of the data received in Europe and North Africa. The ADEN team took part in the Cal/Val activities during the ALOS commissioning phase (January to October 2006). The methodologies used and results obtained are documented in document [1]. Information related to the mission and products are made available to the user through the site: http://earth.esa.int/object/index.cfm?fobjectid=3738. As part of the ADEN operations, a series of quality checks are undertaken in order to assess the ground segment and instrument performance and the product quality for products requested by European users. Checks are currently made on a weekly basis (header parameters, PDS status) to have a constant view on the mission status. Details on the commissioning phase will be placed on the ALOS PCS website, location http://earth.esa.int/pcs/alos/. The current PALSAR acquisition plan can be found at: http://www.eorc.jaxa.jp/ALOS/obs/alos_scenario/palsar_desc/palsar_desc.htm

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2 SUMMARY Cyclic Report 22 Cycle Start 09 September 2008 Cycle End 25 October 2008 The main issues during this cycle have been as follows: • The JAXA v5.02 processor became operational on the 19th September 2008 at all three

ADEN sites (ESRIN, Matera and Tromsø).

• Visual inspections have highlighted a number of problems with Wide Swath (WS) mode data, including visible subswath boundaries, scalloping, ADC saturation effects and azimuth ambiguities. Some acquisitions have been processed with inappropriate antenna patterns. It is understood that prior to 7th August 2006 there were problems with WS raw data saturation for some of the sub-swaths but the elevation antenna pattern was measured directly from Amazon data and so was not affected. On 7th August 2006 the attenuator levels were changed to reduce the raw data saturation but the elevation antenna pattern was not modified which has led to the problems seen in the wideswath data. The new version of the JAXA processor (v5.02) includes a new WS antenna pattern to remove this problem, positive feedback has been received from users on this new antenna pattern.

• Interference effects have been identified in several PALSAR images.

• In fine mode and polarimetric mode, the radiometric error at far range is no longer visible in inspected imagery processed with v 4.02 of the processor and above. Azimuth ambiguity effects have also been noted in fine mode data.

• For wideswath images there are peaks in gamma for certain sub-swaths and an overall trend in gamma across the swath. JAXA are providing a new WS antenna pattern for processor v5.02. Further wideswath analysis will be performed now that the v5.02 products are available.

• Further wideswath imagery of the Maspalomas ground station has been analysed. These results are compatible with previous results that showed an almost 6dB variation in the ground station radar cross-section, which is much larger than expected. In fact there appears to be two groups of values, one around 55dB and another about 60dB. This could be due to two different ground stations being measured within a resolution cell. Further analysis of wideswath imagery will be undertaken.

• For fine mode imagery JAXA have recommended that only 1.1 data be used for point target analysis. Analysis of the Tromsø and Matera ground stations using Level 1.1 products has shown that the spatial resolution measurements are comparable with their

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theoretical values and the data is adequately sampled. However, the ISLR values are quite high, especially for the FBD imagery – this is probably due to the radar cross-section of the ground station being quite low and consequently the background is quite high in relation to the ground station IRF.

• Preparations have continued on a paper "Aden ALOS Palsar Product Verification" for the ESA ALOS PI Symposium to be held in early November 2008.

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3 SOFTWARE AND AUXILIARY FILE VERSION CONFIGURATION The current processor version of the PALSAR instrument, and the date on which it was installed at each of the stations is detailed in Table 3-1:

Current PALSAR Processor Version ESRIN Matera Tromso

5.02 10/09/08 19/09/08 18/09/08

Table 3-1 PALSAR Processor Version

Prior to these dates, the installed PALSAR processor at each station had been v4.03. A history of the PALSAR processor release notes will be made available on the ALOS ADEN PCS website, location: http://earth.esa.int/pcs/alos/palsar/userinfo/ We are aware that data which can be processed to level 0 (but no further) was previously used to populate the EOLI catalogue. This has been raised as an issue and the catalogue has been cleaned of such products. On ordering such data at Level 1.1 and Level 1.5, the order was rejected and users received notification that they had ordered “calibration mode data”. Users ordering this data at Level 1.0 would receive products which contained only calibration data. The IDEAS SAR team monitor products distributed electronically for this anomaly. Version 5.02 of the PALSAR processor has undergone validation testing by the IDEAS SAR Team and is now operational at ADEN.

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4 PDS STATUS Please note; one source of information for this document is the ALOS monthly report provided by JAXA. The monthly reporting timescale means that data concerning events conducted within this cycle may not be available at the time of writing. In this event, information will be included in the next report. Instrument information provided by JAXA during the period 01/09/2008 to 31/09/2008 is reported on in this document.

4.1 Planned Instrument Unavailability For the periods described in Table 4-1, JAXA has announced planned instrument unavailability. From (UT) To (UT)

Date Time Date Time Reason

Sep. 12th, 2008 - Sep. 12th, 2008 - OCM Sep. 26th, 2008 - Sep. 26th, 2008 - OCM Oct. 11th, 2008 - Oct. 11th, 2008 - OCM Oct. 18th, 2008 - Oct. 18th, 2008 - OCM

Table 4-1 Planned instrument unavailability

4.2 Unplanned Instrument Unavailability None reported during this cycle.

4.3 Current Platform Status Information on the platform provided by JAXA: Current platform status: Normal

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4.4 Upcoming Instrument Unavailability For the periods described in Table 4-2, JAXA has announced planned instrument unavailability.

From (UT) To (UT)


None

Table 4-2 Upcoming instrument unavailability

4.5 ADEN PDS Unavailability None reported during this cycle.

4.6 Periods of missing precision orbit data For the periods described in Table 4-3, JAXA has announced that precision orbit data is missing.

From (UT) To (UT)


Sep. 12th, 2008 20:28:00.00 Sep. 12th, 2008 21:32:00.00 OCM Sep. 26th, 2008 16:26:00.00 Sep. 26th, 2008 17:30:00.00 OCM Oct. 11th, 2008 10:10:00.00 Oct. 11th, 2008 11:13:00.00 OCM Oct. 18th, 2008 05:01:00.00 Oct. 18th, 2008 06:05:00.00 OCM

Table 4-3 Missing Precision Orbit Data

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4.7 Periods of missing precision attitude data For the periods described in Table 4-4, JAXA has announced that precision attitude data is missing. The information published by JAXA covers the period up to June 25th, 2008.

From (UT) To (UT)


None

Table 4-4 Missing Precision Attitude Data

4.8 Periods lacking Yaw steering For the periods described in Table 4-5, JAXA has announced that Yaw steering was not available.

From (UT) To (UT)


None

Table 4-5 No Yaw steering

4.9 JAXA Observation Strategy The JAXA observation strategy can be found at: http://www.eorc.jaxa.jp/ALOS/obs/overview.htm

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5 DATA QUALITY CONTROL

5.1 Instrument related anomalies ADC saturation effects have been observed in Wide Swath (WS) mode imagery. Interference effects and azimuth ambiguities have also been noted in Wide Swath (WS) mode imagery. The new instrument related anomalies that may have an impact on image quality, radiometric calibration or localisation accuracy during the repeat period are: • Orbit manoeuvres conducted on 12th, 26th September and 11th, 18th October 2008.

A full list of anomalies is given in Appendix C.

5.2 Processor related anomalies Version 4.02 and above of the PALSAR processor appears to have removed the far range radiometric correction error. This situation will continue to be monitored. Visual inspections have highlighted a number of problems with WS mode data including, visible sub swath boundaries, azimuth ambiguities and scalloping. Incorrect antenna patterns have also been observed in wide swath data resulting in across swath variations of up to 3dB (see cycle 15 report for further details).

5.3 Daily Report Issues During the past cycle, daily checks have been undertaken on all PALSAR products generated by ADEN, although reported on a weekly basis due to current data volumes. 332 products have been examined during the course of this cycle. The only issue highlighted during these checks has been the distribution of data at level 1.0 which contains calibration mode data. Of the products which have been visually inspected, none show any evidence of missing lines.

5.4 User Queries A PALSAR FAQ containing the common user requests can be found on the ESA PCS website. The link to this site is: http://earth.esa.int/pcs/alos/palsar/userinfo/.

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6 CALIBRATION/VALIDATION ACTIVITIES AND RESULTS

This section gives the results of the calibration/validation activities undertaken during the reporting period.

6.1 Doppler centroid frequency monitoring Figure 6.1.1 gives the Doppler centroid frequencies of products generated during the cycle, and all previous cycles since April 2007. During Cycle 22, 332 additional products were generated and analysed.

-2000

-1500

-1000

-500

0

500

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0 900 1800 2700 3600 4500 5400 6300 7200 8100

Frame

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requ

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Previous data

Cycle 22

Figure 6.1.1 Doppler Centroid frequency given as a function of the frame number

Note, the collection of points towards the bottom left of the graph corresponds to data ordered from periods when Yaw steering was suspended. This leads to a high Doppler centroid frequency. For periods when yaw steering was suspended during this cycle, see section 4.8. The points taken from frame 600 with a frequency of ~500Hz were acquired on the 17th of June 2008 when an OCM was conducted. The data highlighted by the red rectangle were acquired during periods when yaw steering was suspended. Specifically, during orbit 6161 on the 22nd of March and orbit 6176 on the 23rd of March 2007. The Doppler Centroid frequency as a function of position is shown in Figure 6.1.2 for ascending passes and Figure 6.1.3 for descending passes.

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Doppler centroid for ascending pass

-90

-70

-50

-30

-10

10

30

50

70

90

-180 -80 20 120

Past -100 to 0 Hz

Past 0 to 100 Hz

Past 100 to 200 Hz

Past > 200 Hz

-100 to 0 Hz

0 to 100 Hz

100 to 200 Hz

> 200 Hz

Figure 6.1.2 Doppler centroid frequency for ascending passes

Doppler centroid for descending pass

-90

-70

-50

-30

-10

10

30

50

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90

-180 -130 -80 -30 20 70 120 170

Past 100 to 0 Hz

Past 0 to -100 Hz

Past -100 to -200HzPast < -200 Hz

100 to 0 Hz

0 to -100 Hz

-100 to -200 Hz

< -200Hz

Figure 6.1.3 Doppler centroid frequency for descending passes

6.2 Point Target IRF Analysis An analysis of natural point target measurements carried out with PALSAR data is given in Appendix D. No corner reflectors or transponders were available for analysis by the ADEN

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team in cycle 22. Further stable point target analysis has been performed using PALSAR ground stations in previous cycles.

6.2.1 GROUND STATION ANALYSIS Several PALSAR products acquired over ground stations within Europe have been analysed to assess whether the impulse response functions from the ground stations are suitable for image quality and instrument stability assessment. Images of Maspalomas, Spain; Tromso, Norway; and Matera, Italy have been ordered and analysed. Results for these ground stations are indicated below. Maspalomas The ESA receiving antenna at Maspalomas can be used for IRF analysis of wideswath mode data (the antennas radar cross-section is too high to be suitable for fine mode IRF analysis due to pixel saturation for this acquisition mode). One additional wideswath image of the Maspalomas ground station has been analysed in the current period. A summary of all the Maspalomas results to date is given in Table 6.2.1. The variability in the azimuth and range spatial resolutions is due to the undersampling of the wide swath imagery. It can also be seen that the ISLR is quite variable while the PSLR and SSLR are acceptable for this type of data. However there is a just over 6dB variation in the ground station radar cross-section which is much larger than expected. In fact there appears to be two groups of values, one around 55dB and another about 60dB. This could be due to their being two different ground stations being measured.

Acq Date

Orbit Track Inc Ang

Azi Res (m)

Range Res (m)

ISLR (dB)

PSLR (dB)

SSLR (dB)

RCS (dBm2)

16/04/07 6526 344 39.2 169.10 120.94 -15.07 -8.52 -11.91 55.79 10/07/07 7766 349 20.2 131.65 135.29 0.51 -8.94 -9.01 56.35 25/08/07 8437 349 40.66 166.83 187.61 -4.95 -10.85 -12.11 60.58 10/10/07 9108 349 40.69 128.50 129.41 -7.71 -8.62 -11.50 54.70 25/11/07 9779 349 40.75 165.70 122.98 -12.40 -6.48 -11.68 56.33 02/12/07 9881 344 22.95 170.26 121.27 -0.93 -9.08 -8.96 59.85 11/04/08 11792 349 40.76 165.34 147.51 -2.64 -11.16 -9.62 60.19 03/09/08 13907 344 22.66 133.53 125.83 6.32 -4.55 -6.37 53.93

Table 6.2.1 Maspalomas IRF and RCS Measurements Using corner interpolation, the absolute localisation accuracy is up to 400m (4 pixels) in range and up to 200m (2 pixel) in azimuth. Tromso Five additional products of the Tromso ground station have been analysed in the current period. Table 6.2.2 and 6.2.3 below give the IRF and radar cross-section results from both Level 1.5 and Level 1.1 products. The Level 1.5 FBS and FBD spatial resolution measurements indicate that both product types are undersampled in both azimuth and range

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(the FBS pixel size is 6.25m and the FBD pixel size is 12.5m). The sidelobe measurements are all quite high. There is also a significant difference in the rcs of the FBS and FBD product types and between the FBD measurements (~4dB). The Level 1.1 spatial resolution measurements are comparable with their theoretical values and the data is adequately sampled. However, the ISLR values are quite high, especially for the FBD imagery – this is probably due to the radar cross-section of the ground station being quite low and consequently the background is quite high in relation to the ground station IRF. This is also why the Level 1.1 PSLR and SSLR values are not calculated. Again there are significant differences in the FBS and FBD rcs values (~7dB). Prod Type

Acq Date

Orbit Track Inc Ang

Azi Res (m)

Range Res (m)

ISLR (dB)

PSLR (dB)

SSLR (dB)

RCS (dBm2)

FBS 11/01/07 5146 1390 37.62 12.03 7.87 1.57 -2.59 -6.21 34.00 FBD 02/07/07 7655 1390 39.90 15.69 16.08 8.18 -6.34 -9.10 41.70 FBD 02/10/07 8997 1390 39.85 18.02 15.36 8.67 -6.58 -3.02 42.74 FBD 19/05/08 12352 1390 39.69 17.88 17.99 3.05 -4.04 -6.20 39.21 FBD 19/08/08 13694 1390 40.22 17.35 20.76 7.91 -7.48 -6.52 43.60

Table 6.2.2 Tromso Level 1.5 IRF and RCS Measurements

Acq Date

Orbit Track Inc Ang

Azi Res (m)

Range Res (m)

ISLR (dB)

PSLR (dB)

SSLR (dB)

Total Power (dB)

RCS (dBm2)

11/01/07 5146 1390 37.64 7.54 4.11 -3.08 - - 135.59 30.20 14/02/07 5642 1390 40.01 4.61 4.68 1.53 - - 137.24 33.75

Table 6.2.3(a) Tromso FBS Level 1.1 IRF and RCS Measurements

Acq Date

Orbit Track Inc Ang

Azi Res (m)

Range Res (m)

ISLR (dB)

PSLR (dB)

SSLR (dB)

Total Power (dB)

RCS (dBm2)

02/07/07 7655 1390 39.95 5.29 9.70 5.79 - - 136.77 41.70 02/10/07 8997 1390 39.88 5.86 9.28 5.40 - - 137.60 39.79 14/07/07 7830 1390 37.50 6.31 9.00 10.28 - - 132.29 38.84 17/08/07 8326 1390 39.92 4.54 9.80 8.79 - - 133.54 38.52

Table 6.2.3(b) Tromso FBS Level 1.1 IRF and RCS Measurements

Matera Seven additional Level 1.1 products of the Matera ground station have been analysed in the current period. Tables 6.2.4 and 6.2.5 below give the IRF and radar cross-section results for the Matera ground station using Level 1.5 and Level 1.1 products. The Level 1.5 FBS and FBD spatial resolution measurements indicate that both product types are undersampled in both azimuth and range (the FBS pixel size is 6.25m and the FBD pixel size is 12.5m). The sidelobe measurements are all quite high. There is also a significant difference in the rcs of the FBS and FBD product types and between the FBD measurements (~3dB). The Level 1.1

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spatial resolution measurements are comparable with their theoretical values and the data is adequately sampled. However, the ISLR values are quite high, especially for the FBD imagery – this is probably due to the radar cross-section of the ground station being quite low and consequently the background is quite high in relation to the ground station IRF. This is also why the Level 1.1 PSLR and SSLR values are not calculated. Again there are significant differences in the FBS and FBD rcs values (~5dB). Prod Type

Acq Date

Orbit Track Inc Ang

Azi Res (m)

Range Res (m)

ISLR (dB)

PSLR (dB)

SSLR (dB)

RCS (dBm2)

FBS 20/02/07 5730 800 38.71 8.53 7.74 -9.41 -7.88 -10.66 31.82 FBD 23/08/07 8414 800 38.64 21.22 21.22 11.53 -0.79 10.92 28.36

Table 6.2.4 Matera Level 1.5 IRF and RCS Measurements

Acq Date

Orbit Track Inc Ang

Azi Res (m)

Range Res (m)

ISLR (dB)

PSLR (dB)

SSLR (dB)

Total Power (dB)

RCS (dBm2)

05/01/07 5059 800 38.88 4.47 4.59 -3.47 - - 139.88 34.22 20/02/07 5730 800 38.77 4.47 4.47 -2.10 - - 139.79 34.60 08/01/08 10427 800 38.65 4.59 4.61 -3.78 - - 140.75 35.02 23/02/08 11098 800 38.56 4.28 4.55 -1.34 - - 133.66 28.80 09/04/08 11769 800 38.55 4.23 4.44 -0.00 - - 133.85 29.62

Table 6.2.5(a) Matera FBS Level 1.1 IRF and RCS Measurements

Acq Date

Orbit Track Inc Ang

Azi Res (m)

Range Res (m)

ISLR (dB)

PSLR (dB)

SSLR (dB)

Total Power (dB)

RCS (dBm2)

08/07/07 7743 800 38.72 4.75 9.33 0.93 - - 137.39 36.64 23/08/07 8414 800 38.70 4.61 9.20 1.15 - - 137.41 36.77 25/05/08 12440 800 38.56 5.71 9.56 1.79 - - 142.81 42.57 10/07/08 13111 800 38.77 4.37 10.00 2.61 - - 127.34 27.59 25/08/08 13782 800 38.92 4.71 9.08 4.79 - - 137.52 39.28 25/08/08 13782 800 38.92 5.46 9.91 2.68 - - 139.23 39.51

Table 6.2.5(b) Matera FBS Level 1.1 IRF and RCS Measurements

6.2.2 CORNER REFLECTOR PT ANALYSIS

Appendix E2 gives a comparison of point target measurements between Level 1.5 products from the JAXA and Pulsar processors using the DLR corner reflectors. For the PALSAR products processed by the Pulsar product have been adequately sampled in both azimuth and range. The measurements show that changing the sampling rate of the data has not resulted in significant changes to the relative RCS levels of the corner reflectors. However, the point target resolution and sidelobe properties are closer to their theoretical values.

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6.3 Distributed Target Analysis No suitable candidate distributed targets analysed in this cycle. JAXA measurements indicate a stability of 0.5-1.0dB from measurements over the Amazon rainforest [2].

6.4 Noise Equivalent sigma zero Table 6.4.1 and Figure 6.4.1 gives and show the noise equivalent sigma zero measures for the products analysed where the lowest NESigma0 measurements at each incidence angle have been used. Note that there have not been any VV measurements to date.

Figure 6.4.1 Measured NESigma0 variation with polarization and incidence angle

Product Mean Noise (dB) Fine mode HH -24.84±2.89 Fine mode HV -30.61 ±1.96 Fine mode VH -27.44±3.23

Table 6.4.1 PALSAR Noise equivalent sigma zero measurements by polarisation.

6.5 Radiometric Resolution and Equivalent Number of Looks No new ENL analysis has been performed in cycle 22. Previous results are given in Appendix E3.

6.6 Elevation Antenna Pattern Monitoring Fine mode data processed with processor versions prior to v4.02 have a radiometric fall off of around 7dB at far range (see earlier cyclic reports for examples and further details). Users should not use the far range pixels of such products for analysis. Analysis to date indicates that products processed with processor v4.02 are not affected by this problem. Full details of processor installation dates at each processing facility are given in section 3 (a more detailed

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processor history can be found on the PALSAR PCS website: http://earth.esa.int/pcs/alos/palsar/userinfo/)

6.6.1 AFRICAN RAINFOREST ANALYSIS – FINE MODE PALSAR images of the African Rainforest have been selected to assess its suitability for the estimation of the elevation antenna pattern since a uniform target with isotropic backscattering characteristics is required, which are assumed for tropical rainforests. Since Amazon rainforest data is not available for PALSAR data within the ADEN node, an alternative site within the African rainforest has been selected (at 2.91°N, 14.32°E). Figure 6.6.1 shows an example of the selected PALSAR frame together with the corresponding profile of gamma (�0/cos(i)) across the swath. Although there is more structure visible within this scene than a typical C-band image of the Amazon rainforest image, it is suitable for elevation pattern estimation. This is because there appears to be no large scale variations within the scene and the pattern is estimated using the whole image. As Figure 6.6.1(b) shows there is almost no trend from near to far range indicating that the elevation antenna pattern has been implemented correctly (assuming that gamma follows the same incidence angle variation as the Amazon rainforest).

Figure 6.6.1(a) Fine Mode Level 1.5 PALSAR image of the African Rainforest from an

acquisition on 9th October 2007 (orbit 9100, frame 0040, HH polarisation)

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-6.2

-6.0

-5.8

-5.6

-5.4

36 37 38 39 40 41

Incidence Angle (deg)

Gam

ma

(dB

)

Figure 6.6.1(b) Gamma profile for a Fine Mode Level 1.5 PALSAR image of the African

Rainforest from an acquisition on 9th October 2007 (orbit 9100, frame 0040) All of the fine mode images analysed are from the same track and frame and hence are of the same region. The table below gives a summary of the mean gamma for each scene and the change in gamma from near to far range. As can be seen there is some variability in the mean gamma (max – min = 0.18dB) but more importantly the shape of the gamma profile in range has changed with there being a reduction in gamma and then a rise in gamma from near to far range. The most recent image shows again no change in gamma from near to far range. The mean gamma for all 6 images is -5.76±0.07 dB. This indicates an excellent radiometric stability of just 0.07dB.

Acq Date Orbit Mean Gamma Trend

21st February 2007 5745 -5.75 dB -0.02 dB

9th October 2007 9100 -5.81 dB -0.10 dB

24th November 2007 9771 -5.82 dB -0.23 dB

9th January 2008 10442 -5.84 dB 0.27 dB

24th February 2008 11113 -5.70 dB 0.37 dB

10th April 2008 11784 -5.66 dB 0.00 dB Table 6.6.1 Summary of fine mode antenna pattern analysis to date.

6.6.2 AFRICAN RAINFOREST ANALYSIS – WIDESWATH MODE

There is no further analysis to report here. Results to date are given in Appendix E1. Further results will be generated now that the v5.02 wideswath antenna pattern is available at the ADEN Node processing facilities.

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6.7 Localisation Accuracy The ESA ground station at Maspalomas has been used to assess the image localisation accuracy, derived using the image corner coordinates, use of which can result in poorer localisation accuracy than use of the orbit state vectors. The results are presented in Table 6.7.1. Note that JAXA quote a nominal measurement of 9.2m for fine resolution data and 70m for scanSAR data (100m specification) [2].

Data

Orbit/Frame Target Interpolation

Method Range ALE (m) Azimuth ALE

(m) 8437/3050 Ground Station Corner -413.8 184.0 9108/3050 Ground Station Corner -389.4 100.9 9779/3050 Ground Station Corner -213.2 103.3 9881/3050 Ground Station Corner 207.3 66.3

11792/3050 Ground Station Corner -158.8 189.6 Table 6.7.1 Point Target Absolute Localisation Accuracy for the Maspalomas ground station

in Wideswath imagery

6.8 Ambiguities No new ambiguity measurements have been made in this cycle. Previous results are given in Appendix E4.

6.9 Dual and Quad Polarisation Calibration Where data is not well calibrated (i.e. residual channel imbalances or high cross talk is measured) there will be an impact on the validity of retrieved geophysical parameters from the data. In this section the polarimetric calibration of the data is assessed.

6.9.1 CO- REGISTRATION For Level 1.1 polarimetric data the mean channel registration in range is 0.94m (standard deviation 0.8m) and 0.83m in azimuth (standard deviation 0.98m) (i.e. sub-pixel). For FBD data, the mean channel registration in range is 1.34m (sd 1.04) and in azimuth is 1.06m (sd 0.71).

6.9.2 CHANNEL COHERENCE, BALANCE AND SYMMETRY

In the following, parameters that may indicate problems with the data calibration are provided in Table 6.9.1. The coherence measures are calculated for level 1.1 polarimetric products only. The measures have been calculated using the Calix tool. HV-VH coherence is used for the signal to noise ratio (SNR) calculation. The phase of the HVVH correlation (see Appendix B equ. (2)) is expected to have a zero mean distribution.

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Deviations from zero mean phase indicate a non compensated phase imbalance in the data calibration. The HV/VH amplitude ratio (see Appendix B equ. (3)) is also expected to have a zero mean distribution. Deviations from zero mean indicate an uncompensated amplitude imbalance. The HHHV and VVVH coherence values should be zero, if greater than 0.3 they indicate the presence of uncorrected cross talk and/or Faraday rotation. If the values are not similar, they indicate a non reciprocal cross talk. A HH-VV (see Appendix B equ(4)) mean phase deviation from zero may indicate uncorrected phase imbalance, depending on the scattering surface. Orbit Frame HVVH

phase Mean

HV/VH amplitude Mean (dB)

SNR

Mean (dB)

VVVH coherence

Mean

HHHV coherence

Mean

HHVV phase. Mean

6940 1260 23.06±24.55° 3.20±5.50 6.14±3.82 0.26±0.11 0.23±0.11 19.26±9.61° 7072 1020 2.17±22.64° -0.16±6.55 1.35±5.76 0.14±0.08 0.17±0.11 6.17±27.69° 6321 2640 3.04±33.07° 0.21±6.53 1.11±6.20 0.20±0.10 0.22±0.11 6.05±26.61° 5650 2640 2.11±21.11° 0.15±5.77 5.31±5.69 0.14±0.08 0.15±0.09 -4.62±23.68° 7024 800 3.12±15.17° -0.09±6.66 1.77±4.51 0.21±0.11 0.23±0.12 3.94 ±10.71° 6474 1080 26.52±22.84° -0.97±7.41 -3.31±2.59 0.19±0.08 0.19±0.07 4.32±7.41° 6575 1380 1.21±2.39° 0.09±4.77 9.80±2.62 0.12±0.06 0.14±0.07 0.02±3.90° 6327 1370 0.91±2.79° 0.05±4.99 8.01±2.65 0.11±0.61 0.14±0.07 -2.04±5.21° 7189 100 24.01±2.00° 3.35±3.96 11.67±1.57 0.10±0.05 0.11±0.06 21.01±10.61° 7233 100 0.90±1.22° 0.25±3.50 12.23±1.81 0.09±0.05 0.09±0.05 -1.58±14.80° 7261 100 3.29±15.28° 0.18±4.39 11.78±4.61 0.10±0.06 0.11±0.06 0.55±6.66° 7276 100 1.08±1.34° 0.05±3.64 11.73±2.07 0.09±0.05 0.1±0.05 7.14±9.55° 6248 2690 4.79±11.6° 0.03±6.33 3.65±3.72 0.19±0.12 0.22±0.14 3.72±14.7° 4230 7150 0.33±2.71° -0.27±3.47 11.67±1.47 0.09±0.05 0.09±0.05 6.58±13.59°

Table 6.9.1 PALSAR polarimetric coherence measures. The greyed out values are from previous cycles.

6.9.3 CROSS TALK ANALYSIS

Table 6.9.2 gives the cross talk values calculated using SARCON, where: A is the channel reciprocity W is the transmit H to V cross talk U is the receive H to V cross talk V is the transmit V to H cross talk Z is the receive V to H cross talk The cross talk is calculated for polarimetric level 1.1 products only. In general the values are consistent with those measured by JAXA [2] and are as good as or better than the instrument specification of -30dB. Using this technique, areas within the image are selected to perform the cross talk calculation.

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Calculated values (mean) Orbit Latitude Frame A U(dB) Z(dB) W(dB) V(dB)

7072 51.077 1020 0.966 -32.69±4.98 -31.11±0.96 -35.65±2.57 -36.08±4.89 6940 62.286 1260 0.923 -29.68±0.00 -30.24±0.03 -30.81±0.10 -31.64±2.32 6321 48.137 2640 0.862 -21.19±2.38 -25.83±1.51 -23.66±0.54 -31.75±5.07 5650 48.136 2640 0.976 -33.03±0.10 -33.26±1.84 -34.77±2.82 -36.94±0.64 7204 40.248 800 0.829 -26.19±8.43 -31.75±5.71 -25.29±5.76 -29.33±2.89 7189 5.5 100 1.19 -48.57±0.81 -34.44±0.51 -32.43±8.14 -31.25±2.53

Table 6.9.2 Cross talk measured using SARCON for selected image regions

Cross talk measurements are also performed using the CALIX software tool, which uses the entire image to calculate cross talk. These measurements are given in Table 6.9.3

Calculated values (mean) Orbit Latitude Frame

A U(dB) Z(dB) W(dB) V(dB) 7204 40.248 800 0.99 -25.76±6.22 -23.63±6.13 -24.34±6.01 -23.39±5.92 6474 54.004 1080 1.16 -26.98±5.79 -27.43±6.22 -27.75±6.53 -27.83±6.52 6575 68.546 1380 0.94 -28.44±5.66 -27.84±5.47 -27.98±5.5 -27.92±5.55 6327 68.053 1370 0.98 -29.95±5.57 -29.72±5.54 -29.62±5.52 -29.59±5.52 7189 5.500 100 0.75 -24.35±5.47 -24.35±5.48 -24.09±5.44 -24.23±5.45 7233 5.499 100 0.77 -25.10±5.42 -24.99±5.42 -24.99±5.42 -25.16±5.42 7261 5.495 100 0.87 -27.57±5.59 -27.54±5.62 -27.16±5.54 -27.29±5.56 7276 5.500 100 0.9 -26.44±5.45 -26.65±5.43 -25.66±5.43 -26.77±5.43 6248 45.36 2690 1.00 -25.66±6.27 -23.58±5.86 -24.88±6.12 -23.84±5.64 4230 -1.96 7150 1.24 -25.43±5.42 -25.48±5.41 -25.00±5.41 -24.87±5.42

Table 6.9.3 Cross talk measured using Calix over the entire image.

The mean and standard deviation for the product cross talks measured using the whole image are perhaps slightly worse than those measured from selected sites. In addition the alpha value for product 4230 indicates that there is a channel imbalance issue with this product.

6.10 Faraday rotation analysis For any given point in the solar cycle, Faraday rotation (FR) is expected to be greatest at mid latitudes, at around 1-2pm local time, and at the equinoxes. Conversely, FR can be expected to be a minimum just before dawn, at polar and equatorial locations and at solstices. These generalisations can be used as a guide to assess whether the calculated FR and FR trends are plausible for a given location and time. Faraday rotation has the effect of rotating the plane of polarisation of the transmitted and received signal. This can result in a much lower return than expected in the co-polarisation channels and a much higher return than expected in the cross-polarisation channel. This reduces the dynamic range of the co-polarised channels and drives the cross-polarised channel to resemble the co-polarised channels. This also reduces sensitivity to ground parameter variations and, for large values of FR, effectively turns a multi-polarisation radar

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into a single-channel system. Information products relying on the classification of L-band HV SAR data, such as crop and forest inventory or land cover maps, are likely to be affected by FR levels exceeding 10°. The accuracies of retrieved geophysical parameters such as soil moisture or vegetation biomass, which require good calibration and data accuracy, will be adversely affected once FR exceeds 5-8° (depending on land cover) [3]. The following measures have been calculated using the Calix tool. Only level 1.1 polarimetric products are used to calculate Faraday rotation.

Orbit Latitude (deg)

Longitude (deg)

Frame Acq. Date UT Local time1

Calculated FR

(deg) 7072 51.077 11.017 1020 23/5/07 21:21 21:50 1.20±0.53 6940 62.286 23.88 1260 14/5/07 20:13 21:26 3.02±0.34 6321 48.137 11.276 2640 2/4/07 10:06 11:06 2.54±1.14 5650 48.136 11.285 2640 15/2/07 10:05 11:06 1.13±1.03 7204 40.248 -3.475 800 01/06/07 22:29 22:00 1.95±0.32 6474 54.004 8.294 1080 12/4/2007 21:28 21:50 0.76±0.24 6575 68.546 27.594 1380 19/4/2007 19:43 21:05 0.95±0.17 6327 68.053 28.538 1370 2/4/2007 19:41 21:18 0.90±0.18 7189 5.500 14.496 100 31/5/2007 21:38 22:26 0.7±0.29 7233 5.499 8.597 100 3/6/2007 22:02 22:26 0.59±018 7261 5.495 37.564 100 5/6/2007 20:06 22:26 0.35±0.2 7276 5.500 27.374 100 6/6/2007 20:47 22:26 0.41±0.16 6248 45.36 11.92 2690 28/3/2007 10:00 11:06 2.5±0.34 4230 -1.96 -61.69 7150 10/11/2006 10:02 10:48 -0.98±0.21

Table 6.10 Calculated Faraday rotation. The FR values measured are consistent with those expected for the time of year, day and solar activity. The measures are also within the FR tolerance, hence these images data do not need to be corrected for FR before use in geophysical retrieval. The four equatorial products (Frame 100) provide a baseline mean FR value of 0.51degrees. This provides a measure of the uncertainty in the FR measurement process (the equator is unaffected by Faraday rotation). The non equatorial day time products from around the vernal equinox provide a consistent FR measure of around 2.5 degrees

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1 Calculated for 22:30 hrs ascending node crossing time and spacecraft nadir at latitude of scene.

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7 DISCLAIMERS During the cycle no disclaimers were issued.

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8 EVENTS The following section details events that may be of interest to ALOS data users.

� The second ALOS PI Symposium will be taking place from the 3rd to the 7th of

November in Rhodes, Greece. For more information, please see http:/earth.esa.int/ALOS2008.

� ALOS Simulations:

o Results of first stage simulation #11 available on Oct. 15th 2008. o The submission of request files for the second stage simulation is due on Oct.

28th.

8.1 Past Events

� Analysis report and Adoption/Rejection information of simulation 10 were released by JAXA on 21/08/2008.

� The due date of Observation/Acquisition request files for ALOS simulation 11 was

25/09/2008. This simulation covers the period 10/12/2008 to 11/06/2008.

� ADN-14 meeting was held at ASF from Sep. 9th to 11th

� Analysis report and Adoption/Rejection information of simulation 9 were released by JAXA on 09/06/2008.

� Result files and statistics for ALOS cycle #10 simulations will be available on

August 21st, 2008.

� Request files for the second stage of simulation 10 are due on Aug. 28th, 2008.

� The submission of request files for ALOS simulation number 10 was due by 20th of June.

� Note that the deadline for abstract submission to the ALOS PI Symposium was June

15 2008.

� The submission of request files for ALOS simulation number 10 is due by 20th June 2008.

� The submission of request files for ALOS simulation number 9 was due by March

21, 2008

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� 29 January 2008: Users are now able to submit orders for ALOS future acquisitions via EOLI-SA (email [email protected] for more information)

� The ALOS PCS Site is now available at:

http://earth.esa.int/pcs/alos/

APPENDIX A PALSAR PRODUCT TYPES Product identifier Meaning P High resolution polarimetric data W Low resolution wideswath mode data H High resolution single (FBS) or dual (FBD)

polarisation data 1.0 Level 0 – raw data 1.1 Level 1 SLC data 1.5 Level 1 multi-look data G Geocoded P Polar Stereographic projection U Universal Transverse Mercator projection A/D Ascending/Descending

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APPENDIX B COHERENCE MEASURES Cross polarisation coherence measure

1)(11||

: −∗∗

∗

− −=

>><<><=

HVVHVHHVHV

VHHVVHHV SNROOOO

OOγ (1)

Cross polarization phase Imbalance: )OOarg(:� VHHV)VHHV(

∗= (2)

Cross polarisation amplitude imbalance |O||O|

:AVH

HV)VHHV( = (3)

Co polarization phase Imbalance: )OOarg(:� VVHH)VVHH(∗= (4)

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APPENDIX C INSTRUMENT ANOMALIES Below is a list of PALSAR anomalies that may have an impact on image quality, radiometric calibration or localisation accuracy (from 24th October 2006).

� Orbit manoeuvres conducted on 5th, 8th August 2008 � Orbit manoeuvres conducted from 2nd August 2008 14:27 – 3rd August 2008 06:05 � Inclination and related in plane orbit manoeuvres conducted from 29th July 22:26 –

31st July 05:42 � Orbit manoeuvres conducted on 19th July 2008.

� LSSR acquisition failure 11th June 2008,

� Orbit manoeuvres conducted on 11th, 14th, 17th, 20th, 23rd June 2008,

� Yaw steering suspended 11th/12th and 14th/15th June 2008.

� Calibration operations for Star Tracker conducted on 11th and 13th of May 2008,

� Orbit manoeuvres conducted on 16th May 2008,

� Orbit manoeuvres conducted on 26th April 2008,

� Orbit manoeuvres conducted on 4th April 2008.

� Orbit manoeuvres conducted on 8th March 2008 .

� Orbit manoeuvres conducted on 2nd, 15th and 29th February 2008.

� Orbit manoeuvres conducted on 26th January and 2nd, 15th, 29th February 2008.

� YAW steering was suspended on 28th January 2008

� Orbit manoeuvres conducted on 4th, 11th, 18th and 26th January 2008.

� Orbit manoeuvres conducted on 15th December 2007, 4th, 11th & 18th January 2008.

� Observation, yaw steering, and precision attitude system suspended on 31st October 2006 between 03:50 and 15:50 UT due to change AOCS on-board orbit model to that of 15th order.

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� Yaw steering suspended during 23rd February 00:12 UT to 24th February 2007 23:01 UT (yaw steering suspended due to calibrating operations for Star Tracker (STT) and Precision Attitude Determination).

� Yaw steering suspended during 22nd March 00:24 UT to 23rd March 2007 23:17 UT

(yaw steering suspended due to calibrating operations for Star Tracker (STT) and Precision Attitude Determination).

� Yaw steering on/off switching on 10th April 2007:

Yaw steering on to off: 12:57 – 13:22 UT (data unavailable) No yaw steering operation: 13:22 – 14:42 UT (data available) Yaw steering off to on: 14:42 – 15:45 UT (data unavailable)

� Orbit manoeuvres on 25th, 27th and 29th April 2007.

� Orbit manoeuvres on 8th and 22nd June 2007.

� Orbit manoeuvres conducted on 7th and 20th July 2007.

� Yaw steering on/off switching on 31st July 2007:

Switching in progress: 00:00 – 00:30, 21:57 – 22:46 UT (Observation suspended) No yaw steering observation: 00:30 – 21:57UT (Data available)

� An anomalous operation found in PALSAR observations on 23rd March, 12th July,

6th August, 17th August, 21st August, and 23rd August 2007. PALSAR shifted into Standby mode in the middle of the observations. Some of PALSAR data observed during the anomaly are corrupt.

� Orbit manoeuvres conducted on 3rd and 25th August 2007.

� An anomalous operation found in PALSAR observations on 5th September and 8th

September 2007; PALSAR shifted into standby mode in the middle of its observation.

� Orbit manoeuvres conducted on 6th, 12th and 26th October 2007.

� Orbit manoeuvres conducted on 10th and 23rd November 2007.

� Orbit manoeuvres conducted on 7th and 15th December 2007.

� Orbit manoeuvres conducted on 4th, 11th, 18th and 26th January 2008.

� Orbit manoeuvres conducted on 2nd, 15th and 29th February 2008.

� Orbit manoeuvres conducted on 8th March 2008.

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� Orbit manoeuvres conducted on 4th and 26th April 2008.

� Orbit manoeuvres conducted on 16th May 2008.

� Orbit manoeuvres conducted on 11th/12th, 14th/15th, 17th, 20th June 2008.

� Yaw steering suspended 11th/12th and 14th/15th June 2008.

� Orbit manoeuvres conducted on 19th and 29th to 31st July 2008.

� Orbit manoeuvres conducted on 2nd/3rd, 5th, 8th August 2008.

� Orbit manoeuvres conducted on 12th & 26th September 2008.

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APPENDIX D NATURAL POINT TARGET ANALYSIS Until cycle 16 no point targets (transponder or corner reflectors) with known NRCS have been identified in the PALSAR products analysed at the ADEN Node, natural point targets have been used instead. Table C.1 gives the natural point target NRCS values for a range of PALSAR products analysed during the cycle. Table C.1 gives measurements for the HH polarisation per product type only. This allows measurements from all beams and products to be compared. Table C.2 gives the polarimetric measurements averaged for all beams.

Product/ swath

B3 B7 B9 B18 B21

P1.1 47.76 ±3.87

W1.5P 40.87 W1.5GP 49.39

±5.28 W1.5GU 55.83 52.77

±0.51 H1.1 (FBD)

49.18 ±6.14

H1.5U (FBS)

34.39 ±2.36

H1.5GU (FBS)

34.40 ±2.92

H1.5GU (FBD)

41.04

Table D.1 Average PALSAR Image Radar Cross-Sections per product and beam in HH polarisation.

Table D.2 gives RCS results per polarisation. As there is high NRCS variation across the various polarimetric channels, the results in the table are for strong point targets in each polarisation (i.e. the same point target is not necessarily used to obtain measurements in all four polarisations). Note the polarimetric mode data are all from Beam 3, while the fine mode data are all from beam 7.

NRCS (dB) Product VV

Mean dB HH

Mean dB VH

Mean dB HV

Mean dB P1.1 49.30±6.31 47.76±3.87 41.13±5.91 44.38±5.51 H1.1(FBD) 49.18±6.14 39.18±6.30

Table D.2 Average PALSAR Image RCS per product and polarisation.

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The above measurements indicate typical NRCS values of non-saturated natural point targets that can be derived from PALSAR products. It is not possible to comment on the radiometric accuracy or stability of the natural point target results. Note that JAXA report a radiometric accuracy of 0.64dB compared to a 1.5dB specification and a stability of 0.5-1.0dB from measurements over the Amazon [2]. Tables D.3 & D.4 give the impulse response function (IRF) results for a variety of PALSAR products. In this table results for different polarisations are not segregated. For comparison, the predicted resolution values are also indicated. For fine and polarimetric mode, the resolutions are generally as expected. An exception is the dual polar ground range products where the azimuth resolution is double that predicted. It should be noted however that these products have 12.5 meter pixels. For wide swath mode, the azimuth resolution is higher than the nominal value by about 25-30m while in range the measurements are higher than the predicted values by up to 60m. However, it should be noted that the wide swath pixel size is 100m and thus these differences are not excessive.

Product Azimuth res (m)

Range res (m)

Predicted Azimuth res (m)

Predicted range res

(m)

No. results

P1.1 5.74±1.35 9.97±0.40 4.48 10.71 40 W1.5P 132.2 125.2 100 Fig 6.2.1 1 W1.5GP 126.38±1.20 126.24±4.20 100 Fig 6.2.1 2 W1.5GU 133.50±9.81 124.23±5.61 100 Fig 6.2.1 11 H1.1(FBD) 4.87±0.35 9.75±0.47 4.52 10.71 8 H1.5U(FBS) 9.31±1.11 11.03±2.71 9.04 Fig 6.2.2 7 H1.5GU(FBS) 9.83±0.07 10.56±3.35 9.04 Fig 6.2.2 4 H1.5GU(FBD) 19.38±2.37 19.97±4.14 10.0 Fig 6.2.3 9

Table D.3 Average PALSAR resolution per product type. Note that the wide swath azimuth bandwidth is not available in the product headers therefore the nominal resolution from [2] is quoted.

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WB1

020406080

100120140160180

15 25 35 45

incidence angle

grou

nd r

ange

res

olut

ion

(m)

predictionmeasurements

Figure D.1 Ground range resolution for wide swath mode (WB1) data.

single polarisation- FBS

0

5

10

15

20

25

30

35

0 20 40 60

incidence angle

grou

nd r

ange

res

olut

ion

(m)

predictionmeasurements

Figure D.2 Ground range resolution for FBS data.

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dual polarisation

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60

incidence angle

grou

nd r

ange

res

olut

ion

(m)

Figure D.3 Ground range resolution for FBD data.

Product ISLR (dB)

PSLR (dB)

SSLR (dB)

No. results

Specification -8.0 -10.0 - - JAXA measure -8.6 -12.5 - - P1.1 -6.25±3.13 - - 31 W1.5P -9.95 -7.76 -13.55 1 W1.5GP -7.15±3.54 -8.03±0.49 -13.11±0.34 2 W1.5GU - -8.28±1.80 -10.89±3.28 5 H1.1(FBD) -5.26±1.84 - 8 H1.5GU(FBS) -2.19±1.38 -7.85±0.17 -5.93±3.71 2 H1.5GU(FBD) -1.16 -12.06±7.79 -11.07±4.52 5 H1.5U(FBS) -3.21±1.55 -8.96±1.59 -13.55±1.77 7 H1.5GU(FBS) -2.19±1.37 -7.85±0.17 -5.93±3.71 2

Table D.4 Average PALSAR sidelobe measures per product type. Note that it has not been possible to measure some of the IRF parameters using natural points. For comparison, the commissioning phase corner reflector measurements [1] are given in Table D.5. In general, the natural point target IRF measurements are as expected.

Product Azimuth res (m)

Range res (m)

ISLR (dB)

PSLR (dB)

SSLR (dB)

1.5(FB) 7.67: 10.5

7.76: 11.23

-9.55 : -1.77

-14.2: -4.99

-15.15: -12.28

1.1(FB) 4.71: 4.78

4.72: 4.78

-8.47 : -5.49

-13.37: -10.84

-20.45: -18.82-

Table D.5 Corner reflector measurement ranges from the commissioning phase [1].

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APPENDIX E UNCHANGED ANALYSIS

E1 AFRICAN RAINFOREST ANALYSIS – WIDESWATH MODE Two wideswath images of the African rainforest have also been analysed – these extend the area of the African rainforest analysed above. These are shown in Figure E.1 where the acquisition dates are 22nd June 2007, 09:24 UT (left) and 17th September 2007, 09:18 UT (right).

Figure E1.1 Browse image of African Rainforest products

ALPSRS075023550_L1.5GEC_20070622092449490

ALPSRS087713550_L1.5GEC_20070917091809106

Figure E1.2 shows the variation in gamma from the central azimuth portion of the 22nd June 2007 scene and from near to far range. There are some variations in gamma across the swath of about 0.5dB – this indicates an incorrectly implemented elevation antenna pattern for some of the sub-swaths. Note that the two bright peaks can also be seen in the full scene in Figure E1.1 (left). There also appears to be a drop off at near and far ranges. Overall there is an increase in gamma of about 0.7dB across the swath as indicated by the straight line fit.

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-7.5

-7.0

-6.5

-6.0

-5.5

0 500 1000 1500 2000 2500 3000 3500 4000

Pixels

Gam

ma

(dB

)

Figure E1.2 Range Gamma profile for the African Rainforest (HH polarisation)

Figure E1.3 shows the variation in gamma from the central azimuth portion of the 17th September 2007 scene and from near to far range. There are some variations in gamma across the swath of about 0.5dB – again this indicates an incorrectly implemented elevation antenna pattern for some of the sub-swaths. Note that the two bright peaks can also be seen in the full scene in Figure E1.1 (right). There also appears to be a drop off at near and far ranges. Overall there is an increase in gamma of about 0.7dB across the swath as indicated by the straight line fit. These results are similar to the previous wideswath image.

-7.5

-7.0

-6.5

-6.0

-5.5

0 500 1000 1500 2000 2500 3000 3500 4000

Pixels

Gam

ma

(dB

)

Figure E1.3. Range Gamma profile for the African Rainforest (HH polarisation)

For the two wideswath images analysed, there are variations in gamma for some of the sub-swaths and a gamma slope across the image.

E.2 CORNER REFLECTOR PT MEASUREMENTS One of the issues from the analysis of the 6 DLR corner reflectors using ALOS Palsar data was the difference in relative radar cross-section between the three Level 1.5 product types

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of single polarisation (FBS), dual polarisation (FBD) and quad polarisation products (PLR) – see ref [1]. Similar results have been obtained in the ground station PT analysis detailed in section 6.2.1. The JAXA processor used for this analysis generates products that are under-sampled in both azimuth and range. A first step in understanding the differences in Level 1.5 relative RCS measurements was to process the Palsar data with adequate pixel sampling. This has been done using the Pulsar processor (the ESA JERS processor) and a preliminary comparison of three Palsar scenes for the two processors has been performed. Data: FBS 1st August 2006, 21:33 UT, Orbit 2769 Figure E2.1 shows the IRF for the Gilching corner reflector from the JAXA processor (HH polarisation). The pixel size is 6.25m by 6.25m and consequently the data is under-sampled, as shown by the sidelobe structure in the re-sampled image, the slices through the peak of the IRF and the power spectra. The IRF parameters of all 6 corner reflectors is shown in Table E2.1 – note that there is quite a variation in the spatial resolution measurements between the corner reflectors, the ISLR values are particularly high and that there is a spread of 2dB in the main lobe total power.

Figure E2.1 Gilching Corner Reflector IRF from the JAXA Processor

(original image, resampled image, IRF slices and power spectra)

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Name Azimuth Resolution

(m)

Range Resolution

(m)

ISLR (dB) PSLR (dB) Main Lobe Total Power

(dB) Gilching 8.67 13.16 -3.31 -9.51 101.50 Etterschlag 10.76 7.79 -8.59 -7.13 100.43 Unterbrunn 8.22 9.86 -1.91 -7.96 99.52 Tietenbrunn 7.95 12.48 -1.05 -6.11 101.09 Frieding 8.32 10.03 -3.65 -8.58 99.76 Maising 9.30 10.37 -7.38 -7.32 100.74 8.87±1.04 10.62±1.94 -4.32±3.02 -7.77±1.19 100.51±0.76

Table E2.1 JAXA Processor DLR Corner Reflector IRF Parameters

Figure E2.2 shows the IRF for the Gilching corner reflector from the Pulsar processor. Since the pixel size is 3.5m by 3.5m, the data is adequately sampled. Now the IRF sidelobe structure is not dominated by the pixel size but by the spatial resolution as is shown in the re-sampled and IRF slices. The power spectra shows the data is in fact slightly over-sampled. The IRF measurements are shown in Table E2.2. Now the spatial resolution measurements are consistent between the corner reflectors, the ISLR values are close to the theoretical value (-13.3dB) and the spread of main lobe total powers is quite small. The corner reflector RCS values are just over 2 dB lower than the nominal RCS of the corner reflectors (37.9dB).

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Figure E2.2 Gilching Corner Reflector IRF from the Pulsar Processor

(original image, resampled image, IRF slices and power spectra)


(m)

Range Resolution

(m)

ISLR (dB) PSLR (dB) Main Lobe Total Power (dB)

Rel RCS (dB)

Gilching 9.07 8.48 -7.62 -18.23 83.21 -1.77 Etterschlag 8.72 8.55 -13.43 -18.41 82.53 -2.97 Unterbrunn 8.91 8.30 -3.88 -17.60 82.67 -1.49 Tietenbrunn 9.16 9.49 -7.89 -18.60 83.31 -1.71 Frieding 8.86 8.54 -12.57 -19.68 83.16 -2.30 Maising 9.04 8.46 -13.04 -19.18 83.08 -2.38 8.96±

0.16 8.64± 0.43

-9.74± 3.87

-18.62± 0.73

82.99± 0.32

-2.10± 0.55

Table E2.2 Pulsar Processor DLR Corner Reflector IRF Parameters The measured spatial resolutions for the Pulsar data are quite close to the theoretical values: azimuth 8.96±0.16m c.f. 8.65m and range 8.64±0.43m c.f. 8.39m. The standard deviation of the JAXA spatial resolutions are much larger than for the Pulsar values and the JAXA range resolution of 10.62±1.94m is quite different from the theoretical values of 7.57m. Note that the number of effective azimuth looks is different for the Pulsar (1.89) and JAXA (2) data. Data: FBD 14th July 2006, 09:42 UT, Orbit 2499 The IRF parameters of all 6 corner reflectors are shown in Table E2.3 for the JAXA processor and Table E2.4 for the Pulsar processor. Note that for the Pulsar data, the average relative RCS is quite close to zero.

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(m)

Range Resolution

(m)


(dB) Gilching 20.61 15.40 -3.11 -8.42 100.20 Etterschlag 15.23 16.33 -0.23 -8.78 97.18 Unterbrunn 15.18 15.39 -3.97 -8.35 97.61 Tietenbrunn 17.11 15.62 -1.23 -8.22 98.38 Frieding 15.16 17.49 -0.30 -8.96 97.98 Maising 15.26 16.14 -3.22 -8.68 97.89 16.43±2.19 16.06±0.80 -2.01±1.63 -8.57±0.28 98.21±1.06

Table E2.3 JAXA Processor DLR Corner Reflector IRF Parameters


(m)

Range Resolution

(m)


Rel RCS (dB)

Gilching 17.17 14.62 -12.70 -18.10 80.60 0.41 Etterschlag 17.36 14.50 -11.13 -19.78 79.32 -0.79 Unterbrunn 17.35 14.75 -12.30 -18.72 80.42 0.27 Tietenbrunn 17.31 14.71 -12.27 -18.33 80.56 0.40

Frieding 16.81 14.71 -6.59 -19.87 80.25 0.69 Maising 16.97 14.67 -10.52 -20.17 80.33 0.30

17.16± 0.23

14.66± 0.09

-10.92± 2.27

-19.16± 0.88

80.25± 0.47

0.21± 0.51

Table E2.4 Pulsar Processor DLR Corner Reflector IRF Parameters The measured spatial resolutions for the Pulsar data are quite close to the theoretical values: azimuth 17.16±0.23m c.f. 17.09m and range 14.66±0.09m c.f. 14.46m. This is not the case of the JAXA data: azimuth 16.43±2.19m c.f. 18.09m and range 16.06±0.80m c.f. 14.41m. Note that the number of effective azimuth looks is different for the Pulsar (3.25) and JAXA (4) data. Data:PLR 15th November 2006, 10:05 UT, Orbit 4308 The IRF parameters of all 6 corner reflectors are shown in Table E2.5 for the JAXA processor and Table E2.6 for the Pulsar processor. Note that for the Pulsar data, the average relative RCS is quite close to zero.

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(m)

Range Resolution

(m)


(dB) Gilching 15.14 18.08 0.08 -3.84 95.76 Etterschlag 18.91 22.26 -1.69 -8.70 98.81 Unterbrunn 17.05 20.73 0.99 -10.39 98.46 Tietenbrunn 24.67 15.32 -4.69 -7.00 98.46 Frieding 15.11 38.87 -9.39 -7.43 97.85 Maising 14.94 30.21 -4.00 -8.45 99.46 17.64±3.78 24.25±8.76 -3.12±3.79 -7.64±2.20 98.13±1.28

Table E2.5 JAXA Processor DLR Corner Reflector IRF Parameters The spatial resolution measurements are much more consistent between the corner reflectors in Table E2.6 but the ISLR values are quite variable from corner reflector to corner reflector due to the weak sidelobes. The spread of main lobe total powers is quite small. The average relative RCS is below zero but with quite a large standard deviation (due to the variation in ISLR). In this case the ISLR should not be included in the calculation of the RCS which would give a mean relative RCS for all the corner reflectors of -3.12±0.42dB.


(m)

Range Resolution

(m)


Rel RCS (dB)

Gilching 17.69 25.85 1.01 -13.91 76.59 -0.26 Etterschlag 17.36 26.07 -1.83 -14.29 77.29 -0.96 Unterbrunn 17.28 27.11 3.71 -11.10 77.04 1.97 Tietenbrunn 17.41 26.64 -14.52 -15.74 77.63 -2.58 Frieding 17.02 25.77 1.05 -10.06 76.58 -0.26 Maising 16.49 26.50 -6.85 -16.40 77.13 -2.38 17.21±

0.41 26.32±

0.52 -2.91± 6.73

-13.58± 2.52

77.04± 0.41

-0.75± 1.67

Table E2.6 Pulsar Processor DLR Corner Reflector IRF Parameters The measured spatial resolutions for the Pulsar data are quite close to the theoretical values: azimuth 17.21±0.41m c.f. 17.09m and range 26.32±0.52m c.f. 26.19m. The standard deviation of the JAXA spatial resolutions are much larger than for the Pulsar values while the measured JAXA values are comparable with the theoretical values (within the standard deviation). Note that the number of effective azimuth looks is different for the Pulsar (3.25) and JAXA (4) data.

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Summary For the three PALSAR datasets processed by the Pulsar processor, an initial assessment is that changing the sampling rate of the data has not resulted in significant changes to the relative RCS levels of the corner reflectors. However, the point target resolution and sidelobe properties are closer to their theoretical values.

E3 RADIOMETRIC RESOLUTION

Table E3.1 gives the radiometric resolution and the equivalent number of looks for a range of products. The measures quoted are averaged over different beams and polarisations. The measured ENL are close to the actual ENL used in the processing.

Product Actual ENL

Equ. No. Looks(ENL)

Rad Res (dB)

No. Results

P1.1 1 0.87±0.08 3.17±0.10 9 P1.5 4 4.23±0.20 1.72±0.03 4

H1.1 (FBS) 1 0.98 3.04 1 H1.5 (FBS) 2 1.28±0.34 2.79±0.30 5 H1.1 (FBD) 1 0.82±0.02 3.24±0.04 2 H1.5 (FBD) 4 3.35±0.26 1.89±0.06 6

W1.5 8 7.21±2.45 1.41±0.20 7 Table E3.1 PALSAR measured equivalent number of looks and radiometric resolution.

E4 AMBIGUITY MEASUREMENTS

JAXA [2] indicate that range ambiguities of -23dB have been observed, compared to a specification of -16dB. Azimuth ambiguities of -11dB have been observed (in both fine and wide swath imagery) in ADEN node data from the 17th May 2007 (compared to a specification of -16dB). Azimuth ambiguities have been measured up to -13.54dB in HV polarisation and up to -15.05dB in HH polarisation for orbit 5728, frame 6760 (acquired 20th February 2007). Further HH ambiguity measurements have been made in this cycle in the range -13.45dB to -14.3dB have been made for a product from orbit 11558, Frame 2800 from the 26th March 2008. Range ambiguities have also been observed in ADEN node data, to date only in fine mode data.

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APPENDIX F BEAM NUMBERS This table has been extracted from [4].

Table 8-1 – Beam numbers vs. Off nadir angle

ADEN ALOS PALSAR CYCLIC REPORT 09 SEPTEMBER 2008 TO 25 OCTOBER 2008 · 2015. 3. 27. ·...

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