CRYOSAT ICE DATA QUALITY STATUS SUMMARY

Transcription

1 esrin Via Galileo Galilei Casella Postale Frascati Italy T F CRYOSAT ICE DATA QUALITY STATUS SUMMARY 3 rd August 2017

2 Prepared by: R.Mannan (Telespazio UK) CryoSat Quality Team (IDEAS+) Approved by: J.Bouffard (ESA-ESRIN) P.Femenias (ESA-ESRIN) CryoSat Data Quality Manager CryoSat, ESA Technical Officer 2

3 TABLE OF CONTENTS 1 Introduction Purpose and Scope Applicable Ice Processing Baseline and Ice Products Referenced Documents Acronyms and Abbreviations Overview Summary Table of Tracked Anomalies Summary Table of Sporadic Anomalies Summary Table of Planned Evolutions Anomalies Level 1 Data Anomalies Level 2 Data Anomalies Anomalies affecting L1 and L2 Data Issues Affecting Sporadic Products Planned Evolutions IPF Anomalies Closed With The Latest CryoSat Processing Baseline

4 1 INTRODUCTION 1.1 Purpose and Scope This document provides details of all known anomalies and planned evolutions which are being tracked, and that could affect the quality of the CryoSat Ice Level-1 and Level-2 data products operationally generated by the Ice Processor and distributed by ESA. This list of anomalies and potential evolutions is complete and up to date as of 03 August An updated version of this document is released on a quarterly basis and includes any additional anomalies identified since the previous version of this document. 1.2 Applicable Ice Processing Baseline and Ice Products The anomalies and evolutions discussed in this document are related to CryoSat data products processed with the latest version of the CryoSat IPFs; Baseline-C (IPF1 vm1.0.2 & IPF2 vm1.0.4). Further information on historic processor versions and dates of when operational CryoSat data production with each processor was commenced is available on the CryoSat IPF Baseline webpage. Figure 1 highlights (in red) the applicable CryoSat Ice Products which are relevant to this document. Further information on the products is also provided below. Figure 1 CryoSat Data Products 4

5 Level 1B & Level 2 CryoSat Ice Products are distributed in order to specifically achieve the Mission objectives over the cryosphere. CryoSat L1B Ice Products consist of an echo for each point along the ground track of the satellite. In all three modes, the data consist of multi-looked echoes at a rate of approximately, 20 Hz. The L1B products contain time and geo-location information as well as SIRAL measurements in engineering units. Calibration corrections are included and have been applied to the window delay computations. CryoSat L2 Ice Products consist of individual estimates of the surface elevation and other surface parameters, such as the radar backscattering coefficient, determined from each echo in the Level 1B data. L1B and L2 offline Ice Products (LRM, SAR & SARIn) are generated 30-days after acquisition using a Precise Orbit file and the geophysical corrections are computed from analysis ADFs. The L1B and L2 FDM products are generated in NRT, 2-3 hours after acquisition, using a Predicted Orbit file and the geophysical corrections are computed from forecast ADFs. In both cases all corrections are included in the data products and therefore the range can be calculated by taking into account the surface type. 1.3 Referenced Documents The following list is a list of documents with a direct bearing on the content of this report. Where referenced in the text, these are identified as RD.n, where 'n' is the number in the list below: RD.1 RD.2 CRYOSAT Ground Segment Instrument Processing Facility L1b Products Format Specification, CS-RS-ACS-GS-5106, 6.4 CRYOSAT Ground Segment Instrument Processing Facility L2 Products Format Specification, CS-RS-ACS-GS-5123, Acronyms and Abbreviations ADF AR DEM ESA FDM GDR IDEAS IPF Auxiliary Data File Anomaly Report Digital Elevation Model European Space Agency Fast Delivery Marine mode Geophysical Data Record Instrument Data quality Evaluation and Analysis Service Instrument Processing Facility L0/L1B/L2 Level 0/Level 1B/Level 2 5

6 LRM NRT PCONF PDS RMS SAR SARIn SID SIRAL SPR SW TTO Low Resolution Mode Near Real Time Parameter Configuration File Payload Data System Root Mean Square Synthetic Aperture Radar mode SAR Interferometric mode SARIn Degraded SAR Interferometric Radar Altimeter Software Problem Report Software Transfer to Operations 6

7 2. OVERVIEW 2.1 Summary Table of Tracked Anomalies The table below lists all the current anomalies which have been tracked for operational CryoSat Ice Baseline-C products and shall be fixed in an upcoming processing baseline. The table also summaries which specific data processor and product mode/level is affected by each anomaly. Further details on each anomaly can be found in Section 3 of this document Anomaly ID Product Mode/Level Affected Level 1B Level 2 LRM SAR SIN FDM LRM SAR SIN FDM GDR To be fixed in Baseline CRYO-IDE-182 No No No Yes No No No No No D CRYO-IDE-205 No Yes Yes No No No No No No D CRYO-IDE-214 No No No No No Yes Yes No No D CRYO-IDE-217 No No No No No No No Yes No D CRYO-IDE-221 No No No No No Yes No No No D CRYO-IDE-223 No Yes Yes No No No No No No D CRYO-IDE-224 Yes Yes Yes Yes No No No No No E CRYO-IDE-226 No No Yes No No No No No No E CRYO-IDE-233 No No No No No No No No Yes D CRYO-IDE-241 Yes Yes Yes Yes Yes Yes Yes Yes No D CRYO-IDE-243 No Yes Yes No No No No No No D CRYO-IDE-248 Yes Yes Yes Yes No No No No No D CRYO-IDE-254 No Yes Yes No No No No No No D CRYO-IDE-258 No No No No Yes Yes Yes Yes Yes D CRYO-IDE-260 Yes Yes No No No No No No No D CRYO-IDE-263 Yes Yes Yes No No No No No No D CRYO-IDE-272 No Yes Yes No No Yes Yes No No D CRYO-IDE-273 Yes Yes Yes Yes Yes Yes Yes Yes No D 7

8 CRYO-IDE-274 Yes No No No No No No No No D CRYO-IDE-275 No Yes Yes No No No No No No D CRYO-IDE-276 No No No No No Yes No No No D CRYO-IDE-277 No No No No Yes Yes Yes No No D 2.2 Summary Table of Sporadic Anomalies The table below lists some anomalies, which have been detected for only specific periods or datasets. The table below also provides a summary of which specific data processor and product mode/level is affected by each anomaly. Full details of each notice can be found in Section 4 of this document. AR ID Product Mode /Level Affected Data Validity Period Affected CRYO-IDE-196 L2 FDM 09/09/ :44:00-10/09/ :40:00 CRYO-IDE-197 L1 & L2 LRM, SAR & SARIn 08/09/ /09/2013 CRYO-IDE-220 L2 FDM 01/11/ :30:00-02/11/ :15:00 CRYO-IDE-251 L1 SAR (FBR) 04/03/ Summary Table of Planned Evolutions The table below lists all the Ice Baseline-D (Q2 2018) and Baseline-E evolutions, which have been planned for CryoSat Ice products. Further details for each evolution can be found in Section 5 of this document. Evolution ID Title Future Ice Processing Baselines CRYO-IDE-210 Perform IPF1 multi-look without zeroes introduced by contributing beam alignment E (TBC) CRYO-IDE-219 Freeboard computation over the SARIn Sea Ice area D CRYO-IDE-222 Along-track slope calculation from the Doppler shift E (TBC) CRYO-IDE-232 Freeboard computation over the SARIn Sea Ice area D CRYO-IDE-235 Star Tracker File Format Change D CRYO-IDE-239 USO frequency correction on window delay D 8

9 CRYO-IDE-244 Inconsistency between L1b 1Hz waveform and L2 1Hz height D CRYO-IDE-245 Pitch estimation from CS-2 data in L1B D CRYO-IDE-249 New L1b-S Stack Product for CryoSat E (TBC) CRYO-IDE-250 Pseudo LRM Processing from SARIn Acquisition E (TBC) CRYO-IDE-252 Change the EECFI flag for aberration correction to Reverse and Update attitude biases D CRYO-IDE-255 SAR/SARIn Stack Peakiness parameters for new sea-ice discrimination D CRYO-IDE-256 Uncorrected range and altitude to be included in L2/L2i/GDR D CRYO-IDE-257 New High Resolution tidal model over the Polar Oceans E (TBC) CRYO-IDE-261 Switch from EE to NetCDF Format D CRYO-IDE-262 STR Process with Auxiliary File for varying mispointing angle biases D CRYO-IDE-264 Tune/Improve the Baseline C retrackers over sea-ice (Artic + Antarctic) and Land ice areas D CRYO-IDE-266 Improved information on surface characteristics D CRYO-IDE-269 Link between 1Hz and 20 Hz measurements D CRYO-IDE-270 Decommissioning of FDM production D (TBC) CRYO-IDE-278 New Snow Depth correction dedicated to sea-ice areas and land ice areas D 9

10 3. ANOMALIES 3.1 Level 1 Data Anomalies AR ID CRYO-IDE-182 AR Title FDM not using DORIS navigator orbit IPF1 Task Table FDM FDM orbit data processing preferably uses the DORIS Navigator Orbit (DOR_NAV). However, when this is not available the FOS Predicted Orbit (MPL_ORBPRE) is used instead. However, the usage of the FOS Predicted Orbit causes FDM outliers. This issue currently affects ~6% of FDM products and will be closed following an update of the FDM Task Tables within the next IPF update (Baseline-D) Solution identified due to be closed with Baseline-D AR ID CRYO-IDE-205 AR Title Spike Correction in CAL2 SAR and SARIn Products IPF1 CAL2 SAR & SARIn The CAL2 SAR code was unintentionally changed in Baseline-C. The reason of this unwanted modification is that both CAL2 SAR and CAL2 SARIN code share the same spike correction routine that was initially modified for Baseline-C to implement a new algorithm for CAL2 SARIn spike interval. The modification of the L1 Processor Configuration File (PCONF1) is now required in order to have one spike correction algorithm specific to CAL2 SAR and one specific to CAL2 SARIN. The changes expected are: PCONF1 has a new parameter for SAR called SpikeNumIterations set to 0 PCONF1 has a new parameter for SARIn called SpikeNumIterationsSARIN set to 12 Solution identified due to be closed with Baseline-D 10

11 AR ID CRYO-IDE-223 AR Title Issue in L1B Time Increment IPF1 SAR & SARIn There is currently an anomaly in the L1B data whereby there is a jump in time, after which time increments slowly and oscillates. This currently has a bad effect on latitude, longitude and altitude and, as expected, window delay is also affected. The net effect of this anomaly is seen in the Surface Height Anomaly, which impacts the interpolated sea-surface used for freeboard recovery. This origin of the issue is now understood and an implementable solution designed. Solution identified due to be closed with Baseline-D AR ID CRYO-IDE-224 AR Title Outliers in CAL1 LRM Gain Variation Type2 corrections IPF1 FDM, LRM, SAR & SARIn Within the framework of Baseline-C, outliers were detected in the CAL1 LRM gain Variation Type-2 corrections, which are used in the high level science processing. The issue has already been investigated and it has been confirmed that the problem is not related to the processor itself, but it relates to a wrong value for the reference power gain of CAL1 LRM within the IPF Data Base (IPF DB) in usage. It has been verified that by updating the L1 Parameter Configuration File (PCONF1) parameters, the outlier in CAL1 LRM Gain Variation correction can be avoided. However, those parameters are shared by all the modes, so changing them would have an impact on CAL1 LRM, CAL1 SAR and CAL1 SARin. This impact is under analysis. Under Investigation - further analysis required. Fix postponed to Baseline-E AR ID CRYO-IDE-226 AR Title Missed quantized values in CAL1 SARin Path Delay correction on Rx1 IPF1 CAL1 SARIn An issue has been detected regarding the CAL1 SARin Path Delay correction on Rx1; the Path Delay Correction on Rx1 from CAL1 SARIn products does not seem to assume the values equal to -9884, or -9886, but instead always assumes values higher or lower than these. Under Investigation - further analysis required.fix postponed to Baseline E 11

12 AR ID CRYO-IDE-243 AR Title Memory issues in Specialized SAR/SARIn IPF1 IPF1 SAR & SARIn During testing of the fix proposed to resolve AR CRYO-IDE-223, some memory issues have been identified, affecting the Specialized SAR/SARIn IPF1 in cases of empty stacks before and after SSS weighting. When there is a (big) time jump within the FBR data, the SSS just after and before the jump contains only contributing beams acquired at the high look angle (in absolute values). When the SSS weighting is applied, those contributing beams are all discarded and the processing steps go ahead on those SSS with no contributing beams. The issue is due to the fact that, when all contributing beams of a given surface sample are discarded (before or after the SSS weighting), the buffer of surface samples is not shifted and the memory occupied by the last SS structure is not released. The IPF1 will be updated to ensure when all the contributing beams of a surface sample are discarded, the buffer shall be shifted and the memory released. Solution identified due to be closed with Baseline-D AR ID CRYO-IDE-248 AR Title Error in writing function of CAL2 Flag in MCD IPF1 FDM, LRM, SAR and SARIn If the CAL2SIN1 file, CAL2SIN2 file or CCAL1 file is not provided as input to the L1B processor, the corrections for both CAL2 and CCAL1 are taken from the IPFDB. In this case, the Measurement Confidence Data (MCD) flag for CAL2 and CCAL1 should be set to =1, indicating that the calibration correction has been taken from IPFDB However, it has been noted that there is currently an issue is in the writing function of the MCD where the flag for Cal2 from IPFDB is not written because the lines of code to package the flag in the MCD word are missing. Solution identified due to be closed with Baseline-D AR ID CRYO-IDE-254 AR Title Time anomaly in last SS in L1b product IPF1 SAR & SARIn There have been instances of time anomalies (in particular non-monotonically increase of the time stamps) in correspondence of mode transitions. In one specific SARIn example, it was found that the product was nominal but that there is one waveform that is around 0.7 seconds afterwards and occurs after the next LRM waveforms. Following analysis of the product, an issue concerning the timestamp 12

13 of the last computed Surface Sample has been found; nominally Surface Samples are placed at ~20Hz distance from each other (~0,05 sec), however due to this anomaly, in this product the last Surface Sample is instead placed at a distance of ~0.7 sec from the previous one. A proposed solution has been tested for SARIn, and further analysis is being performed for SAR. Solution identified due to be closed with Baseline-D AR ID CRYO-IDE-260 AR Title SIRAL LRM/SAR path delay - bias / Trend/Noise IPF1 LRM & SAR During an analysis of SIRAL calibration, the path delay evolution along the mission was investigated and some discrepancies were noted between LRM and SAR: 1. A ratio of 5 in the trend between LRM and SAR (0.007 vs mm/month); 2. LRM measurement is more noisy; 3. A bias of around 7mm, which is known and expected An analysis is currently ongoing in order to determine whether (1) and (2) are caused by a processing issue or even the CAL1 LRM design itself that does not allow to get the same accuracy as CAL1 SAR Under Investigation - due to be closed with Baseline-D AR ID CRYO-IDE-263 AR Title Unavailability of Star Tracker L0 products relevant to the "star tracker in use" IPF1 LRM, SAR & SARIn In its current implementation, the Baseline C Star Tracker Processor uses data of the star tracker next in the priority list if the Star Tracker data of the Star Tracker in use are not available. However, this behaviour doesn t assure the best quality of the STR_ATTREF product and in turn of the higher level CryoSat products at L1B. A full analysis has been performed to identify the occurrence of this anomaly in order to potentially adapt the star tracker processor behaviour for Baseline D. Issue under investigation - due to be closed with Baseline-D 13

14 AR ID CRYO-IDE-274 AR Title Unexpected Values for AGC ch1 IPF1 LRM During an analysis of L1B LRM products, it has been verified that in some products negative AGC commands are annotated and this is not expected as all the AGC corrected gains, which are known by calibration, should be greater than zero. The values annotated in AGC Channel1 are expected to correspond to the AGC corrected gains that are contained in the CCAL1 product which is input to the generation of the L1B products. Solution identified due to be closed with Baseline-D AR ID CRYO-IDE-275 AR Title Interburst Alignment IPF1 SAR & SARIn There is currently a SW bug in the IPF1 chain for SAR and SARIn products. The bug is in the processing function which aligns the bursts for the altitude rate; currently this alignment is not performed in Baseline-C. In order to resolve this issue a switch has to be enabled in the PCONF which will be performed with the Baseline-D update. Solution identified due to be closed with Baseline-D 14

15 3.2 Level 2 Data Anomalies AR ID CRYO-IDE-214 AR Title Window delay is not referred to the central sample of the waveforms IPF2 SAR & SARIn Window delay, prior to the Baseline-B, was referred to the centre of the processed L1B waveforms. During the updates for Baseline-B, due to the fact that the waveforms were cut after the oversampling in order to fit into the L1B product, the window delay was corrected in order to be referred to the centre of the L1B waveform annotated in the product. In Baseline-C the length of the L1B waveform was due to be increased, as a result the window delay also needed to be updated in order to ensure there was not a window delay that still referred to bin 64 for SAR and 256 for SARin; the Window delay was to be corrected in order to be referred to the centre of the L1B waveforms of Baseline-C. However, it was noted that this change in Baseline-C also affected the L2 SARIn products because the same parameter is not only used to refer the window delay to the central sample of the waveform but also for the computation of the Peakiness. The new values of L2 Peakiness computed with this new parameter flag the data as bad. It was therefore agreed to change the window delay to the central sample for SAR only, and to add a new bias value for SARIn. This AR was closed for the IPF L1B products in Baseline-C, but has been kept open for what concerns the IPF2 SARIn products for which a full fix will be provided in Baseline-D Solution identified due to be closed with Baseline-D AR ID CRYO-IDE-217 AR Title FDM Wind Speed Bias IPF2 FDM During the validation of CryoSat LRM Wind and Wave products, ECMWF have presented results showing that the CryoSat FDM Wind Speed presents a bias vs. ECMWF model data. The bias is larger than 1 m/s, which exceeds that of other missions such as Envisat or ERS. The computation and calibration of the FDM sigma0 needs to be reviewed and adjusted at least to the one of the IOP/GOP products. ESA requires that all ESA Altimetry missions generate inter-calibrated and homogeneous wind speed. The resolution for this anomaly requires a recalibration of Sigma0 and will be implemented in a future IPF update of the Ice processors and/or within the upcoming 15

16 NOP (Near Real Time Ocean Products) Under investigation Due to be closed in Baseline D AR ID CRYO-IDE-221 AR Title Define and optimise strategy for L2 NRT SAR Production IPF2 SAR Currently there is a block on the production of SAR data in NRT. The reason for this known and is due to an entry in the L2 Task Table for SAR, which currently requires all SAR processing (Offline and NRT) to wait for the Sea Ice Concentration file. This auxiliary file is only available after 30 days, so whilst this does not pose an issue for the Offline processing it does currently mean NRT processing in this mode cannot proceed. This AR is opened to review, in addition to the Task Table for SAR, all Task Table entries for NRT processing, in all modes. The resolution to this issue requires an update to the L2 SAR Task Table and is envisaged to be included in Baseline-D Fix known due to be closed with Baseline-D AR ID CRYO-IDE-233 AR Title Incorrect usage of NRT L2 products in the GDR chain IPF2 GDR GDR products should be composed of the L2 OFFL products specific to a single orbit. However, the use of the NRT products within GDR processing has been detected. This often leads to meteo corrections being missing from the GDR products where these NRT products are used as input. The usage of the NRT L2 products in the GDR chain is due to the current GDR Task Table setting which is currently set to trigger the L2 products in ALL the possible modes, which means the IPF will download all the L2 products found within the Processing Window, independently from the mode. Fix known due to be closed with Baseline-D AR ID CRYO-IDE-258 AR Title Non-monotonically increase of time stamp at Mode transitions IPF2 LRM, SAR & SARIn A verification activity was completed in order to check if there have ever been any time anomalies, specifically non-monotonically increase of time stamps, corresponding to 16

17 mode transitions Time should monotonically be increasing; mode transitions are about 0.2 seconds in length, which on the ground is ~1.2 km. A SAR surface location could go a bit beyond this due to surface slope, but should not go that much forward. Within a few products it has been noted that there are extra waveforms after the mode transition which should not be present. Solution identified due to be closed with Baseline-D AR ID CRYO-IDE-273 AR Title Missing xref global attributes IPF2 LRM, SAR & SARin Verification of the Baseline-C NetCDF TDS was performed and it has been noted that some products are missing the mandatory global attributes xref_dip_map, ixref_iono_cor and xref_sai Solution identified due to be closed with Baseline-D AR ID CRYO-IDE-276 AR Title Low values of SAR Sea Ice Concentration IPF2 SAR During verification of the Baseline-C NetCDF TDS it has been noted that sea ice concentration values are very low (between 0 and 1 percent). The values in the NetCDF file are between 0 and 100, but the reported scaling factor is 0.01, so that would scale between 0 and 1. The issue is related to the attribute scale factor, which is to be updated with Baseline-D in order to resolve this issue. Solution identified due to be closed with Baseline-D AR ID CRYO-IDE-277 AR Title Increased number of points flagged as bad in inland water areas (from Baseline-B to Baseline-C) IPF2 LRM, SAR & SARIn It has been reported that CryoSat L2 products over in-land waters contains some inconsistent/non-geophysical biases. It has been noted that there is a lack of relevant documentation detailing the recipe to use Baseline-C CryoSat L2 data for Inland applications, in addition there are several aspects which need to be considered; some of them are mode dependant (~59 m bias to compensate the Window Delay not referred to central sample of the SARin 17

18 waveform) whereas others are related to flag applications/warning/ retracker sensitivity. This issue will be further investigated and therefore precisely documented in the light of the inland user community. Based on the outcome of the investigation, ESA will publish a short Technical Note detailing the way to proceed with L2 Baseline-C data over inland areas. Under investigation planned to be included with Baseline-D 3.3 Anomalies affecting L1 and L2 Data AR ID CRYO-IDE-241 AR Title Discrepancy in L1B and L2 Filename Validity IPF1 & IPF2 FDM, LRM, SAR & SARIn An issue has been flagged whereby the L1B products generated have slightly different start/stop validity in the filename to the corresponding L2 product. The discrepancy between L1 and L2 product times only seems to affect SAR and SIN data; the time difference is always just 1 second with the L2 product being the shorter one. Under investigation due to be closed with Baseline-D AR ID CRYO-IDE-272 AR Title Duplicated datation in time_avg_01_ku and time_20_ku variable IPF1 & IPF2 SAR & SARIn During the verification of the Baseline-C NetCDF TDS it has been reported that in some products the last value of time_avg_01_ku is identical to the previous (one but last) value. The issue is also known to affect the current operational Baseline-C Earth Explorer products. It is believed this issue may be related to CRYO-IDE-223. Solution identified due to be closed with Baseline-D 18

19 4 ISSUES AFFECTING SPORADIC PRODUCTS AR ID CRYO-IDE-196 AR Title L2 FDM processing failures on 9th-10th September 2013 IPF2 FDM Between 9th September :44:00 and 10th September :40:00, all L2 FDM orders failed, causing L2 FDM data to be missing for this period. This seems to have been caused by a problem with the geocorrection CFI initialisation indicating a problem with the use of the meteo auxiliary files by the IPF. For the whole period 8th-10th September 2013, some auxiliary analysis files and forecast files have an incorrect format. The cause of this issue was due to corrupted Auxiliary Data Files; however the issue has not affected any further operational data. Period Affected 09/09/ :44:00-10/09/ :40:00 AR ID CRYO-IDE-197 AR Title Meteo corrections missing in L1B and L2 products IPF1 & IPF2 LRM, SAR & SARIn All L1 and L2 offline products from 00H to 18H on the 8th September 2013 are missing the meteo corrections. Checks show that all the necessary files were available at the time of offline processing (8th-9th October), but were not used. This problem is related to CRYO-IDE-196. Both anomalies are related to the same problem where for the whole period 8th-10th September 2013, some auxiliary analysis files and forecast files have an incorrect format. The cause of this issue was due to corrupted Auxiliary Data Files; however the issue has not affected any further operational data. Period Affected 08/09/ /09/2013 AR ID CRYO-IDE-220 AR Title L2 FDM Processing Errors IPF2 FDM Between 1 st November 2014 ~0530h and 2 nd November ~1215h all L2 FDM orders failed, causing L2 FDM data to be missing for this period. The cause of this issue was due to corrupted Auxiliary Data Files; however the issue has not affected any further operational data or the corresponding L1 FDM dataset Period Affected 01/11/ :30:00-02/11/ :15:00 19

20 AR ID CRYO-IDE-251 AR Title Problematic SIRSAR_FR files IPF1 SAR There are 5 SAR FBR files which contain invalid data inside. For example, the number of pulses per burst is a huge number, not 64. The five file names of the.tgz files are below: CS_LTA SIR1SAR_FR_ T004442_ T011559_C001.TGZ CS_LTA SIR1SAR_FR_ T011632_ T015508_C001.TGZ CS_LTA SIR1SAR_FR_ T071049_ T074630_C001.TGZ CS_LTA SIR1SAR_FR_ T081217_ T083827_C001.TGZ CS_LTA SIR1SAR_FR_ T085009_ T092009_C001.TGZ Following investigation, it has been confirmed that this issue of the 5 corrupt FBR products was due to a problem on the reprocessing platform the issue did not affect any operational processing and is limited to the list of products above. Period Affected 04/03/2013 (see above for specific filenames affected) 20

21 5 PLANNED EVOLUTIONS Evolution ID CRYO-IDE-210 Evolution Title Perform IPF1 multi-look without zeroes introduced by contributing beam alignment The multilooking process within the L1 SAR and SARIn processors should not take into account the zeroes introduced by the alignment of the contributing beams. For each surface sample, i.e. a point on Earth surface, a 20Hz Level-1B waveform is computed by multilooking (averaging) of the corresponding Surface Sample Stack (SSS). The SSS is the collection of all the single-look waveforms that are referred to the current surface sample. By averaging all the single-look waveforms in the SSS, the 20Hz level1b multilooked waveform is obtained. The main objective of averaging the SSS is to reduce the impact of the speckle. Averaging is the crucial operation in the multilooking and it determines the shape of the 20Hz Level-1B waveform. The stack is constructed by aligning the single look echoes with respect to the delay of each burst with respect to the surface sample. Since the acquisition window of the instrument is limited, the single look echoes from different bursts cannot cover the same interval of delays; when there is no data the samples of the stack matrix are set to zero. The problem arises from the fact that the multilook average is computed dividing by the number of the contributing beams and it does not take into account that lot of samples are equal to zero because they were out of the acquisition window for the corresponding single look echo. Further R&D required studying impact on L2. Potentially included in ice Baseline-E Evolution ID CRYO-IDE-219 Evolution Title Freeboard computation over the SARin Sea Ice area Output of freeboard measurements within the L2 product are due to be activated with the new Baseline-C and will be included in the data release from the next reprocessing campaign. Baseline-C now allows computing the freeboard over the sea-ice areas, where CS-2 generally operates in SAR mode. However, CS-2 previously operated in SARin mode over a relatively limited sea-ice area of the Arctic Ocean for which the freeboard will not be computed with Baseline-C. Since 15/09/2014 (CW-38), it has been agreed to switch to SAR mode over this region in order to allow for a freeboard computation over this particular zone. It is however relevant to upgrade the IPF2 in order to calculate the freeboard in the SARin Arctic area, from the beginning of the mission to CW-38. Such a freeboard computation over a sea-ice SARin area without SAR/SARin discontinuity is indeed feasible as recently demonstrated in the paper from Kurtz et al (2014, The Cryosphere). Evolution planned to be included with Baseline-D 21

22 Evolution ID CRYO-IDE-222 EvolutionTitle Along-track slope calculation from the Doppler shift An observation was noted about the about the along track slope calculation from the Doppler shift. It has been proposed to calculate this extremely useful parameter from the L0 data and include it in the L1b/L2 product. It is currently not possible to do this with the L1 data because the doppler data have been previously summed. The feasibility of extracting this parameter and integrate it in L1 and L2 product is under investigation and may be included within the framework of Baseline D. Further R&D required. Potentially included in ice Baseline-E Evolution ID CRYO-IDE-232 Evolution Title New improved Slope Correction/DEM for LRM The DEM used for SARIN ambiguity currently shows a projection issue which may affect the quality of LRM data in the interior of Antarctica. The high differences at crossovers could be potentially the consequence of such projection errors. A new improved Slope Correction/DEM for LRM has been proposed. Evolution planned to be included with Baseline-D Evolution ID CRYO-IDE-235 Evolution Title Star Tracker File Format Change Within the framework of the Second CryoSat reprocessing activity and from the analysis of the STR_ATTREF products, it has been suggested that it may be worthwhile to add some additional information to the STR_ATTREF products. For sake of clearness, these fixes can be considered as improvements for the STR processor. Evolution planned to be included with Baseline-D Evolution ID CRYO-IDE-239 Evolution Title USO frequency correction on window delay The window delay at L1 is currently not compensating for the USO frequency correction. From CryoSat Products Handbook and L1 Product Format Specification: L1B_Window_delay_corrected = L1B_window_delay * (field#2*10^-15+1) Field #2 within the L1B products corresponds to the USO correction factor, which 22

23 allows for the correction of the delay for the deviation of the Ultra Stable Oscillator from its expected frequency. This correction is currently left for users to apply as they wish; however, since the L1B product is defined as an engineering product with all instrument corrections applied, the USO correction should be applied at L1 and not left to be applied to users. IPF1 will be modified to add this correction at L1B in Baseline-D. Solution identified due to be closed with Baseline-D Evolution ID CRYO-IDE-244 Evolution Title Inconsistency between L1b 1Hz waveform and L2 1Hz height It has been noted that the upcoming switch to NetCDF would provide an opportunity to cleanup some inconsistencies between the 1Hz waveforms that are currently provided in the L1B products, which are currently not aligned with the 1 Hz height provided in L2 product (average of 20 Hz height). Solution identified due to be closed with Baseline-D Evolution ID CRYO-IDE-245 Evolution Title Pitch estimation from CS-2 data in L1B It is foreseen to annotate in the CryoSat L1B product the pitch estimation from the data. However, the estimated value is only for monitoring purposes and it is not used during the L1 processing. It is also foreseen to mark invalid values if estimated pitch. Evolution planned to be included with Baseline-D Evolution ID CRYO-IDE-249 Evolution Title New L1b-S Stack Product for CryoSat ESA points out that the features of L1b-S Stack products would be very useful for the end users and this is why the possibility to generate these products is being assessed. This potential modification would involve CryoSat Ice products only. The objective of the L1b-S product should be to provide the users with the as much complete as possible stack information and not to provide the stack information of the waveforms used in the multilooking of the corresponding L1B product. The planning at the moment is to start with offline production of L1b-S and then consider the introduction of NRT L1b-S in case of relevant applications from user need the NRT production. Further R&D required. Potentially include in ice Baseline-E Evolution ID CRYO-IDE-250 Evolution Title Pseudo LRM Processing from SARin Acquisition 23

24 During the last CryoSat QWG, the Mission Manager reported that it is possible to acquire all data over Greenland in SARin mode, as this is compatible with the on-board resources. Different arrangement of the LRM+SARin acquisitions can be done and three potential masks were presented. The major concern of scientists is the difficulty to compute homogeneous elevation time series. The processing of Pseudo-LRM from SARIn data can provide time-series continuity between LRM & SARIn acquisitions, and corresponding ice volume and elevation. It is planned to proceed with the development of SW to generate pseudo-lrm at 20 Hz from SARin data. First results obtained indicates that it would be feasible to process PLRM from SARin within the operational ice IPFs Further R&D required. Potentially included in ice Baseline-E Evolution ID CRYO-IDE-252 Evolution Title Change the EECFI flag for aberration correction to Reverse and Update attitude biases A review of the calibration of the CryoSat interferometer, with particular attention to the performance of the CryoSat interferometer in terms of instrument phase noise and end-to-end performance, was performed. Then the impact of the aberration correction configuration, which is applied when the Star Tracker L0 files are processed to compute the roll mispointing angle, has been evaluated on the end-to-end performance of the interferometer. As an outcome, it has been decided to amend the EECFI flag in the IPF Data Base (IPFDB) for aberration correction in order to reverse and to update in the IPFDB the roll/pitch/yaw biases with values as function of the Star Tracker ID. Evolution planned to be included with Baseline-D Evolution ID CRYO-IDE-255 Evolution Title SAR/SARin Stack Peakiness parameters for new sea-ice discrimination Stack peakiness is a potential new parameter to be added within Baseline-D SAR/SARin L1B products as a Stack Characterization parameter (also known as Beam Behaviour Parameters). The objective of this is that it can be useful to improve the sea-ice freeboard measurements if we added it as an input to the surface type discrimination done at Level 2. (MSSL) Evolution planned to be included with Baseline-D Evolution ID CRYO-IDE-256 Evolution Title Uncorrected range and altitude to be included in 24

25 L2/L2i/GDR Following requests expressed during the CryoSat User Workshop (Prague, June 2016) and at the French Altimetry/Glaciology Workshop (Toulouse, France), it follows that some CryoSat Users would like to have access to altitude and uncorrected range parameters in the L2/L2i/GDR products. Indeed, it is currently feasible, however very difficult to recover these parameters (there are many flags to checks and even data lost if some corrections are not available). Altitude and uncorrected range parameters would be particularly relevant in order to choose/ apply the most adapted/recent corrections or even test alternative corrections wrt the ones included in the L2/L2i/GDR. Evolution planned to be included with Baseline-D Evolution ID CRYO-IDE-257 Evolution Title New High Resolution tidal model over the Polar Oceans The Arctic Ocean is a challenging region for tidal modelling, because of its complex and not well-documented bathymetry, together combined with the intermittent presence of sea ice and the fact that the in situ tidal observations are rather scarce at such high latitudes. As a consequence, the accuracy of the global tidal models decreases by several centimetres in the Polar Regions. Better knowledge of the tides would improve the quality of the high latitudes altimeter sea surface heights and of all derived products, such as the CryoSat-derived Freeboard. NOVELTIS and DTU Space have recently developed a regional, high-resolution tidal atlas in the Arctic Ocean, in the framework of an extension of the CryoSat Plus for Oceans (CP4O) project funded by ESA. This Tidal atlas might be used to improve the Freeboard retrieval, especially over polar shallow-water areas of the Arctic and Antarctic Oceans (generally operating in SARin). Potential evolution under discussion Potentially included in Baseline-E Evolution ID CRYO-IDE-261 Evolution Title Switch from EE to NetCDF Format It is widely recognised that NetCDF is more user-friendly than the current Earth Explorer (EE) formats used for CryoSat L1 and L2 products. The NetCDF format is self-describing with data stored in a fashion that allows efficient sub setting. Interfaces to NetCDF products (mainly based on C library) are available to users in numerous languages (Matlab, IDL, Python, Octave ). Moreover wide ranges of NetCDF-compliant application software have been developed for quick visualization 25

26 (e.g. Ferret, nc_view ) and easy conversion to ASCII (e.g. ncdump). As a result, a format change to NetCDF is in the process of being designed and will be implemented for CryoSat Ice products with the next IPF update. Evolution planned to be included with Baseline-D Evolution ID CRYO-IDE-262 Evolution Title STR Process with aux file for varying mispointing angle biases For the next CryoSat reprocessing campaign (Baseline-D), the STR Processor can be improved in order to apply a roll bias which varies as function of time and as function of the Star Tracker (low priority). An analysis can be done on the Transponder passes in SARin mode to evaluate, as function of the STR, the variation of the phase difference in time. An ocean patch in SARin mode shall be added in the CryoSat Mode Mask in order to monitor the calibration of the interferometer in the period between two successive roll campaigns This AR is directly related to CRYO-IDE-252 entitled Change the EECFI flag for aberration correction to Reverse and Update attitude biases Evolution planned to be included with Baseline-D Evolution ID CRYO-IDE-264 Evolution Title Tune/Improve the Baseline C retrackers over seaice (Artic + Antarctic) and Land ice areas The Baseline-C elevations retrieved using the current retrackers provide satisfying results which are in line with the mission requirements. However, new approaches and outcomes from the LI and SI CryoVal projects should be now exploited in order to guarantee that the quality of the CryoSat operational products are always at their best. Mode-dependence and elevation bias shall be also reduced in order to exploit the mission over different surfaces with changing geographical mode masks. Evolution planned to be included with Baseline-D Evolution ID CRYO-IDE-266 Evolution Title Improved information on surface characteristics It is proposed to add in the COP products new flags aimed at providing information on the surface, such as surface classification (mask used in Sentinel-3), distance to the coast and waveform classification. This proposal is also put forward for the CryoSat Ice Baseline-D. 26

27 This could be done via the user Sentinel-3 mask or in alternative it is suggested to generate a new version of the 4-states surface type mask from the 7-states Surface classification mask. The format of the new mask would be the same as the current 4- states surface type mask used in CryoSat processing and this would allow considering the information from MODIS and GlobCover included in the 7-states Surface classification mask. This choice would increase the mask resolution from 2min to 30sec. Evolution planned to be included with Baseline-D Evolution ID CRYO-IDE-269 Evolution Title Link between 1Hz and 20 Hz measurements It is proposed to add a new set of variables allowing to link the 1Hz and 20Hz measurement in both L1B and L2 Ice products by means indexes. The following indices are already used in the Baseline-C CryoSat Ocean products : Variable Name Definition L1b L2 ind_first_meas_20hz_01 Index of the first 20Hz measurement of the 1Hz packet x I x ind_first_meas_20hz_01_plrm_ku Index of the first 20Hz PLRM measurement of the 1Hz packet I x ind_meas_1hz_20_ku Index of the 1Hz measurement to which belongs the 20Hz measurement x I x ind_meas_1hz_20_plrm_ku Index of the 1Hz measurement to which belongs the 20Hz PLRM measurement I x The same approach is now also proposed for Ice products in Baseline-D. Evolution planned to be included with Baseline-D Evolution ID CRYO-IDE-270 Evolution Title Decommissioning of FDM production It is ESA s intention to deliver to the user community a new COP L1B product in NRT (so- called NOP). This product is designed to replace the current FDM. This is planned to happen ~6 months after COP Baseline-C is made operational (currently planned for September 2017) in order to provide an overlap period for performing an inter-comparison between the Ocean NOP and Ice FDM. Evolution planned to be included with Baseline-D 27

28 Evolution ID CRYO-IDE-278 Evolution Title New Snow Depth correction dedicated to sea-ice areas and land ice areas The snow model currently used (Warren) is obsolete. Moreover, in the current IPF2 Sea-Ice specialised processing no snow depth correction is applied to the Freeboard computation because the kind of correction to be applied would depend on the underneath surface and there is at present no way to determine this. There is currently some analysis ongoing in order to check whether an improved model for the snow depth can be used (e.g. a modified Warren) and whether there is room to implement some kind of snow depth correction in Baseline-D. Evolution planned to be included with Baseline-D 28

29 6 IPF ANOMALIES CLOSED WITH THE LATEST CRYOSAT PROCESSING BASELINE Details of the last IPF upgrades are provided on the ESA webpage. The table below lists all of the anomalies, which were resolved with the Ice Processor versions in operation since April Anomaly ID Anomaly Title Status Implemented in Release CRYO-IDE-43 LRM time-tag bias Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-53 FDM time-tag bias Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-75 Pitch sign mismatch and attitude biases Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-85 Wrong SAR window delay computation Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-111 UT1 Field in Product Header to be filled Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-112 Gain Ingestion from AutoCal products Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-127 IPF1 SIN beam and baseline vectors set to nominal values Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-141 Wrong code for bursts in IPF1 SAR 1 Hz Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-142 Blurring of IPF1 SAR & SIN 1Hz waveforms with high orbit height rate Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-143 Wrong sign of CAL1 correction Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-167 Datation bias in SAR and SIN modes Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-170 Integrated power in L1B product Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-171 LRM one range gate shift Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-173 LRM 1-FAI shift Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-176 Range error due to CoM reference Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-177 Range error due to IPFDB parameters Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-179 Intraburst power decay not fully calibrated Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-185 List of all stack looks (indices) in SAR and SIN L1B product format Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-186 Power normalisation for the azimuth window Resolved Baseline-C: IPF1 vm

30 CRYO-IDE-187 H0 computation for LRM Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-191 ADC calibration application in IPF1 SIN Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-193 Calibrations missing in L1B products Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-194 Bad cut in slant range correction Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-199 Negative window delay in first 1Hz record Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-201 Tide computation anomaly Resolved Baseline-C: Documentation CRYO-IDE-203 1Hz Corrections Time and Location Computation Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-204 IPF1 SAR/SIN power scaling Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-206 Problems of rounding values in IPF1 Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-211 Beam Behaviour Parameters do not take account of oversampling factor Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-213 Strategy when an insufficient number of samples are available for processing the last 1Hz waveform Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-151 SAR/SIN power calibration error in IPF1 SP Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-155 Intraburst alignment for IPF1 SAR&SIN 20-Hz waveforms Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-161 Bad DAC Values Over Ocean Resolved Baseline-C: IPF1 vm1.0.1 CRYO-IDE-115 Wrong IPF2 SARIn Ambiguity Flag Resolved Baseline-C: IPF2 vm1.0.2 CRYO-IDE-117 IPF2 Failure Rate for Surface Height flag too high for LRM over land Resolved Baseline-C: IPF2 vm1.0.2 CRYO-IDE-135 SIN L2 across-track angle error flag Resolved Baseline-C: IPF2 vm1.0.2 CRYO-IDE-149 IPF2: Multiple SIR_GDR_2A versions Resolved Baseline-C: IPF2 vm1.0.2 CRYO-IDE-195 GDR Header File field Resolved Baseline-C: IPF2 vm1.0.2 CRYO-IDE-202 Wrong flagging strategy at L1B and L2I Resolved Baseline-C: IPF2 vm1.0.2 CRYO-IDE-238 Attitude fields in L2 SAR and L2i (all Mode) set to zero Resolved Baseline-C: IPF2 vm