Ice Level 1

The main purpose of this Full Bit Rate (FBR) dataset is to allow independent investigation of the synthetic aperture processor (beam-formation and direction, slant range correction and multi-looking). Data is raw time-ordered, and for SAR and SARIn modes, it is provided prior to the application of the synthetic aperture, interferometric or accumulation processing.

The main purpose of this Full Bit Rate (FBR) dataset is to allow independent investigation of the synthetic aperture processor (beam-formation and direction, slant range correction and multi-looking). Data is raw time-ordered, and for SAR and SARIn modes, it is provided prior to the application of the synthetic aperture, interferometric or accumulation processing.

To support such investigations, the data will have instrument and geophysical corrections appended, together with a precise orbit. Not all of these corrections will be applied however. In conventional pulse-limited altimetry, as part of the radar pulse-compression technique, echoes are fast-Fourier transformed into the 'spectral domain' prior to multi-looking.

In the LRM, the SIRAL echoes are incoherently multi-looked on-board the satellite prior to altimetry (as with, for example, ERS satellite radar altimeters). In this mode, the FBR data consist of the multi-looked echoes at a rate of ~20 Hz.

In the SAR and SARIn modes consists of the individual, complex (I and Q) echoes. In SARIn mode, there are two such echoes, one for each antenna of the interferometer. In these modes, data are sent to ground in the 'time domain' prior to the on-board FFT. Some corrections (such as those for the IF ant-alias filter) can only be performed once this transformation is performed. The user will have to apply these corrections.

For more information on the format specification of Level 1 (FBR), please download the CryoSat L1b Product Specification.

For users still working with the Baseline-C Earth Explorer Format products (i.e. .DBL), please see the previous L1B Product Specification.

Ice Level 1b

The CryoSat Ice Processor generates Level 1B and Level 2 Ice products from L0 LRM, SAR and SARIn products. These products are primarily designed for the study of land ice and sea ice, although they are also relevant and useful to a wide range of additional applications.

Products are generated at both Near-Real Time (NRT) and Offline latency. NRT products are generated 2-3 hours after data sensing acquisition, and are generated using the DORIS Navigator Orbit with geophysical corrections computed from the Forecast meteorological Auxiliary Data Files (ADFs) where available. 

Previously NRT SAR and SARIn production was delayed awaiting the Refined Star Tracker File (ATTREF). At Baseline-D, in order to meet the expected near real time latency (2-3 hours after acquisition), the NRT chain was separated from the Offline Baseline-D IPFs. This allows processing to use the L0 Star Tracker products instead of the Star Tracker ATTREF products without delay.

Following the implementation of Near Real Time Ocean Products (NOP), FDM production was discontinued in February 2021, however NRT SAR and SARIn products will continue to be generated operationally.

Offline products are generated typically 30 days after data sensing acquisition using consolidated DORIS precise orbits (CNES Precise Orbit Ephemeris) and processed with geophysical corrections computed from the Analysis meteorological ADFs.

Level 1B data consist, essentially, 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.

In LRM, the contents of the level 1b data are the same as that of the FBR data. These data are similar to the "WAP" data of the ERS-1 and ERS-2 altimeters.

In SARIn mode, the multi-looked echo is complex, consisting of the echo power and interferometer phase. As with the FBR data, the data will have instrument and geophysical corrections appended and, in addition, the precise orbit. An important source of geophysical information is the variation in echo power as a function of the incidence angle of each Doppler beam. This information may also help determine Doppler beam ambiguity. This information is parameterised prior to multi-looking and included as part of the Level 1B data.

In addition, in SARIn mode, the coherence of the interferometer phase is also estimated as part of the phase multi-looking and added to the Level 1B waveform.

For more information on the format specification of Level 1B products, please download the CryoSat L1B Product Specification.

General information about the Baseline-D Ice Processor is available in the following documents:

For users still working with the Baseline-C Earth Explorer Format products (i.e. .DBL), please see the previous L1B Product Specification.

All registered users can access this dataset provided they have signed the Terms & Conditions for use of the CryoSat data. For more information about registration, please contact the ESA Earth Observation Missions Helpdesk Team: eohelp@esa.int

Ice Level 2

Level 2 products are again generated at both Near-Real Time (NRT) and Offline. Level 2 data (LRM_2, SAR_2 and SIN_2), consists 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. In LRM, these data are similar to the "OPR" data of the ERS altimeters. For elevations over ice sheets, the correction will be obtained from a Digital Elevation Model (DEM). In SAR mode, over sea-ice covered water, data will also include an estimate of ice thickness and other information derived from the echo power and its behaviour as a function of delay time and incidence angle. Over land ice, the data will be "slope-corrected". Where the data are derived from SARIn mode echoes, the correction will be determined from the interferometer phase.

Level 2 products are considered to be most suitable for users, as they contain surface height measurements fully corrected for instrumental effects, propagation delays, measurement geometry and additional geophysical effects such as atmospheric and tidal effects. In the Offline Level 2 products, the value of each geophysical correction provided is the value applied to the corrected Surface Height.

In-depth L2 products (LRMI2, SARI2, SINI2) are also available; these can be identified with the 'I' in the file type. These products provide access to many low level parameters originating from the L1B, which are not available in the L2 product. The in-depth format is required as the input to the second pass of the L2 SAR processing chain for Sea Ice areas, and it is also useful for detailed analysis.

The Level 2I Measurement Dataset has a single format which is independent of mode. However the meaning of some fields is mode dependent, whilst other fields are entirely unused in some modes. The Level 2I format has been designed with the goal of ease of use rather than reduction of data volume. This means that there is repetition of some information that varies slowly. Geophysical corrections are interpolated at 1Hz and will therefore nominally be the same for 20 consecutive records. The corrections are interpolated at the latitude/longitude position given in the first of those 20 records.

In addition, Level 2 GDR (GDR_2) is also provided to users; this product is the outcome of the second step of Level 2 processing and is generated from the Level 2 mode dependent products collected over an entire orbit, specifically from ANX to ANX. This second step does not imply any specific processing, but simply a concatenation of input Level 2 files in chronological order.

For more information on the format specification of Level 2 product, please download the CryoSat L2 Product Specification document.

General information about the Baseline-D Ice Processor is available in the following documents:

For users still working with the Baseline-C Earth Explorer Format products (i.e. .DBL), please see the previous L2 Product Specification.

All registered users can access this dataset provided they have signed the Terms & Conditions for use of the CryoSat data. For more information about registration, please contact the ESA Earth Observation Missions Helpdesk Team: eohelp@esa.int

Ocean Level 1b

The CryoSat Ocean Processor (COP) generates Level 1B and Level 2 ocean products from L0 LRM, SAR and SARIn products. These products are dedicated to the study of ocean surfaces, and provided specifically for the needs of the oceanographic community.

The COP provides three classes of products, which vary according to their delivery latency:

  • Near-Real Time Ocean Products (NOP)
  • Intermediate Ocean Products (IOP)
  • Geophysical Ocean Products (GOP)

These products are then further classified according to the acquisition mode (LRM, SAR and SARIn). The processing applied to generate these products is the same in all cases and the only difference lies in the use of different input auxiliary files. This refers to the use of different orbit files, and different corrections included and applied.

NOP are delivered within 3 hours from sensing (i.e. outside the blind orbits) and are generated using the DORIS Navigator Orbit with geophysical corrections computed from the Forecast meteorological Auxiliary Data Files (ADFs) where available. This NRT processing is a new feature of the Baseline-C IPF, and will replace FDM before the end of 2019.

IOP are generated 2-3 days after data sensing acquisition for medium-range ocean forecasting and use DORIS preliminary orbits (CNES Medium Orbit Ephemeris) with geophysical corrections computed from Analysis metrological ADFs, and when these are not available in time, the Forecast metrological ADFs.

GOP are typically generated 30 days after data sensing acquisition using consolidated DORIS precise orbits (CNES Precise Orbit Ephemeris) and processed with geophysical corrections computed from the Analysis meteorological ADFs.

The CryoSat NetCDF Ocean products are designed to contain LRM/ Pseudo-LRM and SAR/ SARIn altimeter data together in the same product file. The formats of the L1B products are the same whatever the operating mode, and therefore the SAR/ SARIn-derived parameters are redundant in LRM/ Pseudo-LRM. L1B NOP, IOP and GOP contain all the engineering parameters needed to generate the Level 2 products, together with corrections to be applied for range and tidal effects.

For more information on the format specification of the NetCDF L1B Ocean Products, please download the Ocean Product Format Specification document.

General information about the Baseline-C Ocean Processor is available in the following documents and article:

All registered users can access this dataset provided they have signed the Terms & Conditions for use of the CryoSat data. For more information about registration, please contact the ESA Earth Observation Missions Helpdesk Team: eohelp@esa.int

Ocean Level 2

The CryoSat Ocean Processor (COP) generates Level 1B and Level 2 ocean products from L0 LRM, SAR and SARIn products. These products are dedicated to the study of ocean surfaces, and provided specifically for the needs of the oceanographic community.

The CryoSat Ocean Processor (COP) generates Level 1B and Level 2 ocean products from L0 LRM, SAR and SARIn products. These products are dedicated to the study of ocean surfaces, and provided specifically for the needs of the oceanographic community.

The L2 NOP, IOP and GOP contain all the information necessary for the correct usage of the altimeter parameters over ocean surfaces, and therefore are considered to be more suitable for users. Geophysical corrections are provided in the L2 NOP, IOP and GOP however following the oceanographic convention the corrections are not applied to the range. The corrections are provided in the products to allow the user to apply them as required.

L2 NOP include geophysical corrections computed from the Forecast meteorological Auxiliary Data Files (ADFs) where available. L2 IOP include geophysical corrections computed from Analysis metrological ADFs, and when these are not available in time, the Forecast metrological ADFs. L2 GOP should always include geophysical corrections computed from the Analysis meteorological ADFs.

Additionally new global Pole-to-Pole (P2P) products are generated by the Baseline-C Ocean processor. These are concatenated multi-mode L2 products generated for IOP and GOP. The products have half-orbit coverage, and therefore two P2P products are generated per orbit, spanning between the North and South poles and combining successive L2 IOP and GOP products respectively. These P2P products are delivered with the same latency as the input IOP and GOP products, i.e. 2-3 days and 30 days respectively.

It should be noted that the Baseline-C P2P products have been given the same product name as the Baseline-B L2 IOP and GOP but do not have the same content, frequency or size. Users should also note that NOP P2P products do not exist due to the 3-hour latency constraint.

For more information on the format specification of the NetCDF L2 Ocean Products, please download the Ocean Product Format Specification document.

General information about the Baseline-C Ocean Processor is available in the following documents and article:

All registered users can access this dataset provided they have signed the Terms & Conditions for use of the CryoSat data. For more information about registration, please contact the ESA Earth Observation Missions Helpdesk Team: eohelp@esa.int

CryoTEMPO EOLIS

EOLIS DEMs
Example of DEM time-series in the Jakobshavn Isbrae region of west-Greenland showing general thinning of the ice sheet margin and revealing seasonal and long-term trends in ice thickness change.

The CryoTEMPO-EOLIS (Elevation Over Land Ice from Swath) is the first of the CryoTEMPO products and has been in operation since 7 May 2020.

The EOLIS products exploit CryoSat's SARIn mode and the novel Swath processing technique to deliver increased spatial and temporal coverage of time-dependent elevation over land ice, a critical metric for tracking ice mass trends.

The dataset consists of systematic reprocessing of the entire CryoSat archive to generate new L2-Swath products, increasing data sampling by 1 to 2 orders of magnitude compared with the operational L2 ESA product. In addition, the EOLIS dataset is joined with the ESA L2 Point-Of-Closest-Approach to generate monthly DEM (Digital Elevation Model) products.

This dataset will further the ability of the community to analyse and understand trends across the Greenland Ice Sheet margin.

Two types of products are generated by CryoTEMPO EOLIS:

  • CryoTEMPO EOLIS Point Products: Contain a dense set of elevation measurements for individual observations. Due to the high volume of data, the data has been split into tiles of 100 x 100 km in size.
  • CryoTEMPO EOLIS Gridded Products: Contain monthly 2 km resolution DEM with the data sourced from a rolling three month window.

For more information on the format specification of EOLIS products, uncertainty indicators and data content, please download the EOLIS product handbook.

For more information about th e project please visit the EOLIS website.