Minimize Data Quality for L1B and L2 Cat-2 data

Contents

1.      Definition of L1b and L2 Cat-2 Product Baseline and Dataset

2.      Latest_baseline Dataset

2.1        Orbit and Attitude Products

2.1.1        Important Notes

2.1.2        Quality Information

2.2        Magnetic Products

2.2.1        Important Notes

2.2.2        Quality Information

2.3        Plasma Products

2.3.1        The Preliminary Plasma Dataset: Description and Quality Information

2.3.2        Plasma "EFIx_PL_1B" Dataset: Quality Information

2.3.3        The Extended Langmuir Probe Dataset: Description and Quality Information

2.3.4        The 16 Hz electron density derived from Faceplate current: Description and Quality Information

2.3.5        The 2 Hz TII Cross-Track ion flow dataset: Description and Quality Information

2.3.6        The 16 Hz TII Cross-Track ion flow dataset: Description and Quality Information

2.4        Accelerometer Products

2.5        Precise Swarm Orbit Counter

3.      Level 2 - Cat2 Products

3.1        Important Notes

3.1.1        FAC - Field Aligned Currents, and IBI - Ionospheric Bubble Index

3.1.2        Changes in L2 Cat-2 data format

3.2        Product Baseline: Quality Information

3.2.1        EEF - Equatorial Electric Field

3.2.2        FAC – Field Aligned Currents

3.2.3        IBI – Ionospheric Bubble Index

3.2.4        TEC – Total Electron Content

4.      Entire_mission_data

4.1        Important Notes

4.1.1        Magnetic Data

4.1.2        Plasma Data

 

1.    Definition of L1b and L2 Cat-2 Product Baseline and Dataset

LATEST_BASELINES FOLDER: contain all the interoperable products generated in a consistent way with the application of all significant data quality improvements, but not necessarily covering the entire mission.

ENTIRE_MISSION_DATA FOLDER: contain the full data coverage of the entire mission, regardless of any consideration of interoperability among the same product type. In other words the data might have been produced with strategies or knowledge that does not make the products necessarily interoperable for certain type of science. This information can be still be captured by looking at the Product Baseline number.

N.B. It might occur that not all of the old data is immediately regenerated or reprocessed into the "Latest_baselines" Folder. Therefore if the user does not find the improved product in the "Latest_baselines" Folder but you are nonetheless interested in accessing the data without the significant data quality improvements, you can find them in the "Entire_mission_data" Folder.


Please refer to the following sections to check the Product Baselines details of the "Latest_baselines" and "Entire_mission_data" Level 1b and Level 2 Cat-2 Datasets.


PRODUCT BASELINE: is a number associated to a specific product type and satellite. The Product Baseline is identified by the first two of the four digits placed at the end of the file name, i.e. the first two digits of the File_Version field represent the Product Baseline, while the last two represent an incremental File Counter.

Example:
SW_OPER_STRCATT_1B_20140218T000000_20140218T235959_0301_MDR_SAT_AT.cdf
Where 03 is the Product Baseline number, while 01 is only an incremental File Counter.

The Product Baseline is increased when upgrades lead to significant improvements in the data quality of the related products. This subsequently leads to a reprocessing of the affected product types. Data with previous Product Baseline are moved into the Previous Folder. Products with an older File Counter but same Product Baseline are erased, with a few exceptions documented in the following Sections.

Please note that a Dataset may contain products with different Product Baselines, as shown in the example of Figure 1 below.

Figure 1: Schematics of a Swarm "Dataset"

Information on the Level 1B and Level 2 Category 2 Swarm products, can be found in the Swarm Level 1b Product Definition and Swarm Level 2 Product Specification

For information on how to access and download Swarm data, please refer to the Data Access page.

 

2.    Latest_baselines Dataset

The tables below present the "Latest_baselines" Level 1b and Level 2 Cat-2 Datasets with their respective Product Baselines. Detailed explanations of the most relevant data quality features are given in the following sections.

Table 1: L1B Product Baselines included in "Latest_baselines" Folder

  Sat Alpha Sat Bravo Sat Charlie
Level 1b Product Baseline Validity Product Baseline

Validity

Product Baseline

Validity

Orbit and Attitude products (ORBATT)

03

From 25/11/2013 to present

03

From 25/11/2013 to present

03

From 25/11/2013 to present

1 Hz Magnetic products (MAGx_LR_1B)

04

From 25/11/2013 to present

04

From 28/11/2013 to present

04

From 04/12/2013 to present

50 Hz Magnetic products and other auxiliary magnetic products (MAGx_HR_1B, MAGx_CA_1B, VFMxAUX_1B, ASMxAUX_1B)

04

From 18/07/2015 to present

04

From 18/07/2015 to present

04

From 18/07/2015 to present

Plasma products (EFIx_PL_1B)

04

From 18/07/2015 to present

04

From 18/07/2015 to present

04

From 18/07/2015 to present

Precise Swarm Orbit Counter

00

From 22/11/2013 to present

00

From 22/11/2013 to present

00

From 22/11/2013 to present


Table 2: L2 Cat-2 Product Baselines included in "Latest_baselines" Folder

 

Sat Alpha

Sat Bravo

Sat Charlie

Level 2 - Cat2

Product Baseline

Validity

Product Baseline

Validity

Product Baseline

Validity

Field Aligned Currents – Single

02

From 26/11/2013 to Present

02

From 28/11/2013 to Present

02

From 04/12/2013 to Present

Field Aligned Currents - SW A and C combined

02

From 15/14/2014 to Present

02

N/A

02

From 15/04/2014 to Present

Ionospheric Bubble Index

02

From 09/12/2013 to present

02

From 09/12/2013 to present

02

From 11/12/2013 to present

Total Electron Content

02

From 25/11/2013 to present

02

From 25/11/2013 to present

02

From 25/11/2013 to present

Equatorial Electric Field

01

From 27/08/2015 to present

01

From 27/08/2015 to present

N/A

N/A

2.1          Orbit and attitude Products

2.1.1    Important Notes

  • From 19 January 2017 the following changes have been introduced in the Swarm Orbit and Attitude data production:
    • The GPS related L1B products (GPSx_RO_1B and GPSx_RN_1B) are delivered in RINEX format as usual, but the extension changes from .DBL to ".rnx"
    • The Ephemerides (position) related Swarm L1B products (MODx_SC_1B and STRxATT_1B) are delivered in SP3c format as usual, but the extension changes from .DBL to ".sp3"
  • All these changes are applicable from 19 January 2017 onwards. There are no changes to the previously disseminated files.

2.1.2    Quality Information

  • On 20 October 2014, some modifications have been introduced in the way GPS products are computed:
    • Deactivation of antenna and receiver corrections
    • Deactivation of the carrier smoothing algorithm that uses carrier range observations to smooth code range observations
  • Following such modifications, all GPSx and MODx_SC_1B products from the beginning of the mission have been regenerated with File Counter 02. All the GPSx and MODx_SC_1B products from the beginning of the mission to 20/10/2014 with File Counter 01 have been removed.
  • The Medium-accuracy Orbit (MOD) calculation has been improved. In the previous processing strategy, the rejection criteria for the GPS observations were too strict, which often caused a large number of observations to be discarded and, consequently, degraded accuracy of the orbit solution. Currently, in the "Latest_baselines" dataset products, the rejection criteria have been relaxed and the solution is more stable. Moreover, new steps have been introduced in the MOD, which make the processing of MOD products more robust.
  • Starting from 10 April 2016, a correction has been introduced when decoding the Instrument Measurement Time (IMT) from raw GPS observation data into Level 1B Rinex products (GPSx_RO_1B file types). The IMT scale was not read with the right precision, and this introduced a high level of noise in the pseudo-range gradients. As the impact on the final orbit determination is negligible, previous data will not be regenerated right now.
  • Due to an error in the quaternions computation, the q(:,4) element of the STRxATT_1B products was not correctly set to zero in case of data gap (Flags_q = 255). In the "Latest_baselines" dataset products this issue has been fixed.
  • STRxATT_1B attitude products: The conditions for considering single cameras attitudes samples for combination have been relaxed such that the "Sequence" flag is no longer checked. This implies that attitudes computed on-board the spacecraft using the lost-in-space algorithm are used on equal terms as others. Moreover, attitudes with BBO ("Big, Bright Objects") flag set are also considered, though with additional conditions. The update of the algorithm is expected to decrease the occurrence of attitudes based on a single camera head unit (CHU), so improving overall the quality of the attitude determination.

 

2.2          Magnetic Products


2.2.1    Important Notes

  • The magnetic data MAGx_LR_1B are available with Product Baseline 04 from beginning of mission to present. The following magnetic data: MAGx_HR_1B (50 Hz vector field), MAGx_CA_1B, VFMxAUX_1B and ASMxAUX_1B are available with Product Baseline 04 only starting from 18/07/2015 onwards.
  • The ASM instrument on Swarm Charlie stopped providing data on 5 November 2014. The failure is likely permanent. This required a major review of the magnetic calibration for Swarm Charlie, as briefly described in Sect. 2.2.2, point 3.


2.2.2    Quality Information

The improvements in the new Product Baseline of magnetic data have been made possible with the joint efforts of a dedicated group of experts, who analysed instrument and housekeeping data and elaborated a model for correcting data from external disturbance effects, predominantly Sun-driven and manifested as scalar residuals between the ASM and VFM data. After the application of this correction model, we have reduced significantly the differences between ASM and VFM data. The overall rms of such differences were around 1 nT before the correction while we have obtained a rms around 200 pT after the correction, for all spacecraft. The expert group is still working to identify the exact root cause of the disturbance and possibly further improve the disturbance models.

The key points are the following:

  1. Early in the Swarm mission it was recognised that the measurements from the two magnetometer instruments onboard each spacecraft slightly differed. The effect has been analysed and interpreted as a magnetic disturbance of varying strength and direction. Such disturbances are highly correlated with the Sun incident angle with respect to the spacecraft and are manifested as scalar residuals between the ASM and VFM data. The experts endeavoured to model the disturbance parameterized in terms of a spherical harmonic model as a function of Sun incident angles, and this model has proven to provide excellent results.
  2. In the current processing strategy, the calibration parameters for the vector measurements estimated on a daily basis are replaced by the co-estimation of the adjustment of the VFM pre-flight calibration parameters and the magnetic vector disturbance model. This disturbance model (the so-called "dB_Sun)" is considered as a stray field vector at the VFM instrument location. A detailed description of this correction model can be found here.
    The applied dB_Sun for the correction is then stored in the following magnetic products: MAGx_HR_1B, MAGx_LR_1B and MAGx_CA_1B.
  3. In order to cope with the permanent failure of the ASM onboard Swarm Charlie, the magnetic scalar reference measurements for the disturbance model characterisation and VFM calibration described above have successfully been generated using the ASM measurements from Swarm Alpha. For more detailed information, please refer to the Scalar Mapping Technical Note.
  4. Due to an old bug in the L1b data processor, the ASM stray fields, dF_AOCS and dF_other, stored in the Swarm MAGx_LR_1B and MAGx_CA_1B data with Product Baseline 03 and 04 from the beginning of the mission to 21/02/2015 have not been computed correctly. Please note that this issue has no impact on the full correction of the ASM data from the total of the stray fields (dF_Total) which is indeed implemented and applied in the right way.


2.2.2.1  Original Residuals


Due to recent modifications in the disturbance model in the operational processor, it is not possible to recover the original BVFM values and, as a consequence, the original ASM-VFM residuals from the magnetic products (MAGx_LR_1B, MAGx_HR_1B, MAGx_CA_1B) available in the "Latest_baselines" Dataset. Therefore in order to facilitate the data validation, ESA has made available the original non-corrected magnetic field vector data, in VFM frame (BVFM).

Such data can be found in the ESA FTP server at the following path:

~/Advanced/Magnetic_Data/ASM_VFM_Residuals/Sat_x

where x=A,B,C is the spacecraft identifier.

This dataset shall be used by all those scientists interested in analysing the non-corrected ASM-VFM scalar residuals.


2.2.2.2  Euler Angles Update

 

On 07/12/2015 an update of the rotation angles between the VFM instrument reference frame and the STR common reference frame (Euler angles) has been introduced. All the MAGx_LR_1B and MAGx_HR_1B products contained in the "Latest_baselines" folder have been regenerated accordingly, leading to an increase of the File Counter. The only difference with the old File Counter (i.e. Product Datasets with Baseline 04 and File Counter less than 08) can be observed in the BNEC which is the parameter affected by the Euler angles transformation: the maximum difference is slightly above 1 nT, most pronounced on the BEast component. The products with File Counter less than 08 in the "Latest_baselines" Dataset have been removed.


2.2.2.3 MAGx_LR_1B dataset updated


An updated version of the Swarm MAGx_LR_1B products (Product Baseline and File Counter 0502) has been made available in the "Advanced" folder of the ESA FTP server. This dataset covers the time window from the beginning of the mission to 31/08/2017 for all three spacecraft. The new dataset includes:

  1. the Star Tracker temperature correction
  2. an update of Star Tracker interpolation and
  3. an update of the vector data calibration and disturbance characterisation
  4. a further improvement of the VFM scaling evolution

Due to technical issues in the processing of these Baseline 05 data there are gaps not present in the Baseline 04 products. The gaps will be recovered in the next full mission data reprocessing.

 

2.3  Plasma Products

Currently five main datasets exist for Swarm Plasma products:

  • A Preliminary Plasma Dataset: it is the result of the efforts of the Swarm Electric Field Instrument (EFI) Principal Investigators (PIs) and their teams, and is meant to partly replace the official dataset when it is not available. It is described in Sect. 2.3.1.
  • The Plasma "EFIx_PL_1B" Dataset: it consists of the official Swarm plasma products as from Swarm Level 1b Product Definition, available in the "Latest Baselines" folder of the ESA FTP server. It is described in Sect. 2.3.2.
  • An "Extended" Langmuir Probe dataset: this is an experimental dataset where separate measurements from the single probes are given, in order to investigate open issues on data and for data validation purposes. More details are given in Sect. 2.3.3.
  • Electron density derived from Faceplate current: this is an experimental dataset which offers a different evaluation of the electron density, based on the measurements of the faceplate current at 16 Hz rate. More details are given in Sect. 2.3.4.
  • 2 Hz TII cross-track ion flow dataset: this is an experimental dataset, based on measurements of the TII cross-track data at 2 Hz. More details are given in Sect. 2.3.5.
  • 16 Hz TII cross-track ion flow dataset: this is an experimental dataset, based on measurements of the TII cross-track data at 16 Hz. More details are given in Sect. 2.3.6.


2.3.1    The Preliminary Plasma Dataset: Description and Quality Information

Temporarily, in addition to data contained in the "Latest_baselines" folder, a preliminary set of Swarm Plasma data for all three spacecraft has been made available to the Swarm science users thanks to the efforts of the Swarm Electric Field Instrument (EFI) Principal Investigators (PIs) and their teams.

This dataset is actually composed of two separate datasets, corresponding to the two instruments which compose the EFI:

  1. the Langmuir Probes derived data (plasma density, electron temperature and spacecraft potential) have been prepared by the Swedish Institute for Space Physics (IRF) at Uppsala;
  2. the Thermal Ion Imagers derived data (O+ bulk velocity and temperature, ionospheric convection electric field) have been prepared by the University of Calgary (Canada).

Due to thorough calibration activities on the instruments and the processing algorithms evolutions still ongoing to achieve the best possible data quality, this plasma dataset is a work in progress and can be considered as preliminary. The use of such data by the scientific community is encouraged by the EFI PIs, provided interested scientists and users carefully read the User Note concerning the state of the art of plasma data quality and the information about data formats and content. In case of doubts, the PIs will be pleased to answer your questions:

Please always include ESA in CC in your communications: swarm@eo-sppa.org

The dataset is available on the ESA FTP server accessible by all users, under the path: ~/Advanced/Plasma_Data/Provisional_Plasma_dataset

The dataset is structured as follows:

  • Thermal_Ion_Imagers_Data: Due to anomalies in the raw TII images and consequent difficulties in performing a continuous calibration of the instrument, the instrument experts have made available selected periods when data quality is certified and data can therefore be used for science studies. Such periods could be possibly extended in the future, depending on the progresses made in the instrument investigations and in the data calibration. The available data are in daily files, CDF format.
  • Langmuir_Probe_Data: This dataset is produced in daily files in ASCII format by the Langmuir Probes Instrument experts and is continuous from the instrument first light in early December 2013 up to 17 July 2015. From 18/07/2015, official Swarm plasma products, EFIx_PL_1B, are produced. The two datasets are generally interoperable, taking into account the following points:
    • The timestamps in the preliminary dataset correspond to the true Langmuir Probe measurement times, while the CDF epochs in the EFIx_PL_1B shall be incremented by a time lag "dt_LP" as described in Sect. 2.3.2.
    • S/C position and velocity are calculated differently in the two datasets: in the preliminary dataset the coordinates (latitude, longitude, height and radius) are calculated from Two-Line Elements predicted orbits and are geodetic, while in the EFIx_PL_1B the input data for calculating coordinates are the very Swarm GPS position measurements, and coordinates are geographic (NEC system). This has two consequences:
      1) The difference in geolocation of the measurements between the two datasets is about 13-14 km;
      2) the S/C velocity enters in the calculation of the electron density, therefore the difference in the absolute value of the density between the two datasets can be up to 103 m-3, which is about two orders of magnitude below the lowest "physical" value one can measure in the ionosphere.


2.3.2    The Plasma "EFIx_PL_1B" Dataset: Description and Quality Information

Official Swarm Plasma products are available since 18/07/2015. The user is recommended to read carefully the following notes before using the data:

  1. EFIx_PL_1B only includes plasma parameters derived from the Langmuir Probes: electron density (N), electron temperature (T_elec) and S/C potential (U_SC). All the plasma parameters derived from the Thermal Ion Imagers (v_ion, v_ion_error, E, E_error, T_ion, T_ion_error, v_ion_H, v_ion_H _error, v_ion_V_error, rms_fit_H, rms_fit_V, var_x_H, var_y_H, var_x_V, var_y_V, dv_mtq_H, dv_mtq_V, Flags_TII) are set to zero. Selected TII data periods with good quality are distributed in the TII preliminary dataset (see Sect. 2.3.1).
  2. The correct Langmuir Probe epochs, ti, shall be computed as follows: ti = CDF_epoch + dt_LP, where dt_LP is a time lag parameter (given in seconds), also contained in EFIx_PL_1B products.
  3. TIIx_CA_1B products containing the daily determined TII detector centres are currently not distributed, because the occurrence of the TII image anomaly still does not allow an automated calibration process.
  4. Information on the quality of the Langmuir Probes derived parameters contained in the EFIx_PL_1B products can be found in the same technical note associated with the preliminary plasma dataset. Statistically, both the electron density and temperature behave as expected, and the general features of the ionosphere can be recognised. The electron temperature is still prone to possible overestimates in regions where the density is low, and high temperature shears and spiky events are often observed.
  5. The Langmuir Probes work in sweep mode for one second every 128 seconds. The sweep mode data are still under validation and are not included in the EFIx_PL_1B products. In order to guarantee data continuity, the sweep mode records are replaced with a replica of the preceding normal mode records. However the timestamps when the sweep mode occur are flagged with Flags_LP = 9.
  6. The Sweep mode itself seems to influence the following two-three measurements in normal mode, introducing small hicks up in the spacecraft potential and, to a lesser extent, in the electron temperature. Such small dips, where the magnitude is a few per cent of the absolute value of the affected parameters, should be filtered/interpolated away. The cause of such effect is still unknown; the most likely hypothesis points to a local charging of the probes induced by the voltage sweep, which requires a couple of seconds to decay towards the baseline level.
  7. The Langmuir Probe data calibration and validation requires a huge statistics of conjunctions with ground-based measurements (above all, incoherent scatter radars which measure the same parameters at roughly the same height as the Swarm S/C), so that, overall, it is not yet possible to associate reliable errors or quality flags to data. Therefore all the error parameters in the EFIx_PL_1B products are set to fixed values: N_error = 429496729.5, T_elec_error = 429496729.5 and U_SC_error = 32.767.
  8. The quality flag for the electron density (Flags_LP_N) is set to "20" for the whole dataset, which simply means data have to be used with caution and EOhelp should be contacted in case of doubts. The quality flags for the electron temperature and the S/C potential (Flags_LP_T_elec, Flags_LP_U_SC) can show values greater than 20: in such cases data are not usable at all for science purposes and shall be discarded.
  9. It has recently been noticed that the electron density contained in the EFIx_PL_1B products are at times affected by spike events, or overflows, of about 4.2 x 108 cm-3, whose duration usually does not exceed 1-2 seconds. This is due to a technical bug in the data processor which mostly affects the calculation in regions of the ionosphere characterised by very low electron densities. The lower spacecraft pair (Swarm A and C) is the most affected, while on Swarm B data such overflows occur very seldom. For the purpose of science analyses, such artefacts can be safely filtered away and remaining gaps can be linearly interpolated.


2.3.3    The Extended Langmuir Probe Dataset: Description and Quality Information

This dataset has been delivered by the Swedish Institute of Space Physics (IRF) for instrument validation purposes and advanced studies involving ionospheric plasma. It is intended to be an experimental dataset, and before using such data in papers or other scientific publications, please contact IRF (Dr. Stephan Buchert, scb@irfu.se).

The Swarm payload includes two Langmuir Probes, each carrying on independent measurements of ionospheric electron density, electron temperature and spacecraft potential. Then, the measurements from the two probes are "blended" together according to an algorithm which takes into account several environmental and instrument variables: different sensitivity of each probe to different plasma density regimes, saturation due to instrument factors, and more.

The final results are single values of electron density and temperature and spacecraft potential as a function of time, contained in the official Swarm plasma product type EFIx_PL_1B, and in the Langmuir Probe preliminary dataset described above (Sects. 2.3.1 and 2.3.2)

One of the major challenges the Swarm experts are presently facing is the validation and correct interpretation of the electron temperature and spacecraft potential measurements. Several features are being observed such as: unusually high temperature regions, trains of spikes apparently related with Sun illumination angle on the Swarm solar panels, small jumps in the spacecraft potential after the activation of the sweep mode.

Therefore, in order to help scientists in investigating these peculiar aspects, an extended dataset has been released, containing the electron temperature and spacecraft potential measured separately by the two probes. Data are in format of daily CDF files, spanning, for the time being, from the start of the mission to 11/06/2016 for all three spacecraft. Further updates are regularly expected.

Data are available in the ESA FTP server under the path:

~/Advanced/Plasma_Data/2_Hz_Langmuir_Probe_Extended_Dataset/Sat_x

Where X=A,B,C is the spacecraft identifier.

Before using this data, please read carefully the Release Note


2.3.4    The 16 Hz electron density derived from Faceplate current: Description and Quality Information

An extended dataset including ionospheric electron density at 16 Hz has been made available by the Swedish Institute of Space Physics (IRF Uppsala). The density is derived from the current measured at the EFI faceplate and offsets can be present with respect to the 2 Hz plasma density measured by the Swarm Langmuir probes.

Before using this data, please read carefully the Release Note, and, in case of doubt, please contact IRF for further clarifications (Dr. Stephan Buchert, scb@irfu.se).

Data are available on the ESA FTP server at the following path:

~/Advanced/Plasma_Data/16_Hz_Faceplate_plasma_density/Sat_x

where X=A,B,C is the spacecraft identifier.

Data cover from beginning October 2014 to end February 2016 for all spacecraft, in daily compressed (ZIP) CDF files. Please note the continuity of the coverage is not assured, as the settings of the faceplate bias are not always suitable for density measurements. The dataset is meant to be regularly updated with the most recent data.

The Faceplate dataset at 16 Hz has the following caveats:

  1. due to an initial misevaluation of the Faceplate area, an offset exists on the density. Users shall take into account that: Ne_true = 0.8 * Ne_data
  2. due to a bug in computation, coordinates in the dataset are not correct. Users interested in precise geolocation are suggested to use the coordinates stored in the "Experimental 2 Hz product" and interpolate to 16 Hz.

In the updated version of this dataset that will be available soon, the above mentioned issues will be fixed.


2.3.5    The 2 Hz TII Cross-Track ion flow dataset: Description and Quality Information

An experimental dataset of Cross-Track ion flow at 2 Hz has been made available by the University of Calgary (Canada).

This dataset includes MJD2000 timestamp, latitude, longitude, radius, quasi-dipole lat, magnetic local time, ion cross-track components, satellite velocity components, co-rotation signal, velocity flow angles for the two sensors, offset corrections for the two sensors (as explained in the Release Note), electric field components, magnetic field components in the same coordinate reference frame. Data are accompanied by quality flags (for the y and z component of ion velocity and for the electric field, separately).

Before using this data, please read carefully the Release Note where more details on data processing and data content are given. In case of doubt, please contact:

for further clarifications. Please always include ESA in CC in your communications: swarm@eo-sppa.org

Data are available on the ESA FTP server at the following path:

~/Advanced/Plasma_Data/2Hz_Cross-Track_Dataset/Sat_x

where x=A,B,C is the Spacecraft identifier.

Data coverage ranges from beginning of December 2015 to end of April 2017 for S/C A and from beginning of January 2016 to end of April 2017 for S/C B, in daily compressed (ZIP) CDF files. Data coverage is not continuous. Starting in 2014 EFI TII operations have been limited to a small number of orbits per day. The dataset is meant to be regularly updated with the most recent data.


2.3.6    The 16 Hz TII Cross-Track ion flow dataset: Description and Quality Information

An experimental dataset of Cross-Track ion flow at 16 Hz has been made available by the University of Calgary (Canada).

These data flow products contain geocentric coordinates, cross-track velocity components, electric field components and related quality flags.

Before using this data, please read carefully the Release Note where more details on data processing and data content are given. In case of doubt, please contact:

for further clarifications. Please always include ESA in CC in your communications: swarm@eo-sppa.org

Data are available on the ESA FTP server at the following path:

~/Advanced/Plasma_Data/16Hz_Cross-Track_Dataset/Sat_x

where x=A,B,C is the Spacecraft identifier.

Data coverage ranges from beginning of January 2016 to end of April 2017 for S/C A and B, in daily compressed (ZIP) CDF files. Data coverage is not continuous. Starting in 2014 EFI TII operations have been limited to a small number of orbits per day. The dataset is meant to be regularly updated with the most recent data.

 

2.4          Accelerometer Products

The Level 1B accelerometer data (ACCx_PR_1B) are not distributed to the regular users as they are heavily perturbed by a variety of disturbances. The main problems are:

a) High number of steps, spikes, pulses observed in linear and angular acceleration;

b) Strong dependency on temperature variations.

Intensive investigations resulted in the conclusion that a fully automatic correction of the disturbances is not reliable, at least in the foreseeable future. Therefore, the accelerometer data is corrected by a team of experts and delivered together with all corrections as Level 2 Cat-1 data in product ACCxCAL_2_ (Corrected and calibrated accelerometer observations).


2.5         Precise Swarm Orbit Counter

The AUXxORBCNT product provides precise Swarm orbit number information to the scientific user community. The start of an orbit is defined as the Equator crossing of the ascending node (i.e. the northbound Equator crossing). Detailed information for this product is available here.


3.    Level 2 - Cat2 Products

3.1      Important Notes

3.1.1    FAC - Field Aligned Currents, and IBI - Ionospheric Bubble Index

Following the correction of the Magnetic Level 1B data (MAGx_LR_1B), a new Baseline (02) of FAC and IBI products has been introduced since 16/07/2015. For the product types: FACxTMS_2F and IBIxTMS_2F, data have been therefore regenerated since, approximately, the beginning of the mission. For the product type: FAC_TMS_2F (FAC from combined S/C A and C measurements) the coverage does not start from beginning of mission, but from 15/04/2014.

 

3.1.2    Changes in L2 Cat-2 data format

From 19 January 2017 the L2 Cat-2 products (EEF, IBI, TEC and FAC) are delivered in CDF format as usual, but the extension changes from ".DBL" to ".cdf". These changes are applicable from 19 January 2017 onwards. There are no changes to the previously disseminated files.

 

3.2       Quality Information

3.2.1    EEF - Equatorial Electric Field

Equatorial Electric field data were made available for the first time since 27/08/2015, only for S/C Alpha and Bravo. Unfortunately, the unavailability of the ASM instrument on S/C Charlie makes impossible the production of EEF data for such spacecraft. Detailed quality information on this products is available here.

 

3.2.2   FAC – Field Aligned Currents

Detailed quality information for the following products is available: FAC - single S/C solution and FAC - dual S/C solution.

 

3.2.3   IBI – Ionospheric Bubble Index

Detailed quality information for this product is available here.

 

3.2.4   TEC – Total Electron Content

Due to the insufficient precision of double precision values (64 bit floating points) in the CDF data, there are duplicated TEC values in the Swarm L2 TEC product (TECATMS_2F, TECBTMS_2F and TECCTMS_2F). Please note that the duplicates are not always next to each other in the time series, but they occur on the same PRNs (GPS satellite number). More detailed quality information on this product is available here.

 

4.    Entire_mission_data

In the "Entire_mission_data" folder on the ESA FTP server users will see full data coverage of the entire mission, regardless of any consideration of interoperability among the same product type. In other words the data might have been produced with strategies or knowledge that does not make the products necessarily interoperable for certain types of science. This information can still be captured by looking at the Product Baseline number.


4.1      Important Notes

4.1.1   Magnetic Data

In the MAGx_HR, MAGx_CA, VFMxAUX and ASMxAUX folders under the "Entire_mission_data" folder, the users will find the Magnetic data with Product Baseline 03 from beginning of the mission to 17/07/2015 and with Product Baseline 04 from 18/07/2015 onwards. Please note that the Magnetic data with Product Baseline 03 are NOT CORRECTED from external disturbances effects and they are therefore NOT interoperable with Magnetic data with Product Baseline 04.


4.1.2   Plasma Data

In the EFIx_PL_1B folder present under the "Entire_mission_data" folder, the users will find only the Product Baseline 04 from 18/07/2015 onwards. The EFIx_PL_1B product with Product Baseline 03 are not distributed to the regular users as they are produced with a non-consolidated algorithm.