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        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_LP_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

3.2        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

 

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. Data with previous Product Baseline are then moved into the "Older_baselines" Folder, while products with an older File Counter but same Product Baseline are erased, with a few exceptions documented in the following Sections. Every time the baseline is increased, all the products that use the new Product Baseline data as an input, need to be reprocessed.

 

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 (GPSx_RO_1B, GPSx_RN_1B, MODx_SC_1B, GPSxNAV_1B, STRxATT_1B)

04

From 25/11/2013 to present

04

From 25/11/2013 to present

04

From 25/11/2013 to present

Magnetic products (MAGx_LR_1B, MAGx_HR_1B, MAGx_CA_1B, VFMxAUX_1B, ASMxAUX_1B)

05

From 25/11/2013 to present

05

From 25/11/2013 to present

05

From 26/11/2013 to present

Plasma products (EFIx_LP_1B, EFIxLPI_1B, LP_x_CA_1B)

05

From 02/12/2013 to present

05

From 02/12/2013 to present

05

From 04/12/2013 to present

Accele products (SC_xDYN_1B)

04

From 28/11/2013 to present

04

From 28/11/2013 to present

04

From 28/11/2013 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

03

From 26/11/2013 to Present

03

From 28/11/2013 to Present

03

From 04/12/2013 to Present

Field Aligned Currents - SW A and C combined

03

From 15/14/2014 to Present

03

N/A

03

From 15/04/2014 to Present

Ionospheric Bubble Index

03

From 09/12/2013 to present

03

From 09/12/2013 to present

03

From 11/12/2013 to present

Total Electron Content

03

From 25/11/2013 to present

03

From 25/11/2013 to present

03

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    Quality Information

On 17 September 2018, some modifications have been introduced in the way GPS and STR products are computed:

1. GPS

  • Change in ORBATT of carrier phase observation to get full-cycle ambiguities
    Until now, the Swarm carrier phase observations were affected by half cycle ambiguities. The Swarm GPS receivers report in a dedicated flag whether the navigation data stream is inverted or not. The new RINEX converter uses the flag to generate carrier phase observations with full cycle ambiguities. It is noted that full cycle ambiguities allow using algorithms for integer ambiguity fixing, which enable more accurate precise orbit determination.
     
  • Align data in RINEX files to GPS time (GPS_RO clock offset and drift)
    The Swarm GPS receiver clocks have a clock offset of roughly 0.2 µs, which corresponds to an offset of 60m in the pseudo-range observations. This offset is used to correct the pseudo-range observations and to align the clock offset with the receiver internal navigation solution. This bias has been hardcoded in the processor to avoid changes in interfaces. The value is documented in the header of the Rinex files.
    The old RINEX files are aligned with the drifting IMT (Instrument Measurement Time), which causes large jumps at midnight, when the daily clock offset is adjusted by the processor. In order to avoid such large jumps, the new RINEX files are aligned with GPS time instead of IMT.
     
  • Reduction of receiver clock noise
    In the previous baseline of L1B data, a navigation solution and clock offset are computed on-ground from the observations and ephemerides. The clock offset calculated in that way shows a noise level of about 30 ns, corresponding to noise level of 10 m for pseudo-range observations. The new processor uses instead the on-board navigation, which lead to a noise level for clock offsets of 3 ns, corresponding to a noise level of 1 m for pseudo-range observations.
    In the previous version of the processor, GPS time was not stored with sufficient precision, resulting in noise in the code observations, which increased as GPS time increased. The new processor avoids that the fractional part of the GPS time is lost and the code observations therefore show constant low noise level over time.


2. Star Tracker

  • STR Inter-Boresight Angles correction model
    An anomalous variation (up to ~ 0.85 arc-sec/°C) in the Star Tracker (STR) Inter Boresight Angle (IBA) for Camera Head Unit (CHU) pairs has been observed. A STR IBA correction model that uses as input CHU and STR temperatures has been proposed by the instrument manufacturers. After an extensive validation process it has been decided to include this model in the L1B algorithm and operational processor. This model allows pre-flight and in-flight IBA measurements to match mostly within arc-seconds for Alpha and Charlie, and with slightly larger offsets for Bravo. An improvement (higher than 10 arc-seconds) of the STR attitudes accuracy is also observed.
     
  • An increase of the frequency of the STR L0 product from 1 Hz to 2 Hz
    A high noise in the STR attitude accuracy is observed on the STR data at 1 Hz rate. Tests performed on-ground demonstrated that by doubling the STR data rate from 1Hz to 2Hz would improve significantly the pointing measurement is obtained. For this reason, the L1B processor has been adapted to handle STR data at 2 Hz. This means that very soon the time accuracy of the STR data will change from 1 to 2 Hz.

 

2.2          Magnetic Products


2.2.1    Important Notes

  • 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 after the correction the rms is roughly 300 pT, for all spacecraft. The expert group is working hard to further improve the disturbance models.

The key points are the following:

  1. 1. Early in the Swarm mission it was recognised that the measurements from the two magnetometer instruments (ASM and VFM) on-board each spacecraft measured slightly different absolute magnetic field values. This 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.
  • Separation of pre-flight from the in-flight VFM calibration parameters
    In the current version of the L1B operational processor a separation of the pre-flight and the in-flight VFM calibration parameters is introduced. More precisely, the pre-flight calibration parameters are applied to Level1binst.VFM (i.e., calibrated vector field components), while the inflight estimated calibration parameters are added to the diagonal scaling matrices in the computation of B'VFM (i.e., fully calibrated and corrected vector field components). In this way, we have the parameter B_pre (= Level1binst.VFM) parameter in MAGx_CA_1B products as a source of "original residuals".
     
  • Change the data resampling used for the interpolation of the ASM measurements to UTC second
    Experts have found that the resampling of the ASM data from t_ASM to exact UTC is removing a part of the high frequency content of the ASM data. In order to avoid this, a change of the ASM data resampling (non-smoothing cubic B-splines) has been implemented in the Level 1B processing algorithms.
     
  • Fixes in the computation of ASM stray fields
    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. This issue has no impact on the full correction of the ASM data from the total of the stray fields (dF_Total) which is instead implemented and applied in the right way.
     
  • Update of vector data calibration and disturbance characterization
    An update of the VFM pre-flight calibration parameters and of the dB_sun has been implemented in the Level 1B processing algorithms.

 

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_LP_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 that 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) 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) 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.


2.3.2    The Plasma "EFIx_LP_1B" Dataset: Description and Quality Information

Official Swarm Plasma products are available from the beginning of the mission to the present. The user is recommended to read carefully the following notes before using the data:

  1. EFIx_LP_1B only includes plasma parameters derived from the Langmuir Probes: electron density (Ne), electron temperature (Te) and S/C potential (Vs). All the plasma parameters derived from the Thermal Ion Imagers are not present in this product. Two plasma products are available: one at LP timestamp (EFIx_LP_1B) and the other one interpolated at exact UTC (EFIxLPI_1B). Both products contain exactly the same variables. 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.
  2. 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_LP_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.
  3. 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.
  4. 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_LP_1B products are set to the same fixed value: Ne_error = Te_error = Vs_error = 9.9999e9
  5. 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.
  6. It has recently been noticed that the electron density contained in the EFIx_LP_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. However, it has been noted that 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.
  7. The electron temperature (Te) is computed using mainly the high gain probe. In very few cases, when the high gain data are flagged with errors, the low gain will be used.


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_LP_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 the current date - 14 days for all three spacecraft.

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 the current date - 14 days 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 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 01/11/2015 to 31/07/2017 for S/C A and B and from 01/11/2015 to 22/11/2015 and from 01/05/2017 to 31/07/2017 for S/C C, 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 01/01/2016 to 30/04/2017 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.

The ACCx_PR_1B products with baseline 04 contain the accelerometer data as well as data relevant for POD and spacecraft dynamics investigations, e.g. the mass of the spacecraft. Since the decision not to disseminate accelerometer data is preventing Swarm data users from accessing data relevant for POD and spacecraft dynamics investigations, it was decided to split the ACCx_PR_1B data products into two products:

  • Revised ACCx_PR_1B data products that contain only the accelerometer data
  • New SC_xDYN_1B data products that contain all data that were present in the old ACCx_PR_1B data products, but will not be contained in the revised ACCx_PR_1B data products

The new SC_xDYN_1B data products will also contain three new variables that specify which thrusters were activated for how long, including the resulting thrust force acting on the spacecraft. The information will be extracted from the Level 1a AOCS and BUS house-keeping data contained in the HK_xAOCS1A and HK_xBUS_1A data products, respectively, which are also not available to Swarm data users.

The revised ACCx_PR_1B data products will remain inaccessible to Swarm data users, whereas the new SC_xDYN_1B data products will be disseminated to all Swarm data users. For accessing accelerometer data, Swarm data users are advised to use the Level 2 ACCCCAL_2 data products.

 


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 (03) of FAC, IBI and TEC products has been introduced. For the product types: FACxTMS_2F, IBIxTMS_2F, and TECxTMS_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, when the lower pair reached their definitive orbit configuration.

 

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 full coverage might be guaranteed by data from different baselines, which will not allow interoperability among them for certain types of science.