Swarm is an ESA Earth Explorer Mission, launched in November 2013, dedicated to unravel one of the most fundamental aspects of our planet: The Earths magnetic field from the Core to the Magnetoshpere. The Swarm mission consists of three identical satellites (Swarm-Alpha, -Bravo and -Charlie) placed in two different polar orbits - the two lower spacecrafts side-by-side at approximately 440 km and the upper at approximately 510 km. In addition the Third-Party e-POP mission adds the fourth spacecraft to the Swarm constellation as Swarm Echo

This presentation will provide an overall status of the Swarm mission and products and an outlook for the short and long term future.

Swarm is the magnetic field mission of the ESA Earth Observation program composed of three satellites flying in a semi-controlled constellation: Swarm-A and Swarm-C flying in pair and Swarm-B at an higher altitude. Its history in-orbit began in the afternoon of the 22nd of Novem-ber 2013, when the three identical spacecraft separated perfectly from the upper stage of the Rockot launcher at an altitude of about 499 km. Control of the trio was immediately taken over by the ESA’s European Space Operations Centre (ESOC) in Darmstadt, Germany. Following the successful completion of the Launch and Early Orbit Phase (LEOP), commissioning was con-cluded in spring 2014 and precious scientific data have been provided since then.

In order to deliver extremely accurate data to advance our understanding of Earth’s magnetic field and its implications, each Swarm satellite carries a magnetic package, composed by an Absolute Scalar Magnetometer (ASM) and a Vector Field Magnetometer (VFM), an Electrical Field Instrument (EFI) and an Accelerometer (ACC). Unfortunately Swarm-C, due to a failure in LEOP and commissioning, does not carry an ASM.

Two daily ground station contacts per spacecraft are needed to support operations and downlink the scientific data stored in the on-board Mass Memory Unit. Only one ground station pass, however, is supervised by an operator, while in general the missions routine operations are automated, thanks to the Mission Control System used at ESOC and the relevant expertise in mission automation gained from the other Earth Explorers, from GOCE to CryoSat-2.

Many activities and campaigns have been performed through the years to improve instrument anomalies, such as changing the EFI operation’s concept to a limited number of daily science orbits and scrubbing operations to counteract image degradation. In particular, the operations on the EFI, implying a consistent workload for the teams, have been automated with the creation of a new interface with the University of Calgary, in charge of producing a set of files with the required configuration and requests, that are ingested in the FOS Mission Planning System.

Similarly, in the last years the ASM instrument has undertaken more and more sessions in Burst Mode, producing data at 250Hz on request of the Instruments team. Also this activity has been recently integrated in the automated operations concept, to offer flexibility to target this mode based on the space environment’s short-term evolution.

On the platform side, a few anomalies happened and were reacted upon very quickly, e.g. the Swarm-A science data downlink anomaly in 2020, that was solved by routing all science data to the housekeeping storage and re-designing part of the ground segment’s processing to handle this change of concept.

The operations were not affected by the COVID-19 pandemic, in the worst periods of which the teams were mostly working remotely and the operations supervised at ESOC by a reduced team: no outage of science nor change of core operations concept was necessary due to the pandemic.

On the orbits side, a major orbital manoeuvring campaign was undertaken in 2019 to change the relative local time of Swarm-A and Swarm-C, such to meet Swarm-B when the orbital planes were at the closest angular location in Summer to Winter, 2021. This particular scenario called “counter-rotating orbits” implied Swarm-B counter-rotating with respect to the lower pair in a similar orbital plane, a very exciting opportunity for science. In addition to this, the separation along-track of Swarm-A and Swarm-C was tuned down to 4 seconds, then 2 seconds and then kept variable up to 40 seconds to provide different scenarios for science data collection, requiring in total more than 20 orbital manoeuvres.

The presentation will describe the Swarm specific ground segment elements of the Flight Operations Segment (FOS) and explain some of the challenging operations performed so far during this almost-9-years-long journey, from payloads operations to resolution of anomalies and the last orbital dance during the “counter-rotating orbits”. This will offer an interesting overview of the mission’s satellite trio, ready to collect science during the upcoming Solar Cycle… and more.

When not operated in their experimental vector mode (see “Self-calibrated absolute vector data produced by the ASM absolute magnetometers on board the Swarm satellites: results, availability and prospect” by Hulot et al.), Absolute Scalar Magnetometers (ASM) on board the Swarm satellites can be operated in a so-called burst mode, allowing the scalar magnetic field to be sampled at 250 Hz with 1 pT(Hz)-1/2 resolution in the [1-100 Hz] frequency range. Originally, this mode was only intended to be run during the commissioning phase for ASM instrument validation purposes. However, as early short burst mode sessions revealed the ability of these data to detect whistlers produced by lightning in the ELF (Extremely Low Frequency) band, the decision was later made by ESA and IPGP to run regular burst mode sessions and start producing a new L1b Swarm data product. Regular one-week sessions are currently run on Swarm Alpha and Bravo every month, usually during different weeks, with occasional overlap. These data are processed within IPGP in the context of Swarm DISC activities and delivered to ESA as a L1b product known as the ASM burst-mode L1b data.

These ASM burst-mode L1b data revealing many whistlers with high scientific value for investigating both lightning events and the ionosphere (see “Whistler in ELF detected from LEO: lightning detection and ionospheric monitoring using Swarm satellites and the future NanoMagSat mission” by Coïsson et al.), it was further decided to systematically analyse these data, to identify and characterize all whistler events. This led to the production of a new Swarm L2 daily product (one daily file per satellite, whenever the satellite is running in burst mode), providing detailed information (such as time of occurrence, location of satellite at time of detection, dispersion, energy) about each whistler detected during the burst mode session. This product is also processed within IPGP in the context of Swarm DISC activities and delivered to ESA as a L2 product known as the Swarm L2 whistler product.

In this presentation, both the burst mode L1b data and the L2 whistler product will be described with the purpose of further encouraging their use by the community. Details about the data/product format, content and availability will be provided, as well as the way the processing chains are designed and operated. The possibility of permanently and systematically producing such magnetic burst mode data and whistler products within an even wider ELF frequency range using miniaturized magnetometers on board nanosatellites, such as envisioned in the context of the NanoMagSat constellation proposed as a Scout ESA NewSpace Science mission, will also be discussed.

The ESA Swarm Mission is the fourth Earth Explorer of the agency and it was launched at the end of November 2013. It is composed of three identical satellites (A, B and C) flying in a constellation, which varied throughout the course of the mission. The main objective of Swarm is the analysis and modelling of the Earth’s magnetic field at an unprecedented accuracy, through combined measurements of scalar and vector magnetometers. In addition, each satellite carries a set of other instruments, which are useful not only to nominal operations, but also to achieve secondary mission’s objectives. In particular, each of them carries an accelerometer intended to measure the non-gravitational forces acting on each single satellite. However, as this instrument did not function as expected, a significant amount of post-processing was necessary to calibrate the signal, often disturbed by spikes, steps and other types of noise. The calibration focused mainly on Swarm C, for which the data are available since the beginning of the mission and are disseminated monthly. Recently, a Swarm A dataset was also released and it comprises some months of the early mission phase, i.e. February - October 2014, when the solar activity was quite high. Swarm A and Swarm C are the so-called “lower pair” because they have been flying for most of the mission side by side, with a variable separation of four to ten seconds. Therefore, the calibrated accelerometer measurements that they provide, when compared, should be in line with the aforementioned separation.

In this work, an analysis on the newly available Swarm A data is presented, in correlation with data of Swarm C for the same period. After applying a high pass filter, very similar signatures are visible, both at the equator and at the poles, for both satellites. These features agree with signals measured by other instruments on board, and they are in line with current literature on LEO satellites (e.g. CHAMP). Having Swarm A and Swarm C data sets available for overlapping period, allows to finally exploit the accelerometer data from the lower pair of the Swarm constellation. For the first time, scientific results are obtained from two Swarm accelerometers, some of which enable Joule heating estimates, to address one of the secondary objectives of the Swarm mission. Therefore, this analysis could be a precursor of a possible full exploitation of the constellation in case Swarm B calibrated accelerometer data will become available.

Current Swarm density estimations rely on key assumptions to infer these ionospheric parameters from ion admittance on the Langmuir Probe. Namely, the existing methodology assumes a 100% O+ plasma, ignores any ion drifts, and neglects any plasma sheath effects. In a realistic plasma environment, these assumptions are expected to be routinely violated, particularly on the nightside (where light ions constitute a significant minority of plasma) and in the auroral zone (where ion flows are non-negligible). This compromises the accuracy of the existing density product, leading at times to significant residuals when compared with independent estimates such as the International Reference Ionosphere or ground radar conjunctions. Here we report on the status of the ESA DISC SLIDEM project, which aims to relax the above assumptions by incorporating current data from the frontal Thermal Ion Imager faceplate, thus delivering an improved and more robust ion density product. In addition, by utilizing the additional source of information, instead of being neglected, along-track ion drift and effective mass may be explicitly derived or estimated. These parameters, valuable in their own right to the wider geophysics community, are also compared with independent estimates in the form of empirical models (IRI-2016 and Weimer 2005 electric field model), conjunctions with other satellites and with ground radar sites, and with data from alternate instruments aboard the same spacecraft. Finally, particle-in-cell simulations are carried out using the Ptetra code to ensure that the assumptions inherent in the mathematical methodology are robust and hold for the Swarm spacecraft geometry under realistic ambient plasma conditions. Uncertainties and potential sources of error are identified and discussed. The SLIDEM project is currently in a mature state, with the output ionospheric parameter estimates having been validated against a range of independent benchmarks. It is therefore hoped the data products derived using SLIDEM will be widely used by the wider geophysics community to obtain accurate and robust estimates of density, plasma flows, and ion composition.

ESA Swarm Earth Explorer mission consists of three identical spacecraft launched in November 2013 in almost polar orbits, with an altitude of approximately 500 kilometers. Swarm spacecraft are providing very accurate measurements of plasma parameters and magnetic field in the Ionosphere F region for 8 years now, from the various dedicated instruments on-board. Since the beginning of the mission, a particular effort from ESA and Swarm community aimed at improving the data quality, addressing various issues or artefacts in the measurements. This presentation, in particular, illustrates the main findings of a project called SPike-trains in ElecTron TempeRAture measured from Swarm Langmuir probEs (SPETTRALE), focussing on plasma parameters measured by Langmuir probes, and in particular on Electron Temperature (Te).
Since early measurements from Swarm, it was evident that the Te measured by Swarm spacecraft shows sometime very large values, not predicted by the models (e.g. IRI 2016, NeQuick), which have unknown origin. SPETTRALE project has demonstrated that a significant fraction of these Te-Spikes appear for specific orientations of Swarm solar panels with respect to the Sun, and they are ordered as continuous lines as a function of the angle with respect to the Sun, and therefore, could be due to instrumental issues or artefacts.
The second phase of the SPETTRALE project has extended the analysis of Te-spikes as a function of Swarm House Keeping parameters relative to potential and currents from solar panels, in order to clarify the origin of these very high values and characterise the main mechanism and the physical nature of Te Spike-trains observed by Swarm. A statistical analysis has been performed on higher resolution (1 Hz) Swarm House Keeping parameters, acquired during a dedicated campaign in Summer 2021 to improve the analysis of SPETTRALE project.
The main findings of this project, together with the next step to implement a new quality Flag for Swarm Te, will be discussed in this presentation.