Three Times Three: Three Years of Swarm Routine Operations and Beyond
ESA, European Space Operations Centre (ESOC), Germany
Swarm is the magnetic field mission of the ESA Earth Observation program composed by three satellites flying in a semi-controlled constellation. Its history in-orbit began in the after-noon of the 22nd November 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 Space Operations Centre (ESOC) in Darmstadt, Ger-many. Following the successful completion of the Launch and Early Orbit Phase and plat-form check-out, during the commissioning phase operations focused on two main activities: the first in-flight calibration and characterization of the four instruments and the acquisition of the initial nominal orbit constellation for science exploitation.
The payload commissioning was concluded in spring 2014 and precious scientific data has been provided almost without interruption since then. Several contingencies and the need for improving science data quality have translated into a number of activities not foreseen before launch and which have kept the operations team very active during the first three years of routine operations.
The main focus of this paper is to provide a summary of the most significant activities per-formed by the Flight Control Team to support payload investigations to improve science quality: the progressive tests and continuous parameter update for the Electrical Field Instru-ment (EFI); the slew manoeuvres performed to support the investigation of the scalar meas-urements residual between the Absolute Scalar Magnetometer (ASM) and the Vector Field Magnetometer (VFM); the thermal and dynamic tests performed for the characterisation of the Accelerometers (ACC) signals and the increase of the GPS field-of-view and the fine-tune of its loop bandwidths to improve its performance.
Furthermore this paper provides an overview of the Swarm operational concept with a special emphasis of the multi-spacecraft aspect of the mission and its impact in the ground segment design and the day-to-day management by the Flight Control Team (FCT). The Swarm con-stellation is described and some details on the routine manoeuvres are provided together with the impact of contingency collision avoidance manoeuvres.
Finally, the paper concludes with some considerations of the operational impact of extending the mission beyond the nominal phase and the challenges the Flight Control Team will face to keep the Swarm satellites safely flying and providing many more years of fruitful science data.
CASSIOPE e-POP Mission Development and Operation
1University of Calgary, Canada; 2MDA Systems Ltd.
The CASCADE Smallsat and Ionospheric Polar Explorer (CASSIOPE) mission was successfully launched on September 29, 2013, and is currently in its fourth year of continuous operation. CASSIOPE uses the Canadian small satellite bus to carry the Enhanced Polar Outflow Probe (e-POP) scientific (space weather research) payload and the CASCADE communications technology demonstration payload into an elliptic polar orbit of 325 × 1500 km at an 80.9º inclination. This orbit makes possible the sampling of data over the full altitude range and at latitudes and local times of interest over the course of each year during the mission. The e-POP payload is comprised of a suite of eight high-resolution plasma, magnetic field, radio, and optical instruments designed for in-situ observations in the topside polar ionosphere at the highest-possible resolution. The payload utilizes the advanced data storage and telemetry downlink capability of CASCADE to meet its large data downlink bandwidth requirements while demonstrating the capabilities of CASCADE in the process. We give a brief description of the mission design, and operational experience to date in the context of opportunities for coordinated observations with other low-altitude polar-orbiting satellites such as the Swarm constellation.
Options for the Swarm Orbit and Constellation Evolution
1ESA/ESOC, Germany; 2CS GmbH at ESA/ESOC, Germany, Germany; 3SCISYS Deutschland GmbH at ESA/ESOC
ESA's Swarm magnetic field mission consists in three satellites flying in different circular Low Earth Orbits to form a constellation. Since completion of the orbit acquisition phase in April 2014 one satellite (B) is flying in a higher orbit while the other two satellites (A/C) form the lower pair with an ascending node difference of 1.4 deg. Along-track separation between A and C is maintained between 4 and 10 seconds. No altitude maintainance is performed.
Orbital planes are currently drifting: separation in LTAN between the lower pair and the highest one is increasing at a rate of 1.5 h per year, mainly due to inclination difference between the orbits (0.4 deg).
In the next future the constellation evolution will experience new phases: indeed, the decay rate of the satellites is strongly dependent on solar activity, which is foreseen to reach its minimum at the end of 2019, with a new maximum in 2024.
Basing on currently available predictions of solar activity, different options can be chosen in order to maximise the scientific return of the mission. The poster focuses on these options.
A major constrain is the availability of fuel. During the initial orbit acquisition phase 40% of the fuel was consumed. Since then the yearly consumption has been less than 1% of the initial fuel and is mainly spent by the on-board attitude control.
Taking into account future attitude control and orbit maintainance manoeuvres, still some fuel is remaining to reach various constellation configuration.
A list of options and their feasibility from the flight dynamics point of view is presented. Simulation results are shown for:
- control of LTAN difference between B and A/C to stay around 6 h (90 deg) for an extended time period.
- keep the LTAN difference increasing to reach counter-rotating orbits (delta LTAN = 12h around 2021).
- special formations of the lower pair satellites, i.e. reducing as possible their separation or let them follow the same ground track.
- increase mission lifetime beyond 2024 solar maximum to reach the following solar minimum in 2030. Possibilities are different for B only and for A/C.
- collect high accuracy measurement with A/C during the 2019 solar minimum at low altitude. A trade-off between amount of orbit lowering and length of subsequent altitude maintainance until fuel depletion is needed.
Finally some considerations are given on how the various options can be combined.
SWARM Instruments Performance Issues since Commissioning: Identification and Mitigation
1ESA/ESTEC, Netherlands, The; 2ESA/ESRIN, Italy
Each SWARM satellite embarks a complex Payload. Several issues have affected the performance of the three Payloads since Commissioning. The purpose of this paper is to indicate how each issue has been addressed by the Phase E2 teams, providing first a short description of each issue, then informing on the progress in its characterisation or identification. The aim is to provide any SWARM interested reader with an overview of the problems encountered, of their current status, and - where relevant - with a plan of additional efforts to complete mitigation.
Thus the paper will elaborate on the following topics: perturbations on the Vector Magnetic Field measurements in sunlight, Absolute Scalar Magnetometer measurements deviation with changing satellite orientation, Star Tracker Boresight Alignment variation and correction, Electric Field Instrument image blurring, optimisation of Global Positioning System Receiver settings, Langmuir Probes measurements issues, Accelerometer measurements pollution, other anomalies.
Swarm Payload Data Ground Segment: Status and Future Outlook
The Swarm Payload Data Ground Segment (PDGS) is in charge of the Swarm data processing, archiving, products quality control; calibration and performance monitoring, and products' dissemination.
This poster provides an overview of the current status of the Swarm PDGS and future outlook, highlighting the aspects more relevant to the end-users as the Level-1 and Level-2 Cat-2 processors’ status, reprocessing plans, new products' integration, user’s registration, and data access.
"VirES for Swarm" - Evolution of the Swarm Data Visualisation Tool
EOX IT Services GmbH, Austria
The virtual research service “VirES for Swarm” (http://vires.services) adds discovery and visual analytics capabilities to the European Space Agency’s online data access services established for the Swarm geomagnetic satellite mission constellation. VirES provides a highly interactive data manipulation and retrieval web interface for the official Swarm product archive and for a number of ancillary data sets. It includes multi-dimensional geographical visualization, interactive plotting and on-demand processing tools for studying Earth magnetic models and their time variations for comparing them to the Swarm satellite measurements at given global context of space weather. Subsets of Swarm data selected by versatile filtering methods can be downloaded in different encoding formats. The data downloaded can be combined to fit various use cases. VirES is also an environment for preparation of publication-ready graphics and charts through an intuitive and powerful yet customizable interface. An embedded online tutorial introduces the features of the VirES service to first-coming users.
The VirES service is actively and continuously being developed by ESA in close collaboration with leading experts of geomagnetism to ensure the best possible user experience and scientific validation of the presented information.
At the 4th Swarm Science meeting the authors present the latest status of the VirES service to further stimulate wide usage of this tool and to collect valuable feedback from users for future evolutions.
Swarm Data Exploitation and Valorisation at CDPP
1IRAP (CNRS/UT3), Toulouse, France; 2Noveltis, Labège, France; 3ESA, Noordwijk, The Netherlands
CDPP (http://cdpp.eu), the French database for space plasma physics, offers a set of services for, among other things, data exploitation and orbit visualisation. For data exploitation, the Automated Multi Dataset Analysis (AMDA, http://amda.cdpp.eu) is a web-based interface that offers plotting facilities, data mining and cross-database access via web services. AMDA archives and makes available data from most of the magnetospheric and planetary missions, and is now being extended to low-Earth orbit satellites such as Swarm. Besides, a 3D orbit visualisation tool (3DView, http://3dview.cdpp.eu) allows the user, on top of all traditional orbit visualisation capabilities, to plot data along the orbit of a spacecraft. We shall show through examples how Swarm data can advantageously be exploited and their use boosted with the tools offered by CDPP. We shall also introduce on-going developments of complementary tools.
Swarm Magnetic Data Quality Overview
1European Space Agency – Esrin, Italy; 2DTU Space, Technical University of Denmark; 3GMV, Poland; 4European Space Agency – Estec, The Netherlands
The ESA Swarm satellites, launched in November 2013, carry on-board instruments devoted to measure extremely accurate data necessary to improve our understanding of Earth’s magnetic field. Each spacecraft carry on-board an Absolute Scalar Magnetometer (ASM) for measuring the Earth’s magnetic field intensity and a Vector Field Magnetometer (VFM) measuring the direction and the strength of the geomagnetic field. The attitude needed to transform the vector readings to an Earth fixed coordinate frame is obtained by a three-head Star TRacker (STR) mounted close to the VFM instrument.
In these three years of operations, the Swarm Magnetic instruments have provided high precision and high resolution data, allowing a better mapping of the Earth’s magnetic field.
This poster aimed at providing an extensive overview of the Swarm magnetic instrument status, magnetic data availability and quality.
Statistical Analysis of Geomagnetic Field Intensity Differences between ASM and VFM Instruments Onboard Swarm Constellation
1Istituto Nazionale di Geofisica e Vulcanologia, Italy; 2INAF-Istituto di Astrofisica e Planetologia Spaziali
From the very first measurements made by the magnetometers onboard Swarm satellites launched by European Space Agency (ESA) in late 2013 it emerged a discrepancy between scalar and vector measurements. An accurate analysis of this phenomenon brought to build an empirical model of the disturbance, highly correlated with the Sun incidence angle, and to correct vector data accordingly. The empirical model adopted by ESA results in a significant decrease of the amplitude of the disturbance affecting VFM measurements so greatly improving the vector magnetic data quality. This study is focused on the characterization of the difference between magnetic field intensity measured by the absolute scalar magnetometer (ASM) and that reconstructed using the vector field magnetometer (VFM) installed on Swarm constellation. Applying empirical mode decomposition (EMD) method we find the intrinsic mode functions (IMFs) associated with ASM-VFM total intensity differences obtained with data both uncorrected and corrected for the disturbance correlated with the Sun incidence angle. Surprisingly, no differences are found in the nature of the IMFs embedded in the analyzed signals, being these IMFs characterized by the same dominant periodicities before and after correction. The effect of correction manifests in the decrease of the energy associated with some IMFs contributing to corrected data. Some IMFs identified by analyzing the ASM-VFM intensity discrepancy are characterized by the same dominant periodicities of those obtained by analyzing the temperature fluctuations of the VFM electronic unit. Thus the disturbance correlated with the Sun incidence angle could be still present in the corrected magnetic data. Furthermore, the ASM-VFM total intensity difference and the VFM electronic unit temperature display a maximal shared information with a time delay that depends on local time. Taken together, these findings may help to relate the features of the observed VFM-ASM total intensity difference to the physical characteristics of the real disturbance thus contributing to improve the empirical model proposed for the correction of data.
Recent Results from Analysis of the Sun Induced Magnetic Disturbance
DTU Space, Denmark
The efforts to investigate and characterise the Sun driven disturbances of the magnetic field measurements are continuing. This presentation show the recent results from the co-estimation of the emperical model of the Sun driven magnetic disturbance and the characterisation of the magnetometer measurements on-board the Swarm satellites. With more than three years of data the estimation of the model characterisation parameters seem to converge towards stable solutions. The recent models employ a homogenous, exponentially decaying sensitivity consistent with the expected behaviour of the vector magnetometer instruments.
Searching for the Cause of Small, but Systematic, Magnetic Field Anomalies Observed on Board the Swarm Satellites when Flying in non-Nominal Attitudes
Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, CNRS, F-75005 Paris, France
On several occasions since the launch of the mission in November 2013, Swarm satellites went through a number of attitude manoeuvres. During these approximately one-day sessions, non-nominal attitudes (sideway, backward, or else) were successively maintained for each satellite over at least half a dozen orbits, allowing inter-satellite comparisons of magnetic field readings (on both the absolute scalar (ASM) and vector (VFM) magnetometers). This revealed small (at the nT level), but systematic, anomalies affecting the two instruments in a qualitatively similar way when a satellite is in non-nominal attitude, the VFM appearing to be slightly more affected. In this presentation, we will report on our systematic investigation of this intriguing effect, which is different from the Sun-driven effect already known to affect the readings of the VFM instrument in nominal attitude, and which does not appear to be due to trivial induced or remanent magnetization effects on board the satellites.
A Comparison of Three Years of Swarm experimental ASM-V and Nominal VFM Data Using a Global Geomagnetic Field Modeling Approach
1Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, CNRS, F-75005 Paris, France.; 2DTU Space, National Space Institute, Technical University of Denmark, Kongens Lyngby, Denmark.; 3CEA, LETI, MINATEC Campus, F-38054 Grenoble, France.
Each of the three Alpha, Bravo and Charlie satellites of the ESA Swarm mission carries an Absolute Scalar Magnetometer (CNES customer furnished ASM instrument designed by CEA-Léti) that provides the nominal 1 Hz scalar data of the mission, but also delivers 1 Hz experimental vector data. Geomagnetic field models have already been published, using one year of such ASM-only data (without resorting to any of the nominal vector field magnetometer (VFM) data of the mission). These models demonstrated the good reliability of the ASM as a standalone instrument and the strong rigidity of the boom mechanically linking the ASM to the star imager (STR). They nevertheless also revealed small (at a few nT level) but systematic disagreements when compared to analogous models built using the nominal VFM data. In this presentation, we will report on our efforts to build a new extended model, now relying on three years of ASM-only data, which we will again compare to an analogous model built in the same way from nominal VFM data. Differences between these models will be discussed. It is hoped that such new comparisons will bring additional insight into the best way to further improve the nominal Swarm data.
An Overview of Results from the Flux-gate Magnetometer on the C/NOFS Satellite
NASA/GSFC, United States of America
The instrument suite that comprises the Vector Electric Field Investigation (VEFI) onboard the C/NOFS spacecraft includes a sensitive fluxgate magnetometer to measure DC and ULF magnetic fields in the low latitude ionosphere. The instrument includes a DC vector measurement at 1 sample/sec with a range of ± 45,000 nT whose primary objective is to enable accurate measurements of both V x B fields and E x B drifts. The magnetic field data also address a variety of important scientific research topics involving ionospheric and magnetospheric current systems. For example, at low latitudes, magnetic field residuals allow studies of the temporal evolution and local-time asymmetry of the storm-time ring current, typically studied as Dst signatures, which provide continuous local time information every 97 minutes, given C/NOFS’s low inclination orbit of 13 degrees. The C/NOFS magnetometer data also provide information concerning low latitude ionospheric currents, such as the equatorial electrojet and F-region dynamo, as well as other distinct variations with local time and geographic location not readily associated with these currents. The VEFI magnetometer also includes an AC-coupled vector measurement in the 0.05 – 8 Hz frequency range sampled at 16 samples/sec with an output range of ± 900 nT in order to measure small-scale filamentary currents, diamagnetic currents, and Alfven waves associated with low latitude plasma depletions, enhancements, and structures. When analyzed in conjunction with the electric field data, the combined magnetic and electric field signatures show Poynting Flux measurements directed poleward, along the magnetic field direction, associated with depleted magnetic flux-tubes. These data are used to help advance our understanding of the electrodynamics of low latitude plasma instabilities and large scale plasma structures. This talk presents an overview of a number of scientific results gathered with the flux-gate magnetometer on the C/NOFS satellite.
Particle-in-cell Modeling of Interaction Between Nanosatellite And Ionosphere
1PINSTECH, Pakistan; 2Dept. Physics, University of Alberta, Canada
We numerically investigate interaction between the nanosatellite, CubeSat and surrounding plasma. The Dynamic Ionosphere CubeSat Experiment (DICE) is a Low Earth Orbit mission which is launched on October 28, 2011 with objectives to understand the near Earth space environment and its impacts on the Earth. The DICE mission consists of the two identical 1.5 U CubeSats.Each CubeSat's payload carry two spherical Langmuir probes mounted on the booms extending out about 8cm from the payload in the opposite direction along the spin axis. The CubeSat payload is spin stabilized with a frequency of 0.2 Hz which gives an apparent rotation to the plasma flow in the frame of reference of the satellite. The payload spin axis tends to align itself with the Geodetic axis such that as the CubeSat moves toward the Northern latitude then the North pointing probe is in the ram and South-pointing probe is in the wake of the spacecraft. However the situation is opposite when the spacecraft moves toward the Southern latitudes. As a result spinning of the CubeSat payload with Langmuir probes deployed on it provides spin-modulated in-situ measurements of plasma parameters in the F2 region of the ionosphere. Therefore the present study aims to elucidate the particular issues related to the nano-satellite-plasma interaction which affect the on-board instruments. The goal is achieved by using the 3D electrostatic particle-in-cell code PTetra. The numerical results of the present study illustrate the effects of the plasma flow and orientation of the ambient magnetic field. It is found that the plasma flow affects the wake structures around the CubeSat payload. This in turn impacts the current characteristics and the floating potentials of the Langmuir probes on the CubeSat. The effect of the magnetic field is quantified by computing the current characteristics with two different orientations of the magnetic field, that is the Northward and Southward pointing magnetic field vectors. The computed current characteristics are then used to estimate the plasma parameters in the ram and wake directions.
This study will be helpful to understand the detailed interaction between the nanosatellites and the mesothermal plasma environment.
The Swarm Langmuir Probes: Status and Ongoing Activities
1ESA, Esrin, Italy; 2Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy; 3Istituto Nazionale di Astrofisica, Rome, Italy; 4IRF – Swedish Institute of Space Physics – Uppsala, Sweden; 5GFZ – German Research Center for Geosciences – Potsdam, DE; 6ESA, Esoc, Germany; 7University of Calgary, Canada
The Swarm Langmuir Probes (LP) are one of the two instruments which compose the Electric Field Instrument (EFI) on board Swarm spacecraft. They are devoted to the measurement of the electron density and temperature in the ionosphere and the measurement of the spacecraft potential which is auxiliary to the data processing of the other EFI instrument, the Thermal Ion Imager.
After three years in operations, the Swarm LPs equipment provides high quality observations especially for electron density, which turns to be the most reliable and stable Swarm plasma parameter product. Swarm electron density data have been used successfully in many scientific studies from polar to equatorial regions.
The operations team support even further improvements of Langmuir Probe operations, in particular: 1) the correct interpretation of the electron temperature measurements, still showing unexplained spikes widely observed throughout the whole dataset; 2) the calibration and validation of LP data by comparisons with models and independent datasets (e.g. Incoherent Scatter Radars, plasma parameters inferred from the measurement of the spacecraft’s faceplate currents).
This work will give an overview of the LP data validation activities and results during the first three years of mission operations, and suggests future validation/calibration plans.
Swarm Thermal Ion Imager Instruments: Overview and Operational Status
1ESA, Esrin, Italy; 2Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy; 3Istituto Nazionale di Astrofisica, Rome, Italy; 4ESA, Estec, Netherlands; 5University of Calgary, Canada; 6ESA, Esoc, Germany
The Thermal Ion Imager (TII) is one of the two instruments which compose the Electric Field Instrument on-board each of the three Swarm spacecrafts. The TII instruments are devoted to measure the velocity and temperature of the bulk O+ distribution in the ionosphere, and to infer the ionospheric Electric field.
Despite the overall good health of the instruments and their associated equipment, in-orbit operations showed an unforeseen behaviour in the three TIIs. This is related to a non-permanent degradation of raw images that take place on continuous operations. After careful analysis of the data and several in-orbit tests, it was concluded that the observed image degradation is most likely due to water contamination in the sensor head. Several tests have been run in-orbit and a summary will be presented in the poster.
In order to tackle the unforeseen in-orbit behaviour, and for maximizing the quality of scientific data, an operational scenario was implemented where the instrument is switch-on for a few orbits per day. Discussions took place inside the science community, in order to achieve a sustainable operation plan for the TII, taking into account the most interesting configurations for science (e.g. particular latitude and local times, operations in conjunction with other spacecraft or ground based facilities). In this poster we will also show the new operational concept that ESA and the science experts developed in order to maximize the amount of good measurements with respect to the prevailing science needs.
CSES Electric Field Detector Calibration Tools Based on IRI, IGRF, and SWARM Data
1INAF, Italy; 2INGV, Italy
CSES (China Seismo-Electromagnetic Satellite) is a scientific mission mainly dedicated to the simultaneous and continuous monitoring of perturbations in the atmosphere, ionosphere, and magnetosphere, and to study their correlations with seismic events. Furthermore, CSES mission will allow to study the physical characteristics of the ionospheric plasma at the satellite altitude, to characterize the ionosphere in quiet and disturbed conditions. The satellite, 3-axis attitude stabilized, will be placed at a 98° Sun-syncronous circular orbit at an altitude of 500 km. The launch is scheduled in the first half of 2017 and the expected lifetime is 5 years.
The Electric Field Detectors (EFD) will measure electric fields in the range DC – 3.5 MHz with a precision ≤ 1 µV/m.
Such kind of measure is strongly affected by instrumental features and environmental parameters. These effects can reach several mV/m, therefore, are orders of magnitude higher than the signal we want to detect. Moreover, these factors show a large variability along the satellite orbit since they also depend on the plasma parameters and the geomagnetic field.
In order to evaluate the data correction factors we analysed data from IRI and IGRF models, and SWARM measurements.
Comparison between CSES simulations and SWARM data will help us to perform calibration tools to be used during their simultaneous flights at longitude close to each other. In particular, the SWARM EFI data will be used to evaluate the ion drift that allow to correct the EFD geometrical factor.
Overview of Swarm Accelerometer Data Quality
1RHEA for ESA - European Space Agency, The Netherlands; 2Leibniz Universität Hannover, Germany; 3Delft University of Technology, The Netherlands; 4GFZ German Research Centre for Geosciences, Germany; 5Technical University of Denmark, Denmark; 6Serenum, a.s., Czech Republic
The Swarm satellites carry accelerometers as part of their scientific payload. These instruments measure the non-gravitational acceleration due to forces like drag or radiation pressure acting on the spacecraft, from which thermospheric neutral densities and potentially winds can be derived.
Unfortunately, the acceleration measurements suffer from a variety of perturbations, the most prominent being slow temperature-induced bias variations and sudden bias changes. Other less prominent perturbation includes spikes and artificial periodic signals. Though all perturbation are visible in the measurements of all Swarm accelerometers, their severity is much different for the three Swarm satellites. In this presentation, we illustrate all known disturbances and assess their severity for scientific exploitation of the accelerometer data separately for each Swarm satellite.
Improvements of the Swarm Accelerometer Data Processing
1TU Delft, The Netherlands; 2RHEA for ESA,The Netherlands; 3GFZ German Research Centre for Geosciences; 4VZLÚ Aeronautical Research and Test Institute; 5Leibniz Universität Hannover, Hanover, Germany; 6Technical University of Denmark
The Swarm satellites carry accelerometers and GPS receivers as part of their scientific payload. The GPS receivers are not only used for locating the position and time of the magnetic measurements, but also for determining non-gravitational forces like drag and radiation pressure acting on the spacecraft. The accelerometers measure these forces directly, at much finer resolution than the GPS receivers, from which thermospheric neutral densities and potentially winds can be derived. Unfortunately, the acceleration measurements suffer from a variety of disturbances, the most prominent being slow temperature-induced bias variations and sudden bias changes. These disturbances required significant changes to the processing algorithms, which as a side effect caused a significant delay of the accelerometer data release.
In this presentation, we describe the new processing that is required for transforming the disturbed acceleration measurements into scientifically valuable thermospheric neutral densities. In the first stage, the sudden bias changes in the acceleration measurements are removed using a dedicated software tools. We present a new option of automated step detection and correction, which should speed up the accelerometer data release. The second stage is the calibration of the accelerometer measurements against the non-gravitational accelerations derived from the GPS receiver, which includes the correction for the slow temperature-induced bias variations. The identification of validity periods for calibration and correction parameters is part of the second stage. In the third stage, the calibrated and corrected accelerations a merged with the non-gravitational accelerations derived from the GPS receiver by a weighted average in the spectral domain, where the weights depend on the frequency. The fourth stage consists of transforming the corrected and calibrated accelerations into thermospheric neutral densities. We describe the methods used in each stage, highlight the difficulties encountered, and comment on the quality of the thermospheric neutral density data set.
Swarm DISC: New Swarm Products and Services
1Technical University of Denmark, Denmark; 2University of Calgary
One task of Swarm DISC (Data, Innovation, and Science Cluster) is the identification, development and production of new products and services to enhance the scientific return of the Swarm mission.
Four new products have been selected during a first “call for ideas” in autumn 2016 and are presently being implemented. A second “call” is planned for early summer 2017.
We will present Swarm DISC, the approach to identify new products, and the status of the new initiatives that were selected in 2016.
Swarm SCARF Comprehensive Inversion, 2017 Production
1DTU Space Denmark; 2NASA / Goddard Space Flight Center USA
The Swarm SCARF (Satellite Constellation Application and Research Facility), a consortium of several research institutions, has been established with the goal of deriving Level-2 products by combination of data from the three satellites, and of the various instruments. Here we present the results of the Swarm SCARF team at DTU Space and NASA Goddard who conducts the Comprehensive Inversion (CI) magnetic field model processing chain; we present the results from using three years of Swarm data. The CI chain takes full advantage of the Swarm constellation by doing a comprehensive co-estimation of the magnetic fields from Earth’s core, lithosphere, ionosphere, and magnetosphere together with induced fields from Earth’s mantle and oceans using single and dual satellite gradient information. Level-2 products containing the corresponding
model parameter estimations will be generated regularly throughout the Swarm mission and distributed via ESA.
Swarm Level-2: Dedicated Core Field Model (DCO)
GFZ German Research Centre for Geosciences, Germany
The DCO (Dedicated Core) geomagnetic model submission for Swarm's third-year Level-2 product generation using Swarm-only data will be presented, as well as comparisons between the submitted version with its variants through adding observatory data or, taken advantage of the Swarm constellation, using data differences only (along-track and/or cross-track satellite data). Results in searching for Ocean Tide signals in the DCO model residuals will be discussed as a benchmark for the achieved quality of the presented models.
Recent BGS Activities for the Swarm Data Innovation and Science Cluster
British Geological Survey, Edinburgh, United Kingdom
The British Geological Survey is responsible for the fast-track magnetospheric field model product (MMA_SHA_2F), geomagnetic observatory data (AUX_OBS*2_) products and Level 2 CAT-1 product validation, as part of the consortium of institutes making up the Swarm Expert Support Laboratory. We summarise these activities and provide updates since the Living Planet Symposium in June 2016.
The fast-track magnetospheric field model product is generated automatically and disseminated on a daily basis after receipt of the Swarm L1b files. With more than three years of accumulated models, we comment on the longer-term behaviour of the magnetospheric field.
The observatory hourly-mean (AUX_OBS_2_) data product is updated every 3 months using a selection of definitive and quasi-definitive data from observatories around the world. Since Swarm was launched, good quality data from about 120 observatories are available.
BGS started issuing new observatory data products in October 2016 with a 4-day lag. Regular updates are made if new data are found. These products consist of 1-second observatory (AUX_OBSS2_) and 1-minute (AUX_OBSM2_) quasi-definitive data from the start of the Swarm mission, and are made available on the BGS anonymous FTP server at ftp://ftp.nerc-murchison.ac.uk/geomag/Swarm/AUX_OBS/.
A summary of temporal and spatial coverage of all observatory data products is provided.
Validation of the Level 2 CAT-1 products comprises comparisons of the Swarm-based models to independent models and data where possible, and inter-comparisons of models from the dedicated and comprehensive processing chains. A selection of plots from recent validation reports is given.
The Canadian Cordillera Array (CCArray): Taking Earth-Based Observations to the Next Level
1Mount Royal University, Canada; 2University of Calgary, Canada
CCArray is a bold initiative to deploy a network of telemetered solar-powered remote observatories, instrumented with riometers, weather stations, GNSS, permafrost monitors, atmospheric gas sensors and broadband seismometers, with the goal of characterizing Earth systems from the core to the magnetosphere. The proposed observation network will span the Canadian Cordillera (all of the mountainous regions of western Canada) from the Beaufort Sea to the US Pacific northwest with a spatial resolution of up to 1 degree.
A recent workshop at Fall AGU explored the potential for monitoring the formation of auroras in the magnetosphere, imaging subducted slabs in the mantle, improving our understanding of earthquake dynamics and tsunami hazards, extending critical zone (region from tree canopy through the soil into bedrock – the portion of Earth critical for life) monitoring stations into regions of permafrost, and improving modeling of atmospheric gravity waves (important for enhancement of numerical weather modeling). Here we will present a summary of some of the potential applications of such a network, expanding on integrated research results that have emerged out of the US Earthscope program together with outcomes from a series of workshops and planning meetings held across Canada and the US over the past year.
CCArray is envisioned as the initial component of a broader research collaboration that will extend within a rolling array across Canada from west to east. While many of the stations will be in place for up to three years, the intention is to leave some stations permanently fixed to enable long-term monitoring of Earth systems across Canada.
While the SWARM satellite program examines magnetic components of our planet from the magnetosphere down to Earth’s core, CCArray represents a complementary initiative with imaging capability that extends upwards to the magnetosphere from the Earth’s surface and downwards from the surface deep into the mantle.
Review of Data Recorded by the e-POP Radio Receiver Instrument (RRI)
1Retired, Canada; 2University of Calgary
The SWARM-ePOP collaborative opportunity comes as the CASSIOPE/e-POP scientific mission enters the second half of its estimated orbital life. ePOP scientists are contemplating how the resources of the remainder of the mission should be allocated. The e-POP Radio Receiver Instrument (RRI) has a 31-kHz bandwidth, and uses four 3-m distributed monopoles to detect spontaneous or artificial electromagnetic waves between 10 Hz and 18 MHz. In all data recordings made so far, the monopoles have been connected to the RRI high-impedance front end as orthogonal 6-m dipoles. In-phase and quadrature voltage signals are sampled on both dipoles at 62500 s-1. CASSIOPE-ephemeris, RRI-Quick-Look, RRI-summary and RRI-detailed-Lv1 data are all available to the public at epop-data.phys.ucalgary.ca. Recently, the ePOP Science Operations Centre also released a free computer application called eDEx for metadata searches of data from all e-POP instruments.
To anticipate RRI experiments of possible interest to the Swarm community, we review principal findings from RRI recorded on about 900 CASSIOPE passes, most of which are 2-3 min long. These include about 350 Very-Low-Frequency (VLF) passes band-centred at 15.6 kHz, largely at high latitude. Thanks to the sampling rate, auroral emissions are seen to exhibit time-space fluctuations down to 10 ms. Signals from powerful VLF communications systems are received near apogee at locations far distant from their transmitters. In the High_Frequency domain, fruitful coordinations with ionospheric heaters and with coherent backscatter radars signals have been planned and carried out on well over 100 passes. These are being analyzed for the purpose of understanding the importance of propagation effects in the interpretation of ionospheric modification and scatter, respectively.
We ePOP/RRI scientists wish to exploit productive coordinated experiments, both with other e-POP instruments and with external facilities throughout the world. We remain open to proposals for collaboration for the rest of the mission.
Statistical Characterisation of Penetrating Radiation Fluxes near 500 km Altitude Based on Swarm EFI Thermal Ion Imager CCD Artefacts
University of Calgary, Canada
The three Swarm satellites have been flying in polar circular low-Earth orbits since November 2013. Each satellite carries one electric field instrument (EFI) having two CCD67 charge-coupled devices from e2v for imaging ion energy distributions. A previous study (Knudsen and Man, 2007) estimated the effects of CCD radiation exposure on EFI measurements based on modelled incoming proton fluxes and radiation transport calculations. That study found that radiation-induced dark current was expected to be negligible at the end of the nominal 4-year Swarm mission, and furthermore provided a global statistical model of radiation fluxes at Swarm altitudes (~500 km). We revisit that study using (brief explanation of new methodology). In particular, we examine TII full images (sampled at a rate of ~1 / minute per sensor) for signatures of penetrating radiation and produce a geographical distribution of affected images. We compare that distribution with a distribution of south-atlantic anomaly (SAA) trapped proton and galactic cosmic ray (GCR) events calculated by ESA.