Data Reanalysis

An ongoing guide that documents updates about Helios 1 & 2 data, gathered documents, and reprocessing efforts.

In 2015, a concerted effort began to collect and document the valuable Helios 1 and 2 mission data in preparation for solar and inner-heliospheric exploration missions, such as Parker Solar Probe (PSP) and Solar Orbiter (SolO). Our team worked on gathering all in-situ data available to-date, codes, mission documents, and basically all available information pertaining to the Helios mission. The team also worked on thoroughly reanalyzing the available data. This reprocessing found inconsistencies in the datasets and lack of information about specific instrument functionality.

European groups looked through their respective institutions' records and reached out to some of the original Helios mission PIs to gather more information and provide the best available documented datasets. A great deal of work has been put into aggregating, reanalyzing, and archiving the datasets from the 1970's joint venture of Helios 1 and 2.

The aggregation process included scanning various instrument reports, notes, bluebooks, and more. The original PIs also provided invaluable information that was otherwise not available. Much of this information is available for download from this present archive.

The reanalysis process was done on the available, but incomplete, datasets; much of the high resolution data was either thrown away in cost saving measures or deteriorated overtime. To better understand the signal measurements, datasets from multiple experiments were used to parse for outliers, missing data, and general errors. In this menu, each experiment page organizes this information and provides links to the documentation for more details.

The archiving process organizes the information from our colleagues around the world to bring you the most complete, comprehensive, and accessible archive for the Helios 1 and 2 data. The goal is to help further the fields of Heliophysics and Solar Astrophysics.

Reanalysis Summaries by Experiment

A thorough reanalysis of the Helios in-situ datasets -- magnetic field and plasma measurements -- has been done prior to the archiving process to understand the dataset and their issues. The entire international team then met in Cologne for a workshop at the end of June 2016, to thoroughly discuss the reanalysis work, findings, issues and ways to address them, and the creation of the archive. The result of this workshop was a wealth of information, some of which was previously unavailable, that served as a foundation for the present archive.

The entire team came up with a list of issues and action items compiled by Chadi Salem (SSL/UC Berkeley) into a document, Action Item List, for the Helios data archive project. It serves as a concise overview of the progress that has been made in aggregating, analyzing, evaluating, documenting and archiving the available Helios 1 and 2 in-situ data.

The following boxes contain brief individualized summaries of this reanalysis process organized by experiment.

E1 Plasma Detectors

The best available and most original E1 dataset, was processed in the 1990’s, by Schwenn's team in Germany, then saved in ASCII files on a set of DVDs.

Our team thoroughly reanalyzed that dataset using modern fit analysis techniques applied to the proton, alpha particle, and electron distribution functions, to more accurately calculate the necessary plasma parameters. Magnetic field data from experiments E2 and/or E3 were used to determine parallel and perpendicular temperatures. Although a lot of progress has been made, this work is ongoing: we have characterized the alpha particle and proton core populations and are working on the next phases of the reanalysis process to characterize the proton beam and electron core/halo/strahl population.

In the repository, we have the best available original E1 data from Schwenn's DVDs, as well as the reprocessed proton core and alpha particle parameters. To support both of these datasets we provide a myriad of documentation, as well as the codes/programs used to calculate both old and new datasets.

E2 Fluxgate Magnetometer for Field Fluctuations

There's been a thorough analysis of the E2 data in conjunction with the E3 data, and discussed in detail at the Cologne Workshop. Various discrepancies were found with the E2 data. The 4Hz dataset has gaps and some of the data has erroneous zero-points. The 40.5 sec averages seem to be immune from the cuts and gaps found in the 4Hz data. They were calculated from a different, possibly more complete, 4Hz dataset.

There are three available datasets for experiment E2: 40.5 sec averages, 8 sec averages, and 4Hz (best dataset). We also have the original instrument documentation and new documents, with previously unavailable information, from the original experiment PI, Neubauer.

E3 Fluxgate Magnetometer for Average Fields

The E3 dataset is incomplete in the sense that the highest resolution measurements, sampled at 8Hz, are lost forever. The only available E3 dataset is that of 6 second magnetic field averages. It was reanalyzed in conjunction with the E2 4Hz dataset to help contextualize gaps and other anomalies.

As for documentation, we have the original E3 bluebook and a short presentation from Roberto Bruno (University of Rome).

E4 Search Coil Magnetometer

Our team reanalyzed the available E4 data alongside the E2 4Hz dataset. The E4 data has good values for measurements taken with a periodicity of 8 seconds but there are still some issues to be aware of.

Only two E4 data products are available: 8 sec max value and 8 sec mean value. Similar story as with the rest of the experiments, most of the E4 data is lost and unrecoverable. Only a very limited subset of it is available. We have various E4 documents, in German, that have not been translated and some newer documents for the reanalysis process, such as graphs depicting the available data/data issues.

E5A Plasma Waves

No reprocessing has been done, by our team, on the available E5A data, so the most recent documentation on the collection and analysis of this data is from the Helios E5A Final Report from 1986. The best available information and data on experiment E5A comes from the University of Iowa's E5A webpage.

Four datasets are available for E5A: average, peak, sn, and vdiff. The data's status of errors and reliability is unknown. There are also original documents about the mission, instrument, and calibration.

Workshops & Presentations

In June 2016 a MiniWorkshop (see agenda and participants) was held in Cologne for the HELIOS mission. A lot of important documentation about the available datasets is contained within these presentations.

Monday Talks (June 27th)

Author Title Description/Abstract Date Size Type
Thierry Dudok de Wit Solar Probe Plus: a mission to touch the Sun... Presentation on Solar Probe Plus mission and relevance of the Helios 1 & 2 mission data. 2016 21M PDF
Milan Maksimovi Solar Orbiter Exploring the Sun-Heliosphere Connection Presentation on Solar Orbiter spacecraft and mission. 2016 9.0M PDF
F M Neubauer The Technical University of Braunschweig (TU-BS) Magnetometer Experiment E2 (Fluxgate) Onboard Helios 1 and 2 The objective of this presentation is to provide information on the Helios fluxgate magnetometer E2 data. Written information unfortunately partly incomplete because of accidental losses of printed documentation. Thus some of the information is available in print and some from memory only. 2016 6.8M PDF
F M Neubauer The Helios Mission Agenda: Historical remarks, Experiments, Orbital Information, Spacecraft, Conclusions. Note that some of the information used is not available in written documentation any more and I had to rely on my memory and sometimes of others. 2016 4.0M PDF
Chadi Salem The Legacy of HELIOS: Why is Helios Important Now and Creation of a Universal Archive at NASA This presentation provides a brief summary of the Helios Mission, talks about the relevance to Parker Solar Probe (PSP) and Solar Orbiter, and describes some preliminary work done on a NASA funded project to aggregate, analyze, document, and archive the Helios Mission data. 2016 4.2M PDF
Lex Wennmacher E2 data history, format, and availability This talk provides a historic overview and technical details pertaining to the current state of the Helios Mission E2 Data. 2016 2.9M PDF

Tuesday Talks (June 28th)

Author Title Description/Abstract Date Size Type
Supratik Banerjee Compressible MHD Turbulence: A Source of Heating in the Fast Solar Wind This presentation begins with a slide about the anomalous temperature profile of the solar wind, follwed by slides discussing a heating source and plasma turbulence. 2016 644K PDF
Roberto Bruno The Rome‐GSFC magnetometer E3 onboard Helios This document gives an overview of the Rome-GSFC magnetic field experiment, E3, and the corresponding available data. 2016 504K PDF
Thierry Dudok de Wit HELIOS Search Coil E4: open questions A technical presentation that analyzes the available E4 data, beginning with a comparison of E2 and E4 data readings. Several graphs are used to visuallize the E4 data. 2016 8.3M PDF
Lorenzo Matteini Alfvénic fluctuations, velocity spikes, and predicting observations close to the Sun How Helios still surprises us after 40 years!
Helios data still offer us new results and unique view of inner Heliosphere.
Velocity enhancements up to 1000km/s at 0.3AU.
Short-living, high-resolution magnetic field show spikes of few seconds
Consequence on particle measurements, VDFs are not trivial to fit during large B rotations
Solar origin of spikes? Signatures of velocity shears in the corona? Intermittent SW acceleration?
2016 3.8M PDF
F M Neubauer The Technical University of Braunschweig (TU-BS) Magnetometer Experiment E4 (Search-Coil) Onboard Helios 1 and 2 The objective of this presentation is to provide information for use of Helios search-coil magnetometer E4 data. Written information unfortunately partly incomplete because of accidental losses of printed documentation. Thus some of the information is available in print and some from memory only. 2016 11M PDF
Anne Schreiner &
Joachim Saur
Dissipation Model for Solar Wind Turbulence at Electron Scales Under the assumption of critically balanced turbulence and KAW damping: Good agreement of model and observations at electron scales, KAW damping leads to ’quasi’ exponentially shaped dissipation range, Dissipation length is related to the electron gyroradius, Dissipation length is independent of the energy cascade rate. 2016 722K PDF
Jan Steinhagen Revisiting HELIOS: The Magnetic Field Data This document discusses the Helios Mission magnetic field data (E1 - E4) and summarizes some of the problems/anomolies with the available data. 2016 4.3M PDF
Lex Wennmacher E4 data availability Documents the availability and format of the E4 data. Includes several plots showing the available data and more importantly gaps in the E4 data. 2016 848K PDF
Lex Wennmacher E4 data High quality PDF (large size for a PDF, is a little sluggish when opened) containing several graphs/plots of the available E4 data. 2016 66M PDF
Lex Wennmacher Helios Spice kernels The need for precise and continous Helios 1 & 2 orbit data arose in 2010
No high prescision orbit information, for the Helios spacecrafts, is available
Low-precision daily position information for Helios 1 and 2, is available from (NSSDC)
I then started a small project to reconstruct the Helios 1 & 2 orbits from this information
As format of the resulting product I chose Spice SPK kernels
2016 1.2M PDF