Double Star Active Archive - STAFF- DWP 1 K.H. Yearby, S.N. Walker, M. Balikhin University of Sheffield

Double Star Active Archive - STAFF- DWP 2 Update for 16th Cross-Cal Workshop Data for 2004 November and December has been delivered (CC15-AI-10). Caveat files reprocessed to put in chronological order, and redelivered. The Sun RAID device holding the raw data has failed. –A new Mac RAID has been populated with data from EDDS, but this now contains only the latest G version of the data, which is not always the best (eg. Sun Reference Pulse datation often missing). –It is presently not clear if the data can be recovered from the Sun RAID, or if the earlier versions can be obtained from elsewhere. As a last resort it can be reloaded from CDROMs. –Production software is in the process of being ported from Sun to Mac.

Double Star Active Archive - STAFF- DWP 3 Introduction The wave experiment onboard the TC1 satellite of the Double Star Program consists of a three-axis search coil antenna, three pre-amplifiers, and a Magnetic Wave Form unit provided by LPP (formerly CETP) and the Digital Wave Processor provided by the University of Sheffield. The three first elements are spares of the Cluster STAFF experiment. The search coil aims to measure magnetic fluctuations in the frequency range 0.1 Hz - 4 kHz to characterise waves and turbulence. The Magnetic Wave Form unit digitises the waveform continuously in the frequency range Hz, with snapshots up to 180 Hz. The Digital Wave Processor is based on the Cluster DWP experiment, but it has been modified to perform an onboard spectral analysis in the 10Hz to 4kHz range, similar to the Cluster STAFF spectrum analyser. DWP also contains a particle correlator experiment which computes the auto-correlation (ACF) of electron counts received by the PEACE HEEA sensor. The correlator detects modulations and short time particle bursts in the electron population as an indicator of wave-particle interactions.

Double Star Active Archive - STAFF- DWP 4 Numerical Data products D1_CP_STA-DWP_PSD - Magnetic field power spectral density –Based on the Cluster STAFF power spectral density data product, but measured along single axis aligned for minimum interference. –Frequency resolution: 27 channels, approximately logarithmically spaced 10Hz to 4 kHz. –Time resolution: 4 seconds. –~1.6MB per day (gzipped). D1_CP_STA-DWP_COR_* - Particle correlator data. –On board auto-correlations of the electron counts measured by PEACE. –Auto-correlation product similar to the Cluster particle correlator data. –In addition, raw particle count time series data. Prime and summary parameter data intended for the Double Star Data Centre –STAFF magnetic wave power in 3 frequency bands. Waveform and spectral matrix data –Due to the high level of interference it is not planned to archive these products, except as part of the raw data.

Double Star Active Archive - STAFF- DWP 5 Graphical Datasets D1_CG_STA-DWP_PSDP –Power spectral density plots, made directly from the power spectral density numerical dataset. 10Hz to 4kHz range, 4s time resolution, ~330kB per day (gzipped PostScript). –CEF detached header has been defined. D1_CG_STA-DWP_COMBI –Spectrum plots combining spectra produced on the ground from the 10Hz bandwidth waveform data with the 20Hz to 4kHz onboard analysis. 2Hz to 4kHz range, 1 minute time resolution. –CEF detached header has been defined. –These plots already exist at LPP and will be copied to DAA.

Double Star Active Archive - STAFF- DWP 6 Raw Data Reprocessing DOMC have started reprocessing the raw data. Presently we have reprocessed data up to –A few days missing: , , to , However, the reprocessed data is not always better than the original. –Sun Reference Pulse datation often missing in spacecraft housekeeping (SH) files. Reprocessed data often appears to come from a different ground station to the original. Information from DOMC suggests the ground station ID in the reprocessed data represents the computer used to reprocess the data, not the actual ground station. Some data is present in one version, but not the other. –In that case, a good strategy is to take the available data from either dataset. In other cases, data exists in both versions, but is different. –For STAFF-DWP there is no definitive way to determine which, if either, is correct. –Strategy used is dataset dependent.

Double Star Active Archive - STAFF- DWP 7 Science data - Power Spectral Density 1 The data processing pipeline for the PSD data sets has been modified to read both the original and reprocessed raw data, and use the best from both. Firstly, both datasets are subject to basic checks on format and validity. Data that are clearly wrong will be removed. Checks are NOT definitive, and incorrect data may proceed to the next stage. Interference reduction (for boom deployment failure) is also performed. The two datasets are then compared, on a packet by packet basis: –If data is present in one dataset, and not the other, the available data is used. –If data is present in both datasets, and is the same, then it is used. –If data is present in both datasets, and is different, then the dataset with the lowest power integrated over the 10Hz to 4kHz bandwidth is used. The reasoning is that that errors are more likely to increase the spectral power. The combined dataset is then averaged over 4 seconds (approximately one spin). File caveats show which RDM versions have been used to produce each CEF file (eg. A and G). There is also a record varying version flag, which may indicate A to G if a single raw data version is used in that record, or M if both versions were used. A further update to this process was required to work around missing Sun Reference Pulse information in most of the reprocessed spacecraft housekeeping.

Double Star Active Archive - STAFF- DWP 8 STAFF/DWP PSD data processing pipeline

Double Star Active Archive - STAFF- DWP 9 Science data - Power Spectral Density 2 A record varying quality flag has been added to the numerical and graphical PSD datasets (D1_CP_STA-DWP_PSD, and D1_CG_STA-DWP_PSDP). Given the interference due to boom deployment failure, the best indicated quality is ‘Survey Quality’ (2). The quality is reduced to ‘Known problem’ (1), during eclipses, when the STAFF sensor is saturated near perigee, and when there is a high rate of bit errors in the raw data. The quality is set to ‘Not applicable’ (0) during calibration mode. The combined plots D1_CG_STA-DWP_COMBI already exist at LPP and will not be reprocessed.

Double Star Active Archive - STAFF- DWP 10 Science data - Particle Correlator The data processing pipeline for correlator data is ready for use. However, it is planned to update it to include pitch angle information as done for Cluster. This includes DSDS prime and summary parameters, fixed and stepped energy ACFs, particle count time series, and validation plots. This process does not use the spacecraft housekeeping files, so is unaffected by the lack of Sun Reference Pulses in the reprocessed data. It is presently not planned to adapt this software to merge reprocessed and original data on a packet by packet basis (as done for PSD datasets). –Limited manpower. –Difficulty in deciding which version is better. –Limited scientific value of this data. It is possible to select a specific version of the raw data on a file by file basis. By default the highest available version is used, which will be the reprocessed ‘G’ version if available.

Double Star Active Archive - STAFF- DWP 11 Technical Status It is proposed that STAFF-DWP DAA data production will be performed by the University of Sheffield, except for the combined plots which already exist at LPP. The ICD and User guide are delivered. Production software and procedures in place for numerical and graphical datasets. Minor changes have been made for new data product naming convention (DP to CP, DWP_STA to STA-DWP, etc.). Header files and PSD datasets delivered for to Assuming the production and validation will be performed by existing staff, in parallel with other work, we estimate that the Double Star data can be processed at a rate of one month per week. The 45 months of data could be completed within one year, for example by end 2012 if we had started in January 2012.

Double Star Active Archive - STAFF- DWP 12 Funding status There has never been any formal UK national agency (PPARC/STFC/UKSA) funding for Double Star. Preliminary work on Double Star archiving has been done by Keith Yearby. We estimate that 6 months FTE is required to complete the Double Star archiving, and request that this be included in any extension to the ESA funding for Cluster DWP archiving. The UK research council (STFC) has withdrawn from Cluster - funding for University of Sheffield terminated at the end of November Completion of Double Star archiving will depend on ESA funding.