Swarm EFI Cal/Val and Quality Working group summary I. Coco, R. Haagmans, S. Buchert, J. Burchill, D. Knudsen, C. Stolle Swarm Cal/Val Meeting Copenhagen 18/06/2014

Summary Langmuir probe data (Ne, Te, Vs) general quality and open issues: investigation strategy, way forward and requests to ESA. Langmuir probe data validation: first results from IRS and IRI model comparisons. TII data (Vion, Ti) general quality and open issues: investigation strategy, way forward and requests to ESA. On plasma data distribution to general users: timeline and caveats. EFI summary | I. Coco | Copenhagen | 18/06/2014 | Swarm Cal/Val Meeting | Pag. 2

Langmuir probe data quality and issues (1/5) Density and temperature data show well known statistical features of a “good” ionosphere (equatorial “double peak” density distribution, latitude and local time dependencies, reasonable orders of magnitudes, etc...) EFI summary | I. Coco | Copenhagen | 18/06/2014 | Swarm Cal/Val Meeting | Pag. 3

Langmuir probe data quality and issues (2/5) Still the effect of SC charging due to the sweep mode activation causes some concern: SC potential small dips (up to 20 mV) and little jumps in the el. temp. (0.01 eV) are regularly reported during the sweeps. All the settings modifications that could be done without major changes in the onboard sw have been done and the effect has been strongly mitigated since the “first light” data. Impacts on TII velocity calculation: 1 mV variation  1 m/s variation. A 20 m/s excursion is within the error budget for the velocity calculation and does not affect TII processing that much. EFI summary | I. Coco | Copenhagen | 18/06/2014 | Swarm Cal/Val Meeting | Pag. 4

Langmuir probe data quality and issues (3/5) The sweep mode itself does not give the expected quality data: sweeps are about the 1% of the total and can be safely discarded in science analyses. IRFU is investigating the sweep mode outcomes for improvements: discarding it completely is not recommended! Sweep mode remains useful for diagnostic purposes. EFI summary | I. Coco | Copenhagen | 18/06/2014 | Swarm Cal/Val Meeting | Pag. 5

Langmuir probe data quality and issues (4/5) Other issues: 1) Datation analysis by GFZ has been taken into account and LP timing has been modified: a residual time shift of 24-25 ms still persists between VFM and LP timestamps but it is considered acceptable due to the uncertainties in the datation analysis and the VFM comparable timestamp resolution (20 ms). 2) Analysis of the time series sub-mode data taken during recent yaw maneuvers (for investigating LP cross-talk effects) not done yet (minor). 3) Observations of SC potential increases after sunset, which seems weird: ...to be better investigated with more statistics. EFI summary | I. Coco | Copenhagen | 18/06/2014 | Swarm Cal/Val Meeting | Pag. 6

Langmuir probe data quality and issues (5/5) LP Summary: 1) Sweep mode should be kept for now as it is: SC charging has been highly reduced and SM is suitable for diagnostics. It is not worth to play further with settings, because one would like to have a still meaningful sweep range for investigations. Ion velocity calculation is not dramatically affected. Work on algorithms improvements for SM is ongoing. 2) To IRFU to look up into the literature for known charging effects in other past missions: see whether historical lessons learnt can prove useful for Swarm too. 3) Investigations are also needed ESA side: go to industry (through PLSO) and find SC electrical cleanliness tests/modeling results done during the development phase. We have to characterize which part of the SC nearby the probes is more likely to be charged. 4) Investigations are needed for characterizing the sunset increase of the SC potential: systematic time series analysis will be done on the 3 SC, comparing with density and temperature. We need a more clear assessment before the end of the summer. 5) To IRFU to produce a technical note on the possible LP cross-talk effects and the strategy for investigating them (low priority activity). EFI summary | I. Coco | Copenhagen | 18/06/2014 | Swarm Cal/Val Meeting | Pag. 7

Langmuir probe validation: comparison with IRI (C. Stolle) LP captures well geophysical variations Ne: Absolute values too low at northern mid-latitudes (IRI radar + ionosonde availability) Absolute values too high in regions of high Ne (e.g. low latitudes) LP Te about 700K above IRI (at northern mid-latitudes) LP shows lower variability in Te than does IRI – clouds of constant LP Te? Concentrate point-to-point LP-IRI comparison on mid-latitudes only Validation of LP with low-latitude radars (Jicamarca?) and radars at different latitudes All points: LP=1.5669*IRI-1.8246*10+5 IRI above 2*10+5: LP=1.8712*IRI -3.470*10+5 Point-by-point comparison 10-14 LT Ne_LP (cm-3) Ne_IRI (cm-3) Suggestion: investigate different behaviors of P1 (high gain) and P2 (low gain) on a statistical basis in a suitable density range. EFI summary | I. Coco | Copenhagen | 18/06/2014 | Swarm Cal/Val Meeting | Pag. 8

Langmuir probe validation: comparison with ISR (S. Buchert) EISCAT VHF and ESR 2014-04-04 Ne seems too low, factor 1.3–2? Te seems too high, of about 300 K We are nonetheless far from assessing a reliable “scale factor” to be applied to un-calibrated data. EFI summary | I. Coco | Copenhagen | 18/06/2014 | Swarm Cal/Val Meeting | Pag. 9

TII data quality and issues (1/6) Extended good quality periods can be selected where most ionospheric features clearly show up (example on the left: southern cusp characterization and evolution for a particular event). EFI summary | I. Coco | Copenhagen | 18/06/2014 | Swarm Cal/Val Meeting | Pag. 10

TII data quality and issues (2/6) Since March meeting: New gain map technique refined and implemented on all three satellites. No more need of slew maneuvers: defocusing by means of a VG sweep only in nominal attitude conditions and AGC off proved to be safer and as reliable as with maneuvers. Request from ESA: update of the calibration and characterization plan including a description of the new calibration procedures. EFI summary | I. Coco | Copenhagen | 18/06/2014 | Swarm Cal/Val Meeting | Pag. 11

TII data quality and issues (3/6) Most images improved after correction... But some do not... This is physical: low density regions (solstice winter high-lat, dawn-dusk orbits) host a much less dynamic plasma. Such events result in high 2nd moments (and eventually ion temperature) and are quality-flagged in the final 1B data. EFI summary | I. Coco | Copenhagen | 18/06/2014 | Swarm Cal/Val Meeting | Pag. 12

TII data quality and issues (4/6) TII Image anomaly Anomalous Good EFI summary | I. Coco | Copenhagen | 18/06/2014 | Swarm Cal/Val Meeting | Pag. 13

TII data quality and issues (5/6) TII Image anomaly It affects about 10% of images of SW A and B, and, in the last period, a large part of SW C images. The 2nd moment grows high and this leads to a worsening of the TII quality flag (flag becomes > 10). Actual reason unknown but most likely instrumental (phosphor residual charging?). There are indication that the issue disappears for several orbits after a HV switch-off of at least 24 hours. A “workaround” is possible: mask the halo region out imposing a gain =0 outside the detector region most sensitive to the O+ signal. The new gain maps already include such settings. In the meanwhile UoC could figure out a dedicated test campaign on SW C. EFI summary | I. Coco | Copenhagen | 18/06/2014 | Swarm Cal/Val Meeting | Pag. 14

TII data quality and issues (6/6) TII Summary: Image anomaly: On SC C new gain maps already uploaded, image anomaly already mitigated. Impacts: a) data with anomalous images are flagged as no good. b) routinely calculation of detectors parameters (detector centers, direction cosines, etc...) not possible. This, for now, will be done “by hand” by J. B. 2) Image anomaly investigation: to UoC to provide a test plan to be submitted to ESA for dedicated calibration campaigns on SW C. 3) Request to ESA: products derived from the 16Hz first moments existing in L0 data are desired as a L1b product or added to an existing L1b product for scientific analysis. 4) UoC will analyze results of the MTQ datation maneuvers on A and B for characterizing MTQ effects on the velocity calculation (low priority activity) 5) First validation comparisons with ISR: comparisons with several Poker flat radar passes show a TII velocity way too high wrt to radars, but the comparison technique is under refinement. EFI summary | I. Coco | Copenhagen | 18/06/2014 | Swarm Cal/Val Meeting | Pag. 15

On Plasma data distribution to users. New version (6796) of the EFI prototype just released to DTU (11/06/2014). Industry has started to work on the implementation of the changes in the operational processor. CCDB will be updated with new settings, cross-verifications OP-Prototype will be done and, crossing fingers and touching wood, we will start the reprocessing and plasma data distribution in mid-september. Users will be made aware of: NOT use sweep mode data (clearly flagged) NOT use TII data characterized by Flags_TII > 10. NOT use density, el. temp and Sc potential errors EFI summary | I. Coco | Copenhagen | 18/06/2014 | Swarm Cal/Val Meeting | Pag. 16