Version:2.4.1
NumericalData
ResourceID
spase://CNES/NumericalData/CDPP-AMDA/Rosetta/LAP/ros-lap-efl
ResourceHeader
ResourceName
Rosetta - LAP - e-field component (EFL)
AlternateName
Electric field component, calculated on ground by
taking the difference between floating probe measurements on both probes and
dividing by distance
ReleaseDate
2019-09-02 09:15:31Z
Description
two LAP probes could be used to measure the component of the electric field along their
separation vector, by measuring the voltage of them, taking the difference and dividing by the
separation distance (5.0 m). Each probe could be fed by a bias current as is typically done on
electric field instruments in tenuous plasmas, or be disconnected from the bias circuitry to
ensure a good zero bias current (floating probes) as is typically done on sounding rockets.
Bias currents were used in the early part of the mission, but when the comet ionosphere
developed, the floating mode was found to give much more consistent data. Only data from
the floating mode have been used for providing E-field data, and only when both probes are
sunlit.
Positive value refers to electric field pointing in the direction from probe 1 to probe 2.
The booms are not equal in length (2.24 and 1.62 m) and mounted on a big spacecraft (solar
panel wingspan 32 m), so one cannot expect LAP to provide a useful DC electric field estimate.
A moving average of the E-field over 32 s is therefore subtracted from the data in the EFL files.
The effective bandwidth of the data therefore is about 0.03 Hz to 20 Hz, the upper
limit set by the analog anti-aliasing filters. Note that the filtering may distort the lowest
frequencies.
There are no external comparison data for assessing the absolute accuracy of the LAP E-field
measurements. The data themselves look very clean and well behaved [Karlsson et al., 2017;
André et al, 2017], with very little of common mode signal remaining, despite the s/c poten tial
being both high and highly variable. The technique with floating probes is proven on numerous
sounding rockets in the terrestrial ionosphere [Maynard, 1998].
This is a preliminary data set which will be replaced by another in a few months.
Contacts
InformationURL
InformationURL
Name
RPC LAP User Guide
URL
InformationURL
Name
RPC-LAP to Planetary Science Archive Interface Control Document
URL
InformationURL
Name
RPC-LAP Report on cross-calibration of LAP data to measurements by other RPC instruments
URL
AccessInformation
RepositoryID
Availability
Online
AccessRights
Open
AccessURL
Name
CDPP/AMDA HAPI Server
URL
Style
HAPI
ProductKey
ros-lap-efl
Description
Web Service to this product using the HAPI interface.
Format
CSV
Acknowledgement
Thank you for acknowledging the use of AMDA in publications with wording like "Data analysis was performed with the AMDA science analysis system provided by the Centre de Données de la Physique des Plasmas (CDPP) supported by CNRS, CNES, Observatoire de Paris and Université Paul Sabatier, Toulouse". See the Rules of the road at https://amda.cdpp.eu/help/policy.html . Please acknowledge the Data Providers.
AccessInformation
RepositoryID
Availability
Online
AccessRights
Open
AccessURL
Name
CDPP/AMDA Web application
URL
Description
Access to Data via CDPP/AMDA Web application.
Format
CSV
Format
VOTable
Format
CDF
Format
PNG
Acknowledgement
Thank you for acknowledging the use of AMDA in publications with wording like "Data analysis was performed with the AMDA science analysis system provided by the Centre de Données de la Physique des Plasmas (CDPP) supported by CNRS, CNES, Observatoire de Paris and Université Paul Sabatier, Toulouse". See the Rules of the road at https://amda.cdpp.eu/help/policy.html . Please acknowledge the Data Providers.
ProviderName
PSA
ProviderResourceName
RO-C-RPCLAP-5-xxx-DERIV2-V1.0
InstrumentIDs
MeasurementType
ThermalPlasma
TemporalDescription
TimeSpan
StartDate
2015-05-20 15:17:20Z
StopDate
2016-09-30 10:30:20Z
CadenceMin
PT0.05S
CadenceMax
PT35S
Caveats
Sampling config : Value | Averaged Samples | DownSampling Rate
* 0 | 1 | 1
* 1 | 2 | 1
* 2 | 2 | 2
* 3 | 4 | 4
* 4 | 64 | 4
* 5 | 32 | 32
* 6 | 64 | 32
* 7 | 64 | 64
* 8 | 128 | 128
* 9 | 256 | 256
Quality Flag :
A quality flag is a (base 10) integer that is constructed in the two steps below:
* Add together the constants associated with the relevant quality-related effects listed below. Note that these constants are chosen such that every digit represents up to three true/false values for the presence/absence of three specific separate quality-related effects.
* Should the three quality-related effects be irrelevant for the given data product, then that digit is replaced by the digit “9”.
Quality flag event description :
* +1 - Low quality sweep analysis model fit
* +2 - One of two meanings: (1) Low sample size; an average is based on fewer data points than nominal (due to filtering or otherwise) and applies to sweep steps and downsampled time series. (2) zero-padding; zeros replace lost samples for the purpose of calculating PSD.
* +10 - One of two meanings: (1) Sweep data product and data products based on sweeps: SAA rotation of more than 0.05° during sweep. (2) Downsampled time series data product: Bias change within the 32 s downsampling period.
* +20 - Probe in partial or full shadow
* +100 - Rosetta wheel off-loading (WOL) or Orbit-control-maneuver (OCM)
* +200 - One of two meanings: (1) For LAP1: LDL disturbance (LAP2 in LDL mode); (2) For LAP2: Contamination signature possibly present
* +400 - Saturation
Example: suppose that one encounters the quality flag “109”. 109 = 100 + 9 means (1) that there is an ongoing wheel off-loading (+100), and (2) that the quality-related effects associated with +1 and +2 cannot occur even in principle for the kind of data that one is looking at.
Parameter #1
Name
e-field comp
ParameterKey
ros_lap_efl
Description
Electric field component, calculated on ground by
taking the difference between floating probe measurements on both probes and
dividing by distance, (V_P2-V_P1)/L. Positive value refers to electric field
pointing in the direction from probe 1 to probe 2.
Units
mV/m
RenderingHints
FillValue
-1.e+09
Field
Qualifier
Scalar
FieldQuantity
Electric
Parameter #2
Name
sampling conf
ParameterKey
ros_lap_efl_s
Description
Number that describes the exact combination of onboard s/w averaging and downsampling. The exact values are pointers into a table
that describes both the number of samples that are averaged over and the downsampling rate
RenderingHints
Support
Parameter #3
Name
quality flag
ParameterKey
ros_lap_efl_f
Description
Quality flag constructed as the sum of multiple terms, depending on what quality related effects are present. Each digit is either in
the range 0 (best) to 7 (worst), or 9 (not used).
RenderingHints
Support
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