CASSIOPE SPACECRAFT (Swarm-E)
PROCESSED DATA HANDBOOK
IRM Averaged Sensor Surface Current L1B HDF5 File
The sensor surface current (SSC) measurements on IRM are designed to monitor the rapid (sub-second scale) variations of the F-region and topside ionosphere at high cadence (1kHz), independent of the time-of-flight data.
The IRM Averaged SSC L1B HDF5 file is generated for each IRM SSC file.
The data from the SSC file is averaged at 500ms, 250ms, 125ms with timestamps centered in the averaging ranges.
The filename format is IRM_YYYYMMDD_HHMMSS_HHMMSS_SSC_AVG_XYZ.v.v.r.l1b.h5.zip
| IRM | Instrument identifier |
| YYYYMMDD | UTC day of data |
| HHMMSS | UTC start time of data |
| HHMMSS | UTC end time of data |
| SSC_AVG | Product identifier |
| Flag X | log2(Number of measurements in file) as a hexadecimal digit maximum 0xF. Based on the 250ms data. |
| Flag Y | log2(Number of measurements with temperature flag set) as a hexadecimal digit maximum 0xF. Based on the 250ms data. |
| Flag Z | log2(Number of measurements with auto-ranging flag set) as a hexadecimal digit maximum 0xF. Based on the 250ms data. |
| v.v.r | Major.Minor version of the software to generate the file. Revision number of the file. |
| l1b | L1B data product. |
| h5.zip | File extension (hdf5 zip) |
The IRM SSC HDF5 file consists of an IRM Data Group containing data for each average range, and a Satellite Data Group relating to CASSIOPE location and attitude data.
IRM Attributes (repeated for IRM Data/125ms, IRM Data/250ms, IRM Data 500ms):
| utc_string | Timestamp centered in the average timespan |
| sensor_surface_current | Averaged current on the surface of the IRM instrument (mA). Positive indicates a net positive current flux on the surface (e.g. ions impinging or electrons leaving). |
| temperature | IRM sensor temperature (deg C). |
| detect_count | Number of ions detected on at least one preamplifier on the IRM anode |
| hit_count | Number of ions detected on both preamplifiers on the IRM anode at the same time |
| vd_negative | Voltage on the negative plate of the outer ion deflection system (V) |
| vd_positive | Voltage on the positive plate of the outer ion deflection system (V) |
| manipulated_sensor_surface_current_data_flag | Truth array indicating if sensor surface measurements and temperature measurements were transposed and fixed. (It is recommended to use the data if this flag is set. This is a well-understood fix) |
| range_quality_flag | Truth array indicating if sensor surface measurements are greater than absolute 9.5mA. In this case there is a risk that the instrument is autoranging the measurement. (This data should be used with caution) |
| temperature_quality_flag | Truth array indicating if temperature is < -20C. In this case there is a risk that the instrument survival heater is on. (This data should be used with caution) |
Satellite Atrributes:
| Attribute | Definition |
| geodedic_altitude | Geodetic spacecraft altitude (m) |
| geodedic_latitude | Geodetic spacecraft latitude (deg) |
| geodedic_longitude | Geodetic spacecraft longitude (deg) |
| geographic_x | Geographic cartesian x-component of the satellite position, in the International Terrestrial Reference Frame (m) |
| geographic_y | Geographic cartesian y-component of the satellite position, in the International Terrestrial Reference Frame (m) |
| geographic_z | Geographic cartesian z-component of the satellite position, in the International Terrestrial Reference Frame (m) |
| j2k_vx | X-component of the satellite velocity, in geographic equatorial inertial coordinates (J2000 epoch, m/s) |
| j2k_vy | Y-component of the satellite velocity, in geographic equatorial inertial coordinates (J2000 epoch, m/s) |
| j2k_vz | Z-component of the satellite velocity, in geographic equatorial inertial coordinates (J2000 epoch, m/s) |
| j2k_x | X-component of the satellite position, in geographic equatorial inertial coordinates (J2000 epoch, m) |
| j2k_y | Y-component of the satellite position, in geographic equatorial inertial coordinates (J2000 epoch, m) |
| j2k_z | Z-component of the satellite position, in geographic equatorial inertial coordinates (J2000 epoch, m) |
| local_time | Local time of measurement (h) |
| magnetic_latitude | Magnetic latitude of satellite (IGRF) (deg) |
| magnetic_local_time | MLT (h) = (Magnetic_Longitude – Subsolar_Magnetic_Longitude + 180)/15, with longitudes expressed in degrees |
| magnetic_longitude | Magnetic longitude of satellite (IGRF) (deg) |
| yaw | Satellite attitude yaw angle (deg) |
| pitch | Satellite attitude pitch angle (deg) |
| roll | Satellite attitude roll angle (deg) |
| satellite_eclipse | Eclipse condition of satellite (“Umbra”, “Penumbra”, or” Sunlit”) |
| sun_azimuth | Solar azimuth angle (deg) |
| sun_beta | Solar beta angle (deg) |
| sun_zenith | Solar zenith angle (deg) |
| utc_string | Date and time for each satellite ephemeris data point. String format ‘%Y-%m-%dT%H:%M:%S.%fZ’ (UT) |
| irm_shadow_eclipse | Eclipse condition of IRM instrument (“Sunlit” when sunlit, “Eclipse” when in eclipse, “Shadow” when in the shadow of CASSIOPE) |