Study On The Validation And Calibration Of The LAP Measurements On Board The ZH-1 Satellite

The China Seismo-Electromagnetic Satellite(CSES),also called ZhangHeng-1 or ZH-1 for short,can obtain global observation data of the electromagnetic field,ionospheric plasma and high-energy particles.Langmuir Probe(hereinafter referred to shortly as LAP),one of the ionospheric observation payloads,can provide in-situ electron density and electron temperature observations,making it the main data source for ZH-1 satellite ionospheric measurements.A preliminary validation of the in-site electron densities measurements obtained by the LAP payload on board the ZH-1 satellite using the plasma density observations(LP for short)from the Swarm B satellite orbiting at a similar altitude as the ZH-1 satellite indicates that the LAP data and the Swarm data have consistent relative variations based on the comparisons of global scale distribution patterns,of intersecting ground track probe data between the two missions with similar location and time,and of the nighttime enhancement space climatology phenomenon calculated using relative variations between the daytime and nighttime measurements.However,the absolute data values from LAP measurements are much smaller than that from the Swarm satellite.Further validation of the LAP measurements using the COSMIC RO measurements also shows this similar problems.Although the consistent relative variations between LAP measurements and other data sets will not affect the applications on the relative variations,the differences in the observed values will affect the application of data modeling and other applications.Therefore,in order to solve the problem of the underestimation of the LAP measurements,this paper intends to obtain the calibration relation for the LAP measurements through the selecting the reference data sources and evaluating the consistency of the calibrated LAP data with other datasets.Meanwhile,the pros and cons of the calibration relationship will also be evaluated.In order to achieve the research goals,the following specific research works have been carried out:(1)Choosing reference datasets.According to the orbit altitude and flight characteristics of ZH-1 satellite,incoherent Scatter Radar(hereinafter referred to as ISR)data,the RO(Radio Occultation)data from the COSMIC missions and the LP measurements from Swarm B satellite orbiting at a similar altitude as ZH-1 satellite are selected to validate LAP data.(2)Calibrating the LAP measurements.Data examing of the ISR(Incoherent Scatter Radar)measurements indicates that the measurements are fluctuated dramatically at around 500 km,where the ZH-1 satellite is orbiting;and only very short period of co-located data can be found between the LAP and the LP measurements,both of which indicate these measurements are not suitable for calibration work of the LAP measurements.The global observations of the COSMIC satellite can support a considerable amount of co-located data,which covers a large spatial coverage and a long temporal range,making it a suitable dataset for calibration of the LAP measurement.However,radio occultation data in the region of Equatorial Ionization Anomaly(EIA)has a large error,therefore RO(Radio Occultation)data observed at mid-latitudes from the COSMIC and COSMIC 2 missions are used to conduct the calibration work.(3)Validating the calibrated LAP data.In order to evaluate the calibrated LAP data,three datasets are adopted to carry out the validation work.First,the co-located data between the Swarm B satellite and the ZH-1 satellite is used to validate the calibrated dataset.Secondly,the co-located data between the LAP measurements and ISR observation is used for the validation of the calibrated data.Finally,new measurements from the COSMIC 2 measurements are used to validate the calibrated results.All the validation results show that the deviation between the LAP measurements and then other datasets can be eliminated in general,but there are still some differences between LAP data and the other datasets.As the variations of the global LAP measurements are very complicated,in-depth works are necessary to carry out when more data are accumulated.