The S-520 is a powerful single-stage rocket which is optionally equipped with three-axis attitude control and a recovery system. It has a capability for launching a 100 kg payload far above 300 km and provides more than five minutes of micro-gravity flight environment.

Sounding rockets S-520-27 and S-310-42 were launched from Uchinoura Space Center, Japan (31.3°N, 131.1°E) on 20 July 2013 at 14:00 and 14:57 to measure plasma and neutral atmosphere simultaneously.
The nose fairing was opened at 53 seconds after liftoff to start observations and the highest alititude reached 316 km at 286 seconds after liftoff.

Number Density Measurement of Electrons by Impedance Probe (NEI)

The NEI (Number Density Measurement of Electrons by Impedance Probe) is an instrument designed to determine the electron number density. It measures the impedance of a 1.2-meter probe extended into the ionospheric plasma across a frequency range from 0.1 to 25 MHz. The following datasets are publicly available for scientific use:

1. Spectrogram of Probe Capacitance:

   • File: s_520_27_nei_c_v01.cdf
   • Details: This data captures the capacitance of a probe within the ionospheric plasma across 394 frequency steps from 0.1 to 25 MHz, recorded at intervals of 129.7 milliseconds.
   • Format: CDF

2. Electron Number Density:

   • Files:
     • Ascent phase: s_520_27_nei_ne_a_v01.txt
     • Descent phase: s_520_27_nei_ne_d_v01.txt
   • Details: Electron number density derived from probe capacitance measurements taken during the ascent (X < 285 seconds; X is the time from the launch) and descent (X > 285 seconds) of the sounding rocket.
   • Format: Text with columns below.

     TIME(sec): Time from the launch [sec]
     LAT(deg): Geodesic latitude of the rocket [deg]
     LON(deg): Geodesic longitude of the rocket [deg]
     HEIGHT(km): Height of the rocket [km]
     FC(MHz): Electron cyclotron frequency [MHz]
     FUH(MHz): Upper hybrid frequency [MHz]
     FP(MHz): Plasma frequency [MHz]
     NE(/cc): Electron number density [/cc] 
     

Electric Field Detector (EFD)

The EFD is an instrument to determine the electric field using the double probe method. The natural electric field was derived by subtracting the induced electric field generated by the rocket crossing the earth’s magnetic field from the observed electric field. The following dataset is publicly available for scientific use:

1. Electron Number Density:
   • File: s_520_27_efd_nef.csv
   • Details: This data is expressed in Magnetic field Orthogonal Coordinate System (MOCS) using IGRF model. In the MOCS, the Z-axis is the inverse component of the magnetic field, the X-axis is the east component orthogonal to the magnetic field, and the Y-axis is a right-handed system, i.e., the Y-axis is north and upward.
   • Format: CSV with columns below.

     Xtime [sec]: Time after launch [sec]   
     NEF_MOCS_X [mV/m]: Detrended natural electric field (MOCS) X axis [mV/m]  
     NEF_MOCS_Y [mV/m]: Detrended natural electric field (MOCS) Y axis [mV/m]  
     Lat [deg]: Latitude [deg]    
     Lon [deg]: Longitude [deg]  
     Alt [km]: Altitude [km]    
     IGRF east [nT]: Magnetic field (IGRF model) east [nT]  
     IGRF north [nT]: Magnetic field (IGRF model) north [nT]  
     IGRF up [nT]: Magnetic field (IGRF model) up [nT]  
     

     Latitude, longitude, altitude are linear interpolation of the data in S-520-27_LatLonAlt.xlsx.

Ancillary Data

1. Location Data:
   • File: S-520-27_LatLonAlt.xlsx
   • Details: Latitude, Longitude, and Altitude data of the rocket.
   • Format: Excel