The S-310 is a middle-size rocket for carrying various payloads. It is a single-stage sounding rocket, 310 mm in diameter, and can reach an altitude of 150 km.
It is spun positively in the atmosphere to overcome resonance, and thus avoids continued resonance problems. It also corrects attitude disturbance by aerodynamic damping.

The S-310-40 sounding rocketrocket was launched from Uchinoura Space Center, Japan (31.3°N, 131.1°E) at 14:48 UT on 19 December 2011 to investigate high-density plasma layer in the nighttime lower ionosphere, which can cause extra ordinal propagation of Medium Frequency radio wave.

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 21 MHz. The following datasets are publicly available for scientific use:

1. Spectrogram of Probe Capacitance:

   • File: s_310_40_nei_c_v01.cdf
   • Details: This data captures the capacitance of a probe within the ionospheric plasma across 390 frequency steps from 0.1 to 21 MHz, recorded at intervals of 258.4 milliseconds.
   • Format: CDF

2. Electron Number Density:

   • Files:
     • Ascent phase: s_310_40_nei_ne_a_v01.txt
     • Descent phase: s_310_40_nei_ne_d_v01.txt
   • Details: Electron number density derived from probe capacitance measurements taken during the ascent (X < 209 seconds; X is the time from the launch) and descent (X > 209 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] 
     

Ancillary Data

1. Location Data:
   • File: traj-S310-40.txt
   • Details: Latitude, Longitude, Altitude, etc… data of the rocket.
   • Format: Text