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.

The S-520-26 sounding rocketrocket was launched from Uchinoura Space Center, Japan (31.3°N, 131.1°E) at 20:51 UT on 11 January 2012 to clarify the combining process of the neutral atmosphere and plasma in the thermosphere. The experiment was performed as a part of the WIND-2 (Wind measurement for Ionized and Neutral atmospheric Dynamics study-2) project, which followed the WIND campaign (Uemoto et al., 2010) carried out in 2007.
One of the onboard devices (the ion mass energy analyzer) did not perform observations successfully, but other devices, including an impedance probe, Langumuir probe, beacon transmitter, electromagnetic measurement device, and solar sensor, worked properly throughout the ascending and descending of the rocket.

Number Density Measurement of Electrons by Impedance Probe (NEI)

The NEI (Number density measurement of Electron by Impedance probe) is an instrument to determine the electron number density. It measures the impedance of a 1.2-meter probe extended in the ionospheric plasma. The frequency range was changed at X = 398 s (X is the time from the launch) to prepare for an increase in electron density due to lithium releases scheduled to begin at X = 401 s, 441 s, and 459 s, however, the ejection system worked successfully only the third in this experiment. The frequency range before X = 398 s was from 0.1 to 13 MHz, and from 0.1 to 25 MHz after that.
The following datasets are publicly available for scientific use:

1. Spectrogram of Probe Capacitance:

   • Files:
     • X < 398 s: s_520_26_nei_c_0_v01.cdf
     • X > 398 s: s_520_26_nei_c_1_v01.cdf
   • Details: This data captures the capacitance of a probe within the ionospheric plasma across 400 frequency steps from 0.1 to 13 MHz (X < 398 s) and from 0.1 to 25 MHz (X > 398 s), recorded at intervals of 259.4 milliseconds.
   • Format: CDF

2. Electron Number Density:

   • Files:
     • Ascent phase: s_520_26_nei_ne_a_v01.txt
     • Descent phase: s_520_26_nei_ne_d_v01.txt
   • Details: Electron number density derived from probe capacitance measurements taken during the ascent (X < 279 seconds) and descent (X > 279 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] 
     

Plasma Wave Monitor (PWM)

The PWM (Plasma Wave Monitor) is a receiver for observation of plasma waves in a frequency range from 300 Hz to 22 MHz. The following dataset is publicly available for scientific use:

1. The Spectrogram of Plasma Waves:
   • File: s_520_26_pwm_v01.cdf
   • Details: This data captures the electric field intensities of plasma waves across 800 frequency steps from 300Hz to 22 MHz, recorded at intervals of 129.7 milliseconds.
   • Format: CDF

Ancillary Data

1. Location Data:
   • File: S-520-26_Lat_Lon_H.txt
   • Details: Latitude, Longitude, and Altitude data of the rocket.
   • Format: Text