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Spec_Atmosphere.md

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Specification for Atmosphere model

1. Overview

1. Functions

  • The Atmosphere class calculates an air density at the satellite's position.
  1. Related files
  • src/environment/local/atmosphere.cpp, .hpp
    • Atmosphere class is defined.
  • src/environment/local/local_environment.cpp, .hpp
    • Atmosphere class is used here as a member variable of LocalEnvironment class.
  • src/library/external/nrlmsise00/wrapper_nrlmsise00.cpp, .hpp
    • An air density is calculated using an external library, NRLMSISE00 atmosphere model.

3. How to use

  • Select a model and set a standard deviation as air_density_standard_deviation for random noise in the local_environment.ini file
    • Model
      • STANDARD
        • The air density is calculated using scale height.
      • HARRIS_PRIESTER
        • The air density is calculated using the Harris-Priester model.
      • NRLMSISE00
        • The air density is calculated using the NRLMSISE00 model.
        • If users use this model, the following additional parameters must be set in the .ini file.
          • nrlmsise00_table_file: The space weather table path
          • is_manual_parameter_used: The manual setting parameter defined as follows are used or not
            • manual_daily_f107: User defined f10.7 (1 day)
            • manual_average_f107: User defined f10.7 (30 days average)
            • manual_ap: User defined ap
  • The public functions
    • CalcAirDensity_kg_m3: Update the air density (kg/m3) based on the selected model
    • GetAirDensity_kg_m3: Return the calculated air density (kg/m3)

2. Installation of NRLMSISE00

3. Explanation of Algorithm

STANDARD

1. Air density calculation

  • Inputs

    • Altitude

  • Outputs

    • Air density

  • Algorithm
    The STANDARD model assumes the air density as follows.

$$\rho \left(h \right) = \rho_0 \exp \left(-\frac{h - h_0}{H} \right)$$

where $h_0$ is a reference height, $\rho_0$ is an air density at the reference height, and $H$ is a scale height. These parameters are referred from the table shown in References [2].

NRLMSISE00

Read Space weather table

  • F10.7 and Kp/Ap index, which indicates the solar activity cycle, are necessary as inputs for NRLMSISE00.
    These parameters, which are only during the simulation period, are read from SpaceWeather.txt.
  • Note
    • If SpaceWeather.txt cannot be read, the atmosphere model is automatically set to STANDARD.
    • SpaceWeather.txt includes data between 2015 and 2044. If the simulation date is out of range, the air density cannot be calculated accurately.

Air density calculation

  • Inputs
    • Decimal year
    • Latitude
    • Longitude
    • Altitude
  • Outputs
    • Air density
  • Algorithm
    • Please refer the following reference.
      • Picone, J. M.; Hedin, A. E.; Drob, D. P.; Aikin, A. C. (2002-12-01). “NRLMSISE-00 empirical model of the atmosphere: Statistical comparisons and scientific issues”. Journal of Geophysical Research: Space Physics 107 (A12)

4. Verification

NRLMSISE00

  1. Overview

  2. Conditions for the verification

    1. input file
    • Default initialize files
    1. initial values
    • Case1 : Default initialize files
    simulation_start_time_utc = 2020/01/01 11:00:00.0
simulation_duration_s = 200
simulation_step_s = 0.1
orbit_update_period_s = 0.1
log_output_period_s = 0.1
simulation_speed_setting = 0
    • Case2 : Start year only was changed to 2015.
    simulation_start_time_utc = 2015/01/01 11:00:00.0
simulation_duration_s = 200
simulation_step_s = 0.1
orbit_update_period_s = 0.1
log_output_period_s = 0.1
simulation_speed_setting = 0
    • Especially, we chose following TLE for orbit calculation
    tle1=1 38666U 12003B   12237.00000000 +.00000100  00000-0  67980-4 0 00008
tle2=2 38666 098.6030 315.4100 0000010 300.0000 180.0000 14.09465034  0011

  3. Results

    • The calculated air density at t = 0.5 [s] was compared with the result of web-based model.

    • S2E

      • Case1 : 2.27E-15 kg / m3
      • Case2 : 1.01E-14 kg / m3

    • Web-based NRLMSISE00

      • Case1 : 2.454E-15 kg / m3
      • Case2 : 1.000E-14 kg / m3

5. References

  1. Picone, J. M.; Hedin, A. E.; Drob, D. P.; Aikin, A. C. (2002-12-01). “NRLMSISE-00 empirical model of the atmosphere: Statistical comparisons and scientific issues”. Journal of Geophysical Research: Space Physics 107 (A12)
  2. 半揚稔雄，ミッション解析と軌道設計の基礎，現代数学社, p.324 (in japanese)
  3. NRLMSISE-00 Atmosphere Model , https://ccmc.gsfc.nasa.gov/modelweb/models/nrlmsise00.php