Level 2A EGS

SEE Level 2A EGS Solar Irradiance Data

Download multiple days from the TIMED MDC

EGS Calendar Access: Useful for finding data for a specific day.

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023

EGS Level 2A Data Directory– download any data file

EGS Level 2A LISIRD – interactive data access and plotting

Detailed Level 2A EGS Description

README_EGS_L2A_012.TXT – information for using EGS_L2A data

The EUV Grating Spectrograph (EGS) aboard SEE performs measurements of the Sun for about 3 minutes every orbit (97 minutes) which usually gives 14-15 measurements per day. The Level 2A data is time averaged over each measurement, after being 1-AU corrected and removing flares. The 1-AU correction is provided.

Reading the Data with IDL

With read_netcdf.pro individual data files may be read using an IDL command such as:


The data will then reside in the returned structure “d”, with each tag in the structure defined in the attributes array “att”.

SEE Level 2A EGS Software

  • TIMED-SEE NetCDF README – Described IDL source code and gives examples using read_netcdf.pro and write_netcdf.pro
  • read_netcdf.pro – IDL procedure for reading NetCDF files as a structure
  • write_netcdf.pro – IDL procedure for writing a data structure (or array of structures) to a NetCDF file
  • plotegs_sp.pro – IDL procedure for plotting the spectrum from one EGS Level 2A data file.
  • plotegs_ts.pro – IDL procedure for plotting a time series of EGS Level 2A data.

SEE Level 2A EGS Solar Irradiance Data Format

Each data file contains a structure with 8 elements

L2A_EGS_DATA    STRUCT    = ->  Array[8]

The L2A_EGS_DATA structure has the following form:

** Structure <2e41c8>, 15 tags, length=50728, data length=50722, refs=1:
   DATE            LONG           2002039
   WAVE            FLOAT     Array[1690]
   FLUX_MEDIAN     FLOAT     Array[1690]
   DIFF_MA         FLOAT     Array[1690]
   ERR_TOT         FLOAT     Array[1690]
   ERR_MEAS        FLOAT     Array[1690]
   STDEV_MEAS      FLOAT     Array[1690]
   NUMPT           INT       Array[1690]
   COR_OS_MED      FLOAT     Array[1690]
   COR_1AU         FLOAT           1.02768
   SLIT            BYTE         1
   START_TIME      FLOAT           3292.00
   STOP_TIME       FLOAT           3452.00
   ODC_ID          BYTE        20
   FLARE           FLOAT           1.00223

NetCDF file attributes for day 2002039


    Title = SEE Level 2A EGS Observation Averaged Data Product - calibrated 0.1nm
      EGS data averaged over ~ 3 minutes

    Source = SEE POC at LASP / CU

    Mission = TIMED

    Data_product_type = SEE EGS Level 2A

    Data_product_version = 011

    Data_product_revision = 02

    Product_format_version = 010

    Software_version = 11.01

    Software_name = write_netCDF.pro called from egs_level2_main.pro

    Calibration_version = 09.01

    Description = Calibrated SEE EGS science data averaged over each solar
      observation $ at 0.1 nm bins with degradation, atmospheric, and 1AU corrections

    History = 7/03/03 Don Woodraska Original creation

    Filename =

    Date_generated = Tue Sep 11 19:41:02 2012


    Units = YYYY-DOY

    Description = Date of observations


    Units = nm

    Description = Array of wavelength intervals, half-Angstrom centers


    Units = W / m^2 / nm

    Description = Array of median solar irradiances for each wavelength interval.
      This is the spectrum


    Units = W / m^2 / nm

    Description = Array of differences between the median and weighted averaged
      solar irradiances for each wavelength interval


    Units = Fractional

    Description = Accuracy of solar irradiance


    Units = Fractional

    Description = Measurement precision


    Units = Fractional

    Description = Standard deviation of the median


    Units = NONE

    Description = Array of the Number of points (1-Angstrom-gridded measurements)
      used in determining the observation average for each wavelength interval


    Units = 1 / (AU^2)

    Description = AU correction factor for date


    Units = none

    Description = 0 is calibration slit, 1 is normal slit


    Units = UT seconds of day

    Description = Array of observation start times


    Units = UT seconds of day

    Description = Array of observation stop times


    Units = none

    Description = Array of observation identifiers (1-254), A value of 0 means
      the observation did not produce data used in routine products.
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