profile data stored in the .scn file

basic structure

Spectroscopic data is stored in a file with the extension ".scn". A file corresponds to a single profile. The file is dirctly managed by UNIX-OS or Linux-OS. Therefore you can easily mv, cp, rm, ls. The file contains actural values of spectrum and additional data as "header".

headers

A .scn file and flow has the following information in its header. The following number, name, etc. shows the type or possible selection.
They correspond a member of structure in the C-language but not the same name. See depevolper's page in detail.

  1. Section "System Header"
    file_length number
    Total file length of the .scn file in bytes. If the .scn file is the latest version, this value should be the same as the result of "ls -l".
    header_length number
    Total header length in bytes.
    format_id spectrum | cube
    The basic structure of file. The file of ".sdb" is "spectrum".
    version number
    The version number of the file.
    data_type Ta | frequency_switch | Tmb |Integ_Ta | Integ_Tmb | RawLong | RawFloat | ID_number
    The type of the data in physical meaning.
    Ta - in antenna temperature (K)
    frequency_switch - unfolded frequency switch output in antenna temperature (K)
    Tmb - in mainbeam brightness temperature (K)
    Integ_Ta - in integrated antenna temperature (K km/s)
    Integ_Tmb - in integrated mainbeam brightness temperature (K km/s)
    RawLong - in raw output (total power)
    RawFloat - in raw output (total power) but convert to float formally.
    history_step number
    The number of the history steps ("end" step is not counted).
    history_line number
    The number of lines in the history.
    original_scan_number number
    An original sequencial number of the scans (.scn). This number should be given by ASTROS, an observation program.
    backup_version version_number
    The version number for backup, which is valid at using the command "save". The created backup file will have a name with this number.
    composed_scans number
    The number of the original scans (.scn). This number should increase after "integ" process.
  2. Section "Observation Paramaters"
    project name
    Name of the project. Less than or 16 characters.
    scd_name file_name
    Name of the original .scd file which was used by ASTROS. Less than or 8 characters.
    scd_line_number number
    The line number in the .scd file which was used by ASTROS.
    sw_mode total_power | onoff | frequency_switch | Dicke | ID_number
    Switching mode to obtain the data.
    total_power - total power mode. Direct output of a recevier.
    onoff - after on-off switching.
    freqency_sw - after frequency switching
    Dicke - after Dicke switching
    observed_mjd MJD
    The observed date in the modified Julian day.
    observed_start_time in_sec_from_1970.0
    The observation start time for the profile. The time is given by sec from 1970/1/1 0:0:0 UTC. (The UNIX/Linux standard).
    observed_stop_time in_sec_from_1970.0
    The observation stop time for the profile. The time is given by sec from 1970/1/1 0:0:0 UTC. (The UNIX/Linux standard).
    integration_on_time sec
    Total integration time as the on-position in seconds.
    integration_off_time sec
    Total integration time as the off-position in seconds.
    observer1 name
    The name of primary observer. Less than or 8 charcters.
    observer2 name
    The name of secondary observer. Less than or 8 charcters.
    observer3 name
    The name of another observer. Less than or 8 charcters.
    observer4 name
    The name of another observer or data processor. Less than or 8 charcters.
  3. Section "Object Information"
    object name
    The name of object. Less than or 15 charcters.
    coordinates lb | radec | radec-app | ID_number
    The basic coordinate to use. The local xy coordinate is also defined by referring the coordinate assigned this selection.
    lb - the Galactic coordinate. Some refers as l(II) and b(II).
    radec - the equitorial coordinate at the epoch B1950.0. The mean poisiton.
    radec-app - the equitorila coordinate at the present epoch of the observations. The appearent position.
    l angle_value
    The galactic longitude position of the on point. If angle_value is given only the number, the command takes it as in degrees.
    b angle_value
    The galactic latitude position of the on point. If angle_value is given only the number, the command takes it as in degrees.
    ra angle_value
    The equitorial longitude (B1950.0) mean positon of the on point. If angle_value is given only the number, the command takes it as in degrees.
    dec angle_value
    The equitorial latitude (B1950.0) mean positon of the on point. If angle_value is given only the number, the command takes it as in degrees.
    az angle_value
    The azimath positon of the on point. If angle_value is given only the number, the command takes it as in degrees.
    el angle_value
    The elevation positon of the on point. If angle_value is given only the number, the command takes it as in degrees.
    off_l angle_value
    The galacitc longitude positon of the off point. If angle_value is given only the number, the command takes it as in degrees.
    off_b angle_value
    The galacitc latitude positon of the off point. If angle_value is given only the number, the command takes it as in degrees.
    off_ra angle_value
    The equitorial longitude (B1950.0) mean positon of the off point. If angle_value is given only the number, the command takes it as in degrees.
    off_dec angle_value
    The equitorial longitude (B1950.0) mean positon of the off point. If angle_value is given only the number, the command takes it as in degrees.
    orig_x angle_value
    The longitude positon of the origin of the local XY coordinate. If angle_value is given only the number, the command takes it as in degrees. The referring coordinate is assigned by the keyword "-coordinates".
    orig_y angle_value
    The latitude positon of the origin of the local XY coordinate. If angle_value is given only the number, the command takes it as in degrees. The referring coordinate is assigned by the keyword "-coordinates".
    position_angle deg
    The positon angle of the local XY coordinate at the origin. The value is in degree. The value 0 means the X and Y axes are parallel to the longitude and latitude line of the referring coordinate, respectively. The value 90 means the Y axis is parallel to the longitude line. The referring coordinate is assigned by the keyword "-coordinates".
    x angle_value
    The longitud positon of the on poing in the local XY coordinate. If angle_value is given only the number, the command takes it as in degrees. The referring coordinate is assigned by the keyword "-coordinates".
    y angle_value
    The latitude positon of the on point in the local XY coordinate. If angle_value is given only the number, the command takes it as in degrees. The referring coordinate is assigned by the keyword "-coordinates".
  4. Section "Telescope/Antenna Information"
    telescope_name name
    The name of telescope used to get the profile. Less than or 8 characters.
    ap_eff absolute_value
    The appature efficiency of the telescope. In absorute value between 0.0 and 1.0, not in percent.
    mb_eff absolute_value
    The main beam efficiency of the telescope. In absorute value between 0.0 and 1.0, not in percent.
    fss_eff absolute_value
    The forward scattering and spilover efficiency of the telescope. In absorute value between 0.0 and 1.0, not in percent.
    beamsize arcmin
    The full width at the maximum of the antenna power beam in arcmin.
  5. Section "Receiver Information"
    rx_name name
    The name of receiver used. Less than or 7 characters
    sideband lsb_ssb | lsb_dsb | usb_ssb | usb_dsb | ID_number
    The observation sideband mode and signal sideband.
    lsb_ssb - Signal in LSB and observation made in SSB.
    lsb_dsb - Signal in LSB and observation made in DSB.
    usb_ssb - Signal in USB and observation made in SSB.
    usb_dsb - Signal in USB and observation made in DSB.
    v_lsr km/s
    The "center velocity" of the profile in km/s respect to the Local Standerd of the Rest. The "center velocity" means the standerd referring velocity for the profile. In most cases this should be the same as that of the main targetting object. In some cases the actual center of the profile may be different.
    v_off km/s
    The "center velocity" of the profile in km/s respect to the Local Standerd of the Rest for the off point. This is almost meaningless if the data is not taken in frequency switching. The "center velocity" means the standerd referring velocity for the profile. In most cases this should be the same as that of the main targetting object. In some cases the actual center of the profile may be different.
    rest_freq GHz
    The rest frequency of the emission/absorption line to observe in GHz.
    obs_freq GHz
    The observation frequency of the receiver in GHz.
    local_freq GHz
    The frequency of the local oscilator in GHz.
    if_freq GHz
    The frequency of the first IF line in GHz.
    local_multiplier_order number
    The order of the multiplier attached to LO. Doubler is 2 and tripler is 3.
    T_sys K
    The system noise temperature including the atmospheric extinction in Kelvin.
    T_rx K
    The receiver noise temperature in Kelvin.
    data_rms K
    The rms noise level of the profile in Kelvin.
    calibrator_temperature K
    The brightness temperature of the thermal calibrator.
    data_weight value
    The weight of the profile. Usually it is caliculated based upon the value of the rms noise level. If you give the word "rms" instead of the value, the command gives new weight value estimated from data rms level stored in the header. This is used by the command integ and others.
    data_scale_factor value
    The scaling factor of the data to adjust in Kelvin. The value should be multiply to the floating value of "profile.data[ch-1]" to get intensity in K. If you give the word "norm" instead of the value, the command scales the data values stored directly and resets the scaling value to be unity.
  6. Section "Backend/Detector Information"
    backend name | -be_name name
    Name of the backend spectrometer. Less than or 8 characters.
    backend_channel_number number
    The total number of channels in the backend used. Less than or 2048.
    backend_basis_ch number
    After version 3 it is meaningless. It was the same meaning of "-be_center_ch".
    backend_ch_sign 1 | -1
    Backend channel polarity. Positive means the RF frequency increases when the backend frequency increases. Negative means the RF frequency decreases.
    data_ch number
    The number of data channel. Originally it should be the same as the number of channel in the backend used but may change by processing such as smooth.
    be_center_ch value
    The "center channel" of the backend used. The "center channel" means the standerd referring channel for the profile to estimate the relation between channel number and frequency on the spectrometer. In some cases the "central channel" may be half of the "backend_channel_number".
    be_center_freq MHz
    The "center frequency" of the backend in MHz. The "center frequency" means the standerd referring frequency for the profile to estimate the relation between channel number and frequency on the spectrometer. In some cases the "central frequency" may be the actual center of the full span of the profile.
    be_disp0 MHz
    The 0th order coefficient of the despersion function of the spectrometer. The unit is MHz.
    be_disp1 MHz/ch
    The 1st order coefficient of the despersion function of the spectrometer. The unit is MHz per channel. The channel means present data channel for ver.3 and later data.
    be_disp2 MHz/(ch^2)
    The 2nd order coefficient of the despersion function of the spectrometer. The unit is MHz per square-channel
    be_disp3 MHz/(ch^3)
    The 3rd order coefficient of the despersion function of the spectrometer. The unit is MHz per cubic-channel
    be_disp4 MHz/(ch^4)
    The 4th order coefficient of the despersion function of the spectrometer. The unit is MHz per 4th-powers-of-(channel)
    be_freq_resolution MHz
    The frequency resolution of the backend in MHz. This is the original but not for the present effective resolution.
    be_ch_width value
    The binning width of the original channel. For the ver.3 and later data this parameter is meaningless.
    be_ch_origin value
    The binning start position on the original. For the ver.3 and later data this parameter is meaningless.
  7. Section "Observation Log"
    site_name name
    Name of the observation site location. Less than or 8 characters.
    atm_temp C
    The atmospheric temperature in Centigrade when the observations were done.
    atm_water hPa
    The partial pressure of water vaper in mbar or hecto-Pascal when the obervations were done.
    atm_press hPa
    The atmospheric pressure in mbar or hecto-Pascal when the observations were done.
    optical_depth_at_zenith value
    Measured optical depth at zenith when the observations were done.
    observation_memo free_memo
    Free memorundom in ASCII code. Less than or 64 characters.
    observation_comment free_comment
    Free comment in ASCII code. Less than or 64 characters
  8. Section "Data Processing History"
    history
    Data processing history with time and parameters.
  9. Section "Data Flag"
    spurious_flag 0 | 1
    Every data channel has spurious flag. The number 0 means off (non-spurious) and 1 means on.
    baseline_flag 0 | 1
    Every data channel has baseline flag. The number 0 means off (non-baseline) and 1 means on.
  10. Section "Profile Data"
    data[ch-1]
    Actual spectrum data. The array starts argument 0 but we call it channel 1. Therefore, data[ch-1] in C-language corresponds the data for channel ch.

SEE ALSO

headlist, headcorr, sdbselect

BUGS

HISTORY

ver.1
1992/4/17 T.Handa
ver.3
1997/11/12 T.Handa

MANUAL VERSION

1998/5/13 T.Handa
1999/4/20 T.Handa