
                    NGS Format for VLBI Data Transfer

                      Revised June 11, 2007.

                   (See modification history at end.)


 1.  Header Card - 80 column ASCII descriptor for the data set
      a.  DATA IN NGS FORMAT FROM DATA BASE YRMONDYxx VERSION ####
      b. Hellings theoretical delays and rates into card #2. 
           OR
         Observed delays and rates into card #2.


 2.  Site Cards
       Col  1- 8: Eight character site name
       Col 11-25: X-component of the site position (meters)
       Col 26-40: Y-component of the site position (meters)
       Col 41-55: Z-component of the site position (meters)
       Col 57-60: Axis type (must be AZEL, EQUA, X-YN (for 
                   X axis N), X-YE, or RICH (RICHMOND, an EQUA antenna
                   from Maryland moved to Florida)
       Col 61-70: Axis offset (meters)

    End of site cards is indicated by a card with $END in Col 1-4

 3. Radio source position cards
       Col  1- 8: Eight character source name
       Col 11-12: Right ascension hours
       Col 14-15: Right ascension minutes
       Col 17-28: Right ascension seconds
       Col    30: Declination sign
       Col 31-32: Declination degrees
       Col 34-35: Declination minutes
       Col 37-48: Declination seconds

    End of source cards is indicated by a card with $END in Col 1-4

 4. Auxiliary parameters
       Col  1-20: Reference frequency (MHz)
       Col 21-30: Group delay ambiguity spacing (nsec)
       Col 32-33: Delay type (GR-group, PH-phase)
       Col 35-36: Delay rate type (GR-group, PH-phase)

    This card must be followed by a card with $END in Col 1-4

 4. Data Cards

    Card #1:
       Col  1- 8: Eight character site name for site 1
       Col 11-18: Eight character site name for site 2
       Col 21-28: Eight character source name for radio source
       Col 30-33: Year of observation (e.g. 1993)
       Col 35-36: Month 
       Col 38-39: Day
       Col 41-42: Hour
       Col 44-45: Minute
       Col 47-60: Seconds
       Col 61-70: Run identification code (if desired)
       Col 71-78: Sequence number
       Col 79-80: 01

    Card #2:
       Col  1-20: Observed delay (ns)
       Col 21-30: Formal error for the observed delay (ns)
       Col 31-50: Observed delay rate (ps/sec)
       Col 51-60: Formal error for the observed delay rate (ps/sec)
       Col 61-62: Data quality flag (blank or 0 indicates good data)
       Col 64-65: Delay type (blank if same as in Auxiliary Parameters)
       Col 67-68: Delay rate type (blank if same as in Auxiliary Parameters)
       Col 71-78: Sequence number
       Col 79-80: 02

    Card #3:
       Col  1-10: Correlation coefficient (0-1)
       Col 11-20: Formal error for correlation coefficient
       Col 21-30: Fringe amplitude (J)
       Col 31-40: Formal error for fringe amplitude (J)
       Col 41-60: Total fringe phase (radians)
       Col 61-70: Formal error for total fringe phase (radians)
       Col 71-78: Sequence number
       Col 79-80: 03

    Card #4:
       Col  1-10: System temperature at site 1 (K)
       Col 11-15: Formal error for system temperature at site 1 (K)
       Col 16-25: System temperature at site 2 (K)
       Col 26-30: Formal error for system temperature at site 2 (K)
       Col 31-40: Antenna temperature at site 1 (K)
       Col 41-45: Formal error for antenna temperature at site 1 (K)
       Col 46-55: Antenna temperature at site 2 (K)
       Col 56-60: Formal error for antenna temperature at site 2 (K)
       Col 71-78: Sequence number
       Col 79-80: 04

    Card #5:
       Col  1-10: Cable calibration correction (one-way) for site 1 (ns)
       Col 11-20: Cable calibration correction (one-way) for site 2 (ns)
       Col 21-30: Water vapor radiometer parameter at site 1 (ns)
       Col 31-40: Formal error for water vapor radiometer at site 1 (ns)
       Col 41-50: Water vapor radiometer parameter at site 2 (ns)
       Col 51-60: Formal error for water vapor radiometer at site 2 (ns)
       Col 62   : Water vapor radiometer parameter definition code for
                   site 1 as follows:
                  0 - parameter is zenith path delay
                  1 - parameter is path delay along line-of-sight
       Col 64   : Water vapor radiometer parameter definition code for
                   site 2 (see above)
       Col 71-78: Sequence number
       Col 79-80: 05

    Card #6:
       Col  1-10: Ambient atmospheric temperature at site 1 (deg. C)
       Col 11-20: Ambient atmospheric temperature at site 2 (deg. C)
       Col 21-30: Ambient atmospheric barometric pressure at site 1 (mb)
       Col 31-40: Ambient atmospheric barometric pressure at site 2 (mb)
       Col 41-50: Ambient atmospheric humidity parameter at site 1
       Col 51-60: Ambient atmospheric humidity parameter at site 2
       Col 62   : Humidity parameter definition code for site 1 as follows:
                  0 - humidity parameter is relative humidity (%)
                  1 - humidity parameter is dew point (deg. C)
                  2 - humidity parameter is wet bulb temperature (deg. C)
       Col 64   : Humidity parameter definition code for site 2 (see above)
       Col 71-78: Sequence number
       Col 79-80: 06

    Card #7:
       Col  1-10: Time difference between the reference epoch (card 1) and
                   the start of the observations (e.g. -60.) (seconds)
       Col 11-20: Duration of the observation (seconds)
       Col 21-30: A priori UTC offset at site 1 (if any) (seconds)
       Col 31-50: Observation frequency (MHz) (blank if same as in 
                   Auxiliary Parameter)
       Col 51-60: Group delay ambiguity (ns) (blank if same as in Auxiliary
                   Parameter)
       Col 71-78: Sequence number
       Col 79-80: 07

    Card #8:
       Col  1-20: Delay ionosphere correction (ns)
       Col 21-30: Delay ionosphere correction formal error (ns)
       Col 31-50: Delay rate ionosphere correction (ps/s)
       Col 51-60: Delay rate ionosphere correction formal error (ps/s)
       Col 62-63: Ionosphere error flag (0 = ionosphere correction OK)
       Col 71-78: Sequence number
       Col 79-80: 08

    Card #9: Same as card #2, except modified formal errors.
       Col  1-20: Observed delay (ns)
       Col 21-30: Modified formal error for the observed delay (ns)
       Col 31-50: Observed delay rate (ps/sec)
       Col 51-60: Modified formal error for the observed delay rate (ps/sec)
       Col 61-62: Data quality flag (blank or 0 indicates good data)
       Col 64-65: Delay type (blank if same as in Auxiliary Parameters)
       Col 67-68: Delay rate type (blank if same as in Auxiliary Parameters)
       Col 71-78: Sequence number
       Col 79-80: 09


    Notes:

 1. All values should include a decimal point or be right-hand justified in
    the indicated fields.

 2. Station coordinates are given in a Greenwich right-hand Cartesian 
    coordinate system (e.g., Z-axis toward the CIO pole, X-axis toward 
    the Greenwich meridian and Y-axis toward the 90 deg. east meridian).

 3. Source coordinates are given in J2000.0 coordinates using the IAU 1984
    definitions for precession, nutation, aberration, etc.

 4. The reference frequency is defined as the frequency to which the total 
    fringe phase observable (Card #4) is referred.

 5. The epoch of the observation is defined as the UTC epoch at which the 
    signal arrived at site 1; i.e., the site identified in columns 1-8 of
    card #1.

 6. The sequence number in columns 71-78 of the data cards is to be the same
    number for each data card associated with a given observation.  The 
    numbers in columns 79-80 serve to sequence the cards within a given
    observation.

 7. The delay is defined as:

                    D = T2 - T1

    where

                   T1 = time of signal arrival at site 1 as measured 
                        by the site clock at site 1
                   T2 = time of signal arrival at site 2 as measured
                        by the site clock at site 2

    No calibration corrections (e.g. atmosphere corrections) have been added
    to or subtracted from these values.

 8. The delay rate is defined as the derivative of delay with respect to time
    as measured by the clock at site 1.

 9. The sense of the cable calibration is that an increase means an increase
    in the (one-way) electrical length of the cable carrying the phase
    calibration signal to the receiver box.

10. The barometric pressure should not be corrected to sea level.

11. It is not necessary to include blank data cards for missing data.  For 
    example, if no meteorological data are available, card #6 may be deleted.

12. Card #1 may not be deleted.

13. Data should be arranged in time order.

14. If the cards are put on tape, the tape should be 9 track with the 
    following DCB:

                   DCB = (RECFM=FB,LRECL=80,BLKSIZE=3200)

------------------------------------------------------------------------

Modifications:

1999.02.08      File creation date.  Format itself dated "10/20/83".
1999.06.29 BA   - Removed last part of file, which was e-mail message
                from Mike Abell to Jim Ryan of 1994.05.09, mostly
                containing just a copy of the first part of this file.
                - Added antenna type RICH for RICHMOND antenna.
2007.06.12 DG/GSFC - PC Linux version. Card nine created to match Zinovy
                Malkin's version.

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