NGS Format for VLBI Data Transfer 10/20/83 1. Header Card - 80 column ASCII descriptor for the data set 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), or X-YE) 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 ascention hours Col 14-15: Right ascention minutes Col 17-28: Right ascention 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 5. 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 chacacter source name for radio source Col 30-33: Year of observation (e.g. 1979) 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 (pa/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 Aux. Par.) Col 67-68: Delay rate type (blank if same as in Aux. Par.) 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 coeficient Col 21-30: Fringe amplitude (J) Col 32-40: 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 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 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 observation (eg. -60.) (seconds) Col 11-20: Duration of the observation (seconds) Col 21-30: A priori UTC offste at site 1 (if any) (seconds) Col 31-50: Observation frequency (MHz) (blank if same as in Aux. Par.) Col 51-60: Group delay ambiguity (ns) (blank if same as in Aux. Par.) 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: Col 1-70: Comment text 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 Gweenwich right-hand Catesian coordinate system (e.g. Z axis toward the CIO pole, X axis toward the Greenwhich 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, ect. 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, 1.e., the site identified in col 1-8 of the 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 col 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)