User's Guide

SATRACK

Read ephemeris data from a file and process it

Function:

Reads both one-line NAVSPASUR data and two-line NORAD data from an input file. The NAVSPASUR data is written to an update file, and the NORAD data is used in calculations to create an input data string for the Antenna Control Unit (ACU).

Example:

    LAS> SATRACK INFILE=s4865r PRINT=s4865rout SATNUM=12

    The input file "s4865r" is read and processed. The correct ephemeris data file is updated and parameters are calculated for the ACU. An output file " s4865rout.prt" will be generated. The output file contains input NORAD parameters (satellite data for calculating ACU values), output orbital parameters, and a data string to be sent to the ACU. Output to file "s4865rout" will be generated only for the NOAA-12 satellite.

Description/Algorithm:

SATRACK reads both one-line NAVSPASUR data and two-line NORAD data from an input file. The NAVSPASUR data is used to update files containing ephemeris data. If the information already exists within the appropriate file, the record is written to a duplicate entry file. These data files are located in ADAPSTABLES and have names based on their international satellite ID number (e.g., "16969.dat") except for the duplicate entry file "dupfile.dat".

The NORAD data is used in calculations from which a data string of satellite information is created. This data string is used by the Antenna Control Unit (ACU) and contains values relating to the nodal period and the orbital radius. An output NORAD data file is also generated and sent to either a user-specified file, line printer, or terminal. The one-line NAVSPASUR input data is defined as follows:

 Columns       Description
 -------       -----------
  1 -  5       Satellite Number
  6 - 10       Revolution Number
 11 - 18       Mean Anomaly
 19 - 26       Mean Motion
 27 - 31       Decay
 32 - 39       Eccentricity
 40 - 47       Argument of Perigee
 48 - 55       Longitude of Ascending Node
 56 - 63       Inclination
 64 - 69       Epoch (Year/Month/Day)

The two-line NORAD input data is defined as follows:

                             Line 1
                             ------
 Columns       Description
 -------       -----------
  1 -  1       Line Number of Element Data
  3 -  7       Satellite Number
 10 - 11       International Designator (Last two digits of launch year)
 12 - 14       International Designator (Launch number of the year)
 15 - 17       International Designator (Piece of launch)
 19 - 20       Epoch Year (Last two digits of year)
 21 - 32       Epoch (Julian Day and fractional portion of the day)
 34 - 43       First Time Derivative of the Mean Motion
               or Ballistic Coefficient (Depending on ephemeris type)
 45 - 52       Second Time Derivative of Mean Motion (Blank if N/A)
 54 - 61       BSTAR drag term if GP4 general perturbation theory was 
               used.  Otherwise, radiation pressure coefficient.
 63 - 63       Ephemeris type
 65 - 68       Element number
 69 - 69       Check Sum (Modulo 10)
               (Letters, blanks, periods = 0; minus sign = 1; 
               plus sign = 2)

                             Line 2
                             ------
 Columns       Description
 -------       -----------
  1 -  1       Line Number of Element Data
  3 -  7       Satellite Number
  9 - 16       Inclination [Degrees]
 18 - 25       Right Ascension of the Ascending Node [Degrees]
 27 - 33       Eccentricity (decimal point assumed)
 35 - 42       Argument of Perigee [Degrees]
 44 - 51       Mean Anomaly [Degrees]
 53 - 63       Mean Motion [Revs per day]
 64 - 68       Revolution number at epoch [Revs]
 69 - 69       Check Sum (Modulo 10)
 
 All other columns are blank or fixed.

Nonfatal Error Messages:

  1. [put_navsp-dup] Duplicate record found on date <xxxx> in file <xxxx>, Duplicate record written to <xxxx>

    A duplicate record was found in the ephemeris data file; the duplicate record will be written to "dupfile.dat" in ADAPSTABLES.

Fatal Error Messages:

  1. [satrack-fatal] Fatal error encountered

    A fatal error was encountered; processing is terminated. A more descriptive message was displayed immediately preceding this message.

  2. [satrack-outopn] Error opening output file

    Check the permissions of the path and file that is to be opened.

  3. [satrack-inopn] Error opening input file

    The user-specified input file could not be opened. Check the specified file, as well as its permissions.

  4. [satrack-inread] Error reading input file

    An error was encountered while trying to read the input file. Check the permissions of the input file.

  5. [put_navsp-inseek] Error seeking input file

    Check the permissions of the path and file in which the seeking is being attempted.

  6. [put_navsp-write] Error writing data to file

    Check the permissions of the path and file in which the writing is being attempted.

  7. [satrack-locf] Error locating file

    The specified file does not exist or does not have the proper file permissions set.

User Notes:

  1. The ephemeris data files updated by SATRACK are located in ADAPSTABLES and have names based on the international satellite ID number (e.g., "15427.dat"). Duplicate records are written to the duplicate data record file "dupfile.dat" in ADAPSTABLES.

  2. Related modules are NORAD and NAVSPASUR. NORAD is used to generate Antenna Control Unit information much like SATRACK. NAVSPASUR is used to update the same ephemeris data files that SATRACK updates. However, user-specified parameter values supply NORAD and NAVSPASUR with input data rather than reading the data from a file.