SPAS Package

Full name of the package: Space VLBI Assistance Software (SPAS)

Developer (authors) and institution: I. Fejes, T. Szarka, FÖMI Satellite Geodetic Observatory, H-1373 BUDAPEST Pf.546, Hungary

Purpose: The package in its present form should be considered as a prototype. It is intended for space VLBI education, training and proposal preparation assistance.

Intended Audience: General space VLBI users (first time users to very experienced).

Hardware Requirements: IBM compatible PC/AT 80386

Software Requirements: DOS 3.1

Capabilities, subprograms:The prototype program handles 2 satellites, maximum 10 ground based VLBI telescopes, and 10 telemetry stations. Elevation cut off angle and telemetry line of sites conditions are considered, but satellite constraints are not included. The package consists of subprograms which display graphically the UV coverage; the 3 dimensional view of satellite orbit as seen from the direction of the selected radio source; the subsatellite ground track; the satellite line of site diagram from telemetry stations as a function of UTC including a numerical table of rise and set times; the source observability diagram of the different space and ground radio telescopes as a function of UTC including a numerical table of start and stop times; a station based AZ - EL track of the satellite(s) and the selected radio source including a numerical table of AZ,EL positions in preselected time steps.

User Interface: Keyboard driven setup for selecting: source, elevation cut off angle for the source , satellites, ground VLBI stations, telemetry stations, elevation cut off angle for telemetry, start and stop epoch. The latest of this parameter set is always saved in a parameter set up file for easy retrieval at the next session. The choice of subprograms are from keyboard driven menu including a database (source, satellite, ground VLBI, telemetry stations catalogues) handling submenu.

I/O Data Format: Input is via keyboard or disc files. Output is disc file or Epson compatible matrix printer depending on the selected subprogram.

Documentation: For the time being no detailed documentation is available. A short "User Guide" can be obtained on request.

Distribution Method: The SPAS program is not yet released. The prototype program can be obtained in executable code on floppy disc by written request to the authors.

Future developments: A major overhaul of the program is in progress. The scope of functions/subprograms will be extended from 6 to 12. Satellite constraints will be considered. The user interface will be changed from keyboard driven to windows based mause driven.