Introduction

The Green Bank Telescope Laser Ranging System[1] will be made up of approximately 20 laser ranging instruments to be used for active surface and precision pointing. These instruments are identified as ZY101--ZY120[2]. Groups of ZYs will be under the control of computers identified as ZIYS for active surface control, and ZIYP for precision pointing[3]. Under normal operation, the active surface, precision pointing, and monitor and control interface to the Laser Ranging System will be through the ZIYs. The ZIYs will be responsible for coordinating the operation of the ZYs to obtain 3-D coordinates of retroreflectors on the GBT. This document is a draft of the software reference manual for the ZY instruments--and thus primarily of interest to the ZIY software designer[4]. It does, however, give others a basic understanding of the ZY system operation, and therefore a fundamental understanding of potential capabilities of the ZIYs. It should be noted that the list of functions includes only the completed and tested functions. A number of additional functions are under development--particularly in the area of tracking. Comments and questions are solicited on both the content and format of this draft, so that corrections and enhancements can be made to the final document. Reference documents exist for other components and procedures used by the Metrology System, such as the ZIY[4], ZP[5], software release and revision control procedures[6], etc. Contact David H. Parker (dparker@nrao.edu) or Ramón E. Creager (rcreager@nrao.edu), or visit our Web site

http://freya.gb.nrao.edu/GBTMetrology/index.html

for more details. This document supersedes GBT Memo 111[7].