Cycle 11 VLBI Acceptance: Delay Fix Final Report

Abstract

This report presents details of changes to the VLBI software system made on the path to the Cycle 11 Acceptance. The principal new feature is the long-awaited "delay fix" to the APS that is presented in considerable detail here. This was proposed for a new ADF implementation project, APP2. The delay fix is a technology that allows the full 2-GHz continuum band to be used in active phasing, resulting results in a lower flux density limit for direct observation of science targets. It also allows a greater range of passive phasing targets to support weaker targets. Work on the delay fix began during Cycle 3 and is only now concluded in time for additional testing as desired in Cycle 11 and then full use in Cycle 12. Other than the delay fix, a new software device was delivered to support the new hydrogen maser, and there was the usual round of minor scripting updates in the SSR component. This report is written to present a largely self-contained history of the delay fix effort and its fruit, and it also covers the other, minor development items which are formally part of the Cycle 11 Acceptance. As the software phasing engine which supports this mode is also now the recommended engine for the APS, this document also serves to present relatively complete documentation on the final implementation of the SSR as well as TelCal sides of the APS. The underlying VOM remains as it was deployed and used in Cycle 4.