OAPI: the OPUS Application Programming Interface

The OPUS pipeline processing environment at the Space Telescope Science Institute (STScI) supports the automated conversion of gigabits of raw telemetry from the Hubble Space Telescope (HST) to useful science and engineering products each day. OPUS provides a flexible, fully concurrent, distributed control system in which a set of processes operate. The applications that form the HST data processing pipeline communicate with the blackboard architecture employed by OPUS through a library of C functions. Currently, that library is being ported to C++ as part of an effort to establish and document a standard programming interface to OPUS. The OAPI will facilitate OPUS application development for future HST instruments as well as other spacecraft and ground-based data processing projects. 1. OPUS: An Operational Pipeline System The OPUS pipeline processing environment at the Space Telescope Science Institute supports the automated conversion of gigabits of telemetry from the Hubble Space Telescope to useful science and engineering products each day. OPUS provides a flexible, fully concurrent, distributed control system in which a set of processes operate (Rose 1994, 1998; Rose et al. 1995; Rose, Choo & Rose 1996; Boyer & Choo 1997; Swade & Rose 1998a). Applications in an OPUS pipeline specify, through simple text files, the criteria under which they are to be triggered by OPUS to perform some action. OPUS takes care of polling the necessary information sources (termed “blackboards”) given the application’s trigger conditions, and generating the appropriate events when those conditions are met. The interaction between pipeline applications and OPUS differs depending on whether the application was developed for use with OPUS or is an off-theshelf software product– OPUS does support both OPUS-savvy and off-the-shelf pipeline applications. In the latter case, a shell process acts as a proxy for communicating with OPUS by executing the “external” application when an event is delivered to it. With the release of the OPUS Sample Pipeline on CD-ROM last year (see Swade & Rose 1998b), it became possible for groups http://www.stsci.edu/opus