Commands generated by the crew or telemetered to the shuttle from the POCC operate HUT through the Spacelab Experiment Computer (EC) and its Experiment Computer Operating System (ECOS) and Experiment Computer Applications Software (ECAS). The EC communicates with HUT through the Remote Acquisition Unit (RAU). The RAU directly commands and monitors the essential instrument survival subsystems (such as main power, heater power, the Vac-Ion pumps, and DEP power and initialization). Once the DEP is operational, it processes commands and monitors HUT's basic subsystems and science subsystems. The HUT science subsystems provide data to the SP for analysis. The SP feeds the processed data to the DEP for formatting in the High Rate Multiplexer (HRM) data stream for transmission to the ground.
HUT commands are issued from five display pages which can be brought up on the PS's DDU. (Copies of these display pages may also be viewed in the POCC.) These displays provide a visual reminder of the discrete commands required for each function, display associated status data, and provide visual and audio alerts when parameters exceed pre-specified warning limits or when errors occur. The display pages are
and their basic format is shown in Figures 3-1 to 3-5. The HAC display is generated by an ECAS task using data directly from the RAU, while the others are DEP allocated displays which require the DEP to be active for use. As one might gather from the names, the HAC page is used to perform the most basic functions necessary for powering HUT up and down. Most observational procedures are controlled by high level sets of commands issued from the HOP page. HSP, HDC, and HMH provide control of individual subsystems on HUT.