What the Spectral Processor Does. Using different setups, the mode of the spectral processor can be configured to acquire various types of data. These configurations vary widely, but can be organized into three separate categories (each capable of variations within itself):
Under spectral line observing, modes included are Standard Spectral Line and Time-Synchronous Spectra observing. Spectral line observations normally record a limited number of spectra whose accumulations are synchronized with front-end switching functions such as cal-on/cal-off and frequency, load, or beam switching.
Under pulsar-synchronous spectra observing, modes included are Synchronous Frequency/Time Matrix and Pulse Phase Spectra observing. Observing under these modes is very similar to that of spectral line observing except that provisions are made for tracking pulse period changes during an integration using special pulse period predicting software.
Dedispersion refers to the recombining of something that has been separated or "dispersed". Looking at time sampling modes, those included are Dedispersed Continuous Time Sampling and Signal Averaging with Dedispersion (Pulsar Synchronous). With continuous sampling, all frequency channels are combined into one time sample and recorded to provide a continuous stream of time samples with higher time resolution. In the signal averaging mode, the methods stated above are combined with synchronized averaging (which reduces data rates) to achieve the maximum time resolution possible.
The diagram shown in Figure 5 depicts the significant components of the spectral processor and illustrates the basic path signals take through the instrument
Figure 5
The GBT operator is responsible for assisting astronomers in carry out observing programs using the Spectral Processor. Please refer to the GBT Operations Manual, procedures and checklists for specific guidance on setting up and operating this complex system.
Monitoring the state, status, and controlling additional set-ups of equipment for Spectral Processor observing is done using Control Library for Engineers and Operators (CLEO) applications. These applications are run from the operator's control room workstation. In addition to their primary monitoring function, this software package can also be used to manually control equipment setups. Specific information concerning CLEO applications is included in the on-line CLEO Manual.
Observing with the GBT and using its variety of backend instruments will be done interactively through graphical control screens or by running pre-planned observing tables. This interface software uses a "windows" type environment. Setting up various GBT instruments and backend devices may be accomplished in both automated and manual modes depending on the observers plan. Specifics' concerning this software, and how it can be used in connection with Spectral Processor observing is discussed in the software's users manual. Please refer to it as necessary.