NRAO Home  >  Green Bank  |  Wiki Topic:    GB > Data > DataPreprocessingAPI

Changes | Index | Contents | Search | Statistics | Jump to Topic

Data Preprocessing API

The GB Data Preprocessing Application Programming Interface (API) is a suite of utilities accessible from the command line which are typically used outside the boundaries of a data reduction package. A completed package will include:

• Determining Antenna Positions
  • One approach is currently available. Using an integration midpoint and duration, we retrieve all of the antenna position readings within the range and average over them. Moreover, we interpolate to arrive at the endpoints of this range (necessary because most always, the ends of the range do not coincide with specific readings). These endpoints are weighted by their distance from the nearest measured reading within the range. The closer the interpolated endpoint is to a reading, the closer its weight is to that of an interior point. This approach is best for integrations of any duration.
• Van Vleck corrections
• Smoothing
• FFT
• Reducing the data by channel (if windowed)
• Determining Tcal and Tsys
• Data Flagging
• Other Calibration and Averaging steps
• Translation of Data into Output Formats (AIPS++ MS, IDL, CLASS binary, etc.)

The package is being developed to initially support production of SDFITS output from GBT data. After it is benchmarked against known correct results from the current AIPS++ gbtmsfiller, and the modules are effectively segmented from one another for more general purpose use, it is intended that the same data preprocessing components will be used regardless of the data reduction package that is chosen by the astronomer. Also, a gap analysis was performed on these capabilities from the alpha release of SDFITS in late August 2003 to determine what changes were necessary to support the equivalent capabilities of the gbtmsfiller. This can be viewed at PreProcessingComponents.