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GFM Spectral Line

• Available Plugins
• Proposed Plugins
• Introduction
  • Spectral Line
  • Spectrometer Engineering
• Known Issues
  • Spectral Line
  • Spectrometer Engineering

Available Plugins

Plugin	Description	Alpha	Beta	Production	Additional Information
Spectral Line	Displays all spectra from Spectrometer and Spectral Processor				Currently available by default. Online limitations sited below.
Spectrometer Engineering	Displays all spectra from only Spectrometer FITS files				Not available by default. See instructions below.

Proposed Plugins

None

Introduction

Spectral Line

The Spectral Line plugin is a tool for browsing spectral line data, either offline, or in online mode. When offline, one integration at a time can be selected, while, in online mode, the most recent integration is automatically plotted. See the the Examples section for screen shots.

The spectra displayed are identical to the data written in an SDFITS file in Raw Mode. As of this writting, this does not include any Hanning Smoothing. When displaying Raw Power, only the inner 96% of data is displayed.

All user interaction for this plugin occurs in the right-hand side options panel. The check boxes allow inclusive selection of spectra to plot via astronomical variables: Beams, Polarizations, IF Numbers, and Phases. The integration can be selected either using the up/down arrows, or by typing in a value in the edit box.

As spectra are plotted, information about each plot is printed in the console window. Each line is color coded to match the color of that spectra in the plotting window. In addition, some of the information for the very first spectra are used to annotate the plot. The plot title is parsed as project_name:scan_number:integration_number.

The options panel also includes three buttons and a radio box for plot viewing. The 'Views' radio box offers plotting Raw Power vs. Channels, and Raw Power vs. Sky Frequency for all backends. In addition, Spectrometer data will include a Lags vs. Channels option. The 'Keep Zoom' toggle button will maintain the current zoom, even as new spectra are plotted. Using the unzoom command (mouse right-click, or through the tool bar) will bring the plot back to the original scale. The 'Overlay' toggle button can be used to overplot spectra from different integrations or scans. Finally, the 'Clear' button erases the plotting window.

Spectrometer Engineering

The Spectrometer Engineering plugin is a tool for browsing spectrometer data. It is quite similar to the Spectral Line Plugin mentioned above. The significant difference is that this plugin is designed to work with Spectrometer FITS files alone, and it comes with some simple analytical commands as well. See the Examples page for screen shots.

This plugin does not come up automatically. You must edit your ~/.sparrow file by hand. In the [Plugins] section include the line: Spectrometer: plugins.spectrometer.SpectrometerPlugin, and place Spectrometer in your Sort Order (ex: Sort Order: Focus Pointing Spectrometer)

GFM is an observors tool that has been designed to interact with current or past observations. This means that GFM relies on the existence of a ScanLog.fits in the projects top-level directory, and listens to the ScanCoordinator Manager when in online mode. Since engineers typically are recording only Spectrometer FITS files during their tests, and are not using the ScanCoordinator to produce a ScanLog.fits file, an additional step is required in order to read in their Spectrometer data using this GFM plugin. This step involves running a utility application, scanlogsim, to produce/update a ScanLog.fits file that can read by GFM. Follow the link to read more.

As spectra are plotted, information about each plot is printed in the console window. Each line is color coded to match the color of that spectra in the plotting window.

All user interaction for this plugin occurs in the right-hand side options panel. The browsing options for this plugin are simpler then those presented by the Spectral Line Plugin; this is due to the presummed absence of IF Manager and LO1A Manager FITS files. Check boxes allow inclusive selection of spectra to plot via Sampler Name, and Phase Name. In addition, there is a multiple selection drop list for selecting 1 to N integrations as well.

The options panel also includes several analytical tools as well. Simple differences can be made between spectra by entering the integer id numbers listed in the most recent console information and clicking 'Difference'. The user can also choose between computing a simple 'A-B' difference, or '(A-B)/A'. The average of all integrations for each combination of Sampler and Phase can also be plotted using the 'Average' button. The 'Median Filtering' button has not yet been implemented.

The options panel also includes three buttons and a radio box for plot viewing. The 'Views' radio box offers plotting Raw Power vs. Channels, and Lags vs. Channels. The 'Keep Zoom' toggle button will maintain the current zoom, even as new spectra are plotted. Using the unzoom command (mouse right-click, or through the tool bar) will bring the plot back to the original scale. The 'Overlay' toggle button can be used to overplot spectra from different integrations or scans. Finally, the 'Clear' button erases the plotting window.

Known Issues

Spectral Line

The most significant limitation to this plugin concerns online performance. Due to Network File System delays, backend files may take tens of seconds to update the latest integrations (unless the observor is logged into the backends host machine). As a result, the Spectral Line Plugin may miss integrations if the integration time is small enough. As a rough guideline, problems are rarely seen as integration times of 30 seconds or greater, but as the integration time drops below 10 seconds, integrations will start being missed.

Another known issue concerns the x-axis tick marks. At times the x-axis will label itself using an offset to be added to each tickmark. This style of labeling can be very hard to read. Remember that you can always drag the mouse to the area of interest in the plot, and read the exact coordinates in the lower left-hand corner. This cannot be reproduced regularly, and we are looking into it.

Spectrometer Engineering

The scanlogsim utility does not yet have the capability of updating a ScanLog.fits file as new device files come in. As a result, this plugin does not currently work in online mode.