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Receiver and LO Visualisation

At the top of the Spectral Editor, the graph displays the frequencyrange within which ALMA can observe, the available ALMA frequencybands, the atmospheric transmission curve, and the frequencies andbandwidths of the spectral lines or continua. All frequencyinformation is displayed both in the observed (sky) frame (top) and inthe rest-frame of the source (bottom). If some frequency informationhas been entered, the selected ALMA band will turn blue whilst theremainder of the bands remain grey. This will also cause two verticalrectangles to appear which represent the upper and lower sidebands ofthe receiver - these are located symmetrically around the first localoscillator frequency (LO1).

Spectral windows which are defined by the user must be able to fitinside the sidebands, based on both their positions and widths. If oneor more spectral windows are defined which cannot be fit, thesidebands will be displayed in a grey colour and red errors willappear in the Spectral Setup Errors panel. The frequencies ofthe spectral windows will need to be redefined in order that a tuningsolution can be found. This can be experimented with by dragging thesidebands by grabbing LO1 with the mouse - if the sidebands are grey,the sidebands can be moved and will stay where they are left. Inconjunction with the Select Lines to Overlay... button it ispossible to see which lines it would be possible to observe with asingle tuning.

If spectral windows have been defined which do fit, then the sidebandswill be displayed in yellow and will move to reflect the tuningsolution that was found automatically by the OT. The Spectral Setup Errors panel will also be empty. The sidebands can still bedragged, but as soon as the mouse is released they will spring back totheir original position. This is to emphasise that moving thesidebands does not change the range of frequencies that will beobserved by ALMA. This is set purely by the entered spectral windowinformation which must of course be valid.

Below the graph there are tick boxes that enable the user to selectwhether the ALMA receiver bands, the transmission curve and overlaidspectral lines should be displayed. The latter are chosen using the Select Lines to Overlay... button which launches the SpectralLine Selection Tool (Section  5.6 ). The Viewportbuttons beneath the tickboxes can be used to fine tune the display.



Subsections
next up previous contents index
Next: Zoom and Pan in Up: The Visual Spectral Editor Previous: Overview of the Graphical   Contents   Index
The ALMA OT Team, 2011 May 20