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ASTRO

The software ASTRO can be used to simulate and visualize the receiver/correlator configuration. Astronomers are urged to download the most recent version of GILDAS at http://www.iram.fr/IRAMFR/GILDAShttp://www.iram.fr/IRAMFR/GILDAS to prepare their proposals.

The previous LINE command has been replaced by several new commands (see internal help). The behavior of the LINE command can be changed by the SELECT BURE 1995|2000|2006|2013|2015 command. Default is 2015, equivalent to the new SELECT NOEMA command.

The following ASTRO command will produce a plot of the frequency range covered by WideX and showing the four IF windows of which two must be connected to the narrow-band correlator (an example is shown in Fig. [*]):

 ASTRO\LINE name frequency band [/FIXED_FREQ|/ONGRID]

where

$\circ$
name is a line name to label the plot.
$\circ$
frequency is the tuning frequency in GHz.
$\circ$
band is the sideband: LSB or USB.
$\circ$
/FIXED_FREQ: This option can be used to ignore the 500MHz spaced tuning grid
$\circ$
/ONGRID: This option centers the line frequency automatically on the IF tuning grid

The two IF processor inputs for the narrow-band correlator and the setup of the spectral units are selected by the two commands

 ASTRO\NARROW Qi Qj /RECEIVER Band_Number
 ASTRO\SPECTRAL iunit bandwidth fcent /NARROW Narrow_input -
                                          [/BAND Mode] -
                                          /RECEIVER Band_Number

where

$\circ$
Qi Qj are the two 1GHz wide ``quarters'' to be analyzed by the narrow-band correlator (see Sect.[*] for more details).
$\circ$
Band_Number is the receiver band to which the unit should be connected (1=3mm, 2=2mm, 3=1mm).
$\circ$
iunit is the correlator unit number (1 to 8).
$\circ$
bandwidth is the bandwidth of the corresponding correlator unit in MHz (20, 40, 80, 160 or 320).
$\circ$
fcent is the center frequency (in MHz) of the correlator unit in the third IF (100-1100MHz).
$\circ$
Narrow_input is the IF output (1 or 2).
$\circ$
Mode is used to indicate the sideband code: SSB mode or DSB. The DSB mode provides twice as many channels as the SSB modes for the same bandwidth.

Figure: Example of spectral coverage by the narrow-band correlator, as produced by the ASTRO LINE command. Possible contamination by instrumental interferences are indicated in green.
\includegraphics[width=\textwidth]{noema-intro3}

A session to design the above correlator setup (shown in Fig.[*]) could be:

LINE HCO+-HCN 87.00 LSB 6500    ! Define the receiver tuning. ASTRO displays
                                ! the full 3.6 GHz frequency coverage by WideX.
NARROW Q1 Q3                    ! Selects the 4.2GHz - 5.2GHz and 6GHz - 7GHz windows 
                                ! of the 4-8GHz IF1 band. Polarization is HOR HOR. 
SPECTRAL 1 160 1020 /NARROW 1   ! Correlator unit #1 covers the [940,1100] IF3 band 
                                ! on the first IF input (4.2GHz - 5.2GHz).
SPECTRAL 2  20  210 /NARROW 1   ! Correlator unit #2 samples a narrow line centered at
                                ! 210MHz in the IF3 band of the first correlator input.
SPECTRAL 3  20  770 /NARROW 1
SPECTRAL 4 160  350 /NARROW 1
SPECTRAL 5 160  475 /NARROW 1
SPECTRAL 6  40  750 /NARROW 2   ! Correlator unit #6 covers the [730,770] IF3 band on 
                                ! the second IF input (6GHz - 7GHz).
SPECTRAL 7 320  400 /NARROW 2
SPECTRAL 8 320  925 /NARROW 2


next up previous contents index
Next: Sensitivity Up: Correlators Previous: Spectral units of the   Contents   Index
Gildas manager 2018-10-23