4. Parameters of "Scan Table"

4.1 Line observation

4.1.1 Common parameters

Fig 4.1 Scan Table Window

File Name :

On Positions

Scan Pattern : Select a scan pattern from the list shown by pushing the button. A window to set parameters appears except for Center (one-point).

Center (one-point) :

To observe the coordinate of one source position defined in "Source Table".

5 Points : To observe 5 (or 9) points like a cross. This pattern is mainly used for pointing.

Strip : To observe equally spaced points along a strip.

Map (single-grid) : To observe a rectangular area with a single grid spacing.

Random Positions : To observe random positions. Coordinates of 40 ON positions can be defined.

Spiral : To observe a square area with a single grid spacing like a spiral from the center.

OTF : To observe a rectangular area with On-The-Fly (OTF) method.

Integration Time : Integration time for ON position.

On Point Numbers : Numbers of start point and end point of ON positions. If you observe all ON positions defined in Scan Pattern, enter "1-total number of ON positions". You can observe some specified ON positions among the positions defined in Scan Pattern by using this parameter.

Off/Calib Positions

Coordinate System : Coordinate system for OFF positions.

Coordinate Mode :

Definition of OFF positions.

offset from center :

Offset from the coordinate of a source defined in "Source Table".

absolute value : Absolute value on the specified coordinate system.

Coordinate Values (1) - (4) :

Coordinates of OFF positions. 4 OFF positions can be defined. For frequency switching and beam switching, OFF position (1) is used for calibration.

Integration Time :

Integration time for OFF position.

Sequence :

Observation sequence is defined by On Point Numbers, Sequence Pattern, and Number of Sequence (see examples).

Sequence Pattern : Sequence pattern of ON positions (*) and OFF positions (1 - 4).

Number of Maps : Total number of scan per one ON position.

Calibration :

Parameters for intensity calibration.

Calibration Mode :

Select a calibration system for intensity calibration.

R-SKY :

Default

Integration Time :

Integration time for calibration. In general, this is set to be the same as the integration time of ON position.

Interval : Number of Sequence Pattern between intensity calibrations. Typical value of the interval time of the calibration is 10-20 min. You should decide this parameter considering the weather condition.

Switching Mode Options :

You can use only position switching mode.

Frequency Switch (Not available)

4.1.2 Scan pattern

5 Points

Fig 4.11 5 Points Window

Observation Mode : For pointing observation, select pointing.
Coordinate System : Coordinate system of scan.
Number of Positions : Number of ON positions. Since the center is observed twice in one cycle, total number of ON positions is 6 for 5 points and 10 for 9 points (9 points observation is not available now).
Grid Spacing 1 : Position offset (of the inner points for 9 points) from the center.
Grid Spacing 2 (for 9 points) : Position offset of the outer points from the center.
Position Angle : Position angle of scan on the specified coordinate system. (+ : CCW)

Fig 4.12 Scan pattern of the above Scan Table.

Strip Scan

Fig 4.4 Strip Scan Window

Coordinate System : Coordinate system for ON positions.
Number of Grid : Number of ON position.
Grid Spacing : Grid spacing of ON positions. You can enter only positive (+) value.
Position Angle : Position angle of a strip of ON positions on the specified coordinate system. (+ : CCW)
Reference Position : Coordinates of the reference position (*). The origin is the coordinate of a source defined in "Source Table".

Fig 4.5 Scan pattern of the above Scan Table.

Map (single-grid)

Fig 4.6 Map (single-grid) Window

Coordinate System : Coordinate system for ON positions.

Number of Grid: Grid numbers along X and Y axes. Total number of ON positions must be less than 10000.
Grid Spacing : Grid spacing of X and Y directions. Scan direction is defined by +/- (A positive (+) value is recommended because it has some bugs when a negative value (-) is entered).
Initial Direction : Initial direction of scan.
Position Angle : Position angle of a map on the specified coordinate system. (+ : CCW)
Reference Position : Coordinates of the reference position (*). The origin is the coordinate of a source defined in "Source Table".

Fig 4.7 Scan pattern of the above Scan Table.

Random Positions

Fig 4.10 Random Position Window

Coordinate System : Coordinate system for ON positions.
Point (1) - (20) : Coordinate of ON positions. 20 ON positions can be defined.

Position Angle : Position angle of a map on the specified coordinate system. (+ : CCW)

Spiral Scan

Fig 4.13 Spiral Scan Window

Coordinate System : Coordinate system for ON poisition.
Number of Grid : Grid number (N) of one side of map from the reference position (*). The total number of one side of map will be set to be 2N+1.
Grid Spacing : Grid spacing of ON positions.
Spiral Direction : Initial direction of scan.
Position Angle : Position angle of initial direction of scan. (+ : CCW)
Reference Position : Coordinate of the start position. The origin is the coordinate of a source defined in "Source Table".

Fig 4.14 Scan pattern of the above Scan Table.

OTF

Detailed information is here.

Fig 4.15 OTF (raster) Window

Coordinate System : Coordinate system for ON poisition.
Scan :
dX0, dY0 : Coordinate of the start point of a map (not include Approach).

Direction : Direction of scan (X or Y).

Length : Length of main scan path. Approach is not included. Scan direction is defined by +/- (cf. Fig 4.16).

Spacing : Spacing between scan paths. Direction of the next scan path is defined by +/-.

Begin-End : Numbers of start scan path and end scan path.

Position Angle : Position angle of a map on the specified coordinate system. (+ : CCW)

Time :
Approach : Time for acceleration.

Scan : Scan time of main scan path. Scan speed of the antenna is Scan Length/Scan Time. The typical scan speed is 10-20 arcsec/s.

Transit : Transit time to start point of the next scan path.

Return : Time to return to the start point.

Fig 4.16 Scan pattern of the above Scan Table.

4.1.3 Tips

Total number of ON position

Center (one-point) : 1
Map (single-grid) : X Grid Number × Y Grid Number
Map (multi-grid) : (X Grid Number× Y Grid Number : Smalll Grid) × (X Grid Number × Y Grid Number : Large Grid)
Five points : 6 or 10
Spiral scan : N = (Side Grid Number)² or {(INT)(Area Side Length / Grid Spacing)}²

   If N = even,
   N = (Side Grid Number + 1)² or {(INT)(Area Side Length / Grid Spacing) + 1}²

Observation sequence

e.g.1) On Point Numbers : 1-4
          Sequence Pattern : 1**
          Number of Sequence : 2
               OFF1, ON1, ON2,
               OFF1, ON1, ON2,
               OFF1, ON3, ON4,
               OFF1, ON3, ON4

e.g.2) On Point Numbers : 1-4
          Sequence Pattern : 1**1**
          Number of Sequence : 2
               OFF1, ON1, ON2, OFF1, ON3, ON4,
               OFF1, ON1, ON2, OFF1, ON3, ON4
e.g.3) On Point Numbers : 2-6
          Sequence Pattern : 1**2**
          Number of Sequence : 2
               OFF1, ON2, ON3, OFF2, ON4, ON5,
               OFF1, ON6, ON2, OFF2, ON3, ON4,
               OFF1, ON5, ON6

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