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Open-use_program/aobs

4. Parameters of "Scan Table" in Line Observations†

4.1 Common parameters†

• File Name: Name of "Scan Table" to save.
• 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)

4.2 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 position.
• 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.

4.3 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