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Difmap 载入数据

发表于 更新于 分类于 ， ， 阅读次数： Disqus： Valine：

载入数据

现在我们已经在Difmap环境中了，将有一个如下的提示符：

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0>

现在我们开始输入第一个命令，用于载入数据。

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0> observe YOUR_DATA

提示：这里可以简单地输入obs然后使用Tab即可补全剩余的命令。这项技术有助于在整个Difmap的使用过程中节省宝贵的时间。随时随地掌握这些技巧，可以提升软件使用体验^_^。
此时应该可以看到下述输出了。

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Reading UV FITS file: 3C219.L(A.butDefinitelyB).postProc.uvf
AN table 1: 2454 integrations on 406 of 406 possible baselines.
Apparent sampling: 0.732128 visibilities/baseline/integration-bin.
Found source: 3C219

There are 2 IFs, and a total of 2 channels:

 IF  Channel    Frequency  Freq offset  Number of   Overall IF
      origin    at origin  per channel   channels    bandwidth
 ------------------------------------------------------------- (Hz)
 01        1    1.385e+09      2.5e+07          1      2.5e+07
 02        2    1.665e+09      2.5e+07          1      2.5e+07

Polarization(s): RR LL RL LR

Read 307 lines of history.

Reading 5835496 visibilities.

该命令详细列出了源的相关信息。检查所有的Ifs，通道、频率等都是正确的。如果出现了诸如“”的错误，你可能需要返回AIPS来确定输出了正确的数据。如果需要得到更多的信息，可以输入下述命令：

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0> header
UV FITS miscellaneous header keyword values:
 OBSERVER = "AC149"
 DATE-OBS = "1986-05-18"
 ORIGIN   = "AIPSlocalhost    LOCALHOST            31DEC11"
 TELESCOP = "VLA"
 INSTRUME = "VLA"
 EQUINOX  = 2000.00

Sub-array 1 contains:
406 baselines   29 stations
2454 integrations    4 scans

 Station  name               X (m)            Y (m)             Z(m)
   01     VLA:_N28      -1.600864e+06    -5.041770e+06     3.557965e+06
   02     VLA:_W28      -1.604866e+06    -5.046527e+06     3.552962e+06
   03     VLA:_N16      -1.601062e+06    -5.041898e+06     3.556058e+06
   04     VLA:_W24      -1.604009e+06    -5.045468e+06     3.553404e+06
   05     VLA:_W12      -1.602045e+06    -5.043040e+06     3.554428e+06
   06     VLA:_W04      -1.601316e+06    -5.042139e+06     3.554808e+06
   07     VLA:_W20      -1.603250e+06    -5.044530e+06     3.553798e+06
   08     VLA:_W36      -1.606842e+06    -5.048973e+06     3.551913e+06
   09     VLA:_W08      -1.601614e+06    -5.042508e+06     3.554652e+06
   10     VLA:_E32      -1.597053e+06    -5.036606e+06     3.553059e+06
   11     VLA:_OUT      -1.601185e+06    -5.041978e+06     3.554876e+06
   12     VLA:_N36      -1.600691e+06    -5.041658e+06     3.559632e+06
   13     VLA:_E36      -1.596128e+06    -5.035403e+06     3.552652e+06
   14     VLA:_W16      -1.602593e+06    -5.043718e+06     3.554141e+06
15     VLA:_N32      -1.600781e+06    -5.041716e+06     3.558761e+06
   16     VLA:_N20      -1.601005e+06    -5.041861e+06     3.556610e+06
   17     VLA:_E12      -1.600416e+06    -5.040979e+06     3.554536e+06
   18     VLA:_E20      -1.599341e+06    -5.039580e+06     3.554065e+06
   19     VLA:_E28      -1.597900e+06    -5.037707e+06     3.553432e+06
   20     VLA:_E24      -1.598663e+06    -5.038699e+06     3.553767e+06
   21     VLA:_N08      -1.601148e+06    -5.041953e+06     3.555236e+06
   22     VLA:_N04      -1.601174e+06    -5.041970e+06     3.554987e+06
   23     VLA:_E08      -1.600802e+06    -5.041479e+06     3.554706e+06
   24     VLA:_E16      -1.599926e+06    -5.040341e+06     3.554320e+06
   25     VLA:_E04      -1.601069e+06    -5.041826e+06     3.554825e+06
   26     VLA:_N12      -1.601110e+06    -5.041929e+06     3.555597e+06
   27     VLA:_N24      -1.600930e+06    -5.041813e+06     3.557330e+06
   28     VLA:_W32      -1.605809e+06    -5.047694e+06     3.552459e+06
   29     VPT:_OUT      -1.601185e+06    -5.041978e+06     3.554876e+06

There are 2 IFs, and a total of 2 channels:

 IF  Channel    Frequency  Freq offset  Number of   Overall IF
      origin    at origin  per channel   channels    bandwidth
 ------------------------------------------------------------- (Hz)
 01        1    1.385e+09      2.5e+07          1      2.5e+07
 02        2    1.665e+09      2.5e+07          1      2.5e+07

Source parameters:
 Source: 	 3C219
 RA     = 	 09 21 08.548 (2000.0)	 09 20 14.260 (apparent)
 DEC    = 	+45 38 57.920        	+45 42 30.877
Antenna pointing center:
 OBSRA  = 	 09 21 08.548 (2000.0)
 OBSDEC = 	+45 38 57.920

Data characteristics:
 Recorded units are UNCALIB.
 Recorded polarizations: RR LL RL LR
 Phases are rotated 0 mas East and 0 mas North.
 UVW coordinates are rotated by 0 degrees clockwise.
 Scale factor applied to FITS data weights: 1
 Coordinate projection: SIN

Summary of overall dimensions:
 1 sub-arrays, 2 IFs, 2 channels, 2454 integrations
 4 polarizations, and up to 406 baselines per sub-array

Time related parameters:
 Reference date: 1986 day 249/00:00:00  (1986 Sep 06)
 Julian Date: 2446679.50, Epoch J1986.678
 GAST at reference date: 22 59 10.041
 Coherent integration time   = 0.0 sec
 Incoherent integration time = 0.0 sec
 Sum of scan durations = 26460 sec
 UT range: 249/09:51:21 to 249/23:30:22
 Mean epoch:  JD 2446680.195 = J1986.680

此时在启动目录会生成一个log文件difmap.log，这个文件记录了你在DIFMAP交互环境中输入的所有命令。 It will also include selected output lines though they will be preceded by a ! in order to comment them out.
这个log文件可以通过一种脚本的形式来使用，可以通过在交互命令中输入 @difmap.log来执行这个脚本。
但需要注意的是这个脚本无法与PGPLOT进行交互，所以交互式的flagging都不会发生。所以要特别注意这一点。

The next step is to choose the Stokes parameter you are interested in:

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0> select i

	Where i refers to the Stokes I parameter. You can select any Stokes parameter (e.g. select q or u) to work with.

代码参考 https://www.github.com/shaoguangleo/radio_astronomy

处无为之事，行不言之教；作而弗始，生而弗有，为而弗恃，功成不居!

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