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Lab 4: Mapping a Radio Source

Introduction:

Have you ever seen a contour map of a mountain like Mt. Everest shown here?

Below is the 3-D image that shows a mountain-like feature:

If you look at this same object from overhead, it likes like this:

Now if you take the shading out, just leave the lines, you will have a contour map that looks like this:

The contour map shown above is nothing more than a grid of numbers, where numbers of the same value are connected together.  Sounds like connect-the-dots, doesn’t it? The grid of numbers that make up the map above are:

782

791

792

833

834

868

900

824

846

797

782

830

799

942

853

944

873

849

826

797

848

949

880

1180

961

1234

930

973

810

746

957

1139

1103

1663

1286

1731

1121

1238

838

756

1069

1363

1426

2173

1758

2430

1498

1567

932

799

1177

1551

1825

2707

2415

2971

1505

1882

1045

890

1202

1632

2163

2872

3029

3223

2449

2040

1250

933

1148

1556

2277

2747

3291

3162

2701

1977

1308

920

1018

1372

2170

2302

3185

2694

2632

1768

1310

880

912

1109

1850

1736

2720

2007

2301

1470

1173

840

Print out and try drawing contouring lines on the array of numbers.  Start with the highest number and draw a cirlce around it.  That will be the peak value.  Then draw a closed curve around the next highest set of numbers for the next contour.

The contour lines show the peak and the valleys. In fact the object above is actually the remnant of a supernova!  The map was done at PARI at a frequencyof 1.42 GHz. The map shows the intensity of the supernova remnant over an area on the sky of 1 degree x 1 degree - larger than the moon!  (The moon covers about 1/2 degree diameter on the sky).

You will use Smiley to make an astronomical radio source at a frequencyof 1.42 GHz.

Procedure:

  1. Login to Smiley.  For information on how to use Smiley see the Smiley Users Manual.
  2. You will be mapping the Sun. In Map mode either click on the Sun or select the Sun from the Control Panel Drop Down List.  Now click on GO.
  3. In Continuum mode set your IF GAIN to around 17 and make sure your Base Frequency is set to 1.42 GHz.
  4. Click on Begin Scan.  While scaning use Handpaddle to find the peak intensity (Notice the box that displays the intensity for every point as it is plotted).  This takes practice.  In general the NEW Coordinates should be close to the CURRENT Coordinates.  Keep moving Smiley until you find the peak intensity and record them below.

Peak Intensity

Azimuth

 

Altitude

 

  1. Mapping the Sun means that you need to measure the brightness across the disk of the Sun. Using the Handpaddle set Smiley to -6 degrees of your peak intensity in both Altitude and Azimuth. Record the intensity.
  2. Now move Smiley -4 degrees in the Azimuth from the peak intensity and keep the Altitude the same (-6 degrees from peak intensity). Enter your results in the table below.
  3. Next, move Smiley -2 degrees in the Azimuth from the peak intensity still keeping your Altitude the same.  Enter your results in the table below.
  4. Move Smiley +2 degrees in the Azimuth from the peak intensity still keeping your Altitude the same.  Enter your results in the table below.
  5. Move Smiley +4 degrees in the Azimuth from the peak intensity still keeping your Altitude the same.  Enter your results in the table below.
  6. Move Smiley +6 degrees in the Azimuth from the peak intensity still keeping your Altitude the same.  Enter your results in the table below.
  7. Now move Smiley -6 degrees in the Azimuth from peak intensity and move Smiley -4 degrees in Altitude from the peak intensity. Enter your results in the table below.
  8. Follow the same steps moving the Azimuth from -4, to -2, to +2, to +4 and to +6 degrees from your peak intensity while keeping the Altitude at -4 degrees from your peak intensity and record your results in the table below.
  9. Repeat step 10, this time with your Altitude at -2 degrees from your peak intensity. Enter your results in the table below.
  10. Repeat step 10, this time with your Altitude at +2 degrees from your peak intensity. Again record your results in the table below.
  11. Repeat step 10, this time with your Altitude at +4 degrees from your peak intensity. Again record your results in the table below.
  12. Repeat step 10, this time with your Altitude at +6 degrees from your peak intensity. Again record your results in the table below.

Sun Intensities

 

Az = -6 Degrees

Az = -4 Degrees

Az = -2 Degrees

Az = +2 Degrees

Az = +4 Degrees

Az = +6 Degrees

Alt = -6 Degrees

 

 

 

 

 

 

Alt = -4 Degrees

 

 

 

 

 

 

Alt = -2 Degrees

 

 

 

 

 

 

Alt = +2 Degrees

 

 

 

 

 

 

Alt = +4 Degrees

 

 

 

 

 

 

Alt = +6 Degrees

 

 

 

 

 

 

  1. From your set of measurements, construct a contour map.  Feel free to use any software you may have to also draw the contours.

Discussion:

  1. Does your map show a central peak and some structure? Why is the central peak off center?
  2. What is the area on the sky, in degrees, that you have mapped?
  3. Will every object have the same structure? What might the map look like if you used more points more closely spaced?