3.4 Mapping a Radio Source

For all Unit 3 pages:

• Unit 3 Master Packet
• Unit 3 Student Master
• Unit 3 Teacher Master

For Unit 3.1

• Unit 3.4 Student Guide
• Unit 3.4 Teacher Guide

Objective:

You will use Smiley to map an astronomical radio source at a frequency of 1.42 GHz.

Background Knowledge

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

Pre-lab Activity

Print out (larger and try drawing contouring lines on the array of numbers. Start with the highest number and draw a circle 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 frequency of 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).

Procedure:

1. Login to Smiley. For information on how to use Smiley refer to Unit 2 Smiley Basics.
2. 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 scanning use Hand Paddle to find the peak intensity (Notice the box that displays the intensity for every point as it is plotted). In general the TARGET Coordinates should be close to the CURRENT Coordinates. Keep moving Smiley until you find the peak intensity. Record the peak intensity in the table below along with the CURRENT azimuth and altitude at which it occurs. Allow Smiley to keep scanning.
5. Fill in the top row and left-hand column of the table below with the azimuth – 6 degrees, 4 degrees, etc. Do the same for the altitude.
6. Mapping the Sun means that you need to measure the brightness across the disk of the Sun. Using the Hand Paddle set Smiley to 6 degrees of your peak intensity in both Altitude and Azimuth. Record the intensity in the table below.
7. 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.
8. 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.
9. Move Smiley +2 degrees in the Azimuth from the peak intensity still keeping your Altitude the same. Enter your results in the table below.
10. Move Smiley +4 degrees in the Azimuth from the peak intensity still keeping your Altitude the same. Enter your results in the table below.
11. Move Smiley +6 degrees in the Azimuth from the peak intensity still keeping your Altitude the same. Enter your results in the table below.
12. Continue moving Smiley using the Hand Paddle to adjust the altitude or azimuth and complete the table below.
13. From your set of measurements, construct a contour map.