AST460: Assignment 3
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(Sep 23 2012)

(1) One of the most famous radio telescopes in the whole world is
the 305-m Arecibo radio telescope located in Puerto Rico. 

Read Dr. D. Altschuler's article (provided on the class web site) 
about the history of the Arecibo Observatory. Answer briefly the following questions:
1.1 Why was Arecibo's primary reflector built as a spherical surface
and how did it use to focus radio waves in early days?
1.2 What were the main changes brought by the 2nd upgrade of the Observatory
and why?
1.3 List at least 3 important scientific achievements obtained with Arecibo observations
(feel free to use other sources but provide a full reference).


(2) Use the SRT Simulator in the classroom to produce the following:

2.1 Point at the Sun and run the npoint function which 
performs a 5 by 5 map around the Sun.
Pick another obvious source in your field of view, e.g. PULSAR,
Cass, test, GNpole and repeat npoint.
Notice how only by looking at the Sun you get a very nice 2d plot
of telescope's response pattern. This is because we need both a very strong and a point-like
source for such measurements, therefore more extended and/or weak sources will 
not give suitable results. Provide a printout (screen shot) of your plots.

2.2 Set central frequency to that of the HI line and select
the highest frequency resolution observing mode.
Open a test data file to save your observations.
Then point the telescope in the Galactic anti-center direction (l,b) = (180,0).
(in case this position is not visible feel free to use (l,b) = (90,0))
Take and print a screen shot.

2.3 Use the highest frequency resolution mode, it has a total frequency coverage of
1.21875 MHz over 156 frequency bins.
Using the (non-relativistic) Doppler shift equation 
[(nu_rest - nu)/nu_rest = V/c], we can convert the frequency 
axis into the radial velocity along the line of sight therefore measuring how fast
are observed objects moving away/toward us.
What will be the velocity resolution of your spectrum after this conversion (or
how wide will be the velocity bins in your spectrum)?
If your spectrum is centered on the HI line, what velocity range will it cover?


To take a screen shot: hold simultaneously
command, shift, and number 4 keys on your iMac keyboard.
This will save a screen shot as a file on your Desktop.
Open this file (double click), and go under File --> Print and select
floor3 as your printer, then click print. This will send your printing job to
the printer called "floor3" located on the same floor around Room 3511.
Let me know if you have problems finding the printer or doing this.


Printouts should be included in your homework.
The assignment is due at the next class meeting.