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Introduction to the SRT
The SRT (small radio telescope) measures light collected. Specifically, the SRT collects
non-visible light in the radio range. In this project, you will measure the radio waves
coming from the sun and determine how much “energy” the sun is sending at these
wavelengths. You will take measurements every day using the SRT and compare these
to other data.
Getting familiar with the SRT
This section is a reference that explains how to do some key commands. For now, we
will focus on just a few things you will want to understand. Read through this
description, then try the practice activities at the end. You do not need to understand all
the commands now. A detailed description of the SRT software is given in the SRT
operator’s manual.
Command toolbar
The command toolbar across the top of the screen lists 15 buttons . . . from clear to Vane.
A picture of the command toolbar is shown below. The buttons are green when they are
being used. We will detail the purposes of nine of the buttons.
Stow
The stow button moves the SRT to the stow position. This position has the SRT pointing
east and low in the sky; it is considered the safest position for storing the SRT when it is
not being used. The SRT should be returned to the stow position after data collection.
Track
The track button allows the SRT to track objects in the sky. In other words, when the
track button is green, the SRT follows the specified object (Sun, moon, etc.) as its
apparent position in the sky changes. The SRT automatically tracks if a specific source is
selected.
Azel
Azel stands for azimuth and elevation. This button allows you to enter a specific azimuth
and elevation angle. After clicking the azel button, type the azimuth and the elevation
angle (separated by a space) in the text bar at the bottom of the screen.
Npoint
An npoint is used to make sure that the antenna is pointed in the correct direction. In an
npoint, the SRT is instructed to go to the sun. The SRT is programmed to know where
the sun is; however, it may be off by a degree or so. To check whether it is slightly off
and to correct for this, the SRT measures the energy (technically, power per area per
frequency) coming from where it thinks the sun is and also nearby. It scans around the
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location of the sun and corrects itself if it finds that it is not pointed at the place of
maximum energy. For example, if the maximum energy is found 1 degree away from
where the SRT believes the sun to be, the SRT corrects its pointing by 1 degree. The
npoint also returns a value which can be used as a measurement of the “energy” from the
sun.
Bmsw
This command stands for beamswitch. During beamswitch, the SRT switches between
looking at (“on”) the source and not at (“off”) the source. As a result, both data for the
source and comparison data are obtained. This command is appropriate for use with lowsignal sources such as the moon. The SRT would take data when pointed at the moon
and when pointed not at the moon and then you could compare these measurements.
Freq
This command sets the frequency at which the SRT will be centered. For example, if a
frequency of 1415 (the units are MHz, but we won’t worry about units for now) is
selected, the SRT will look at a number of frequencies which are centered around 1415.
After you click the freq button, enter the desired frequency by hand in the text box and hit
the enter key.
record
The button allows you to record the data the SRT takes in a data file. After you click
record, you will enter the desired name of the data file in the text box. All data files
should have “.rad” for an ending. For example, if you want to name the file “Test”, then
“Test.rad” should be entered in the text box. Hit the enter key. The file is now being
recorded in the SRT folder.
Rcmdfl
This command tells the SRT to run a command file. After the Rcmdfl button has been
activated, the file name must be entered in the text box. All command files should have
“.cmd” as an ending and should be saved as a text file. The entire command file name—
including “.cmd”—should be entered in the text box. Hit the enter key.
Vane
The vane button calibrates the SRT. To use the vane command, point the SRT at an
“empty” part of the sky by using the azel button. Then, click Vane. An absorber will
swing down and block the receiver. This effectively allows the SRT to measure a zero
value. Once the SRT has finished calibrating, a tsys is displayed on the right side of the
screen.