The Ideal Radio Telescope
Joachim Köppen Kiel Oct. 2014
Some quick and basic explanations:
The Ideal Radio Telescop applet is a simulation of such a perfect but
non-existing instrument. With it we can inspect the radio sky at any
frequency (between about 1 and 30 GHz) as seen with a parabolic dish
of any diameter and with a receiving system of any system temperature.
Continuum emission from the quiet Sun, the Moon, an Earth-temperature
flux calibration source, and a number of galaxies and nebulae as well
as the thermal emission from the Earth atmosphere are simulated. For
a number of real telescopes realistic noise can be added to the data.
The applet is organized in several pages which are accessed by the
top buttons. They are
The following steps guide you to some basic operations:
- Telescope allows to define the parameters of the instrument
- Operate is the main page to orient the telescope
and to take measurements
- Skyview presents a view of the sky, with the actual
positions of the Sun, the Moon, the Galactic Plane (Milky Way)
(blue curve with filled dot for the Galactic Centre and open
circles for (90, 180, and 270° longitude) and the Clarke Belt of
geostationary satellites (green curve)
- (Spectrum not yet implemented)
- (Scan permits to take measurements while scanning
an arc in the sky - not yet implemented)
- (Map would scan a rectangular region in the sky to
make a radio image - not yet implemented)
- Output is a feature of the Trainer applet only.
Here we can grab the recorded measurement data, which
is normally written into a file.
- (Batch is a feature to be done, to control the instrument
by a sequence of commands ...)
- Telescope page shows the parameters of the telescope:
one can change the geographical position of the observer,
the sky position of the flux calibrator, and the format of
the output data. There is a Choice between a number of real
telescopes, which set the frequency, diameter and system
temperature. When modifying the frequency, diameter, HPBW or
antenna gain, hit the enter key - the green field indicates
from which datum the other two are computed.
NOTE: click the accept settings button to make your
parameters valid for the telescope
- Operate page:
- The current position is indicated in the two fields
for Azimuth and Elevation in the centre. Below are
the corresponding fields to enter a desired position.
The button Goto will start the movement.
- The button "Az/EL" can be used to switch the display
between "Az/El", "RA/Dec", and galactic coordinates
- several Buttons permit to orient
the telescope: goto Calibrator
goto Astra 1 will start the repositioning.
Sun now and Moon now will only display
the positions of the bodies
- There is also a Choice to select a celestial object:
this will display the present or the future position, with
the number of seconds specified.
- A position can also be entered in the Az/El fields.
Hitting the 'Enter' key will start the movement.
- Likewise, horizontal and vertical offsets can be applied
to the presently used position. Hit the 'Enter' key to
effect repositioning. Note that the horizontal offset
is in proper degrees, and that the azimuth offset is
- Start, Stop, Resume
control the measurements and their recording.
- As long as the measurements take place, we cannot change
the vertical scale of the chart display by using the scroll
bars on its left. Otherwise this could cause problems in the
refreshing of the plot. To avoid these troubles, we simply
Stop the measurements briefly, adjust the display
to our wishes, and then Resume the measurements.
- The main chart gives a tracing of the signal strength as
a function of time. To its right a bargraph gives an analog
display of the current measurement, whose value is also
- SkyView page shows the sky above the telescope:
there are a few features (buildings, trees) which limit
the view of the horizon. The light blue area is the region
into which the telescope is permitted to be operated.
Sun, Moon, and the flux calibrator source are marked
by symbols. The present position is indicated by a small
- The green curve marks the Clarke Belt of geostationary
satellites: as these constitute strong emission in the 10 GHz
band, it is not advisable to try to observe the Moon when
it is close to the Belt.
- The blue curve indicates the middle
line through the band of the Milky Way, the Galactic Plane.
Note that the line and continuum emission from this region
is NOT (yet? ;-) simulated.
- The yellow fields on the left are buttons to change the
time of the display, and of the operation of the telescope.
Thus it is possible to simulate observations at other
- Clicking on the display will cause this position's coordinates
to be displayed on the right hand side. If this happens to be
on or very close to a source (red dots) the name of the source
is displayed as well. Clicking on the yellow
Goto field will cause the telescope to move to this
- Output is a text window, into which the ongoing
measurements are recorded. This is in the same format as the
text files from the real telescope. These data can be
simply copied and pasted into a text editor and then stored
into a file on your own computer.
- Clicking a Start button will wipe the previous data
and start to fill this window with the current data.
- all other options are not yet implemented.