May 2021

Cassiopeia A it’s an important object for radio astronomy, a supernova remnant located in Cassiopeia constellation with a flux of 2400 Jansky at 1420 MHz. For this article we used the SPIDER 300A radio telescope that, thanks to the 3 meter parabolic antenna with high precision WP-100 mount, high sensitivity H142-One receiver, and the advanced features of the RadioUniversePRO software,  is able to detect Cassiopeia A. The radio telescope is connected to the remote control room by using the Radio over fiber kit for SPIDER radio telescope that removes the normal gain loss because of cable length and improve even more performances of the radio telescope.

 

 

 

Cassiopeia A is a very interesting object to study since, in visible frequencies, it’s extremely weak since it’s hidden behind the interstellar dust of the Milky Way plane which absorbs the visible radiation. That’s why Cassiopeia A (also called Cas A) was identified in radio wavelengths only in 1947 (Cassiopea A was one of the first radio sources to be identified) and the optical counterpart was identified in 1950. Most probably Cassiopeia A has been generated by a supernova event (exploded about 11,000 years ago and that reached the Earth about 300 years ago) from sixth magnitude star 3 Cassiopeiae, that John Flamsteed cataloged by August 16, 1680. Cassiopeia A .

 

 

When we want to record weak radio signals coming from Cassiopeia A (this is valid for all the radio sources except for the Sun) we have to be sure that the radio telescope is correctly aimed to the right sky area: in fact we can’t directly see the object we want to study. In order to do so, we took advantage of the high pointing precision of the WP-100 mount of the SPIDER 300A radio telescope. Source Visibilities tab of RadioUniversePRO allows you to check the visibility of many radio sources and we used this feature to verify that Cassiopeia A had a good elevation from the ground. In fact we recommend to study radio sources that are least at 30 degrees from the ground. Then we made a double-click on Cassiopeia A row and SPIDER radio telescope automatically pointed at it. Before starting to record data, we used the BBC Tool feature of RadioUniversePRO to check for interferences in the 50 MHz bandwidth (centered at 1420 MHz) recorded by the SPIDER radio telescope. As you can see in the image below, the neutral Hydrogen line (1420 MHz) is clearly visible along with some artificial interferences. By using the BBC Tool feature of RadioUniversePRO we can easily remove the interferences  and allow the SPIDER radio telescope to record valid data without artificial radio signals.

 

 

Having correctly pointed the radio telescope and removed interferences, we started recording many results on Cassiopeia A. First of all we started capturing a Cross-Scan: this technique involves recording a transit in both Elevation and Azimuth, centered on the object. This way we get a graph of the intensity of the radio emission along a cross centered on the object and that allows to determine the maximum radio emission of Cassiopeia A. In order to perform this operation, we select the “TPI Plot” tab in RadioUniversePRO and we use the Cross-Scan feature. Here you can set the length of the scan, the separation of each record point and the integration time of each record point. The SPIDER radio telescope mount moves the antenna and the software creates a graph like the one you can see in the image below. We clearly noticed the increase in the recorded radio value caused by Cassiopeia A. In this way we also verified that the SPIDER radio telescope mount is perfectly aligned on the radio sources in the sky and that Cassiopeia A was perfectly framed.

 

 

Then, in order to highlight the 1420 MHz neutral Hydrogen emission line, we recorded the Cassiopeia A spectrum. We used the calibrated spectrum On-Off feature of RadioUniversePRO: the software automatically records data from the radio source (“on” position) and then calibrates with a point in the sky away from the radio source (“off” position): the result is a calibrated spectrum as you can see in the image below (for the left and right polarization) where the emission of the hydrogen line at 1420 MHz is clearly visible.

 

 

One of the most advanced features of RadioUniversePRO is the Mapping one and we used it to record a radio map of Cassiopeia A, by setting a capture area of 20×20 degrees, with 1 second of integration for each point and a separation between the points of 0.8 degree. As you can see in the image below, the map shows an increase in the signal at the map center, just where we expected Cassiopeia A to be.

 

 

By saving recorded data in FITS format (just like the professional radio telescopes) we can also extract the data that can be processed with different softwares, like the NASA FITS Viewer. The radio map captured by the SPIDER 300A radio telescope has been compared to an optical image, as you can see in the image below. It is easy to see how, in an area apparently empty of particular objects, the SPIDER 300A radio telescope instead detects a strong radio source, the supernova remnant known as Cassiopeia A in the radio sources nomenclature.

 

 

SPIDER is the radio telescope developed and designed by PrimaLuceLab in order to allow everyone to make real radio astronomy without the need of being a radio astronomer! Click here to discover the full line of SPIDER radio telescopes.

The Sun is one of the most interesting radio sources in the sky and solar radio emission can be studied by using SPIDER radio telescopes. The Sun not only emits visible light but also other frequencies in the electromagnetic spectrum, in fact you can feel the Sun heat on our skin, expression of infrared radiation. In this article with step-by-step guide, by using a 3 meter diameter SPIDER 300A radio telescope, we see how to detect radio waves coming from the Sun and generate various results (like radio images and transits) by using the RadioUniversePRO control software. We perform automatic pointing and tracking on the Sun, detection and removal of eventual artificial signal and capture of results.

 

 

The Sun emits radio waves for both thermal (due to its high temperature) and for non-thermal (for example synchrotron radiation when the electrons are forced in a spiral motion around magnetic field lines) emissions. For wavelengths greater than 1 cm (ie less than about 30 GHz), the solar radio emission is made up of two components: a constant one called “Quiet Sun” due to the heat of our star and a variable one called “Disturbed Sun” that varies over time and depends on the presence of sunspots or flares. SPIDER radio telescopes allow you record these emissions. Start RadioUniversePRO software and connect SPIDER’s mount and receiver. In the IF Monitor tab you will see the radio telescope data in real time, as you can see in the picture below.

 

 

Now select the “Source visibility” tab and double click on the “Sun” radio source. SPIDER radio telescope will automatically point the Sun. In order to verify the perfect alignment on the Sun, you can use the “Offset alignment” feature in the proper tab. Here you can select the proper parameters in order to request the radio telescope “scan” the sky around the Sun position and search for the point of the maximum radio emission, that will correspond to the real position of the Sun in the sky: this way the mount will per perfectly and automatically synced to the sky and will perfectly track and point any radio source. Press the “Start procedure” button to start, SPIDER radio telescope will automatically and precisely detect Sun position.

 

 

Now select BBC Tool tab and check for signal quality. Here you can see if you have interferences caused by artificial signals and easily remove parts of the spectrum, if needed. Please note that interferences caused by artificial signal vary upon your location and the direction pointed by SPIDER radio telescope so you need to check BBC Tools before starting your data recording.

 

 

Being sure that we’re perfectly aligned on the Sun and that we’re not recording artificial signals, we can now start recording data and producing results. Let’s start with a Cross-Scan of the Sun. This technique consists in moving the radio telescope creating a cross centered on the object and recording radiometric data for every point: this will allow us to determine the maximum radio emission. In order to perform this operation, we select the “Total Power Plot” tab in RadioUniversePRO and use the Cross-Scan feature, by selecting the length of the scan, the separation of every recording point and the integration time of every recording point. SPIDER radio telescope mount progressively moves the antenna position and RadioUniversePRO software creates a graph like this one one you can see in the picture below. Cross-Scan feature can also be used to calculate radio telescope parameters like the half power beam width (HPBW).

 

 

Since the SPIDER 300A radio telescope is perfectly aligned with the Sun, we can also keep tracking the Sun for a long period of time and use the TPI Plot feature of the Total Power Plot tab of RadioUniversePRO in order to check for possible variations of radio emission from the Sun. In the graph, every line corresponds to the radiometric value of every BBC filter that we selected in the previous step.

 

 

Now we produce a radio map, a real image of the Sun recorded in the radio frequencies. We select the “Mapping” tab where we can set all the recording parameters of the radio map. The SPIDER radio telescope will scan the sky area around the Sun, depending on the size of the radio map, the separation and the duration of data capture of each point that compose the map. The map will then be displayed by RadioUniversePRO using one of the different user-selectable color scales. In the image below, the result of the capture of the radio map of the Sun, with an area of 15 degrees of side. The effects of the lateral lobes that form the cross pattern around the central figure of the Sun are also visible.

 

 

 

Thanks to SPIDER radio telescope and RadioUniversePRO software, you have a set of data that you can easily compare with data recorded even by professional radio telescopes. Some sources available on the Internet:

Nobeyama Radio Observatory: http://www.nro.nao.ac.jp/en/

Australian Government – Radio and Space Weather Services – Learmonth Observatory: http://www.ips.gov.au/Solar/3/4

Ottawa 10.7cm radio flux: http://www.spaceweather.gc.ca/solarflux/sx-eng.php