An antenna, a radio and a microprocessor: witch kind of observations is possible in meteor radio astronomy? (Radar Astrofilo Meteorico Bolognese)

A meteor scatter observatory At an altitude of around 100 km begins the bremsstrahlung by friction of meteoric particles. This generates a long, narrow cylinder of ionized molecules of a very short time duration Meteors and radio meteors

Like a radar This cylinder behaves like a reflective object for radio waves, in the same way of aircraft and satellites. The meteors observation via radio waves is usually achieved by "traditional" radar The professional radars, thanks to the fact that they transmit pulsed signals and to the fact that use multiple antenna arrays are able to calculate meteors size, speed, direction and position in the sky.

Amatorial radio observatory Like others european observers also RAMBo uses a military radar transmitter that is continuously on air in VHF at great power: it is located in Graves, near Dijion, in France. Advantages: Cheap. High power transmitter Disadvantages: Unknow characteristics and behaviour of the transmitter Radio interference

RAMBo receiving set up 500 Km of distance imply 25° dec A directive antenna (10 elements Yagi). It means: high gain and narrow field of view. Roughly over the Matterhorn A short cable

The radio receiver High sensitivity AM radio setup SSB tuned (Single Side Band) about 1000 Hz below the Graves carrier automatic gain control (AGC) disablited The RAMBo purpose is the output audio signal analysis.

The audio output Normally the audio signal is a continuous rustle (chaotic noise). Overlying this signal we can occasionally listen three different kinds of sound: 1) Meteoric echoes 2) Aircraft and satellites echoes 3) Electrical discharges The worse enemy!!!

RAMBo 6 In order to avoid electrichal discharge only the sixth RAMBo version has finally solved the problem We simultaneously analyze amplitude and frequency through Arduino With the frequency analysis we can discriminate meteor echoes.

Echoes analysis An overdense meteor echo in literature, and a RAMBo ones All the data we have are: - Progressive event number - Hourly number - Date and time (UT) - Echo length (milliseconds) - Echo amplitude (millivolts) - Rise time All these data are recorded in a log file

The results RAMBo records about 2500 meteors/day; the sixth version increase 3 times. 1) The overdense meteors (echoes longer more of 800 ms) are about 1%, according to data in literature. 2) In the days without meteor showers it is noticeable the typical sinusoidal sporadic meteors trend, with the maximum at 6 and the minimum at 18 Local Time. 3) In case of swarms we can easily see the beginning time, the maximum and the end. 4) We also can evalue the shower intensity, referred to the standard sporadic trend.

A shower analysis Quadrantidi 2016 seen from Bologna The shower HR (Hourly Rate) is twice the sporadic trend.

A shower analysis The echoes duration is proportional to the meteors masses. So we can evaluate the mass trend. Here we see the masses average trend. It seems superimposable with the HR ones but they represents two completely different data.

A shower analysis With an apposite program we can calculate the RZHR (RAMBo ZHR) a sort of zhr based on RAMBo data. The green dotted line is the radiant high on the horizon The red line is the expected time for the shower maximum. We can evaluate time and duration of the shower, and also his bipolar structure. We have seen the same bipolar structure for other showers (e.g.Geminidi)

Future developments A meteor scatters observatory can observe night and day, with and without moon, with good and bad weather but it can’t observe a swarm if its radiant is under the horizon. At least for one hemisphere we need almost three observatories to see a radiant ever.

The Marsadl (Meteors Analyzer by Radioreceiver, Sound Analyzer and Data Logger) The RAMBo6 experience has been thought as an example of that “Internet of Things” (IoT) that simplify in various fields the feasibility of many projects. So it leads us to propose this low cost and simple project as an idea for make a meteors scatter observers network. What is needed for every observer: The existence hundreds of kilometers away of a VHF transmitter continuously on air, is it military or television which carrier is tunable in amplitude modulation. An Yagi directive antenna (from 6 to 10 elements) with vertical polarization mount in a fairly unobstructed area with pointing in azimuth to the transmitter direction and declination pointing above the midpoint of the line between Tx and Rx at about 100 km altitude. A receiver with good input sensitivity tuned in SSB mode 1000 Hz over the carrier An Arduino based sound circuit like RAMBo ones. An ANALOG power supply (and therefore not switcher) able to feed all the apparatuses 24 hours 24; A network cable with a web access for the data uploading.

How much does it cost? antenna 74 cable 10 Connectors 5 Radio (2° hand) 500 Sound card 40 Arduino Yun 68 Total 697 (euro) Plus a lot of sandwiches, pizzas and beers