Dip. di  Ingegneria Informazione

Università di Roma Sapienza

 

 


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Laboratory  of Antennas, Readiopropagation and Telesesning (LabART)



 ̃ Lab. RadioMet Objectives

 ̃ Lab. RadioMet Facility

 ̃ Lab. RadioMet Research


 

 


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Laboratory of

Radio Meteorology

Staff: F. S. Marzano, N. Pierdicca, M. Biscarini

Co-staff: F. Consalvi (FUB)

Collaborators: M. Montopoli, E. Picciotti

 

 Laboratory of Antennas, Radiopropagation and Telesensing (LabART)

Dept. of Information Engineering - Sapienza University of Rome

Location: Latitude 41° 53’ 37 N, Longitude 12° 29’ 38 E

 

 Tel. +39.06.44585847; Contatti: frank.marzano@uniroma1.it

https://cispio.diet.uniroma1.it/marzano/LabRadioMet.htm

 

        

Points of view about Atmospheric Engineering Research

 


Lab. RadioMet OBJECTIVES

 

The Laboratory of Radio Meteorology is a joint initiative of DIE and CETEMPS to exploit ground-based remote sensing of the atmosphere in synergy with satellite meteorology. Its first activity dates back to 1980 (thanks to an initiave of Prof. d'Auria and his colleagues) and is a measurements facility of the Laboratory of Antennas, Remote Sensing and Propagation of DIE.

The LabRadioMet has the following objectives:

1.   to manage ground-based remote sensing and in situ instrumentation;

2.  to design and develop new microwave remote sensing instrumentation;

3.   to develop advanced algorithms for atmopheric parameter retrieval;

4.  to exploit sensor synergy within the atmospheric observation;

5.  to operate as a ground-based facility for satellite product validation;

6. to pursue the use of remote sensing for telecommunication applications.

This experimental activity is carried out in close coordination with the:


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Center of Excellence CETEMPS, Univ. of L'Aquila

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Dept. of Electronic and Information Eng., Univ. of Perugia

 

LabRadioMet views

 

 

Lab. RadioMet FACILITY

The Laboratory of Radio Meteorology is placed on the roof terrace of the  Faculty of Engineering  of the Sapienza University of Rome. The test site is exactly located at: Latitude 41° 53’ 37 N, Longitude 12° 29’ 38 E.

The position of the Laboratory is amazing as it is on the top of the highest historical hills of Rome, Colle Fagutal. The view of the old city of Rome is unique, but also the optical visibility is very attractive both towards the Tyrrenian sea and the Appenine range.

The LabRadioMet enumerates both in situ meteorological instrumentation coupled with microwave and optical sensors.

View of the LabRadioMet measurement terrace

Weather stations

Two weather stations, spatially separated by 15 m, are present capable to measure: pressure (hPa), temperature (K), relative humidity (%), and wind velocity (m/s). Three tipping-bicket rain gauges, spatially separated to each other by 15 m, are also avalaible capable to measure the accumulated rain (mm).

Data are acquired every 10 minute through a RS232 line and digitally archived on a PC system. The meteo stations are operated separately with a redudancy principle.

Weather stations

Ka-band Microwave Radiometer

The REC-2 radiometer is a dual channel system at 23.8 and 31.7 GHz, manufactured by the RESCOM company (Aalorg, Denmark). This radiometer is a compact self-contained configuration designed for automatic unattended operation for extended time with a high measuring accuracy.

The radiometer has an elevation and azimuth control and are controlled by a personal computer through an RS-232 serial line. Regular calibration are performed by using the tipping-curve method. The REC-2 radiometer consists of offset-fed antenna parabolic reflectors connected to microwave receivers of the noise balancing type. The noise-balancing type receiver yields a high insensitivity to gain variations and mismatches within the noise injection feedback loop thus ensuring a high long-term stability. The actual temperatures of main microwave components in the front ends and feed assembly are monitored and used for correction of measured data. The antenna reflector and receiver sections are integrated in an outdoor box.

The shape of the antenna surfaces and the configuration of the wide-band feed horns have been designed so that energy outside the main lobes is minimized. Moreover, the extremely low side-lobes can ensure a minimum pick-up of radiation emitted from surrounding surface. By a proper design of the feed horn, nearly equal antenna main-lobes at 20 and 30 GHz have been obtained. The REC-2 corrugated feed horns is protected by an aperture window and is connected to a diplexer by a short waveguide bend. The REC-2 circular horns are horizontally polarized and placed above the antenna reflectors downward so that to be protected against rain drops, snow and condensation layer. The REC-2 antenna reflectors are of carbon-fiber skin-honeycomb construction. They have a very smooth surface with roughness less than 0.2 mm. Their rectangular contour provides a projected aperture of about 60 x 60 cm^2 for REC-2. Heated air is continuously blown across the antenna reflector which presents a set of small holes within its vertex area, thus preventing the formation of the dew and the possible accumulation of rain drops, snow and hail on the surface. Moreover, air from heater box is directed through a tube to the feed horn window. In this way the window will be kept free from condensation or rain drops.

                      

Ka-band microwave radiometer

Ku-band Microwave Radiometer

The REC-1 single channel radiometer is an independent system, designed also by the RESCOM. The operating frequency is 13.0 GHz and, basically, it has almost the same mechanical characteristics of REC-2.

The radiometer has an elevation and azimuth control and are controlled by a personal computer through an RS-232 serial line. Regular calibration are performed by using the tipping-curve method. The REC-1 radiometer consists of offset-fed antenna parabolic reflectors connected to microwave receivers of the noise balancing type. The noise-balancing type receiver yields a high insensitivity to gain variations and mismatches within the noise injection feedback loop thus ensuring a high long-term stability. The actual temperatures of main microwave components in the front ends and feed assembly are monitored and used for correction of measured data. The antenna reflector and receiver sections are integrated in an outdoor box.

The shape of the antenna surfaces and the configuration of the wide-band feed horns have been designed so that energy outside the main lobes is minimized. Moreover, the extremely low side-lobes can ensure a minimum pick-up of radiation emitted from surrounding surface. By a proper design of the feed horn, nearly equal antenna main-lobes at 20 and 30 GHz have been obtained. The REC-1 corrugated feed horns is protected by an aperture window and is connected to a diplexer by a short waveguide bend. The REC-1 circular horns are horizontally polarized and placed above the antenna reflectors downward so that to be protected against rain drops, snow and condensation layer. The REC-1 antenna reflectors are of carbon-fiber skin-honeycomb construction. They have a very smooth surface with roughness less than 0.2 mm. Their rectangular contour provides a projected aperture of about 90 x 90 cm^2 for REC-1. Heated air is continuously blown across the antenna reflector which presents a set of small holes within its vertex area, thus preventing the formation of the dew and the possible accumulation of rain drops, snow and hail on the surface. Moreover, air from heater box is directed through a tube to the feed horn window. In this way the window will be kept free from condensation or rain drops.

Ku-band microwave radiometer

X-band Meteorological Radar

The X-band Meteorological radar, designed by ELDES (Firenze, Italy), is a compact portable scanning radar with the following features: peak power of 10 kW, selectable pulse repetition frequency (PRF) between 800 Hz (maximum range of 180 km), pulse duration of 0.6 ms (range resolution of 90 m) and an antenna directivity of 39.1 dB (about 3° half-power beamwidth). The radar control and data acquisition is completely remote and accessible via Internet connection.

The X-band radar has a low-noise receiver with a noise figure of about 4 dB, a coaxial magnetron transmitter, a parabolic reflector of about 90 cm diameter with a corrugated rectangular horn feeder, and a digital recever sampling the received signal at the intermediate frequency of 40 MHz. The minimum detectable power signal is about -113 dBm, whereas up to 128 samples may automatically integrated. The azimuth scanning is complete with an angular resolution between 1° and 3°, while the zenith scan ranges from 0° to 180°. The entire receiving and transmitting system is mounted on the backside of the reflector and rotates with the antenna itself, protected by a single-component radome. The total weith of the X-band system is about 75 kg and can be easily removed and installed.

 

X-band meteo radar

Near-infrared Mini Lidar

The Vaisala CT25K is a field-proven and popular laser ceilometer for measuring cloud height and vertical visibility at near infrared. It employs pulsed diode laser Light Detection and Ranging (LIDAR) technology at 904 nm to detect clouds, precipitation and other obstructions to vision.

The CT25K's unique single-lens design ensures excellent performance at low altitudes, which really counts for aviation safety. Starting at a height of virtually 0, the Vaisala CT25K Laser Ceilometer measures cloud height - or vertical visibility if the cloud base is obscured - with unmatched accuracy. The single-lens design also ensures reliable measurement in fog, rain, snow and haze. No field adjustments are needed. The CT25K can be tilted on its pedestal base, allowing the beam to be directed manually in any direction between -15...+90º from the vertical. Tilting improves the protection given by the shield to the window, and makes it easy to perform field testing against a hard target. In the measurement unit, a tilt angle sensor automatically corrects the cloud distance reading to the vertical cloud height. The CT25K is fully automatic. It transmits messages containing cloud height and instrument status information to a controller, display unit or central computer. Its software includes an extensive set of self-diagnostic routines to ensure reliable operation and easy trouble-shooting. The CT25K also has a modular structure and easy-access door to ensure fast servicing and high data availability. Vaisala's Sky Condition Algorithm is provided as an option. This algorithm calculates the cloud amounts and the heights of different cloud layers, in order to construct an approximation of the entire sky. Vaisala CT-VIEW software can be used to view backscatter profiles, cloud detection and backscatter density graphs, and to perform data logging and storage functions in the Windows PC environment. The CT25K can be used stand-alone or as an integrated sensor in a weather observation system comprising many sensors, displays and central computers.

Near-infrared mini lidar

W-band Microwave Radiometer

The W-band single-channel polarimetric radiometer is an independent system, designed by DIET. The operating frequency is 90.0 GHz at both horizontal and vertical polarization. It is an indoor installation with an outdoor motorized oscillating reflector.

The W-band radiometer consists of a dual corrugated rectangular horns connected to microwave receivers of the Hach type with two microwave loads. The actual temperatures of main microwave components in the front ends and feed assembly are monitored and used for correction of measured data. The antenna and receiver sections are integrated  and a regular calibration are performed by using the tipping-curve method and the criogenic loads.

W-band microwave radiometer

Ka and Q band Satellite Receiving Station

A Ka-band and Q-band satellite receiver station is also present on the roof terrace. It was previously used for Olympus satellite signal reception and is now at disposal of the research group for AlphaSat TD5 Aldo experiment.

The Ku band system is made by a parabolic reflector of 2 m diameter with a corrugated horn feeder. An LNA block provides the outputs signal at intermediate frequency. At Ku the station has also the capability to trasmit. The Ka band feeder is interachangeable with the Ku-band one.

Ku- and Ka-band satellite receiving station

VLF Lightning Sensor

A VLF receiver has been installed in May 2011. The receiver is part of the internation BlitzOrtung lightning network (www.blitzortung.org) and contributes to the voluntary cloud-to-ground lightning measurement database and geolocation processor, managed in Dusseldorf (De).

The VLF (3-30 kHz) sensor is made by two orthogonal ferrite loop antennas, a pre-amplifier, a GPS receiver and a PC traker program, connect via LAN to the central database. The VLF band is chosen due to the peak of radio-emission generated by cloud-to-ground lightnings.  The receiving antenna is placed within a meteorological box to prevent from rainfall (close to a raingauge, see aside), whereas the GPS and the processor borad are located inside the laboratory at a distance of about 10 m.


VLF lightning sensor

Precipitation Optical Disdrometer

A precipitation optical disdrometer has been installed in November 2011, thanks to the international MarieCurie project HYDREX. The Parsivel disdrometer is produced by OTT and is able to provide the size distribution of precipitation particles and their category (rain, snow, grupel and sub-species).

The Parisevl optical disdrometer by OTT works on the principle to measure the effects of precipitation particles on the optical near-infrared beam transmitted and received within a length of about 40 cm. From the beam attenuation the particle concentration is basically estimated, whereas the size, their distribution and species is dereived from the velocity measurements within the measurement area couple with amplitude perturbation.  


Precipitation optical disdrometer



Lab. RadioMet RESEARCH

The Laboratory of Radio Meteorology current research concerns passive and active remote sensing of the atmosphere from ground-based, airborne, and space-borne platforms, with a particular focus on clouds and precipitation using microwave and infrared data, development of inversion methods, and radiative transfer modelling of absorbing and scattering media

Other main topics of interest are radar meteorology for rain, wind and ash retrieval and synthetic aperture radar data processing for land-use applications.

The LabRadioMet is also deeply involved in radiopropagation studies, including e.m. field scintillation and rain fading modelling and data analysis along satellite microwave and millimeter-wave links.

Joint researches are carried out together with national institutions (e.g., CETEMPS - Univ. of L'Aquila, CIMA - Univ. of Genoa, ARPA-SIM - Bologna, CNR ISAC - Roma, DPC - Roma), international institutions (e.g., NRL - CA USA, Univ. of Washington - WA USA, Colorado State Univ. - CO USA, ECMWF - Reading UK) and industries (e.g., Selex Gematronik - Germany/Italy, ELDES - Italy, Telespazio - Italy, Datamat - Italy).

Within the LabRadioMet tasks, there are also educational purposes. About 30 undergraduatestudents, more than 20 graduate students and 6 Ph.D. students have been working on the topics of interest of the Laboratory.

The LabRadioMet is connected to the Doctorate in Electromagnetics of the University “La Sapienza” of Rome, to the Doctorate in Methodologies and Technologies for Environmenal monitoring of the University of Basilicata, and to the the International Summer School on Atmospheric and Oceanic Sciences (ISSAOS) of L’Aquila. 

 

 

 

Research topics and examples

 

 Electromagnetic theory

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Radiative transfer models through the atmosphere at microwaves (e.g., )

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Scattering and absoprtion of e.m. radiation from particle dispersion (e.g., )

 

 Electromagnetic propagation


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Signal scintillation at microwaves and millimeter-waves due to turbulence (e.g., )

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Radiopropagation via satellite at microwaves and millimeter-waves (e.g., )        

 

 Atmospheric remote sensing


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Methodologies of inversion of remote sensing measurements (e.g., )

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Microwave and infrared radiometry of the Earth atmosphere and surface (e.g., , )

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Radar meteorology and rainfall retrieval at microwaves (e.g., )

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