A Radio Echo Sounding (RES) system is an active remote-sensing instrument that uses electromagnetic wave penetration into the ice to obtain information on the depth of the bedrock and on the ice thickness and its inhomogeneities, i.e. internal layering of glaciers and subglacial lake exploration. In 1995 the INGV developed its own airborne radio echo sounding system, which is continuously being upgraded. During the 1995, 1997, 1999, 2001 and 2003 Italian Antarctic
Expeditions, the RES system was used to investigate different Antarctic regions.
During 2007-2008 campaign, new RES systems will be used. In the following the main characteristics of the systems will be briefly described

Baskaradas, J. A.

Bianchi, C.

Cafarella, L.

Sciacca, U.

Tabacco, I. E.

Zirizzotti, A.

Zuccheretti, E.

Earth-prints Repository

5th Meeting on Italian Antarctic Glaciology 2005
Italian RES Investigation in Antarctica: 
The New Radar System
I.E. TABACCO2, C. BIANCHI1, J.B. AROKIASAMY1, L. CAFARELLA1, U. SCIACCA1, 
A. ZIRIZZOTTI1 & E. ZUCCHERETTI1
1Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, Roma - Italy
2Dip. Scienze della Terra, Sez. Geofisica, Via Cicognara 2, Milano - Italy
*Corresponding author (ignazio.tabacco@unimi.it)
THE ITALIAN RADIO ECHO SOUNDING SYSTEM
A Radio Echo Sounding (RES) system is an active remote-sensing instrument 
that uses electromagnetic wave penetration into the ice to obtain information on 
the depth of the bedrock and on the ice thickness and its inhomogeneities, i.e. 
internal layering of glaciers and subglacial lake exploration. In 1995 the INGV 
developed its own airborne radio echo sounding system, which is continuously 
being upgraded. During the 1995, 1997, 1999, 2001 and 2003 Italian Antarctic 
Expeditions, the RES system was used to investigate different Antarctic regions. 
During 2007-2008 campaign, new RES systems will be used. In the following the 
main characteristics of the systems will be briefly described.
THE OLD  SYSTEM
During the 1997 and 1999 Italian Antarctic Expeditions, the RES system developed 
at the INGV was placed on an aircraft flying 1000 feet above the ice surface; two 
folded dipole antennas, one for transmitting and the other for receiving echo 
pulses, were mounted beneath the aircraft wings (Tabacco et al., 1999; Bianchi et 
al., 2001). This airborne radio sounding system operated at 60 MHz with a pulse 
length of 0.3 μs -1 μs in 1997 and of 0.25 μs - 1 μs in 1999. The maximum delay 
of the received signal was 51.2 μs in 1997 and 64 μs in 1999, corresponding to a 
maximum penetration depth into the ice of about 4.3 km in 1997 and 5.3 km in 
1999. The RF pulsed generator used a Phase Lock Loop (PLL) frequency synthesizer 
which allowed fine frequency corrections, thereby preventing mismatches due to 
the reflected peak power from the folded dipole antenna. The 4 kW transmitted 
power allowed us to obtain an adequate amplitude echo signal at the receiver. The 
receiver consisted of a solid-state low-noise Log envelope detector. The dynamic 
range of the receiver was 80 dB, and the received echo signal was digitised (8 bit) 
at a 20 MHz sampling frequency to obtain a temporal precision of about 50 ns. 
A Trimble 4000 SSE GPS system receiver with antenna mounted on the aircraft 
fuselage was installed and linked to the radar. Navigation relied on an onboard GPS 
receiver which recorded the longitude, latitude, altitude and time of acquisition 
Terra Antartica Reports
2008, 14, 213-216
© Terra Antartica Publication
Proceedings
I.E. Tabacco et al.
214
of each radar trace. The 
horizontal sampling rate was 
10 traces/s, which for a mean 
aircraft speed of about 70 
m/s corresponds to about 
143 traces per kilometre (1 
trace every 7 m). 
The measurements, 
obtained using the RES system 
during five Italian Antarctic 
Expeditions in 1995-2003 
(Fig. 1), have been used in 
different contexts (Tabacco 
et al., 2002; Cafarella et 
al., 2006; Urbini et al., 
2006). For example, these 
measurements were used to 
determine and analyse the 
bottom morphology and ice thickness of the David Glacier-Drygalski ice tongue 
in East Antarctica (Bianchi et al., 2001; Tabacco et al., 2000). Satellite-tracking 
velocity data for the same period were combined with airborne radar surveys of ice 
thickness to calculate the discharge of the Priestley, Reeves, David, Mawson and 
Mackay outlet glaciers (Frezzotti et al., 2000). The calculated changes in ice flux 
of these floating glaciers were subsequently used to determine basal melting and 
Fig. 1 - RES flight paths of five Italian 
Antarctic Expeditions.
Fig. 2 – RADAR signal of Lake Vostok.
© Terra Antartica Publication
5th Meeting on Italian Antarctic Glaciology 2005
Italian RES Investigation in Antarctica: The New Radar System
215
freezing rates. This RES system was also used to make many measurements in 
the Antarctic region in support of different projects such as the European Project 
for Ice Coring in Antarctica (EPICA). Data were used to reconstruct the precise 
bedrock topography at Dome C in Antarctica (Remy and Tabacco, 2000). Knowledge 
of the topography of this region was used to select the optimal location for drilling 
a deep ice core at Dome C (Capra et al., 2000).  
During the 1999 and 2001 Italian Antarctic Expeditions, extensive airborne 
radar surveys were carried out over the Vostok-Dome C region and the Aurora 
trench (about 6000 km of radar traces were acquired). The aim was to define the 
morphological characteristics of the Aurora Trench and to improve subglacial lake 
exploration (in Fig. 2 the RADAR signal of Lake Vostok is shown). The radar data 
was used to determine the ice thickness and bedrock topography in the entire 
area; in addition, analysis of the shape and amplitude of bottom reflections allowed 
the detection of sub-glacial “lake” mirror features in 30 radar tracks (Tabacco et 
al., 2003). The deepest point in the Aurora trench (Fig. 3), located at 118.328° E; 
76.054°S, has a bed elevation of -1549 m and an ice thickness of 4755 m. 
The most extensive Radar measurements (more then 30000 km in 35 flights) 
were completed during the 2003 Italian campaign in order to estimate the bedrock 
topography and the mass balance of the eastern Antarctic ice-cap.  
NEW SYSTEMS
Two enhanced RES systems, with a new antenna system (8 folded dipoles) 
and the implementation of powerful signal processing techniques (time domain 
and frequency domain correlations), are being developed by the INGV (Bianchi 
et al., 2003). 
The new 150 MHz RADAR is an envelope and phased-coded RADAR with a 
better signal-to-noise ratio than the old 60 MHz RADAR. 
Fig. 3 – Aurora trench deepest point
© Terra Antartica Publication
Proceedings
I.E. Tabacco et al.
216
The 300 MHZ Snow RADAR, with a shorter transmitted pulse (subpulse in the 
phase coded RADAR), will have a better vertical resolution (less than 3 m) in the 
ice and the capacity to distinguish internal layers, so that ice accumulation rates 
can be determined based on the depth of known isochronal horizons. These 
improvements will be achieved by a new analog-to-digital (AD) converter card used 
to digitalize the acquired RADAR traces and by mounting the new antenna system 
beneath  the wings of  the Twin Otter. The AD converter is a  PCI 64 bit PC card 
with 2 channels, 14 bit resolution and 100 MHz sampling rate on each channel. 
The antenna system is made up of two arrays of 8 broadband folded dipoles: 4 
antennas for transmitting the signal and 4 for receiving the echo. The antennas 
are fed in phase, and the harness is a single feed point with the splitters in line. 
The array will improve the beam convergence and directionality, while increasing 
the amplitude of the signal.  
The new systems are under construction at the INGV, and the new antennas will 
be mounted on the Twin Otter airplane in spring 2006 for a flight test in Calgary, 
Canada. The first on field test of the two RADAR systems are scheduled for the 
2006 – 2007 Antarctic campaign.  
Acknowledgement - Research was carried out in the framework of a project on Glaciology 
funded by the Italian Programma Nazionale di Ricerche in Antartide (PNRA).
REFERENCES
Bianchi C., Chiappini M., Tabacco I.E., Passerini A., Zirizzotti A., & Zuccheretti E., 2001. Morphology of 
bottom surfaces of glaciers ice tongues in the East Antarctic region. Annali di Geofisica, 44, 1.
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for phase-coded HF-VHF radars. Annals of Geophysics, 46, 4.
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one of Antarctica’s thickest ice covers newly determined by Radio Echo Sounding over the Vostock-
Dome C region. Polar Research, 25, 69-73.
Capra A. , Cefalo R., Gandolfi S., Manzoni G., Tabacco I.E., & Vittuari L. 2000. Surface topography of 
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Italian RES Investigation in Antarctica: The New Radar System

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Italian RES Investigation in Antarctica: The New Radar System

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