The Jicamarca Radio Observatory (JRO)
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The Jicamarca Radio Observatory is the equatorial anchor
of the Western Hemisphere chain of incoherent scatter radar (ISR)
observatories extending from Lima, Perú, to Søndre
Strømfjord, Greenland. It is part of the Geophysical Institute
of Peru (Instituto Geofísico
del Perú, or IGP) and
receives the majority of its financial support from
the National Science Foundation of the U.S. through a Cooperative
Agreement with Cornell University.
The Observatory is the premier scientific facility in the
world for studying the equatorial ionosphere. It has a 2-MW
transmitter and a main antenna with 18,432 dipoles covering an area
of nearly 85,000 square meters.
The Observatory is about a half-hour drive inland (east)
from Lima, Peru at a geographic latitude of 11.95° south and a
longitude of 76.87° west. The altitude of the
Observatory is about 500 m ASL. It is about 10 km from the
Carretera Central, the main highway east in Peru.
The magnetic dip angle is about 1°, and varies slightly
with altitude and year. The radar can be pointed perpendicular to
B throughout the ionosphere. (For critical applications, the dip
angle can be determined extremely accurately with the radar.)
The Jicamarca Radio Observatory was built in 1960-61 by the Central
Radio Propagation Laboratory (CRPL) of the National Bureau of
Standards (NBS). This lab later became part of the Environmental
Science Service Administration (ESSA)
and then the
National Oceanic and Atmospheric Administration (NOAA).
The first incoherent
scatter measurements at Jicamarca were made in late 1961. In 1969
ESSA turned the Observatory over to the
Instituto Geofísico del Perú (IGP),
which had been cooperating with CRPL since at least the IGY in
1957-58, and probably before, and had been intimately involved with
all aspects of the construction and operation of Jicamarca. ESSA and
then NOAA continued to provide some support for the operations for
several years after 1969, but then phased out their financial
National Science Foundation then began partially supporting the
operation of Jicamarca, first through NOAA, and since 1979 through
Cornell University via a Cooperative Agreement.
Closely coupled to the Observatory
operations is a private, nonprofit Peruvian corporation called Ciencia
Internacional (CI). This corporation hires most of the
Observatory staff members and provides their services to the IGP
to run the Observatory.
The 49.92 MHz incoherent scatter radar is the principal facility
of the Observatory. The radar antenna consists of a large square
array of 18,432 half-wave dipoles arranged into 64 separate modules of
12 x 12 crossed half-wave dipoles. Each linear polarization of each module can
be separately phased (by hand, changing cable lengths), and the
modules can be fed separately or connected in almost any desired
fashion. There is great flexibility, but changes cannot be made
rapidly. The individual modules have a beam width of about 7°, and
the array can be steered within this region by proper phasing. The
one way half power beam width of the full array is about 1.1°; the
two way (radar) half power beam width is about 0.8°. The frequency
bandwidth is about 1 MHz. The isolation between the linear
polarizations is very good, at least 50 dB, which is important for
certain measurements. Since the array is on the ground and the
Observatory is the only sign of man in a desert region completely
surrounded by mountains, there is no RF interference.
The original transmitter consisted of four completely
independent modules which could be operated together or separately.
Two of those modules have been converted to a new design using
modern tubes and each of these new modules can deliver a peak power
of ~1.5 MW, with a maximum duty cycle of 6%, and pulses as short
as 0.8-1.0 Ás. Pulses as long as 2 ms show little power droop;
considerably longer pulses are probably possible.
The other two modules are currently unavailable until their
conversion is complete. The third is actually more than 95% complete;
the fourth is well advanced.
The drivers of the main transmitter can also be used as
transmitters for applications requiring only 50-100 KW of peak power.
An additional antenna module with 12 x 12 crossed dipoles
was built in 1996. It is located 204 m to the west of the west
corner of the main antenna and increases the lengths of the
available interferometer base line to 564 m.
There are 3 additional 50 MHz "mattress" array antennas
steerable to +/-70° zenith angles in the E-W direction only.
Each consists of 4 x 2 half-wave
dipoles mounted a quarter wavelength above a ground screen. Two of
these arrays can handle high powers. There is also a single fat
dipole mounted a quarter wavelength above ground that can handle at
least a megawatt. There is a lot of land around the Observatory for
additional antennas for special experiments. Arrays of a kilometer or
more in length could be set up (in certain directions).
There are four phase-coherent (common oscillators) receivers
for the radars.
These mix the signal to baseband (with two quadrature outputs each),
with maximum output bandwidths of about 1 MHz. Filters are available
with nominal impulse response time constants ranging from 1 to 500 Ás. As many as
eight data channels (four complex pairs) can be sampled simultaneously
with 125 m (0.83 Ás) resolution and fed to a large FIFO
buffer/coherent integrator, and from there to one of the computers.
We are in
the process of designing new receivers; we plan to have at least
eight, with more precise digital filtering at the output.
The computing hardware at JRO is constantly evolving. For
many years the main data-taking computer has been a Harris H800
with various tape drives, including two Exabyte 2.2 GByte 8 mm
cassette tape drives (maximum writing speed of 256 KBytes/s).
But now there is also a Harris Nighthawk
computer (UNIX operating system) with an 80-MFLOPS array processor
and various workstations and PCs, all networked together.
Data acquisition can be hosted by any one of a number of these
machines with real-time processing and display capabilities.
The JULIA radar shares the main antenna of the Jicamarca Radio
Observatory. JULIA (which stands for Jicamarca Unattended Long-term
investigations of the Ionosphere and Atmosphere)
has an independent PC-based data acquisition system
and makes use of some of the exciter stages of the Jicamarca
radar along with the main antenna array. Since this
system does not use the main high-power transmitters (which
are expensive and labor intensive to operate and maintain),
it can run unsupervised for long periods of time.
With a pair of 30-kW peak power pulsed transmitters driving
a 290 m by 290 m modular antenna array, JULIA is a formidable
MST/coherent scatter radar. It is uniquely suited for studying
the day-to-day and long-term variability of equatorial plasma
irregularities and neutral atmospheric waves, which until now
have only been investigated episodicly or in campaign mode.
Digisonde Portable Sounder (DPS) from the
University of Lowell is located at the Observatory and operates
nearly continuously. The DPS is
battery operated and therefore is unaffected by power outages. It has
four antennas feeding four receivers and can measure drifts as well as
- A modern magnetometer has been donated to the Observatory
by the University of Tromso.
- A major airglow facility is located at Arequipa in southern Peru.
Instruments include a
Fabry Perot interferometer and an all-sky imager.
These facilities are operated by
Dr. John Meriwether of
- An MST radar has been built at the University
of Piura in northern Peru using components from the former NOAA
Poker Flat MST radar. Piura is
approximately 800 km north of Jicamarca at about 4 deg S geographic
latitude and is the eastern anchor of the NOAA pacific equatorial
chain of MST radars. The University of Piura has been extremely
helpful and competent in this project. There is a good opportunity
for collaborative MST observations with Jicamarca, comparing
equatorial (geographic) and off-equatorial behavior, for example.
Conversely, Piura is at the northern edge of the magnetic equatorial
region, and so there may be opportunities for interesting E- and
F-region plasma instability comparisons. And lastly, the skies at Piura
are almost always extremely clear; it could be an excellent airglow
observing site. For further information about the Piura facilities,
- Satellite scintillation measurements are made at
Ancon on a campaign basis by Santi and Sunandu Basu and their colleagues. Ancon is
about 50 km northwest of Jicamarca on the coast.
- A magnetometer is also located at Ancon.
- There is a rocket range 50 km or so south of Lima at Punto Lobos
that has been used twice by NASA (1975 for project Antarqui, and 1983
for project CONDOR) and once by Germany (1979).
Jicamarca participates in all the IS World Day runs,
thereby supporting assorted
CEDAR initiatives such as GISMOS, LTCS,
MISETA. Some of these are described in more
- Of all the ISR observatories, Jicamarca
provides by far the most accurate drift velocity and electric field
data. This is because of the unique equatorial geometry. Pointing
perpendicular to the magnetic field makes it possible to measure
line-of-sight drift velocities to accuracies of the order of 0.5 m/s
without difficulty. Vertical F-region plasma drifts of this accuracy
translate to zonal electric field accuracies of about 12 ÁV/m.
Determining zonal drifts involves subtracting two slightly off
vertical line-of-sight measurements, and so the uncertainties are
about ten times larger, but the mean drifts are also larger. By
studying the variation of drift velocity with altitude, up to
altitudes of 800-1000 km or perhaps even higher, it is possible to
study the electrodynamics of the entire low-latitude ionosphere, up to
the anomaly latitudes, because of the way the electric field maps
along the geomagnetic field lines.
- Jicamarca also has a unique
capability to probe the ionosphere to very high altitudes. Because of
the long radar wavelength, the incoherent scatter is not affected by
Debye length problems at low electron densities, and usable signals
can be obtained from altitudes of 5000 km and higher, giving densities
and perhaps temperatures (but not drifts since the beam cannot be
simultaneously pointed perpendicular to B).
- Absolute F-region measurements of electron density are performed
using Faraday rotation. Electron and ion temperatures and ion
compositions are obtained with a double pulse technique that generates
the signal auto-correlation function. Pulses are transmitted on
orthogonal polarizations to reduce clutter.
- The Jicamarca radar is the
most sensitive MST radar in the world; in fact, it is the only true MST
radar, capable of probing even the "gap" region near 45 - 50 km,
partly because of its long wavelength (so there are fewer problems with
the turbulent viscous cutoff) and partly because it has the largest
power-aperture product of any VHF radar.
Many visitors to JRO stay at the
El Pueblo resort hotel
(two big pools, two clay tennis courts,
golf course), which is very nice and relatively inexpensive by U.S.
standards. It is outside
of Lima, only a short 10-km drive from the Observatory. There are
also many nice hotels in Lima in assorted price ranges. The food at
the Pueblo is good, but in Lima it is superb at most restaurants. On
the other hand, staying in Lima means fighting the rush hour traffic
every day. The terrorist threat (the Sendero Luminoso) in Peru is
essentially gone now. Lima is probably a lot safer than Miami or New
York, or assorted other U.S. cities.
Scheduling experiments at Jicamarca is
still handled in an informal way. Anyone wishing to observe at
Jicamarca should get in touch with
Donald Farley at Cornell and/or
Ronald Woodman at JRO.
Remember to avoid the IS World Day periods (see the
International Geophysical Calendar). Periods around July 28 (Peruvian
Independence Day, a big holiday period), Easter, and Christmas are
also times when key personnel may be absent. The staff normally works
four 10-hour days per week (Monday-Thursday), partly so that they can
hold other jobs. If you plan to run at night or during Friday-Sunday,
you should be prepared to pay overtime charges to the staff members
involved. These charges might add up to $30-50/hour, depending upon
the number of people involved. The staff members are generally very
happy to work overtime, because the payments represent a substantial
boost to their income.
CADRE (Coupling And
Dynamics of Regions Equatorial) campaign is examining the dynamical
coupling processes operating within, and accounting for the large scale
structure and variability of, the equatorial middle atmosphere.
CADRE employs a
wide range of radar, lidar, optical, rocket, and satellite
instrumentation at various locations. The role of Jicamarca in CADRE
is to study the
effect of small scale gravity waves, specifically the vertical fluxes
of momentum, their interactions with tidal and other equatorial
motions at larger scales, and their forcing of the QBO and SAO at
stratospheric and mesospheric heights.
CADRE campaigns have been carried out in January 1993, March 1994,
and August 1994.
Studies of Equatorial Thermospheric Aeronomy) is investigating
F-region winds and zonal plasma drifts using Fabry-Perot interferometry
and all-sky imaging at 630 and 774 nm from Arequipa, scintillation
drift measurements at Ancon, and digisonde and ISR drift measurements
at Jicamarca. One goal is to understand why the irregularities (that
cause the scintillations) develop on some nights, but not others.
(See also the
MISETA campaigns have been carried out in the Fall of 1994 and 1996.
- Jicamarca has had a long
standing (since the early 1960s) program of radar studies of plasma
instabilities in the equatorial E and F regions. The E-region
instabilities are driven by the equatorial electrojet current and are
quite similar to instabilities found in the auroral E region, but the
equatorial geometry and the power and versatility of the Jicamarca
radar make the essential physics of these phenomena much easier to
study at the equator. The sometimes
spectacular F-region instabilities are unique to equatorial latitudes.
Both are nice examples of fully developed (nearly) 2-D plasma
turbulence, and they provide a unique laboratory for studies of some
fundamental nonlinear plasma processes. The E-region instabilities
may affect the layer conductivity and hence the global Sq current
system, and both instabilities can affect communications and
navigational systems such as GPS.
- The radar can accurately determine where the radar beam is
perpendicular to B via an interferometer method. This capability
has allowed the tracking of small changes in the
Earth's magnetic field during the lifetime of the Observatory.
If your research is sponsored by the National Science
Foundation, there is no charge for observing time, other than for
possible overtime, as just discussed. For those with other funding,
there is a charge of approximately $8000 per day of observing, for
isolated experiments. For longer, on-going programs not supported by
the NSF, special arrangements for Observatory support should be made.
For further details and updates, contact:
Wes Swartz -
Donald Farley -
Ron Woodman -
Last modified on 97/11/17.