The Jicamarca Radio Observatory (JRO)

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Introduction

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.

Location

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.)

History

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 involvement. The 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.

Radar Facilities

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 盜. 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 盜. As many as eight data channels (four complex pairs) can be sampled simultaneously with 125 m (0.83 盜) 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.

Other Instruments at the Observatory

A 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 density profiles.
A modern magnetometer has been donated to the Observatory by the University of Tromso.

Additional Observatories and Facilities in Peru

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 Clemson University and ???
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, contact...
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).

Measurement Capabilities

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 猩/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.

Scientific Programs

Jicamarca participates in all the IS World Day runs, thereby supporting assorted CEDAR initiatives such as GISMOS, LTCS, SUNDIAL, CADRE, and MISETA. Some of these are described in more detail below:

The 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.
MISETA (Multi-Instrumented 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 Homepage.) 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.

Facilities For Visiting Scientists

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 and Costs

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.

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.

Additional Information

For further details and updates, contact:

Wes Swartz - wes@ece.cornell.edu

Donald Farley - donf@ece.cornell.edu

Ron Woodman - ron@geo.igp.gob.pe

Last modified on 97/11/17.