The Jicamarca radar (Long. 76.52W, Lat. 11.56S), located at 20 km from Lima at approximately 500 meters over sea level, is surrounded by mountains which provide a good shield from man-made interference. The radio horizon goes from a few hundred meters, across the dry valley where it is located, to 15 km, along the valley in the direction of the continental divide. This limits the clutter to 15 km, except for one high peak at 21 km. It is the most equatorial of all existing MST radars. Its proximity to the Andes, makes its location unique for the study of lee waves and orographic-induced turbulence. Vertical as well as horizontal projections of MST velocities are obtained by simultaneously pointing with different sections of the antenna into three or four different directions. The transmitters, receivers, and systems for data acquisition, processing, and control are included

Farley, D. T.

Woodman, R. F.

English

NASA Technical Reports Server

315 
5.2A CAPABILITIES AND LIMITATIONS OF THE JICAMARCA RADAR AS AN MST RADAR 
R. F. Woodman*, and D. T. Farleyw. 
* Ins t i t u t e  Geofisico d e l  Peru, Apartado 3747, Lima, Peru 
**Phillips Hall, Cornel1 University, I thaca,  NY 14853 
LOCATION 
The Jicamarca radar (Long. 76.528, Lat .  11.565) i s  located a t  20 km from 
Lima a t  approximately 500 meters over sea level .  It i s  surrounded by mountains 
which provide a good sh ie ld  from man-made interference.  The r ad io  horizon goes 
from a few hundred meters, across the dry val ley where it i s  located, t o  15 km, 
along the  va l l ey  i n  the  d i r ec t ion  of the cont inental  divide. 
c l u t t e r  t o  15 km, except f o r  o m  high peak a t  21 km. 
r i a l  of a l l  ex i s t ing  MST radars. 
t i o n  unique f o r  the study of l e e  waves and orographic-induced turbulence. 
ANTENNA 
This l i m i t s  t he  
Its proximity t o  the Andes, makes i t s  loca- 
It i s  the most equato- 
The Jicamarca antenna i s  the l a rges t  radar antenna i n  the world. 
f l a t  and almost horizontal  array of cross-dipoles, covering an area of 300 m 
by 300 m (9 Ha). It has a center  frequency of 50 MHz with a bandwidth of 1 MHz 
(determined by power combiners and s p l i t t e r s  a t  the feed point of the antenna). 
The antenna consis ts  of 64 iden t i ca l  and fixed squared modules of 144 
They are grouped i n t o  4 squared sect ions with 2 inde- 
It i s  a 
cross-dipoles each. 
pendent feeds f o r  each quarter ,  one f o r  each l i n e a r  polarization. 
the f u l l  antenna, or of each of the quarters ,  can be accomplished by manually 
in se r t ing  phasing cables i n t o  each of the modules. 
can be s teered independently, a t  both the quarter  and f u l l  antenna level .  
Maximum prac t i ca l  s teer ing i s  +3' from the on-axis posit ion.  On-axis posi t ion 
i s  1.4" t o  the SW from zenith.  Exact v e r t i c a l  pointing can be achieved with a 
special  s e t  or cables. 
v e r t i c a l  and E-W and N-W project ions of MST horizontal  ve loc i t i e s  (WOODMAN and 
GUILLW, 1974). Fu l l  aper ture  r ada r  beam width i s  of the order of 0.5 degrees. 
This i s  an important parameter fo r  MST spectral  width interpretat ion,  since i t  
reduces the e f f ec t  of beam width spectral  broadening t o  a f r a c t i o n  of turbulent 
broadening. 
Steering of 
Each l i n e a r  polar izat ion 
Posit ions+3'  from zeni th  have been used t o  determine 
Maximum power handling capacity i s  a t  least 6 MW. 
Performance of the antenna i s  very close t o  t h a t  of a f u l l  squared aper- 
t u r e  with an ohmic eff ic iency of 0.8-0.9. 
Vert ical  as w e l l  as horizontal  projections of MST v e l o c i t i e s  are obtained 
by simultaneously pointing with d i f f e ren t  sections of the antenna i n t o  3 or 4 
d i f f e ren t  direct ions.  
on-axis v e r t i c a l  posi t ion are used f o r  t h i s  purpose. 
Usually posi t ions a t  53' and north or south from the 
The poss ib i l i t y  of s p l i t t i n g  the  antenna i n t o  d i f f e ren t  sect ions permits 
observations i n  an interferometer mode t o  determine s ize ,  posi t ion and veloci ty  
of s t ruc tu re  smaller than the beam width (RUSTER and WOODMAN, 1976). 
TRANSMITTERS 
The t ransmit t ing system consis ts  of a bat tery of 4 independent trans- 
mitters with a nominal power of 1.5 MW each. 
when the tubes are new i s  of the order of 4 MW t o t a l .  
Maximum real obtainable power, 
Maximum duty cycle i s  
https://ntrs.nasa.gov/search.jsp?R=19840019062 2020-03-22T09:43:10+00:00Z
5%, which t r ans l a t e s  i n t o  200 kW of average power. 
The output power of the t ransmit ters  can be combined, or s p l i t ,  i n  a 
va r i e ty  of modes t o  feed e i t h e r  the f u l l  antenna or f r a c t i o n s  of each, forming 
i n  t h i s  way independent transmitter-antenna uni ts .  
t ransmit ters  can be changed a t  ex i t a t ion  l eve l  permitting the synthet izat ion of ' 
d i f f e ren t  polar izat ion v i a  Hybrid combiners. 
' 
The r e l a t i v e  phase of the 
The bandwidth of the t ransmit ters  i s  l imited by a f a i r l y  large cathode 
t o  g r id  capacitance, which, when turned, produces a high Q c i r c u i t  with a 
bandwidth of the order of 50 kHz. This r e l a t i v e  narrow bandwidth l i m i t s  the 
a l t i t u d e  resolut ion t o  2 2  km. 
The combination of antenna s ize ,  power and frequency makes Jicamarca the , 
most sens i t i ve  MST radar  in the world. Even a t  t h i s  l eve l ,  i t s  sens i t i v i ty  t o  
obtain echoes a t  45-km a l t i t u d e  i s  marginal. 
The operating frequency a t  50 MHz i s  an asset .  Given su f f i c i en t  power 
aperture  product the maximum a l t i t u d e  obtainable by an MST radar is determined 
by the a l t i t u d e  a t  which the turbulence inner scale  i s  comparable t o  the radars 
wavelength. The longer the wavelength the higher the a l t i t u d e ,  
The Jicamarca radar i s  the only MST radar i n  existence which can obtain 
echoes a l l  the way from tropospheric t o  mesospheric a l t i t u d e s ,  including a 
region of very weak echoes around 45-km a l t i t ude .  
A par t  of the large power t ransmit ters ,  there  a re  four smaller trans- 
mit ters ,  similar to  the ones used a t  the Poker F l a t  array. 
capable of transmitt ing 10 kW of peak power a t  1% maximum duty cycle. 
bandwidth i s  much wider than the larger  t ransmit ters ,  permitting 1 usec 
pulses which correspond t o  150 meter resolution. 
Each un i t  i s  
Their 
Recently, one of: the 1 MW t ransmit ters  has been modified t o  take a dif-  
f e r en t  f i n a l  amplifier tube. The n e w  tubes, apart  from costing a f r ac t ion  of 
t he  cost  of the present ones, has one order  of magnitude wider baudwidth. Pre- 
liminary tests with the new design indicate  tha t  1.5 MW peak power and 1 psec 
r i s e  could be obtained. A t  present the only l imitat ion of the radar for  
optimum MST observations i s  i t s  reduced a l t i t u d e  resolution. 
modifications a 150-meter resolut ion w i l l  be achieved with the l a rges t  power 
aperture  of a l l  MST radars.  
With the new 
RECEIVERS 
There a re  4 independent receivers,  sharing a common L.O. Signals are 
converted t o  a 30 MHz IF, where most amplification i s  performed and then 
converted down t o  two quadrature s ignals  (complex coherent detection) a t  zero 
frequency. Bandwidth is  determined a t  t h i s  l eve l  with Bessel f i l t e r s .  They 
a re  manually adjusted t o  match 1, 3, 5 ,  10, 30, 50, 100, 300 or 500 usec 
pulses.  Receiver noise f i g u r e  i s  of the order of 3 dB. But s ignal  s e n s i t i v i t y  
a t  these frequencies i s  determined by sky noise. 
DATA ACQUISITION, PROCESSING AND CONTROL 
Data acquis i t ion,  processing and control  i s  based on a general-purpose 
computer and two in-house-designed un i t s ,  one fo r  control  of the radar and 
sampling and the other for data acquisit ion.  
The computer is Harris16 model. with 156 kiloword (24 b i t )  of memory 
running under a Vulcan System. It has two disk un i t s  with 80 Megabytes of 
317 
s to r ing  capacity each. 
800 and 1600 bbi/sec ( th ree  other 24/sec, 800 bbi. 
un i t  are being modified and integrated.) 
1 alphanumeric terminals and 2 Heathkits 2-81 microcomputers connected t o  the 
computer. Usually two, one CRT and one graphics, are assigned t o  the radar for 
operations. There i s  a Versatec e l e c t r o s t a t i c  and an Annadex dot-matrix 
p r in t e r ,  both with graphic p o s s i b i l i t i e s ,  connected t o  the system. 
Bulk recording i s  made on a 25 in/sec tape recorder fo r  
There are two CRT, 1 graphics, 
Transports from a previous 
The data  acquistion system i s  under development. A minimum workiqg 
configuration i s  already i n  operation. Plans include a preprocessor, capable 
of coherent integrat ing and other incoherent s c a t t e r  processing operations, 
which i s  now under construction. 
The working configuration consists of an 8 b i t  ADC with a maximum 
converting speed of 20 Mega-samples per second. 
and processed simultaneously. The 8 input s ignals  a r e  connected t o  8 sample- 
and-hold u n i t s  whose output i s  multiplexed i n t o  the ADC. 
connected t o  a computer channel assigned exclusively t o  t h i s  function, event- 
ual ly  through a buffer memory and preprocessor. Maximum input r a t e  i n t o  the 
computer i s  closed t o  1.2 megabytes per second. When the buffer memory of the 
preprocessor becomes operational,  the maximum sampling r a t e  w i l l  be .8 wsec-l 
f o r  two receiver  channels i n  p a r a l l e l  corresponding t o  a maximum resolut ion of 
125 meters. 
Eight channels can be sampled 
The ADCs a r e  now 
The radar con t ro l l e r  i s  designed around the o r ig ina l  idea of the f i r s t  
A sequence o f  two p a r a l l e l  words, one defining the 
radar control ler  b u i l t  a t  Jicamarca, now a popular scheme i n  many incoherent 
s c a t t e r  and MST radars.  
s t a t e  of 8 control  l i nes  and the other the duration of the state, a r e  read 
consecutively from a memory un i t  preprogrammed by the main computer. 
Experiments can be pre-scheduled using a Harr is  Job Control language 
sequence which is defined by the user. 
can be changed in t e rac t ive ly  by edi t ing the contents of a software panel which 
i s  displayed continuously on a CRT and contains a l l  var iable  parameters. 
parameters can also be preset  by ed i t i ng  a set of the panels t o  be used i n  an 
experiment beforehand, i n  accordance with the requirements. Usual observing 
programs are provided by the Observatory. 
programs. There a r e  ex i s t ing  real-time data  acquis i t ion and control sub- 
rout ines ,  which r e l i eve  the user from the need o f  famil iar iz ing himself with 
the'computer and data-acquisit ion system. 
of the Jicamarca radar.) 
(The reference i n  t h i s  paper i s  included i n  the Publications l i s t e d  below.) 
PUBLICATIONS RELATED TO THE JICAMARCA MST RADAR 
Ochs, G. R., (19651, The l a rge  50 Mc/s dipole array a t  Jicamarca radar obser- 
A t  any t i m e ,  the defining parameters 
These 
The user can also wr i t e  h i s  own 
(See Figure 1 for  schematic diagram 
vatory,  NBS Rep. 8772, dlpp., U.S. Dept. of Commer. Nat. Bur. of Stand. 
Boulder, Colorado. 
Woodman, R. F., and A. Guillen (19741, Radar observations of winds and turbu- 
lence i n  the s t ra tosphere and mesosphere, J. Atmos. Sci., 31, 493-505. 
Rastogi, P. K., and R. F. Woodman (19741, Mesospheric studies using the 
Jicamarca incoherent-scatter radar,  J. Atmos. Terr. Phvs.. 36, 1217- 
1231. 
Ruster, R., and R. F. Woodman, Radar measurements i n  the tropo-strato- and 
mesosphere, Proceedings AMs 19th Conf. on Radar Meteorology, Oct., 1976 
Sea t t l e ,  Wash. 
318 
_-  t; ------I 
-
I t -  7' 
w 
319 
Rastogi, P. K., and S. A. Bowhill (1976a), Gravity waves i n  the equator ia l  
mesosphere, J. Atmos. Terr. Phvs.. 38, 51-60. 
Rastogi, P. K., and S. A. Bowhill (1976b), Scat ter ing of radio waves from the 
mesosphere-1. Theory and observations, J. Atmos. Terr. Phvs.. 38, 399- 
411. 
Rastogi, P. K., and S. A. Bowhill (1976~1, Scat ter ing of radio waves from the 
mesosphere-2. 
Atmos. Terr. Phvs.. 38, 449-462. 
Evidence €or intermit tent  mesospheric turbuience, J- 
Fleisch, D. A. (19761, Stratospheric  s ca t t e r ing  of radio waves and the Jicamarca 
radio telescope, M.S. thesis ,  Rice Univ., Houston, Texas. 
Harper, R. M., and R. F. Woodman (19771, Preliminary multiheight radar observa- 
t i ons  of waves and winds i n  the mesosphere over Jicamarca, J. Atmos. 
Terr. Phvs., 39, 959-963. 
Fukao, S., S. Kato, S. Yokoi, R. M. Harper, R. F. Woodman and W. E. Gordon 
(19781, One full-day radar measurement of lower s t ra tospheric  winds over 
Jicamarca, J. Atmos. Terr. Phvs., 40, 1331-1337. 
Fukao, S., T. Sato, S. Kato, R. M. Harper, R. F. Woodman and W. E. Gordon 
(19791, Mesospheric winds and waves over Jicamarca on May 23-24, 1974, 
J. Geophys. Res.. 84, 4379-4386. 
Countryman, I. D., and S. A. Bowhill (19791, Wind and wave observations i n  the 
mesosphere using coherent-scatter radar,  Aeronomv Rep. No. 89, Aeronomy 
Lab., Dept. Elec. Eng., Univ. of Ill., Urbana-Champaign, 
Fukao, S., K. Wakasugi, and S. K a t 0  (19801, Radar measurement of short  period 
atmospheric waves and r e l a t ed  sca t t e r ing  propert ies  a t  the a l t i t u d e  of 
13-25 km over Jicamarca, Radio Sci.. 15, 431-438. 
Fukao, S., T. Sato, R. M. Harper, and S. Kat0 (19801, Radio wave sca t t e r ing  
from the t rop ica l  mesosphere observed with the Jicamarca radar,  Radio 
sci,, 447-457. 
Fukao, S., T. Sato, I. Hirota,  and S. Kato (19801, A preliminary radar obser- 
vat ion of long-period waves i n  the t rop ica l  mesosphere Over Jicamarca, 
J. Geophvs. Res.. 85, 1955-1957. 
Countryman, I. D., and P. M. Dolas (19821, Observations on t i des  i n  the equa- 
t o r i a l  atmosphere, J. Geophvs. Res., 87, 1336-1342. 


Capabilities and limitations of the Jicamarca radar as an MST radar

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