PDS_VERSION_ID                     = PDS3
RECORD_TYPE                        = STREAM
LABEL_REVISION_NOTE                = "2007-07-11 GEO:JGW"

OBJECT                             = INSTRUMENT
 INSTRUMENT_ID                     = "RTLS"
 INSTRUMENT_HOST_ID                = "ARCB"

 OBJECT                            = INSTRUMENT_INFORMATION
  INSTRUMENT_NAME                  = "RADIO TELESCOPE"
  INSTRUMENT_TYPE                  = RADAR
  INSTRUMENT_DESC                  = "

  Instrument Overview
  ===================
  
  The following information comes from the NAIC website
  (http://www.naic.edu/public/the_telescope.htm):
  
  The radio telescope at Arecibo Observatory is '305 m (1000 feet) in
  diameter, 167 feet deep, and covers an area of about twenty acres. The 
  surface is made of almost 40,000 perforated aluminum panels, each measuring
  about 3 feet by 6 feet, supported by a network of steel cables strung
  across the underlying karst sinkhole. It is a spherical (not parabolic)
  reflector.
    
  Suspended 450 feet above the reflector is the 900 ton platform. Similar in 
  design to a bridge, it hangs in midair on eighteen cables, which are strung 
  from three reinforced concrete towers. One is 365 feet high, and the other
  two are 265 feet high. All three tops are at the same elevation. The
  combined volume of reinforced concrete in all three towers is 9,100 cubic
  yards. Each tower is back-guyed to ground anchors with seven 3.25 inch
  diameter steel bridge cables. Another system of three pairs of cables runs
  from each corner of the platform to large concrete blocks under the
  reflector. They are attached to giant jackswhich allow adjustment of the
  height of each corner with millimeter precision.

  Just below the triangular frame of the upper platform is a circular track 
  on which the azimuth arm turns. The azimuth arm is a bow shaped structure
  328 feet long. The curved part of the arm is another track, on which a
  carriage house on one side and the gregorian dome (installed in 1996) on
  the other side can be positioned anywhere up to twenty degrees from the
  vertical. Inside the gregorian dome two subreflectors (secondary and
  tertiary) focus radiation to a point in space where a set of horn antennae
  can be positioned to gather it. Hanging below the carriage house are
  various linear antennas each tuned to a narrow band of frequencies. The
  antennas point downward and are designed specially for the Arecibo
  spherical reflector. By aiming a feed antenna at a certain point on the
  reflector, radio emissions originating from a very small area of the sky in
  line with the feed antenna will be focused on the feed antenna. Attached to
  the antennas are very sensitive and highly complex radio receivers. These
  devices operate immersed in a bath of liquid helium, to maintain a very low
  receiver temperature. At such cold temperatures the electron noise in the 
  receivers is very small, and only the incoming radio signals, which are
  very weak, are amplified. The Arecibo system operates at frequencies from
  50 megahertz (6 m wavelength) up to 10,000 megahertz (3 cm wavelength).'

  See 'An Astronomer's Guide to the Arecibo 305-m Telescope' [SALTER2005] for
  more information.

  "

 END_OBJECT                        = INSTRUMENT_INFORMATION

 OBJECT                            = INSTRUMENT_REFERENCE_INFO
  REFERENCE_KEY_ID                 = "SALTER2005"
 END_OBJECT                        = INSTRUMENT_REFERENCE_INFO

END_OBJECT                         = INSTRUMENT
END