Re: NavSpaSur
Leo Barhorst (leobarhorst@pi.net)
Fri, 5 Jan 96 10:32:13 PST
> Josh Williams asks about NavSpaSur
> Ted Molczan has answered a lot of the questions about it
In an other book by Desmond King-Hele; "A tapestry of orbits", 1992, ISBN 0 521
39323 X, I've found some more information on NavSpaSur.
I quote from this book (page 135):
"NavSpaSur is short for 'Naval Space Surveillance' and is an (US NAVY -lb) radar
interferometer system. There is a very powerful transmitter at Lake Kickapoo in Texas,
emitting an east-west fan-beam of radio waves. Any satellite crossing this east-west
'fence' reflects back some of the transmitted radiation, which is detected by six
interferometer stations in a line across the United States, from San Diego in the west to
Georgia in the east, at latitudes near 33 degrees N. The NavSpaSur transmitter
consists of 2256 dipoles streching north-south for more than 3 km. The power radiated
continously is 810 kW on a frequency of 217 MHz (wavelenght 1.4 m). The system
became operational in 1961 and has been working 24 hours a day ever since, making
10.000 obsevations of satellites per day."
On page 136 is a photo of the transmitter. It looks like the dipoles are set on a level
plane, with some dips in the ground filled up where the dipoles are on a dyke.
Desmond goes on explaining how he met Dr Roger Easton (Navel Research
Laboratory) in 1968 and how the observations of NavSpaSur (only used for
NORAD orbits and in updating predictions) were made available to his group at RAE for
orbit analyses.
"These NavSpaSur observations provided the essential basis for nearly all our
determinations of orbits by PROP (a computer Program for the Refinement of Orbital
Parameters -lb) for scientific analysis. The observations are unaffected by daylight,
eclipse or bad weather and, for nearly all satellites, several observations per day have
always been available , day in and day out, all through the year, for more than 20 years.
The angular accuracy of the observations is similar to Minitrack or a good visual
observation, about 0.03 degrees."
Desmond warns for the possibility of bias, as the NavSpaSur observations are all made
from 33 degrees N and no other observations are available or used in the orbit
determination.
The book describes the life of D. King-Hele and particially his working life devoted to the
satellite orbit analysis and the production of the RAE Table of Artifical Satellites. I
recommend it for reading to everybody interested in satellites.
Greetiongs
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Name: Leo Barhorst
E-mail: leobarhorst@pi.net
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