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PAPERS & DOCUMENTS
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SPOT
and PEACESAT S-Band Interference Problem: Final Report and Recommendations
Norman
Okamura, Social Science Research Institute, University of Hawaii
Christina Higa, Program Manager, PEACESAT
Eric Aubel, SPOT Operation Manager, Center for Space Studies, France
This
is an abstract of the final report submitted to the Center for Space
Studies (CNES), France, and the National Telecommunications and Information
Administration of the U.S. Department of Commerce.
In
July 1995, PEACESAT was notified by the National Oceanic and Atmospheric
Administration that a French low-earth orbiting (LEO) satellite, SPOT-2,
was having problems that may be related to frequency conflicts with
PEACESAT over Hawaii. PEACESAT was informed by NOAA that the problem
started in March 1995 and was causing the French SPOT satellite to
turn off and on.
The
initial reaction from PEACESAT was that it was likely that it
would
not have been the cause of the problem since there was nothing
different in its operations since March 1995. Further, it was
not clear that
transmissions from PEACESAT would turn off/on a satellite. However,
as a follow-up to that notification, a teleconferences was scheduled
between Eric Aubel, Operations Manager for the SPOT spacecraft
of the Center for Space Studies in France; and, Norman Okamura,
Telecommunications
Specialist of the Social Science Research Institute and Lori Mukaida,
Director of PEACESAT.
During the teleconference, facilitated by Donald M. Topping, who
speaks French, important information was obtained that was not previously
communicated to PEACESAT. Specifically, Aubel informed PEACESAT
of the frequency that the SPOT satellite utilized and stated that
the problem was first noticed in October and November 1994. Aubel
also informed PEACESAT that the satellite was not necessarily being
turned on or off, but being “locked up,” possibly because of the
frequency conflicts for interference. Based on the information provided,
Okamura and Mukaida believed that there was a strong possibility
that the PEACESAT E/F channel was the cause of the interference.
There were two reasons for this suspicion. First, the SPOT receive
frequency in S-Band was only .005 KHz from the PEACESAT F channel
frequency. Second, “locking up” seemed plausible. Third, PEACESAT
initiated a new data service for the Pacific Islands around October
1994 that required the data carriers in E/F channels to be used
for data transmissions and to be left on for users to access.
A series of tests were recommended and agreed to by Aubel, Okamura,
and Mukaida. The tests ultimately confirmed the suspicions that
the E/F full-duplex links of PEACESAT were causing interference.
The result was that a new series of frequencies were established
for the PEACESAT Program and transmission frequencies were changed
at all PEACESAT Sites, after extensive preparation and training.
The analysis and recommendations were accepted by both France and
the United States. PEACESAT modified its frequencies, and the issue
was resolved. PEACESAT also ceased transmissions in the frequencies
requested by CNES during its launch of Telecom 2.
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