From: rdale@mentor.cc.purdue.edu (Robert Dale)
Newsgroups: sci.geo.meteorology
Subject: Future of Geo-Sats
Date: 13 Apr 92 18:11:18 GMT
Organization: Purdue University Computing Center


There have been a lot of questions on the future of our
geostationary satellites, so I'm reprinting an article by
J. Block in the April 1992 National Weather Association newsletter...

**

CHANGES COMING IN GOES OPERATIONS

GOES-7, the current operational geostationary weather satellite,
now approaching the end of its five-year design life, will be
left in its current position to conserve its remaining fuel.
The recent deployment of METEOSAT-3 (M3) by EUMETSAT (European
organization for the exploitation of Meteorological Satellites)
at 50 degrees west longitude has allowed this plan by providing
good coverage of the Atlantic Ocean for hurricanes and tropical
storms.  For the past few years of single GOES operation, GOES-7
has been stationed at 98W for hurricane season and then moved
to 108W for the winter.

GOES-7 is currently slowly drifting west to 112 degrees, where
it will arrive on station in late April 1992.  The satellite
continues to operate normally, still using the first LED encoder
lamp (the previous GOES satellites had shortened lives because of
the failure of this encoder lamp), with one other LED and two
incandescant lamps remaining.  Adjustments to the starting scan
line continue, resulting in the scane starting as far south as
60N, to avoid lubricant buildup on the imager's mirror.  It appears
that the spacecraft will remain healthy for the foreseeable future.

The problem is that the five-year fuel supply is very low.
When GOES-7 is stopped at 112W, it will not have north-south
inclination maneuvers performed to keep the orbital inclination
(distance north or south of the equator) to less than 0.1
degrees.  From now on, maneuvers will only be performed to keep
the inclination below one degree, which may result in a slight
wobble in the imagery, but should be correctable.  By managing
the orbit in this fashion, NESDIS (National Environmental Satllite
Data Information Service) hopes to be able to conserve enough fuel
to maintain GOES-7 through 1993 with usable imagery.

In the meantime, NESDIS is proceeding with the construction of a
METEOSAT Command and Data Acquisition (CDA) station ad Wallops
Island, VA.  The Europeans have agreed to let the U.S. take control
of M3 as soon as the CDA station is completed.  This is necessary
because the existing METEOSAT CDA at Darmstadt, Germany cannot
see M3 if it moves any further to the west.  METEOSAT is a different
satellite than GOES, with lower resolution in the visible,
a south to north scanning regime, and only hourly images.  After
checkout in early 1993, NESDIS will move M3 to 75W, where it
will remain until replaced by GOES-NEXT.

GOES-NEXT continues to experience developmental problems and delays.
In mid-1991, an independent GOES assessment team was formed.  The team
found that the spacecraft is complete, and in storage awaiting launch.
The ground systems are complete.  The only remaining problems are
with the sensor instruments.

There have been a series of problems with the accuracy of the
sounder.  The detectors in the imager have apparently degraded,
and there have been other technical problems uncovered by the
assessment team.  In light of these problems, the assessment team
has recommended that the GOES-I instruments not be flown but
used as pathfinders, as the number of problems uncovered has
created a serious risk that they will not work in space.  The
GOES-I instruments package will be completed, whereupon assembly
of the GOES-J package will commence.  In view of all known problems,
this represents a tight schedule, but is possible.  The actual
launch of GOES-I will not occur before December 1993.

For the next two years, then, GOES imagery will be available at 112W
in a slightly degraded orbit.  METEOSAT data will cover the
Atlantic through this year, and will provide eastern U.S. coverage in
1993; in effect, becoming the second operational U.S. satellite.
Kavouras is currently upgrading ground systems to enhance the
current METEOSAT imagery.  It will be 1995 before the U.S. has
a two-GOES satellite system operational again (Kavouras Newsletter)

						J. Block
Newsgroups: sci.geo.meteorology