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ARIANESPACE FLIGHT 56

The 56th Ariane launch is scheduled to place the Hughes Communications 
GALAXY IV satellite into a geostationary transfer orbit adapted for the
PVA (Perigee Velocity Augmentation) procedure, using an Ariane 42P launch
vehicle equipped with 2 solid strap-on boosters (PAP).  This will be the 
3rd flight of an Ariane 4 in the 42P configuration.  It will be launched 
from the Ariane launch complex ELA 2, in Kourou - French Guiana.

The launch vehicle performance requirement for this mission is 3,055 kg
of which 2,980 kg represents the satellite mass.  The total vehicle mass
at liftoff is 323,173 kg.


Required Orbit Characteristics:
  Perigee Altitude ..... 200 km
  Apogee Altitude ...... 27,673 km at injection (prior to PVA)
  Inclination ..........   7 degrees


The flight was delayed due to OPTUS launch failure investigation.
Ariane 42P lift-off for Flight 56 is now scheduled on Tuesday,
February 2, 1993, as soon as possible within the following launch 
window:

     Kourou Time        GMT (01/03/93)      Washington, DC
     21:50 - 22:45      00:50 - 01:45       20:50 - 21:45


LAUNCH VEHICLE:

Ariane 42P.  This is a three-stage liquid fueled launcher with solid fueled 
strap-on boosters.  The first stage (L220) is built by Aerospatiale, and is 
powered by 4 liquid fueled Viking V engines.  The second stage (L33) is built
by MBB Erno and is powered by a single Viking IV engine.  Both the Viking IV
and V engines are manufactured by SEP.  The first and second stages use a 
biliquid UH25/N2O4 fuel.  The third stage is built by Aerospatiale and is 
the H10 "plus", with larger fuel tanks and increased performance over past
models.  It uses a cryogenic H2/O2 fueled HM-7B engine built by SEP. The two
strap-on boosters (PAP) are built by BPD and use a solid Flexadrine propellant.
The fully assembled launch vehicle stands 54.5 meters high on the pad.  
It uses the Type 01 Ariane Short payload fairing.


Flight Profile:

 +01:31  Solid strap-on booster jettison
 +03:27  First stage separation
 +03:30  Second stage ignition
 +04:35  Fairing jettison
 +05:30  Second stage separation
 +05:43  Third stage ignition
 +18:11  Third stage shutdown / orbit injection
 +20:00  GALAXY IV separation
 +20:46  Third stage avoidance maneuver
 +22:46  End of Ariane mission 52


Perigee Velocity Augmentation (PVA):

The PVA procedure used for the second time by Ariane (after the successful
Flight 54 mission for Galaxy VII) is a method allowing an increase in the
on-orbit life of a satellite by optimizing the combined performance of a
launch vehicle and satellite.  For this mission, the Ariane 42P will lift
around 280 kg of additional satellite propellants.  The resulting apogee,
with respect to standard geostationary orbit, will be 27,600 km instead of
35,975.  The Galaxy IV satellite will use its apogee motor at the 3rd and 6th
perigee to raise the apogee to the altitude normally used for circularization
of the orbit.

The on-orbit life increase is due to the optimization of the combined
performances of satellite/launcher.  The 280 kg of additional fuel in the
satellite tanks will to a significant amount remain after the satellite 
has reached the standard transfer orbit.  This will allow the increase of
the on-orbit life over that obtained by a launch directly to the standard
transfer orbit.

This procedure can only be used by satellites equipped with a liquid 
bi-propellant apogee motor (which can be restarted), and whose tank 
capacity allows fuel in excess of that necessary for a standard GTO.
Due to the small inclination of the Ariane mission (7 degrees), this 
capacity is often available when the satellites are built to be launched
from sites further away from the equator.  

This combination of HS-601/Ariane 42P/PVA allows an increase of more
than one year of orbital life for the commercial use of the satellite.


PAYLOAD:

Galaxy IV is the second satellite with a combined C-band and Ku-band
capability in the Galaxy fleet owned by Hughes Communications.  It is
also the second Arianespace launch of the HS-601 three-axis stabilized
type satellite manufactured by Hughes Aircraft Company.

  Total mass at lift-off .... 2,980 kg
  Mass at GEO insertion ..... 1,692 kg
  Dry mass .................. 1,315 kg     
  On-board power ............ 4,700 W (end of life)
  Nominal lifetime .......... 13.5 years     
  Span of solar panels ...... 26.5 m
  On-Orbit position ......... 99 degrees west, over the East Pacific Ocean.

 Transmission capacity:  
   24/30 Ku-band transponders of 50W each.
   24/30 C-band transponders of 16W each.

 In-flight operations:
   Apogee motor ignition for PVA maneuver is at about 24 hrs after launch 
   at the 3rd perigee, and about 60 hrs after launch at the 6th perigee.

   First regular apogee motor firing is at the 12th apogee, about 5 days 
   after launch.  Further firing will be done at 14th and 15th apogee.
   Deployment of solar panels is at about 10 days after launch.


LAUNCH COVERAGE:

All Ariane missions are broadcast live via satellite from Kourou. Coverage
begins at 30 minutes before launch and continues until all payloads have 
been deployed.  This mission will likely be carried on Galaxy 6, however
it could end up being located on a different satellite such as Galaxy 2.


-{ Dean Adams }-