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[jamsat-news:1112] * SpaceNews 28-Jun-99 *

* SpaceNews 28-Jun-99 *

BID: $SPC0628


		 	  MONDAY JUNE 28, 1999

A team of experts and builders of the various transponders of the AMSAT
P3-D satellite recently arrived at Orlando, Florida from Europe.  The
team included Matjaz Vidmar S53MV, Mirek Kasal OK2AQK, Michael Fletcher
OH2AUE, Wilfried Gladisch, Peter Gulzow DB2OS, Werner Haas DJ5KQ and
Karl Meinzer DJ4ZC.

After testing and calibration of the spacecraft antennas, which were
mostly build by Stan Wood WA4NFY and Freddy de Guchteneire ON6UG, the
antennas were mounted to the spacecraft for the "rollout" when P3-D was
transported outside for an "on air" test in full flight configuration.
The spacecraft is protected from the Florida environment by a big sealed

After several exciting days of testing, the RF communications manager
Werner Haas, DJ5KQ was happy to report to the Project Leader Dr. Karl
Meinzer DJ4ZC of the successful completion of the rollout, and that
all RF subsystems in the P3-D spacecraft worked nominally.

Another big event was the successful testing of the 400N thruster from
MBB and the 100mN ATOS Arcjet developed by the University of Stuttgart
(Germany) with pressurizing of the whole propulsion system and fuel
tanks.  The test firing using Nitrogen gas was performed by Dick Daniels
W4PUJ, Rick Leon KA1RHL, Karl Meinzer DJ4ZC and Peter Gulzow DB2OS.

The next milestones are the Spin Balance test and the Vibration test,
which will take place before the spacecraft is transported to the launch
site.  The vibration test could not be done earlier since designers had
to wait for the final specification of the static and dynamic loads by
the launcher agency.

The P3D Team
Lou McFadin W5DID
P3D Integration Manager

The AMRAD-OSCAR-27 satellite uses a method called Timed Eclipse Power
Regulation (TEPR) to regulate its battery charge.  In simple terms,
TEPR times how long the satellite has been in the eclipse or in the
sun, and decides what subsystems to turn on or off.

The current software onboard AO-27 breaks an orbit into 6 different
states as follows:

TEPR State 1: Starts when the satellite enters the Eclipse
TEPR State 2: Starts a programmed time after TEPR State 1 (still
              during the Eclipse)
TEPR State 3: Starts a programmed time after TEPR State 1 that's
              after State 2 (still during the Eclipse)

TEPR State 4: Starts when the satellite enters the Sun
TEPR State 5: Starts a programmed time after TEPR 4 (Still in the Sun)
TEPR State 6: Starts a programmed time after TEPR 4 that's after
              State 4 (still in the Sun)

Current subsystems by state are as follows:

TEPR 1, 2, 3 : All unneeded subsystems turned off (This is why there
               is no night time use of the satellite)
TEPR 4       : AO-27's transmitter is turned to exciter power only.
               All other transmitters are off.
TEPR 5       : AO-27's transmitter is turned to 0.5 watts (low power)
TEPR 6       : All unneeded Subsystems are turned off

Using this model, during a descending day-time pass, AO-27 will enter
TEPR 4 after coming out of eclipse and will begin to recharge its
batteries.  Controllers program the TEPR 5 time so the satellite will
stay in TEPR 4 until the footprint reaches latitudes equal to the
Northern United States.  At that time, it changes to TEPR State 5 and
the transmitter turns on.  The duration of TEPR State 5 is set for the
longest controllers can leave the transmitter on to keep the satellite's
batteries in a state that will prolong their life.  At the current time
(June 1999), this is 18 minutes.  If controllers were to leave it on
longer, the lifetime of the satellite could be shortened.  The TEPR 6
period needs to be long enough to recharge the batteries before the
satellite enters the eclipse again (TEPR 1).

The time that is needed to stay in TEPR 6 is what places a limit on
the southern latitudes that satellite can work in.

Controllers command OSCAR-27 to charge its batteries for "x" number of
minutes AFTER it enters the Sun.  This is TEPR state 4 expressed in 30
second increments (e.g. TEPR 42 means that the charging time is 21 minutes).
Controllers then set TEPR state 5 to the length of time, expressed in 30
second increments, that the transmitter would be on from the start of
TEPR 4, but not on until the completion of TEPR 4 (e.g. TEPR 78 means
that the transmitter will shut off 39 minutes after the start of TEPR 4,
but the transmitter will be on for 18 minutes (78-42 = 36, or 18 minutes)).

Chuck Wyrick, KM4NZ, acting AO-27 control operator, reset the TEPR states
on AO-27 at approximately 14:20 UTC, 20-Jun-99 as follows:

	TEPR 4: 42
	TEPR 5: 78

to give the best overall coverage during this year's Field Day activities.

[Info via Chuck, KM4NZ, and Michael, N4USI]

The countdown to the launch of Space Shuttle Columbia on mission
STS-93 is proceeding well.  STS-93 will be a SAREX (Shuttle Amateur
Radio Experiment) mission.

STS-93 crew members include:

	Eileen Collins, KD5EDS 
	Jeffrey Ashby 
	Steven Hawley, Mission Specialist
	Catherine Coleman, Mission Specialist, KC5ZTH
	Michael Tognini, KD5EJZ 

WA3NAN, Amateur Radio Club station at the Goddard Spaceflight Center in
Greenbelt, Maryland, is expected to be on the air providing re-transmissions
of air-to-ground communications on the following HF frequencies:

	3.860  MHz LSB 
	7.185  MHz LSB 
	14.295 MHz USB 
	21.395 MHz USB 
	28.650 MHz USB 

Launch of STS-93 is expected to occur no earlier than 20-July-99 at
12:36 AM EDT (21-Jul-99 0426 UTC).  Columbia will be carrying the Chandra
X-Ray observatory into a 153 nautical mile / 28.45 degree inclination orbit
on this mission.

Dr. Dave Larsen, President of MIREX, reports that when in packet
radio mode, the 2-meter transmitter on-board the Mir space station
is transmitting an unmodulated carrier rather than 1200 baud AFSK data.
It is hoped that the problem may be resolved by simply re-seating the
audio connector connecting the TNC to the 2-meter transceiver.

In the meantime, some of the cosmonauts on Mir have been making 2-way
voice contacts with groundstations on 145.985 MHz FM.

Comments and input for SpaceNews should be directed to the editor
(John, KD2BD) via any of the paths listed below:
WWW       : http://www.njin.net/~magliaco/
PACKET    : KD2BD @ N2SMV.NJ.USA.NA   <-------------- New address!
INTERNET  : kd2bd@amsat.org, magliaco@email.njin.net

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