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MIREX/APRS Exp




                          APRS/MIR PACKET TEST
                             11 March 1998
                          Bob Bruninga, WB4APR

On 11 March 1998 a special MIREX/APRS test was conducted via the packet
system on the Space Station MIR.  The test was to show possible methods 
for improving the visibility of MIREX communications to students and 
schools.  The objectives were to:

APRS/MIR TEST:  Since the Mir packet system has been operating well the
last few weeks, Dr. Larsen [ N6CO] of the MIREX group suggested the APRS
Mir test be conducted as soon as possilbe since precession was taking 
Mir passes earlier every day and it would soon be out of view during
school hours.  He authorized the APRS/MIR test on only two orbits on 
the 10th of March.  Unfortunately the MIR packet system went off the 
air on these two orbits, so the test was extended to the next few 
orbits over the USA.  The test was limited to the USA only because 
it had the largest numbers of existing APRS ground stations ready to 
test in sufficient numbers to fully load the system.  But the delay 
further complicated matters since the next orbits over the USA were 
between 0230 AM and 0400 AM local time.  As a result, the test was 
extended for a full 5 orbits to allow testers to choose a pass and 
still get some sleep.

   Although these 5 pass's of MIR covered 70% of the world Hams

To make Mir appear to move on all groundstation maps, three special 
tracking-uplink stations beaconed the moving position of MIR via the 
MIR digipeater.  One from California using the callsign MIR-6, one 
from Michigan using MIR-8, and one in Maryland using MIR-3 to match 
their callsign areas.  West coast stations typically saw the moving 
MIR-6, midwest stations typically saw the incoming MIR-6 change to 
a MIR-8 and then east coast stations saw the moving ICON on their 
maps change to a MIR-3.

To inject the downlink from Mir into the Internet, a few of the normal
APRS I-Gates tuned their radios from the normal APRS frequency to the 
Mir downlink frequency.  These Mir packets were intermingled with the 
normal stream of APRS packets into the APRServe Internet
system.  ALthough they would be seen on the main www.aprs.net maps
they would be hard to distinguish from the usual 1000 to 1200 or more
APRS stations on the air.  To provide a unique display of the APRS/Mir
packets alone, a special WEB page was designated to filter out only 
the APRS/MIR packets and display them spearately to users.  During 
the day of the event there were over 11,000 hits on the server system 
representing a peak load of 150 simultaneous users and as many as 
1000 users.

CONCLUSIONS:   THe test was completely successful in meeting all of the
original objectives.  THe short notice and early morning hours helped
to reduce the number of participants to a nominal 100 stations.  We
think this number is representative of the nominal number of schools
that could be authorized to simultaneously participate in future 
such Mir experiments.  The test demonstrated the value of 
using a UI frame one-to-all packet protocol to improve the delivery
of information to all ground stations.  Further, the test demonstrated
the value of a few special MIREX ground stations to uplink the moving 
Mir position reports and to relay real-time MIREX bulletins and 
announcements that can be received by all stations in the footprint 
including receive-only school stations.  Finally, the test showed 
the value of multiply internet connected ground stations for not
only providing a continuum of data from the downlink across the whole
country, but also for providing WEB access to students and schools
outside of the footprint or without amateur radio equipment.  

All of the APRS stations want to thank the MIREX team and also those 
normal Mir BBS users who were inconvenienced by this test, for this 
opportunity to conduct this important experiment. 





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