Satgen328  Mir Visual Timetables    by GM4IHJ                8 July 95

Over the next few years there will be regular Mir/Shuttle docking missions
and eventually an international Space station will begin to assemble in
Mirs orbit. This is excellent news for Radio Amateurs noting that unlike
the original American Freedom station proposal suggested for a 28 degree
inclination orbit, which gave limited earth coverage, this international
station at 51 degree inclination should be SAREX audible, and visible,
over most of the world. 
Listening to Amateur Radio conversations during the recent Mir/Shuttle
docking suggests that there is some slight confusion regarding when and
where the Space station is visible. Satgen 325 described the conditions
required for the station to be seen from the ground, overflying a darkened
earth looking like a bright sun reflecting star. But the station does not
come over your station at the same time each day . Inclined at 50 degrees
and average height of 400 kms , the orbit plane is pulled sideways every
time the station passes over the earths equatorial bulge. In addition ,
because the earth goes around the Sun once a year its orientation in space
changes about 1 degree each day. You can see the effect of these two
phenomena if you compare Mir Equator crossings several days apart Eg 8
June 95 253W, at 0128ut, then 15 June 95 294W at 0123ut. A massive shift
of 41 degrees west for times differing only by 5 minutes, revealing an
approximate orbit shift of about 6 degrees per day. 
How does this affect viewing opportunities ?  At 6 degrees shift per day ,
Mir returns to roughly the same orbit alignment every 60 days . So if you
see Mir at night on say 25 June 95 you should see it again on the 24
August 95. If you see Mir in the pre dawn morning sky however it will be
at another 60 day cycle not neccessarily half way between the nighttime
encounters because only equatorial stations see a roughly 12 hour day, 12
hour night. The following chart shows the days Mir will be visible at
various latitudes over the rest of this year :- Legend M morning before
dawn, E evening after sunset, lower case =low elevation.

....August....:..September...:....October....:....November..:...December..
London , Moscow , Winnipeg and Vancouver     :              :
MMMMMM        :         MMMMMMMMMM           :      MMMMMMMMMMMM
      EEEEEEEEEEE            :       EEEEEEEEEEEE           :       EEEEEE
              :              :               :              :
Tokyo Japan ,Beirut, Malta, Gibraltar, Los Angeles          :
mmmMMM        :        MMMMMmmMMMMM          :       MMMMmmmMMMM
      EEEEEEEEEEEEE          :     EEEEEEEEeeEEEEE          :      EEEEEee
              :              :               :              :
Sydney Australia , Cape Town , Buenos Aires  :              :
     MMMMMMMmmMMMMMM         :        MMMMMMmmmMMMM         :      MMMMMMm
EEEE          :      EEEEEeeeEEEEE           :   EEEEEeeeEEEEEE
              :              :               :              :
Singapore , Colombo , Nairobi , Quito        :              :
     MMMMM    : MMMMM        :      MMMMM    : MMMMM        :       MMMMM 
EEEEE         :      EEEEE   EEEEE           :   EEEEE     EEEEE

Changes in Mirs orbital altitude may alter these dates slightly . Stations
near the same latitude see Mir at roughly the same local Sun time .