Satgen 127  High Flying Shuttle STS - 48    by GM4IHJ     1 Sep 91

Tentatively planned for 2257 ut on 12th Sep . Space Shuttle Discovery will
launch for STS 48, a 5 day mission which will take the Space Shuttle
higher than it has ever been before. NASA will be trying for an altitude
of about 580 kms so that Discovery can place the UARS Upper Atmosphere
Research Satellite into an orbit high enough to give it 18 months of
useful life, before atmospheric drag pulls it down to a fiery re entry.

Forward link comms to UARS will be on 2106.4MHz via TDRS geostationary
relay, providing a minimum of 15 to 20 minutes per orbit of data transfer.
The corresponding transmit link is on 2287.5MHz. However this may be a
tough flight for TDRS. The problem is that Shuttle has to look up away
from earth as it accesses TDRS, and at this time of the autumn equinox the
Sun will be directly over the equator , further out beyond and behind
TDRS. So a lot of Solar interference is likely on some orbits. This may
cause the crew to revert to UHF links unexpectedly. Most likely from
previous encounters with this problem, is the use of 259.7 MHz Amplitude
Modulated speech from shuttle audible in UK. Less likely is the alternate
UHF voice frequency of 296.8MHz, with the further possibility that two
astronauts are planned to be in spacesuits when UARS is deployed in case
there are any snags ( stuck solar panels, or antennas ). These astronauts
may be heard on the UHF EVA frequency of 279.0MHz particularly during
mission day 3.

Because of the unusually high orbiting altitude and the high orbit
inclination ( 580+kms , 57 degs ) this flight will be seen and heard in UK
on 7 or 8 consecutive orbits roughly 98 minutes between in range passes
,in an orbit window nearly 11 hours wide. Please remember , most orbits
will pass north of UK stations and may be in radio range for up to 13
minutes at a time . Indeed , as orbits come in range of UK , the
astronauts may still be talking direct to USA on the UHF frequencies given
above. This may be particularly important at launch. In the past we in UK
have not heard launch nets direct but this shuttle is going so much higher
than any predecessor that we just might hear them . Equally noteworthy, if
Discovery does launch around 2257 ut , what ever the date, it should give
excellent sunlight reflecting visual tracking runs over UK on subsequent
evenings. The launch orbit is perhaps too late for solar illumination,
which is a pity , as shuttle will be accompanied by the big fuel tank on
its first pass over UK before the latter is de orbited to destruct over
the Indian Ocean. This was a splendid sight some years back when the tank
+ Challenger flew similar but separate lower altitude Glasgow orbits.

Please make a note , if you are attending the Scottish Rally , Dundee 8th
Sep, I will be on GM4JJJ's Pack-Age stall, happy to talk about any and all
space and satellite topics. Look forward to seeing you 73 de GM4IHJ@GB7SAN
PS Hear SARA 145.957MHz around noon utc but sigs very poor. NASA keps day
216 object 91 50E fit,but are not best Jupiter study orbit. Sgen126 refers